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| Publications of Marc A. Sommer :chronological alphabetical combined listing:
%% Journal Articles
@article{fds351254,
Author = {Akbar, N and Yarossi, M and Martinez-Gost, M and Sommer, MA and Dannhauer, M and Rampersad, S and Brooks, D and Tunik, E and Erdoğmuş,
D},
Title = {Mapping Motor Cortex Stimulation to Muscle Responses: A Deep
Neural Network Modeling Approach.},
Journal = {The ... International Conference on PErvasive Technologies
Related to Assistive Environments : PETRA ... International
Conference on PErvasive Technologies Related to Assistive
Environments},
Volume = {2020},
Pages = {15},
Year = {2020},
Month = {June},
ISBN = {9781450377737},
url = {http://dx.doi.org/10.1145/3389189.3389203},
Abstract = {A deep neural network (DNN) that can reliably model muscle
responses from corresponding brain stimulation has the
potential to increase knowledge of coordinated motor control
for numerous basic science and applied use cases. Such cases
include the understanding of abnormal movement patterns due
to neurological injury from stroke, and stimulation based
interventions for neurological recovery such as paired
associative stimulation. In this work, potential DNN models
are explored and the one with the minimum squared errors is
recommended for the optimal performance of the M2M-Net, a
network that maps transcranial magnetic stimulation of the
motor cortex to corresponding muscle responses, using: a
finite element simulation, an empirical neural response
profile, a convolutional autoencoder, a separate deep
network mapper, and recordings of multi-muscle activation.
We discuss the rationale behind the different modeling
approaches and architectures, and contrast their results.
Additionally, to obtain a comparative insight of the trade-o
between complexity and performance analysis, we explore
different techniques, including the extension of two
classical information criteria for M2M-Net. Finally, we find
that the model analogous to mapping the motor cortex
stimulation to a combination of direct and synergistic
connection to the muscles performs the best, when the neural
response profile is used at the input.},
Doi = {10.1145/3389189.3389203},
Key = {fds351254}
}
@article{fds349697,
Author = {Yeung, AH-F and Subramanian, D and Desai, AD and Soltanian-Zadeh, S and Roy, A and Vajzovic, L and Sommer, M and Farsiu, S},
Title = {Spatio-temporal image modulation for enhancing the quality
of vision with potential application in patients with
retinal prostheses},
Journal = {INVESTIGATIVE OPHTHALMOLOGY & VISUAL SCIENCE},
Volume = {60},
Number = {9},
Pages = {3 pages},
Publisher = {ASSOC RESEARCH VISION OPHTHALMOLOGY INC},
Year = {2019},
Month = {July},
Key = {fds349697}
}
@article{fds343771,
Author = {Yarossi, M and Quivira, F and Dannhauer, M and Sommer, MA and Brooks,
DH and Erdoǧmuş, D and Tunik, E},
Title = {An experimental and computational framework for modeling
multi-muscle responses to transcranial magnetic stimulation
of the human motor cortex},
Journal = {International IEEE/EMBS Conference on Neural Engineering,
NER},
Volume = {2019-March},
Pages = {1122-1125},
Year = {2019},
Month = {May},
ISBN = {9781538679210},
url = {http://dx.doi.org/10.1109/NER.2019.8717159},
Abstract = {Current knowledge of coordinated motor control of multiple
muscles is derived primarily from invasive
stimulation-recording techniques in animal models. Similar
studies are not generally feasible in humans, so a modeling
framework is needed to facilitate knowledge transfer from
animal studies. We describe such a framework that uses a
deep neural network model to map finite element simulation
of transcranial magnetic stimulation induced electric fields
(E-fields) in motor cortex to recordings of multi-muscle
activation. Critically, we show that model generalization is
improved when we incorporate empirically derived
physiological models for E-field to neuron firing rate and
low-dimensional control via muscle synergies.},
Doi = {10.1109/NER.2019.8717159},
Key = {fds343771}
}
@article{fds338442,
Author = {Clements, JM and Kopper, R and Zielinski, DJ and Rao, H and Sommer, MA and Kirsch, E and Mainsah, BO and Collins, LM and Appelbaum,
LG},
Title = {Neurophysiology of Visual-Motor Learning during a Simulated
Marksmanship Task in Immersive Virtual Reality},
Journal = {25th IEEE Conference on Virtual Reality and 3D User
Interfaces, VR 2018 - Proceedings},
Pages = {451-458},
Publisher = {IEEE},
Year = {2018},
Month = {August},
ISBN = {9781538633656},
url = {http://dx.doi.org/10.1109/VR.2018.8446068},
Abstract = {Immersive virtual reality (VR) systems offer flexible
control of an interactive environment, along with precise
position and orientation tracking of realistic movements.
Immersive VR can also be used in conjunction with
neurophysiological monitoring techniques, such as
electroencephalography (EEG), to record neural activity as
users perform complex tasks. As such, the fusion of VR,
kinematic tracking, and EEG offers a powerful testbed for
naturalistic neuroscience research. In this study, we
combine these elements to investigate the cognitive and
neural mechanisms that underlie motor skill learning during
a multi-day simulated marksmanship training regimen
conducted with 20 participants. On each of 3 days,
participants performed 8 blocks of 60 trials in which a
simulated clay pigeon was launched from behind a trap house.
Participants attempted to shoot the moving target with a
firearm game controller, receiving immediate positional
feedback and running scores after each shot. Over the course
of the 3 days that individuals practiced this protocol, shot
accuracy and precision improved significantly while reaction
times got significantly faster. Furthermore, results
demonstrate that more negative EEG amplitudes produced over
the visual cortices correlate with better shooting
performance measured by accuracy, reaction times, and
response times, indicating that early visual system
plasticity underlies behavioral learning in this task. These
findings point towards a naturalistic neuroscience approach
that can be used to identify neural markers of marksmanship
performance.},
Doi = {10.1109/VR.2018.8446068},
Key = {fds338442}
}
%% Book Chapters
@misc{fds334788,
Author = {Abzug, ZM and Sommer, MA},
Title = {Supplementary Eye Fields},
Booktitle = {Reference Module in Neuroscience and Biobehavioral
Psychology},
Publisher = {Elevier},
Year = {2017},
ISBN = {9780128093245},
Abstract = {The supplementary eye fields (SEFs) are located in
dorsomedial frontal cortex and contribute to high-level
control of eye movements. Recordings in the SEF reveal
neural activity related to vision, saccades, and fixations,
and electrical stimulation in the SEF evokes saccades and
fixations. Inactivations and lesions of the SEF, however,
cause minimal oculomotor deficits. The SEF thus processes
information relevant to eye movements and influences
critical oculomotor centers but seems unnecessary for
generating action. Instead, the SEF has overarching, subtle
functions that include limb-eye coordination, the timing and
sequencing of actions, learning, monitoring conflict,
prediction, supervising behavior, value-based decision
making, and the monitoring of decisions.},
Key = {fds334788}
}
@misc{fds334803,
Author = {Middlebrooks, PG and Abzug, Z and Sommer, MA},
Title = {Studying metacognitive processes at the single-neuron
level},
Pages = {225-244},
Booktitle = {The Cognitive Neuroscience of Metacognition},
Publisher = {Springer},
Editor = {Fleming, SM and Frith, CD},
Year = {2014},
Month = {June},
ISBN = {978-3-642-45189-8},
url = {http://dx.doi.org/10.1007/978-3-642-45190-4_10},
Abstract = {Over the past few decades, strides have been made toward
understanding how higher level cognitive processes are
mediated by neuronal spiking activity. Neuronal correlates
of functions such as attention, executive control, working
memory, decision-making, and reward processing have all been
elucidated, to an impressive level of detail, at the single
cell and circuit levels.},
Doi = {10.1007/978-3-642-45190-4_10},
Key = {fds334803}
}
@misc{fds334802,
Author = {Sommer, MA and Wurtz, RH},
Title = {The Dialogue between Cerebral Cortex and Superior
Colliculus: Multiple Ascending Pathways for Corollary
Discharge},
Volume = {TBD},
Pages = {TBD},
Booktitle = {The New Visual Neurosciences},
Publisher = {MIT Press},
Address = {Cambridge, Massachusetts},
Editor = {Leo M. Chalupa and Jack S. Werner},
Year = {2014},
url = {https://dl.dropbox.com/u/27738651/Publications/SommerWurtz-NewVisNeurosci-InPress.pdf},
Key = {fds334802}
}
@misc{fds334824,
Author = {Sommer, MA},
Title = {Supplementary eye fields},
Pages = {635-643},
Booktitle = {Encyclopedia of Neuroscience},
Publisher = {Academic Press},
Address = {Oxford},
Editor = {Squire, LR},
Year = {2009},
ISBN = {978-0-08-045046-9},
url = {https://dl.dropboxusercontent.com/u/27738651/Publications/Sommer2009-SEFreview-EncyclOfNeurosci.pdf},
Abstract = {The supplementary eye fields (SEFs) are located in
dorsomedial frontal cortex and contribute to high-level
control of eye movements. Recordings in the SEF reveal
visual-, saccade-, and fixation-related activity, and
stimulations in the SEF evoke saccades and fixations.
Inactivations and lesions of the SEF, however, cause minimal
oculomotor deficits. The SEF thus processes information
relevant to eye movements and influences critical oculomotor
centers but seems unnecessary for generating action.
Instead, the SEF has overarching, subtle functions that
include representing space in multiple ways, supervising
behavior, monitoring conflict, prediction, learning,
planning sequences, and coordination of the limbs and eyes.
© 2009 Elsevier Ltd All rights reserved.},
Doi = {10.1016/B978-008045046-9.01122-0},
Key = {fds334824}
}
@misc{fds334820,
Author = {Crapse, TB and Sommer, MA},
Title = {Corollary Discharge},
Pages = {325-327},
Booktitle = {Encyclopedia of Perception},
Publisher = {SAGE Publications},
Editor = {Goldstein, RB},
Year = {2009},
ISBN = {9781412940818},
Key = {fds334820}
}
@misc{fds334821,
Author = {Shin, SY and Crapse, TB and Mayo, JP and Sommer, MA},
Title = {Visuomotor Integration},
Pages = {4354-4359},
Booktitle = {Encyclopedia of Neuroscience},
Publisher = {Springer},
Editor = {Binder, MD and Hirokawa, N and Windhorst, U},
Year = {2009},
ISBN = {978-3-540-23735-8},
url = {http://dx.doi.org/10.1007/978-3-540-29678-2_6384},
Doi = {10.1007/978-3-540-29678-2_6384},
Key = {fds334821}
}
@misc{fds334822,
Author = {Sommer, MA and Wurtz, RH},
Title = {Single Neurons and Primate Behavior},
Pages = {123-139},
Booktitle = {Methods in Mind},
Publisher = {MIT Press},
Editor = {Senior, C and Russell, T and Gazzaniga, M},
Year = {2009},
ISBN = {9780262513432},
Key = {fds334822}
}
@misc{fds207861,
Author = {Wurtz, Robert H. and Sommer, Marc A.},
Title = {Single Neurons and Primate Behavior},
Pages = {123-139},
Booktitle = {Methods in Mind},
Publisher = {MIT Press},
Address = {Cambridge, Massachusetts},
Editor = {Carl Senior and Tamara Russell and Michael S.
Gazzaniga},
Year = {2006},
ISBN = {978-0262195416},
url = {https://dl.dropbox.com/u/27738651/Publications/WurtzSommer_MethodsInMind2006.pdf},
Abstract = {Understanding the brain mechanisms mediating cognitive
behavior requires combining two experimental steps. First,
the brain must actually be engaged in the cognitive behavior
under study. Second, the brain activity must be measured
during this behavior and the recording sufficiently
described to permit replication of the experiment. There are
a number of ways of meeting the second prerequisite, many
discussed elsewhere in this volume; our chapter will address
one with unsurpassed spatial and temporal resolution: the
recording of the action potentials of single neurons.
Recording single neurons in the brain is a mature technique
that has been used extensively for over a quarter century.
In outlining the technique requirements and comparing them
to those of other techniques, we will focus on what has
become a cornerstone for the study of brain mechanisms
underlying cognitive behavior: single-neuron recording from
awake monkeys trained on behavioral tasks. Our description
and comments are based on our own experience in studying
awake monkeys; we also provide references on specific
technical points not addressed in this chapter.},
Key = {fds207861}
}
@misc{fds207859,
Author = {Sommer, Marc A. and Wurtz, Robert H.},
Title = {The Dialogue between Cerebral Cortex and Superior
Colliculus: Implications for Saccadic Target Selection and
Corollary Discharge.},
Volume = {2},
Pages = {1466-1484},
Booktitle = {The Visual Neurosciences},
Publisher = {MIT Press},
Address = {Cambridge, Massachusetts},
Editor = {Leo M. Chalupa and Jack S. Werner},
Year = {2004},
ISBN = {978-0-262-03308-4},
url = {https://dl.dropbox.com/u/27738651/Publications/SommerWurtz_TheVisualNeurosciences2004.pdf},
Key = {fds207859}
}
@misc{fds349698,
Author = {Wurtz, RH and Sommer, MA},
Title = {Identifying corollary discharges for movement in the primate
brain},
Pages = {47-60},
Booktitle = {Progress in Brain Research},
Publisher = {Elsevier},
Year = {2004},
ISBN = {9780444509789},
url = {http://dx.doi.org/10.1016/s0079-6123(03)14403-2},
Doi = {10.1016/s0079-6123(03)14403-2},
Key = {fds349698}
}
@misc{fds334846,
Author = {Wurtz, RH and Basso, MA and Paré, M and Sommer, MA},
Title = {The Superior Colliculus and the Cognitive Control of
Movement},
Pages = {573-587},
Booktitle = {The New Cognitive Neurosciences},
Publisher = {MIT Press},
Editor = {Gazzaniga, MS},
Year = {2000},
ISBN = {9780262071956},
Key = {fds334846}
}
@misc{fds334859,
Author = {Smith, MA and Sadler, RH and Sommer, MA},
Title = {The Macrophage as the Demyelinative Agent: A Role for
Antimyelin Antibodies},
Pages = {51-66},
Booktitle = {Multiple Sclerosis: Current Status of Research and
Treatment},
Publisher = {Demos Publications},
Editor = {Herndon, RM and Seil, FJ},
Year = {1994},
ISBN = {9780939957286},
Key = {fds334859}
}
%% Papers Published
@article{fds371675,
Author = {Subramanian, D and Pearson, JM and Sommer, MA},
Title = {Bayesian and Discriminative Models for Active Visual
Perception across Saccades.},
Journal = {eNeuro},
Volume = {10},
Number = {7},
Pages = {ENEURO.0403-ENEU22.2023},
Year = {2023},
Month = {July},
url = {http://dx.doi.org/10.1523/ENEURO.0403-22.2023},
Abstract = {The brain interprets sensory inputs to guide behavior, but
behavior itself disrupts sensory inputs. Perceiving a
coherent world while acting in it constitutes active
perception. For example, saccadic eye movements displace
visual images on the retina and yet the brain perceives
visual stability. Because this percept of visual stability
has been shown to be influenced by prior expectations, we
tested the hypothesis that it is Bayesian. The key
prediction was that priors would be used more as sensory
uncertainty increases. Humans and rhesus macaques reported
whether an image moved during saccades. We manipulated both
prior expectations and levels of sensory uncertainty. All
psychophysical data were compared with the predictions of
Bayesian ideal observer models. We found that humans were
Bayesian for continuous judgments. For categorical
judgments, however, they were anti-Bayesian: they used their
priors less with greater uncertainty. We studied this
categorical result further in macaques. The animals'
judgments were similarly anti-Bayesian for sensory
uncertainty caused by external, image noise, but Bayesian
for uncertainty due to internal, motor-driven noise. A
discriminative learning model explained the anti-Bayesian
effects. We conclude that active vision uses both Bayesian
and discriminative models depending on task requirements
(continuous vs categorical) and the source of uncertainty
(image noise vs motor-driven noise). In the context of
previous knowledge about the saccadic system, our results
provide an example of how the comparative analysis of
Bayesian versus non-Bayesian models of perception offers
novel insights into underlying neural organization.},
Doi = {10.1523/ENEURO.0403-22.2023},
Key = {fds371675}
}
@article{fds369379,
Author = {Daw, TB and El-Nahal, HG and Basso, MA and Jun, EJ and Bautista, AR and Samulski, RJ and Sommer, MA and Bohlen, MO},
Title = {Direct Comparison of Epifluorescence and Immunostaining for
Assessing Viral Mediated Gene Expression in the Primate
Brain.},
Journal = {Human gene therapy},
Volume = {34},
Number = {5-6},
Pages = {228-246},
Year = {2023},
Month = {March},
url = {http://dx.doi.org/10.1089/hum.2022.194},
Abstract = {Viral vector technologies are commonly used in neuroscience
research to understand and manipulate neural circuits, but
successful applications of these technologies in non-human
primate models have been inconsistent. An essential
component to improve these technologies is an impartial and
accurate assessment of the effectiveness of different viral
constructs in the primate brain. We tested a diverse array
of viral vectors delivered to the brain and extraocular
muscles of macaques and compared three methods for
histological assessment of viral-mediated fluorescent
transgene expression: epifluorescence (Epi),
immunofluorescence (IF), and immunohistochemistry (IHC).
Importantly, IF and IHC identified a greater number of
transduced neurons compared to Epi. Furthermore, IF and IHC
reliably provided enhanced visualization of transgene in
most cellular compartments (<i>i.e.</i>, dendritic, axonal,
and terminal fields), whereas the degree of labeling
provided by Epi was inconsistent and predominantly
restricted to somas and apical dendrites. Because Epi
signals are unamplified (in contrast to IF and IHC), Epi may
provide a more veridical assessment for the amount of
accumulated transgene and, thus, the potential to
chemogenetically or optogenetically manipulate neuronal
activity. The comparatively weak Epi signals suggest that
the current generations of viral constructs, regardless of
delivered transgene, are not optimized for primates. This
reinforces an emerging viewpoint that viral vectors tailored
for the primate brain are necessary for basic research and
human gene therapy.},
Doi = {10.1089/hum.2022.194},
Key = {fds369379}
}
@article{fds363007,
Author = {Goetz, SM and Howell, B and Wang, B and Li, Z and Sommer, MA and Peterchev,
AV and Grill, WM},
Title = {Isolating two sources of variability of subcortical
stimulation to quantify fluctuations of corticospinal tract
excitability.},
Journal = {Clin Neurophysiol},
Volume = {138},
Pages = {134-142},
Year = {2022},
Month = {June},
url = {http://dx.doi.org/10.1016/j.clinph.2022.02.009},
Abstract = {OBJECTIVE: Investigate the variability previously found with
cortical stimulation and handheld transcranial magnetic
stimulation (TMS) coils, criticized for its high potential
of coil position fluctuations, bypassing the cortex using
deep brain electrical stimulation (DBS) of the corticospinal
tract with fixed electrodes where both latent variations of
the coil position of TMS are eliminated and cortical
excitation fluctuations should be absent. METHODS: Ten
input-output curves were recorded from five anesthetized
cats with implanted DBS electrodes targeting the
corticospinal tract. Goodness of fit of regressions with a
conventional single variability source as well as a dual
variability source model was quantified using a Schwarz
Bayesian Information approach to avoid overfitting. RESULTS:
Motor evoked potentials (MEPs) through DBS of the
corticospinal tract revealed short-term fluctuations in
excitability of the targeted neuron pathway reflecting
endogenous input-side variability at similar magnitude as
TMS despite bypassing cortical networks. CONCLUSION:
Input-side variability, i.e., variability resulting in
changing MEP amplitudes as if the stimulation strength was
modulated, also emerges in electrical stimulation at a
similar degree and is not primarily a result of varying
stimulation, such as minor coil movements in TMS. More
importantly, this variability component is present, although
the cortex is bypassed. Thus, it may be of spinal origin,
which can include cortical input from spinal projections.
Further, the nonlinearity of the compound variability
entails complex heteroscedastic non-Gaussian distributions
and typically does not allow simple linear averages in
statistical analysis of MEPs. As the average is dominated by
outliers, it risks bias. With appropriate regression, the
net effects of excitatory and inhibitory inputs to the
targeted neuron pathways become noninvasively observable and
quantifiable. SIGNIFICANCE: The neural responses evoked by
artificial stimulation in the cerebral cortex are variable.
For example, MEPs in response to repeated presentations of
the same stimulus can vary from no response to saturation
across trials. Several sources of such variability have been
suggested, and most of them may be technical in nature, but
localization is missing.},
Doi = {10.1016/j.clinph.2022.02.009},
Key = {fds363007}
}
@article{fds357280,
Author = {Caruso, VC and Pages, DS and Sommer, MA and Groh,
JM},
Title = {Compensating for a shifting world: evolving reference frames
of visual and auditory signals across three multimodal brain
areas.},
Journal = {Journal of neurophysiology},
Volume = {126},
Number = {1},
Pages = {82-94},
Year = {2021},
Month = {July},
url = {http://dx.doi.org/10.1152/jn.00385.2020},
Abstract = {Stimulus locations are detected differently by different
sensory systems, but ultimately they yield similar percepts
and behavioral responses. How the brain transcends initial
differences to compute similar codes is unclear. We
quantitatively compared the reference frames of two sensory
modalities, vision and audition, across three interconnected
brain areas involved in generating saccades, namely the
frontal eye fields (FEF), lateral and medial parietal cortex
(M/LIP), and superior colliculus (SC). We recorded from
single neurons in head-restrained monkeys performing
auditory- and visually guided saccades from variable initial
fixation locations and evaluated whether their receptive
fields were better described as eye-centered, head-centered,
or hybrid (i.e. not anchored uniquely to head- or
eye-orientation). We found a progression of reference frames
across areas and across time, with considerable hybrid-ness
and persistent differences between modalities during most
epochs/brain regions. For both modalities, the SC was more
eye-centered than the FEF, which in turn was more
eye-centered than the predominantly hybrid M/LIP. In all
three areas and temporal epochs from stimulus onset to
movement, visual signals were more eye-centered than
auditory signals. In the SC and FEF, auditory signals became
more eye-centered at the time of the saccade than they were
initially after stimulus onset, but only in the SC at the
time of the saccade did the auditory signals become
"predominantly" eye-centered. The results indicate that
visual and auditory signals both undergo transformations,
ultimately reaching the same final reference frame but via
different dynamics across brain regions and time.<b>NEW &
NOTEWORTHY</b> Models for visual-auditory integration posit
that visual signals are eye-centered throughout the brain,
whereas auditory signals are converted from head-centered to
eye-centered coordinates. We show instead that both
modalities largely employ hybrid reference frames: neither
fully head- nor eye-centered. Across three hubs of the
oculomotor network (intraparietal cortex, frontal eye field,
and superior colliculus) visual and auditory signals evolve
from hybrid to a common eye-centered format via different
dynamics across brain areas and time.},
Doi = {10.1152/jn.00385.2020},
Key = {fds357280}
}
@article{fds358004,
Author = {Liu, S and Clements, JM and Kirsch, EP and Rao, HM and Zielinski, DJ and Lu, Y and Mainsah, BO and Potter, ND and Sommer, MA and Kopper, R and Appelbaum, LG},
Title = {Psychophysiological Markers of Performance and Learning
during Simulated Marksmanship in Immersive Virtual
Reality.},
Journal = {J Cogn Neurosci},
Volume = {33},
Number = {7},
Pages = {1253-1270},
Year = {2021},
Month = {June},
url = {http://dx.doi.org/10.1162/jocn_a_01713},
Abstract = {The fusion of immersive virtual reality, kinematic movement
tracking, and EEG offers a powerful test bed for
naturalistic neuroscience research. Here, we combined these
elements to investigate the neuro-behavioral mechanisms
underlying precision visual-motor control as 20 participants
completed a three-visit, visual-motor, coincidence-anticipation
task, modeled after Olympic Trap Shooting and performed in
immersive and interactive virtual reality. Analyses of the
kinematic metrics demonstrated learning of more efficient
movements with significantly faster hand RTs, earlier
trigger response times, and higher spatial precision,
leading to an average of 13% improvement in shot scores
across the visits. As revealed through spectral and
time-locked analyses of the EEG beta band (13-30 Hz), power
measured prior to target launch and visual-evoked potential
amplitudes measured immediately after the target launch
correlated with subsequent reactive kinematic performance in
the shooting task. Moreover, both launch-locked and
shot/feedback-locked visual-evoked potentials became earlier
and more negative with practice, pointing to neural
mechanisms that may contribute to the development of
visual-motor proficiency. Collectively, these findings
illustrate EEG and kinematic biomarkers of precision motor
control and changes in the neurophysiological substrates
that may underlie motor learning.},
Doi = {10.1162/jocn_a_01713},
Key = {fds358004}
}
@article{fds353025,
Author = {Tremblay, S and Acker, L and Afraz, A and Albaugh, DL and Amita, H and Andrei, AR and Angelucci, A and Aschner, A and Balan, PF and Basso, MA and Benvenuti, G and Bohlen, MO and Caiola, MJ and Calcedo, R and Cavanaugh,
J and Chen, Y and Chen, S and Chernov, MM and Clark, AM and Dai, J and Debes,
SR and Deisseroth, K and Desimone, R and Dragoi, V and Egger, SW and Eldridge, MAG and El-Nahal, HG and Fabbrini, F and Federer, F and Fetsch, CR and Fortuna, MG and Friedman, RM and Fujii, N and Gail, A and Galvan, A and Ghosh, S and Gieselmann, MA and Gulli, RA and Hikosaka, O and Hosseini, EA and Hu, X and Hüer, J and Inoue, K-I and Janz, R and Jazayeri, M and Jiang, R and Ju, N and Kar, K and Klein, C and Kohn, A and Komatsu, M and Maeda, K and Martinez-Trujillo, JC and Matsumoto, M and Maunsell, JHR and Mendoza-Halliday, D and Monosov, IE and Muers, RS and Nurminen, L and Ortiz-Rios, M and O'Shea, DJ and Palfi, S and Petkov,
CI and Pojoga, S and Rajalingham, R and Ramakrishnan, C and Remington,
ED and Revsine, C and Roe, AW and Sabes, PN and Saunders, RC and Scherberger, H and Schmid, MC and Schultz, W and Seidemann, E and Senova, Y-S and Shadlen, MN and Sheinberg, DL and Siu, C and Smith, Y and Solomon, SS and Sommer, MA and Spudich, JL and Stauffer, WR and Takada,
M and Tang, S and Thiele, A and Treue, S and Vanduffel, W and Vogels, R and Whitmire, MP and Wichmann, T and Wurtz, RH and Xu, H and Yazdan-Shahmorad, A and Shenoy, KV and DiCarlo, JJ and Platt,
ML},
Title = {An Open Resource for Non-human Primate Optogenetics.},
Journal = {Neuron},
Volume = {108},
Number = {6},
Pages = {1075-1090.e6},
Year = {2020},
Month = {December},
url = {http://dx.doi.org/10.1016/j.neuron.2020.09.027},
Abstract = {Optogenetics has revolutionized neuroscience in small
laboratory animals, but its effect on animal models more
closely related to humans, such as non-human primates
(NHPs), has been mixed. To make evidence-based decisions in
primate optogenetics, the scientific community would benefit
from a centralized database listing all attempts, successful
and unsuccessful, of using optogenetics in the primate
brain. We contacted members of the community to ask for
their contributions to an open science initiative. As of
this writing, 45 laboratories around the world contributed
more than 1,000 injection experiments, including precise
details regarding their methods and outcomes. Of those
entries, more than half had not been published. The resource
is free for everyone to consult and contribute to on the
Open Science Framework website. Here we review some of the
insights from this initial release of the database and
discuss methodological considerations to improve the success
of optogenetic experiments in NHPs.},
Doi = {10.1016/j.neuron.2020.09.027},
Key = {fds353025}
}
@article{fds350573,
Author = {Cushnie, AK and El-Nahal, HG and Bohlen, MO and May, PJ and Basso, MA and Grimaldi, P and Wang, MZ and de Velasco Ezequiel and MF and Sommer, MA and Heilbronner, SR},
Title = {Using rAAV2-retro in rhesus macaques: Promise and caveats
for circuit manipulation.},
Journal = {Journal of neuroscience methods},
Volume = {345},
Pages = {108859},
Publisher = {Elsevier BV},
Year = {2020},
Month = {November},
url = {http://dx.doi.org/10.1016/j.jneumeth.2020.108859},
Abstract = {<h4>Background</h4>Recent genetic technologies such as opto-
and chemogenetics allow for the manipulation of brain
circuits with unprecedented precision. Most studies
employing these techniques have been undertaken in rodents,
but a more human-homologous model for studying the brain is
the nonhuman primate (NHP). Optimizing viral delivery of
transgenes encoding actuator proteins could revolutionize
the way we study neuronal circuits in NHPs. NEW METHOD:
rAAV2-retro, a popular new capsid variant, produces robust
retrograde labeling in rodents. Whether rAAV2-retro's highly
efficient retrograde transport would translate to NHPs was
unknown. Here, we characterized the anatomical distribution
of labeling following injections of rAAV2-retro encoding
opsins or DREADDs in the cortico-basal ganglia and
oculomotor circuits of rhesus macaques.<h4>Results</h4>rAAV2-retro
injections in striatum, frontal eye field, and superior
colliculus produced local labeling at injection sites and
robust retrograde labeling in many afferent regions. In
every case, however, a few brain regions with
well-established projections to the injected structure
lacked retrogradely labeled cells. We also observed robust
terminal field labeling in downstream structures.<h4>Comparison
with existing method(s)</h4>Patterns of labeling were
similar to those obtained with traditional tract-tracers,
except for some afferent labeling that was noticeably
absent.<h4>Conclusions</h4>rAAV2-retro promises to be useful
for circuit manipulation via retrograde transduction in
NHPs, but caveats were revealed by our findings. Some
afferently connected regions lacked retrogradely labeled
cells, showed robust axon terminal labeling, or both. This
highlights the importance of anatomically characterizing
rAAV2-retro's expression in target circuits in NHPs before
moving to manipulation studies.},
Doi = {10.1016/j.jneumeth.2020.108859},
Key = {fds350573}
}
@article{fds352422,
Author = {Bohlen, MO and McCown, TJ and Powell, SK and El-Nahal, HG and Daw, T and Basso, MA and Sommer, MA and Samulski, RJ},
Title = {Adeno-Associated Virus Capsid-Promoter Interactions in the
Brain Translate from Rat to the Nonhuman
Primate.},
Journal = {Human gene therapy},
Volume = {31},
Number = {21-22},
Pages = {1155-1168},
Year = {2020},
Month = {November},
url = {http://dx.doi.org/10.1089/hum.2020.196},
Abstract = {Recently, we established an adeno-associated virus (AAV9)
capsid-promoter interaction that directly determined
cell-specific gene expression across two synthetic
promoters, Cbh and CBA, in the rat striatum. These studies
not only expand this capsid-promoter interaction to include
another promoter in the rat striatum but also establish AAV
capsid-promoter interactions in the nonhuman primate brain.
When AAV serotype 9 (AAV9) vectors were injected into the
rat striatum, the minimal synthetic promoter JetI drove
green fluorescent protein (GFP) gene expression
predominantly in oligodendrocytes. However, similar to our
previous findings, the insertion of six alanines into
VP1/VP2 of the AAV9 capsid (AAV9AU) significantly shifted
JetI-driven GFP gene expression to neurons. In addition,
previous retrograde tracing studies in the nonhuman primate
brain also revealed the existence of a capsid-promoter
interaction. When rAAV2-Retro vectors were infused into the
frontal eye field (FEF) of rhesus macaques, local gene
expression was prominent using either the hybrid chicken
beta actin (CAG) or human synapsin (hSyn) promoters.
However, only the CAG promoter, not the hSyn promoter, led
to gene expression in the ipsilateral claustrum and
contralateral FEF. Conversely, infusion of rAAV2-retro-hSyn
vectors, but not rAAV2-retro-CAG, into the macaque superior
colliculus led to differential and selective retrograde gene
expression in cerebellotectal afferent cells. Clearly, this
differential promoter/capsid expression profile could not be
attributed to promoter inactivation from retrograde
transport of the rAAV2-Retro vector. In summary, we document
the potential for AAV capsid/promoter interactions to impact
cell-specific gene expression across species, experimental
manipulations, and engineered capsids, independent of capsid
permissivity.},
Doi = {10.1089/hum.2020.196},
Key = {fds352422}
}
@article{fds351415,
Author = {Gamboa Arana and OL and Palmer, H and Dannhauer, M and Hile, C and Liu, S and Hamdan, R and Brito, A and Cabeza, R and Davis, SW and Peterchev, AV and Sommer, MA and Appelbaum, LG},
Title = {Intensity- and timing-dependent modulation of motion
perception with transcranial magnetic stimulation of visual
cortex.},
Journal = {Neuropsychologia},
Volume = {147},
Pages = {107581},
Year = {2020},
Month = {October},
url = {http://dx.doi.org/10.1016/j.neuropsychologia.2020.107581},
Abstract = {Despite the widespread use of transcranial magnetic
stimulation (TMS) in research and clinical care, the
dose-response relations and neurophysiological correlates of
modulatory effects remain relatively unexplored. To fill
this gap, we studied modulation of visual processing as a
function of TMS parameters. Our approach combined
electroencephalography (EEG) with application of single
pulse TMS to visual cortex as participants performed a
motion perception task. During each participants' first
visit, motion coherence thresholds, 64-channel visual evoked
potentials (VEPs), and TMS resting motor thresholds (RMT)
were measured. In second and third visits, single pulse TMS
was delivered at one of two latencies, either 30 ms before
the onset of motion or at the onset latency of the N2 VEP
component derived from the first session. TMS was delivered
at 0%, 80%, 100%, or 120% of RMT over the site of N2 peak
activity, or at 120% over vertex. Behavioral results
demonstrated a significant main effect of TMS timing on
accuracy, with better performance when TMS was applied at
the N2-Onset timing versus Pre-Onset, as well as a
significant interaction, indicating that 80% intensity
produced higher accuracy than other conditions at the
N2-Onset. TMS effects on the P3 VEP showed reduced
amplitudes in the 80% Pre-Onset condition, an increase for
the 120% N2-Onset condition, and monotonic amplitude scaling
with stimulation intensity. The N2 component was not
affected by TMS. These findings reveal the influence of TMS
intensity and timing on visual perception and
electrophysiological responses, with optimal facilitation at
stimulation intensities below RMT.},
Doi = {10.1016/j.neuropsychologia.2020.107581},
Key = {fds351415}
}
@article{fds349696,
Author = {Gamboa, OL and Brito, A and Abzug, Z and D'Arbeloff, T and Beynel, L and Wing, EA and Dannhauer, M and Palmer, H and Hilbig, SA and Crowell, CA and Liu, S and Donaldson, R and Cabeza, R and Davis, SW and Peterchev, AV and Sommer, MA and Appelbaum, LG},
Title = {Application of long-interval paired-pulse transcranial
magnetic stimulation to motion-sensitive visual cortex does
not lead to changes in motion discrimination.},
Journal = {Neurosci Lett},
Volume = {730},
Pages = {135022},
Year = {2020},
Month = {June},
url = {http://dx.doi.org/10.1016/j.neulet.2020.135022},
Abstract = {The perception of visual motion is dependent on a set of
occipitotemporal regions that are readily accessible to
neuromodulation. The current study tested if paired-pulse
Transcranial Magnetic Stimulation (ppTMS) could modulate
motion perception by stimulating the occipital cortex as
participants viewed near-threshold motion dot stimuli. In
this sham-controlled study, fifteen subjects completed two
sessions. On the first visit, resting motor threshold (RMT)
was assessed, and participants performed an adaptive
direction discrimination task to determine individual motion
sensitivity. During the second visit, subjects performed the
task with three difficulty levels as TMS pulses were
delivered 150 and 50 ms prior to motion stimulus onset at
120% RMT, under the logic that the cumulative inhibitory
effect of these pulses would alter motion sensitivity. ppTMS
was delivered at one of two locations: 3 cm dorsal and
5 cm lateral to inion (scalp-based coordinate), or at the
site of peak activation for "motion" according to the
NeuroSynth fMRI database (meta-analytic coordinate). Sham
stimulation was delivered on one-third of trials by tilting
the coil 90°. Analyses showed no significant
active-versus-sham effects of ppTMS when stimulation was
delivered to the meta-analytic (p = 0.15) or scalp-based
coordinates (p = 0.17), which were separated by 29 mm
on average. Active-versus-sham stimulation differences did
not interact with either stimulation location (p = 0.12)
or difficulty (p = 0.33). These findings fail to support
the hypothesis that long-interval ppTMS recruits inhibitory
processes in motion-sensitive cortex but must be considered
within the limited parameters used in this
design.},
Doi = {10.1016/j.neulet.2020.135022},
Key = {fds349696}
}
@article{fds350632,
Author = {Gamboa Arana and OL and Palmer, H and Dannhauer, M and Hile, C and Liu, S and Hamdan, R and Brito, A and Cabeza, R and Davis, S and Peterchev, A and Sommer, M and Appelbaum, L},
Title = {Dose-dependent enhancement of motion direction
discrimination with transcranial magnetic stimulation of
visual cortex},
Year = {2020},
url = {http://dx.doi.org/10.1101/2020.06.14.151118},
Abstract = {Despite the widespread use of transcranial magnetic
stimulation (TMS) in research and clinical care, the
underlying mechanisms-of-actions that mediate modulatory
effects remain poorly understood. To fill this gap, we
studied dose–response functions of TMS for modulation of
visual processing. Our approach combined
electroencephalography (EEG) with application of single
pulse TMS to visual cortex as participants performed a
motion perception task. During participants’ first visit,
motion coherence thresholds, 64-channel visual evoked
potentials (VEPs), and TMS resting motor thresholds (RMT)
were measured. In second and third visits, single pulse TMS
was delivered 30 ms before the onset of motion or at the
onset latency of the N2 VEP component derived from the first
session. TMS was delivered at 0%, 80%, 100%, or 120% of RMT
over the site of N2 peak activity, or at 120% over vertex.
Behavioral results demonstrated a significant main effect of
TMS timing on accuracy, with better performance when TMS was
applied at N2-Onset timing versus Pre-Onset, as well as a
significant interaction, indicating that 80% intensity
produced higher accuracy than other conditions. TMS effects
on VEPs showed reduced amplitudes in the 80% Pre-Onset
condition, an increase for the 120% N2-Onset condition, and
monotonic amplitude scaling with stimulation intensity. The
N2 component was not affected by TMS. These findings reveal
dose–response relationships between intensity and timing
of TMS on visual perception and electrophysiological brain
activity, generally indicating greater facilitation at
stimulation intensities below RMT.},
Doi = {10.1101/2020.06.14.151118},
Key = {fds350632}
}
@article{fds366058,
Author = {Abzug, ZM and Sommer, MA and Beck, JM},
Title = {Properties of decision-making tasks govern the tradeoff
between model-based and model-free learning},
Year = {2019},
Month = {August},
url = {http://dx.doi.org/10.1101/730663},
Abstract = {<jats:title>Abstract</jats:title><jats:p>When decisions must
be made between uncertain options, optimal behavior depends
on accurate estimations of the likelihoods of different
outcomes. The contextual factors that govern whether these
estimations depend on model-free learning (tracking
outcomes) vs. model-based learning (learning generative
stimulus distributions) are poorly understood. We studied
model-free and model-based learning using serial
decision-making tasks in which subjects selected a rule and
then used it to flexibly act on visual stimuli. A factorial
approach defined a family of behavioral models that could
integrate model-free and model-based strategies to predict
rule selection trial-by-trial. Bayesian model selection
demonstrated that the subjects strategies varied depending
on lower-level task characteristics such as the identities
of the rule options. In certain conditions, subjects
integrated learned stimulus distributions and tracked reward
rates to guide their behavior. The results thus identify
tradeoffs between model-based and model-free decision
strategies, and in some cases parallel utilization,
depending on task context.</jats:p>},
Doi = {10.1101/730663},
Key = {fds366058}
}
@article{fds341566,
Author = {Toader, AC and Rao, HM and Ryoo, M and Bohlen, MO and Cruger, JS and Oh-Descher, H and Ferrari, S and Egner, T and Beck, J and Sommer,
MA},
Title = {Probabilistic inferential decision-making under time
pressure in rhesus macaques (Macaca mulatta).},
Journal = {Journal of comparative psychology (Washington, D.C. :
1983)},
Volume = {133},
Number = {3},
Pages = {380-396},
Year = {2019},
Month = {August},
url = {http://dx.doi.org/10.1037/com0000168},
Abstract = {Decisions often involve the consideration of multiple cues,
each of which may inform selection on the basis of learned
probabilities. Our ability to use probabilistic inference
for decisions is bounded by uncertainty and constraints such
as time pressure. Previous work showed that when humans
choose between visual objects in a multiple-cue,
probabilistic task, they cope with time pressure by
discounting the least informative cues, an example of
satisficing or "good enough" decision-making. We tested two
rhesus macaques (Macaca mulatta) on a similar task to assess
their capacity for probabilistic inference and satisficing
in comparison with humans. In each trial, a monkey viewed
two compound stimuli consisting of four cue dimensions. Each
dimension (e.g., color) had two possible states (e.g., red
or blue) with different probabilistic weights. Selecting the
stimulus with highest total weight yielded higher odds of
receiving reward. Both monkeys learned the assigned weights
at high accuracy. Under time pressure, both monkeys were
less accurate as a result of decreased use of cue
information. One monkey adopted the same satisficing
strategy used by humans, ignoring the least informative cue
dimension. Both monkeys, however, exhibited a strategy not
reported for humans, a "group-the-best" strategy in which
the top two cues were used similarly despite their different
assigned weights. The results validate macaques as an animal
model of probabilistic decision-making, establishing their
capacity to discriminate between objects using at least four
visual dimensions simultaneously. The time pressure data
suggest caution, however, in using macaques as models of
human satisficing. (PsycINFO Database Record (c) 2019 APA,
all rights reserved).},
Doi = {10.1037/com0000168},
Key = {fds341566}
}
@article{fds366059,
Author = {Caruso, VC and Pages, DS and Sommer, MA and Groh,
JM},
Title = {Compensating for a shifting world: evolving reference frames
of visual and auditory signals across three multimodal brain
areas},
Year = {2019},
Month = {June},
url = {http://dx.doi.org/10.1101/669333},
Abstract = {<jats:title>ABSTRACT</jats:title><jats:p>Stimulus locations
are detected differently by different sensory systems, but
ultimately they yield similar percepts and behavioral
responses. How the brain transcends initial differences to
compute similar codes is unclear. We quantitatively compared
the reference frames of two sensory modalities, vision and
audition, across three interconnected brain areas involved
in generating saccades, namely the frontal eye fields (FEF),
lateral and medial parietal cortex (M/LIP), and superior
colliculus (SC). We recorded from single neurons in
head-restrained monkeys performing auditory- and
visually-guided saccades from variable initial fixation
locations, and evaluated whether their receptive fields were
better described as eye-centered, head-centered, or hybrid
(i.e. not anchored uniquely to head- or eye-orientation). We
found a progression of reference frames across areas and
across time, with considerable hybrid-ness and persistent
differences between modalities during most epochs/brain
regions. For both modalities, the SC was more eye-centered
than the FEF, which in turn was more eye-centered than the
predominantly hybrid M/LIP. In all three areas and temporal
epochs from stimulus onset to movement, visual signals were
more eye-centered than auditory signals. In the SC and FEF,
auditory signals became more eye-centered at the time of the
saccade than they were initially after stimulus onset, but
only in the SC at the time of the saccade did the auditory
signals become <jats:italic>predominantly</jats:italic>
eye-centered. The results indicate that visual and auditory
signals both undergo transformations, ultimately reaching
the same final reference frame but via different dynamics
across brain regions and time.</jats:p><jats:sec><jats:title>New
and Noteworthy</jats:title><jats:p>Models for
visual-auditory integration posit that visual signals are
eye-centered throughout the brain, while auditory signals
are converted from head-centered to eye-centered
coordinates. We show instead that both modalities largely
employ hybrid reference frames: neither fully head-nor
eye-centered. Across three hubs of the oculomotor network
(intraparietal cortex, frontal eye field and superior
colliculus) visual and auditory signals evolve from hybrid
to a common eye-centered format via different dynamics
across brain areas and time.</jats:p></jats:sec>},
Doi = {10.1101/669333},
Key = {fds366059}
}
@article{fds343467,
Author = {Subramanian, D and Alers, A and Sommer, M},
Title = {Corollary discharge for action and cognition},
Journal = {Biological Psychiatry: Cognitive Neuroscience and
Neuroimaging},
Volume = {4},
Number = {9},
Pages = {782-790},
Publisher = {Elsevier},
Year = {2019},
Month = {May},
url = {http://dx.doi.org/10.1016/j.bpsc.2019.05.010},
Abstract = {In motor systems, a copy of the movement command known as
corollary discharge is broadcast to other regions of the
brain to warn them of the impending movement. The premise of
this review is that the concept of corollary discharge may
generalize in revealing ways to the brain’s cognitive
systems. An oculomotor pathway from the brainstem to frontal
cortex provides a well-established example of how corollary
discharge is instantiated for sensorimotor processing.
Building on causal evidence from inactivation of the
pathway, we motivate forward models as a tool for
understanding the contributions of corollary discharge to
perception and movement. Finally, we extend the definition
of corollary discharge to account for signals that may be
used for cognitive forward models of decision-making. This
framework may provide new insights into signals and circuits
that contribute to sequential decision processes, the
breakdown of which may account for some symptoms of
psychiatric disorders.},
Doi = {10.1016/j.bpsc.2019.05.010},
Key = {fds343467}
}
@article{fds346630,
Author = {Bohlen, M and El-Nahal, H and Sommer, M},
Title = {Transduction of Craniofacial Motoneurons Following
Intramuscular Injections of Canine Adenovirus Type-2 (CAV-2)
in Rhesus Macaques},
Journal = {Frontiers in Neuroanatomy},
Volume = {In Press},
Pages = {84},
Publisher = {Frontiers Media},
Year = {2019},
Month = {January},
url = {http://dx.doi.org/10.3389/fnana.2019.00084},
Abstract = {Reliable viral vector-mediated transgene expression in
primate motoneurons would improve our ability to
anatomically and physiologically interrogate motor systems.
We therefore investigated the efficacy of replication
defective, early region 1-deleted canine adenovirus type-2
(CAV-2) vectors for mediating transgene expression of
fluorescent proteins into brainstem motoneurons following
craniofacial intramuscular injections in four rhesus monkeys
(Macaca mulatta). Vector injections were placed into
surgically identified and isolated craniofacial muscles.
After a one- to two-month survival time, animals were
sacrificed and transgene expression was assessed with
immunohistochemistry in the corresponding motoneuronal
populations. We found that injections of CAV-2 into
individual craniofacial muscles at doses in the range of
~10^10 to 10^11 physical particles/muscle resulted in robust
motoneuronal transduction and expression of
immunohistochemically identified fluorescent proteins across
multiple animals. By using different titers in separate
muscles, with the resulting transduction patterns tracked
via fluorophore expression and labeled motoneuron location,
we established qualitative dose-response relationships in
two animals. In one animal that received an atypically high
titer (5.7 x 10^11 total CAV-2 physical particles)
distributed across numerous injection sites, no transduction
was detected, likely due to a retaliatory immune response.
We conclude that CAV-2 vectors show promise for genetic
modification of primate motoneurons following craniofacial
intramuscular injections. Our findings warrant focused
attention toward the use of CAV-2 vectors to deliver opsins,
DREADDs, and other molecular probes to improve
genetics-based methods for primate research. Further work is
required to optimize CAV-2 transduction parameters. CAV-2
vectors encoding proteins could provide a new, reliable
route for modifying activity in targeted neuronal
populations of the primate central nervous
system.},
Doi = {10.3389/fnana.2019.00084},
Key = {fds346630}
}
@article{fds337180,
Author = {Abzug, ZM and Sommer, MA},
Title = {Neuronal correlates of serial decision-making in the
supplementary eye field},
Journal = {Journal of Neuroscience},
Volume = {38},
Number = {33},
Pages = {7280-7292},
Publisher = {Society for Neuroscience},
Year = {2018},
Month = {August},
url = {http://dx.doi.org/10.1523/jneurosci.3643-17.2018},
Abstract = {Human behavior is influenced by serial decision-making: past
decisions affect choices that set the context for selecting
future options. A primate brain region that may be involved
in linking decisions across time is the supplementary eye
field (SEF), which, in addition to its well-known visual
responses and saccade-related activity, also signals the
rules that govern flexible decisions and the outcomes of
those decisions. Our hypotheses were that SEF neurons encode
events during serial decision-making and link the sequential
decisions with sustained activity. We recorded from neurons
in the SEF of two rhesus monkeys (Macaca mulatta, one male,
one female) that performed a serial decision-making task.
The monkeys used saccades to select a rule that had to be
applied later in the same trial to discriminate between
visual stimuli. We found, first, that SEF neurons encoded
the spatial parameters of saccades during rule selection but
not during visual discrimination, suggesting a malleability
to their movement-related tuning. Second, SEF activity
linked the sequential decisions of rule selection and visual
discrimination, but not continuously. Instead, rule-encoding
activity appeared in a “just-in-time” manner before the
visual discrimination. Third, SEF neurons encoded trial
outcomes both prospectively, before decisions within a
trial, and retrospectively, across multiple trials. The
results thus identify neuronal correlates of rule selection
and application in the SEF, including transient signals that
link these sequential decisions. Its activity patterns
suggest that the SEF participates in serial decision-making
in a contextually-dependent manner as part of a broader
network.},
Doi = {10.1523/jneurosci.3643-17.2018},
Key = {fds337180}
}
@article{fds334786,
Author = {Abzug, ZM and Sommer, MA},
Title = {Serial decision-making in monkeys during an oculomotor
task},
Journal = {Journal of Experimental Psychology: Animal Learning and
Cognition},
Volume = {44},
Number = {1},
Pages = {95-102},
Publisher = {American Psychological Association},
Year = {2018},
Month = {January},
url = {http://dx.doi.org/10.1037/xan0000154},
Abstract = {Much of everyday behavior involves serial decision-making,
in which the outcome of one choice affects another. An
example is setting rules for oneself: choosing a behavioral
rule guides appropriate choices in the future. How the brain
links decisions across time is poorly understood. Neural
mechanisms could be studied in monkeys, as it is known that
they can select and use behavioral rules, but existing
psychophysical paradigms are poorly suited for the
constraints of neurophysiology. Therefore we designed a
streamlined task that requires sequential, linked decisions,
and trained two rhesus monkeys (Macaca mulatta) to perform
it. The task features trial-by-trial consistency, visual
stimuli, and eye movement responses to optimize it for
simultaneous electrophysiological inquiry. In the first
stage of each trial, the monkeys selected a rule or a rule
was provided to them. In the second stage, they used the
rule to discriminate between two test stimuli. Our
hypotheses were that they could use self-selected rules and
could deliberately select rules based on reinforcement
history. We found that the monkeys were as proficient at
using self-selected rules as instructed rules. Their
preferences for selecting rules correlated with their
performance in using them, consistent with systematic,
rather than random, strategies for accomplishing the task.
The results confirm and extend prior findings on rule
selection in monkeys and establish a viable, experimentally
flexible paradigm for studying the neural basis of serial
decision-making.},
Doi = {10.1037/xan0000154},
Key = {fds334786}
}
@article{fds334785,
Author = {Rao, HM and Khanna, R and Zielinski, DJ and Lu, Y and Clements, JM and Potter, ND and Sommer, MA and Kopper, R and Appelbaum,
LG},
Title = {Sensorimotor Learning during a Marksmanship Task in
Immersive Virtual Reality.},
Journal = {Front Psychol},
Volume = {9},
Pages = {58},
Year = {2018},
url = {http://dx.doi.org/10.3389/fpsyg.2018.00058},
Abstract = {Sensorimotor learning refers to improvements that occur
through practice in the performance of sensory-guided motor
behaviors. Leveraging novel technical capabilities of an
immersive virtual environment, we probed the component
kinematic processes that mediate sensorimotor learning.
Twenty naïve subjects performed a simulated marksmanship
task modeled after Olympic Trap Shooting standards. We
measured movement kinematics and shooting performance as
participants practiced 350 trials while receiving
trial-by-trial feedback about shooting success.
Spatiotemporal analysis of motion tracking elucidated the
ballistic and refinement phases of hand movements. We found
systematic changes in movement kinematics that accompanied
improvements in shot accuracy during training, though
reaction and response times did not change over blocks. In
particular, we observed longer, slower, and more precise
ballistic movements that replaced effort spent on
corrections and refinement. Collectively, these results
leverage developments in immersive virtual reality
technology to quantify and compare the kinematics of
movement during early learning of full-body sensorimotor
orienting.},
Doi = {10.3389/fpsyg.2018.00058},
Key = {fds334785}
}
@article{fds334784,
Author = {Caruso, V and Pages, D and Sommer, MA and Groh, J},
Title = {Beyond the labeled line: variation in visual reference
frames from intraparietal cortex to frontal eye fields and
the superior colliculus},
Journal = {Journal of Neurophysiology},
Volume = {In Press},
Number = {4},
Pages = {1411-1421},
Publisher = {American Physiological Society},
Year = {2017},
Month = {December},
url = {http://dx.doi.org/10.1152/jn.00584.2017},
Abstract = {We accurately perceive the visual scene despite moving our
eyes ~3 times per second, an ability that requires
incorporation of eye position and retinal information. In
this study, we assessed how this neural computation unfolds
across three interconnected structures: frontal eye fields
(FEF), intraparietal cortex (LIP/MIP), and the superior
colliculus (SC). Single unit activity was assessed in
head-restrained monkeys performing visually-guided saccades
from different initial fixations. As previously shown, the
receptive fields of most LIP/MIP neurons shifted to novel
positions on the retina for each eye position, and these
locations were not clearly related to each other in either
eye- or head-centered coordinates (defined as hybrid
coordinates). In contrast, the receptive fields of most SC
neurons were stable in eye-centered coordinates. In FEF,
visual signals were intermediate between those patterns:
around 60% were eye-centered, whereas the remainder showed
changes in receptive field location, boundaries, or
responsiveness that rendered the response patterns hybrid or
occasionally head-centered. These results suggest that FEF
may act as a transitional step in an evolution of
coordinates between LIP/MIP and SC. The persistence across
cortical areas of mixed representations that do not provide
unequivocal location labels in a consistent reference frame
has implications for how these representations must be
read-out.},
Doi = {10.1152/jn.00584.2017},
Key = {fds334784}
}
@article{fds334787,
Author = {Oh-Descher, H and Beck, JM and Ferrari, S and Sommer, MA and Egner,
T},
Title = {Probabilistic inference under time pressure leads to a
cortical-to-subcortical shift in decision evidence
integration},
Journal = {NeuroImage},
Volume = {162},
Pages = {138-150},
Publisher = {Elsevier},
Year = {2017},
Month = {November},
url = {http://dx.doi.org/10.1016/j.neuroimage.2017.08.069},
Abstract = {Real-life decision-making often involves combining multiple
probabilistic sources of information under finite time and
cognitive resources. To mitigate these pressures, people
“satisfice”, foregoing a full evaluation of all
available evidence to focus on a subset of cues that allow
for fast and “good-enough” decisions. Although this form
of decision-making likely mediates many of our everyday
choices, very little is known about the way in which the
neural encoding of cue information changes when we satisfice
under time pressure. Here, we combined human functional
magnetic resonance imaging (fMRI) with a probabilistic
classification task to characterize neural substrates of
multi-cue decision-making under low (1500 ms) and high (500
ms) time pressure. Using variational Bayesian inference, we
analyzed participants’ choices to track and quantify cue
usage under each experimental condition, which was then
applied to model the fMRI data. Under low time pressure,
participants performed near-optimally, appropriately
integrating all available cues to guide choices. Both
cortical (prefrontal and parietal cortex) and subcortical
(hippocampal and striatal) regions encoded individual cue
weights, and activity linearly tracked trial-by-trial
variations in amount of evidence and decision uncertainty.
Under increased time pressure, participants adaptively
shifted to using a satisficing strategy by discounting the
least informative cue in their decision process. This
strategic change in decision-making was associated with an
increased involvement of the dopaminergic midbrain,
striatum, thalamus, and cerebellum in representing and
integrating cue values. We conclude that satisficing the
probabilistic inference process under time pressure leads to
a cortical-to-subcortical shift in the neural drivers of
decisions.},
Doi = {10.1016/j.neuroimage.2017.08.069},
Key = {fds334787}
}
@article{fds334789,
Author = {Rao, HM and Mayo, JP and Sommer, MA},
Title = {Circuits for presaccadic visual remapping.},
Journal = {J Neurophysiol},
Volume = {116},
Number = {6},
Pages = {2624-2636},
Year = {2016},
Month = {December},
url = {http://dx.doi.org/10.1152/jn.00182.2016},
Abstract = {Saccadic eye movements rapidly displace the image of the
world that is projected onto the retinas. In anticipation of
each saccade, many neurons in the visual system shift their
receptive fields. This presaccadic change in visual
sensitivity, known as remapping, was first documented in the
parietal cortex and has been studied in many other brain
regions. Remapping requires information about upcoming
saccades via corollary discharge. Analyses of neurons in a
corollary discharge pathway that targets the frontal eye
field (FEF) suggest that remapping may be assembled in the
FEF's local microcircuitry. Complementary data from
reversible inactivation, neural recording, and modeling
studies provide evidence that remapping contributes to
transsaccadic continuity of action and perception. Multiple
forms of remapping have been reported in the FEF and other
brain areas, however, and questions remain about the reasons
for these differences. In this review of recent progress, we
identify three hypotheses that may help to guide further
investigations into the structure and function of circuits
for remapping.},
Doi = {10.1152/jn.00182.2016},
Key = {fds334789}
}
@article{fds334790,
Author = {Oh, H and Beck, JM and Zhu, P and Sommer, MA and Ferrari, S and Egner,
T},
Title = {Satisficing in split-second decision making is characterized
by strategic cue discounting},
Journal = {Journal of Experimental Psychology: Learning, Memory, and
Cognition},
Volume = {42},
Number = {12},
Pages = {1937-1956},
Publisher = {American Psychological Association},
Year = {2016},
Month = {December},
url = {http://dx.doi.org/10.1037/xlm0000284},
Abstract = {Much of our real-life decision making is bounded by
uncertain information, limitations in cognitive resources,
and a lack of time to allocate to the decision process. It
is thought that humans overcome these limitations through
satisficing, fast but “good-enough” heuristic decision
making that prioritizes some sources of information (cues)
while ignoring others. However, the decision-making
strategies we adopt under uncertainty and time pressure, for
example during emergencies that demand split-second choices,
are presently unknown. To characterize these decision
strategies quantitatively, the present study examined how
people solve a novel multi-cue probabilistic classification
task under varying time pressure, by tracking shifts in
decision strategies using variational Bayesian inference. We
found that under low time pressure, participants correctly
weighted and integrated all available cues to arrive at
near-optimal decisions. With increasingly demanding,
sub-second time pressures, however, participants
systematically discounted a subset of the cue information by
dropping the least informative cue(s) from their decision
making process. Thus, the human cognitive apparatus copes
with uncertainty and severe time pressure by adopting a
“Drop-the-Worst” cue decision making strategy that
minimizes cognitive time and effort investment while
preserving the consideration of the most diagnostic cue
information, thus maintaining “good-enough” accuracy.
This advance in our understanding of satisficing strategies
could form the basis of predicting human choices in high
time pressure scenarios.},
Doi = {10.1037/xlm0000284},
Key = {fds334790}
}
@article{fds334794,
Author = {Rao, HM and San Juan and J and Shen, FY and Villa, JE and Rafie, KS and Sommer, MA},
Title = {Neural network evidence for the coupling of presaccadic
visual remapping to predictive eye position
updating},
Journal = {Frontiers in Computational Neuroscience},
Volume = {10},
Pages = {52},
Publisher = {Frontiers Media},
Year = {2016},
Month = {June},
url = {http://dx.doi.org/10.3389/fncom.2016.00052},
Abstract = {As we look around a scene, we perceive it as continuous and
stable even though each saccadic eye movement changes the
visual input to the retinas. How the brain achieves this
perceptual stabilization is unknown, but a major hypothesis
is that it relies on presaccadic remapping, a process in
which neurons shift their visual sensitivity to a new
location in the scene just before each saccade. This
hypothesis is difficult to test in vivo because complete,
selective inactivation of remapping is currently
intractable. We tested it in silico with a hierarchical,
sheet-based neural network model of the visual and
oculomotor system. The model generated saccadic commands to
move a video camera abruptly. Visual input from the camera
and internal copies of the saccadic movement commands, or
corollary discharge, converged at a map-level simulation of
the frontal eye field (FEF), a primate brain area known to
receive such inputs. FEF output was combined with eye
position signals to yield a suitable coordinate frame for
guiding arm movements of a robot. Our operational definition
of perceptual stability was "useful stability,” quantified
as continuously accurate pointing to a visual object despite
camera saccades. During training, the emergence of useful
stability was correlated tightly with the emergence of
presaccadic remapping in the FEF. Remapping depended on
corollary discharge but its timing was synchronized to the
updating of eye position. When coupled to predictive eye
position signals, remapping served to stabilize the target
representation for continuously accurate pointing. Graded
inactivations of pathways in the model replicated, and
helped to interpret, previous in vivo experiments. The
results support the hypothesis that visual stability
requires presaccadic remapping, provide explanations for the
function and timing of remapping, and offer testable
hypotheses for in vivo studies. We conclude that remapping
allows for seamless coordinate frame transformations and
quick actions despite visual afferent lags. With visual
remapping in place for behavior, it may be exploited for
perceptual continuity.},
Doi = {10.3389/fncom.2016.00052},
Key = {fds334794}
}
@article{fds334793,
Author = {Raghavan, RT and Prevosto, V and Sommer, MA},
Title = {Contribution of cerebellar loops to action
timing},
Journal = {Current Opinion in Behavioral Sciences},
Volume = {8},
Pages = {28-34},
Publisher = {Elsevier},
Year = {2016},
Month = {March},
url = {http://dx.doi.org/10.1016/j.cobeha.2016.01.008},
Abstract = {Recent studies of sensorimotor processing have benefited
from decision-making paradigms that emphasize the selection
of appropriate movements. Selecting when to make those
responses, or action timing, is important as well. Although
the cerebellum is commonly viewed as a controller of
movement dynamics, its role in action timing is also firmly
supported. Several lines of research have now extended this
idea. Anatomical findings have revealed connections between
the cerebellum and broader timing circuits,
neurophysiological results have suggested mechanisms for
timing within its microcircuitry, and theoretical work has
indicated how temporal signals are processed through it and
decoded by its targets. These developments are inspiring
renewed studies of the role of the cerebellar loops in
action timing.},
Doi = {10.1016/j.cobeha.2016.01.008},
Key = {fds334793}
}
@article{fds334791,
Author = {Caruso, VC and Pages, DS and Sommer, MA and Groh,
JM},
Title = {Similar prevalence and magnitude of auditory-evoked and
visually-evoked activity in the frontal eye fields:
Implications for multisensory motor control},
Journal = {Journal of Neurophysiology},
Volume = {in press},
Number = {6},
Pages = {3162-3173},
Year = {2016},
Month = {March},
url = {http://dx.doi.org/10.1152/jn.00935.2015},
Abstract = {Saccadic eye movements can be elicited by more than one type
of sensory stimulus. This implies substantial
transformations of signals originating in different sense
organs as they reach a common motor output pathway. In this
study, we compared the prevalence and magnitude of auditory-
and visually-evoked activity in a structure implicated in
oculomotor processing, the primate frontal eye fields (FEF).
We recorded from 324 single neurons while 2 monkeys
performed delayed saccades to visual or auditory targets. We
found that 64% of FEF neurons were active upon presentation
of auditory targets and 87% were active during
auditory-guided saccades, compared to 75% and 84% for visual
targets and saccades. As saccade onset approached, the
average level of population activity in the FEF became
indistinguishable on visual and auditory trials. FEF
activity was better correlated with the movement vector than
with the target location for both modalities In summary, the
large proportion of auditory responsive neurons in the FEF,
the similarity between visual and auditory activity levels
at the time of the saccade and the strong correlation
between the activity and the saccade vector suggest that
auditory signals undergo tailoring to roughly match the
strength of visual signals present in the FEF, facilitating
accessing of a common motor output pathway.},
Doi = {10.1152/jn.00935.2015},
Key = {fds334791}
}
@article{fds334795,
Author = {Rao, HM and Abzug, ZM and Sommer, MA},
Title = {Visual continuity across saccades is influenced by
expectations.},
Journal = {Journal of vision},
Volume = {16},
Number = {5},
Pages = {7},
Year = {2016},
Month = {January},
url = {http://dx.doi.org/10.1167/16.5.7},
Abstract = {As we make saccades, the image on each retina is displaced,
yet our visual perception is uninterrupted. This is commonly
referred to as transsaccadic perceptual stability, but such
a description is inadequate. Some visual objects are stable
(e.g., rocks) and should be perceived as such across
saccades, but other objects may move at any time (e.g.,
birds). Stability is probabilistic in natural scenes. Here
we extend the common notion of transsaccadic visual
stability to a more general, ecologically based hypothesis
of transsaccadic visual continuity in which postsaccadic
percepts of objects depend on expectations about their
probability of movement. Subjects made a saccade to a target
and reported whether it seemed displaced after the saccade.
Targets had varying probabilities of movement (ranging from
0.1-0.9) that corresponded to their color (spectrum from
blue to red). Performance was compared before and after
subjects were told about the color-probability pairings
("uninformed" vs. "informed" conditions). Analyses focused
on signal detection and psychometric threshold measures. We
found that in the uninformed condition, performance was
similar across color-probability pairings, but in the
informed condition, response biases varied with probability
of movement, and movement-detection sensitivities were
higher for rarely moving targets. We conclude that subjects
incorporate priors about object movement into their
judgments of visual continuity across saccades.},
Doi = {10.1167/16.5.7},
Key = {fds334795}
}
@article{fds334792,
Author = {Zielinski, DJ and Rao, HM and Potter, ND and Sommer, MA and Appelbaum,
LG and Kopper, R},
Title = {Evaluating the Effects of Image Persistence on Dynamic
Target Acquisition in Low Frame Rate Virtual
Environments},
Journal = {3D User Interfaces (3DUI), 2016 IEEE Symposium
on},
Pages = {133-140},
Publisher = {IEEE},
Year = {2016},
url = {http://dx.doi.org/10.1109/3DUI.2016.7460043},
Abstract = {User performance in virtual environments with degraded
visual conditions due to low frame rates is an interesting
area of inquiry. Visual content shown in a low frame rate
simulation has the quality of the original image, but
persists for an extended period until the next frame is
displayed (so-called high persistence-HP). An alternative,
called low persistence (LP), involves displaying the
rendered frame for a single display frame and blanking the
screen while waiting for the next frame to be generated.
Previous research has evaluated the usefulness of the LP
technique in low frame rate simulations during a static
target acquisition task. To gain greater knowledge about the
LP technique, we have conducted a user study to evaluate
user performance and learning during a dynamic target
acquisition task. The acquisition task was evaluated under a
high frame rate, (60 fps) condition, a traditional low frame
rate HP condition (10 fps), and the experimental low frame
rate LP technique. The task involved the acquisition of
targets moving along several different trajectories, modeled
after a shotgun trap shooting task. The results of our study
indicate the LP condition approaches high frame rate
performance within certain classes of target trajectories.
Interestingly we also see that learning is consistent across
conditions, indicating that it may not always be necessary
to train under a visually high frame rate system to learn a
particular task. We discuss implications of using the LP
technique to mitigate low frame rate issues as well as its
potential usefulness for training in low frame rate virtual
environments.},
Doi = {10.1109/3DUI.2016.7460043},
Key = {fds334792}
}
@article{fds334796,
Author = {Mayo, JP and DiTomasso, AR and Sommer, MA and Smith,
MA},
Title = {Dynamics of visual receptive fields in the macaque frontal
eye field.},
Journal = {J Neurophysiol},
Volume = {114},
Number = {6},
Pages = {3201-3210},
Year = {2015},
Month = {December},
url = {http://dx.doi.org/10.1152/jn.00746.2015},
Abstract = {Neuronal receptive fields (RFs) provide the foundation for
understanding systems-level sensory processing. In early
visual areas, investigators have mapped RFs in detail using
stochastic stimuli and sophisticated analytical approaches.
Much less is known about RFs in prefrontal cortex. Visual
stimuli used for mapping RFs in prefrontal cortex tend to
cover a small range of spatial and temporal parameters,
making it difficult to understand their role in visual
processing. To address these shortcomings, we implemented a
generalized linear model to measure the RFs of neurons in
the macaque frontal eye field (FEF) in response to sparse,
full-field stimuli. Our high-resolution, probabilistic
approach tracked the evolution of RFs during passive
fixation, and we validated our results against conventional
measures. We found that FEF neurons exhibited a surprising
level of sensitivity to stimuli presented as briefly as 10
ms or to multiple dots presented simultaneously, suggesting
that FEF visual responses are more precise than previously
appreciated. FEF RF spatial structures were largely
maintained over time and between stimulus conditions. Our
results demonstrate that the application of probabilistic RF
mapping to FEF and similar association areas is an important
tool for clarifying the neuronal mechanisms of
cognition.},
Doi = {10.1152/jn.00746.2015},
Key = {fds334796}
}
@article{fds334797,
Author = {Grigsby, EM and Koval, MJ and Smith, MV and Mueller, JK and Deng, ZD and Peterchev, A and Grill, WM and Sommer, MA},
Title = {Neural Effects of rTMS: Single Neuron Recordings From a
Rhesus Macaque},
Journal = {JOURNAL OF ECT},
Volume = {31},
Number = {3},
Pages = {E33-E33},
Publisher = {LIPPINCOTT WILLIAMS & WILKINS},
Year = {2015},
Month = {September},
Key = {fds334797}
}
@article{fds334798,
Author = {Zielinski, DJ and Rao, HM and Sommer, MA and Kopper,
R},
Title = {Exploring the Effects of Image Persistence in Low Frame Rate
Virtual Environments},
Journal = {Proceedings of the IEEE Virtual Reality Conference},
Pages = {19-26},
Publisher = {IEEE Computer Society},
Year = {2015},
url = {http://dx.doi.org/10.1109/vr.2015.7223319},
Abstract = {© 2015 IEEE. In virtual reality applications, there is an
aim to provide real time graphics which run at high refresh
rates. However, there are many situations in which this is
not possible due to simulation or rendering issues. When
running at low frame rates, several aspects of the user
experience are affected. For example, each frame is
displayed for an extended period of time, causing a high
persistence image artifact. The effect of this artifact is
that movement may lose continuity, and the image jumps from
one frame to another. In this paper, we discuss our initial
exploration of the effects of high persistence frames caused
by low refresh rates and compare it to high frame rates and
to a technique we developed to mitigate the effects of low
frame rates. In this technique, the low frame rate
simulation images are displayed with low persistence by
blanking out the display during the extra time such image
would be displayed. In order to isolate the visual effects,
we constructed a simulator for low and high persistence
displays that does not affect input latency. A controlled
user study comparing the three conditions for the tasks of
3D selection and navigation was conducted. Results indicate
that the low persistence display technique may not
negatively impact user experience or performance as compared
to the high persistence case. Directions for future work on
the use of low persistence displays for low frame rate
situations are discussed.},
Doi = {10.1109/vr.2015.7223319},
Key = {fds334798}
}
@article{fds334799,
Author = {Matthews, WJ and Terhune, DB and van Rijn, H and Eagleman, DM and Sommer, MA and Meck, WA},
Title = {Subjective duration as a signature of coding efficiency:
Emerging links among stimulus repetition, predictive coding,
and cortical GABA levels},
Journal = {Timing & Time Perception Reviews},
Volume = {1},
Pages = {11 pages},
Publisher = {Brill Publishers},
Year = {2014},
Month = {December},
Abstract = {Immediate repetition of a stimulus reduces its apparent
duration relative to a novel item. Recent work indicates
that this may reflect suppressed cortical responses to
repeated stimuli, arising from neural adaptation and/or the
predictive coding of expected stimuli. This article
summarizes recent behavioral and neurobiological studies
linking perceived time to the magnitude of cortical
responses, including work suggesting that variations in
GABA-mediated cortical inhibition may underlie some of the
individual differences in time perception. We suggest that
the firing of cortical neurons can be modified using simple
recurrent networks with time-dependent processes that are
modulated by GABA levels. These local networks feed into a
core-timing network used to integrate across stimulus
inputs/modalities, thereby allowing for the coordination of
multiple duration ranges and effector systems.},
Key = {fds334799}
}
@article{fds334800,
Author = {Mitchell, AS and Sherman, SM and Sommer, MA and Mair, RG and Vertes, RP and Chudasama, Y},
Title = {Advances in understanding mechanisms of thalamic relays in
cognition and behavior.},
Journal = {The Journal of neuroscience : the official journal of the
Society for Neuroscience},
Volume = {34},
Number = {46},
Pages = {15340-15346},
Year = {2014},
Month = {November},
url = {http://dx.doi.org/10.1523/jneurosci.3289-14.2014},
Abstract = {The main impetus for a mini-symposium on corticothalamic
interrelationships was the recent number of studies
highlighting the role of the thalamus in aspects of
cognition beyond sensory processing. The thalamus
contributes to a range of basic cognitive behaviors that
include learning and memory, inhibitory control,
decision-making, and the control of visual orienting
responses. Its functions are deeply intertwined with those
of the better studied cortex, although the principles
governing its coordination with the cortex remain opaque,
particularly in higher-level aspects of cognition. How
should the thalamus be viewed in the context of the rest of
the brain? Although its role extends well beyond relaying of
sensory information from the periphery, the main function of
many of its subdivisions does appear to be that of a relay
station, transmitting neural signals primarily to the
cerebral cortex from a number of brain areas. In cognition,
its main contribution may thus be to coordinate signals
between diverse regions of the telencephalon, including the
neocortex, hippocampus, amygdala, and striatum. This central
coordination is further subject to considerable extrinsic
control, for example, inhibition from the basal ganglia,
zona incerta, and pretectal regions, and chemical modulation
from ascending neurotransmitter systems. What follows is a
brief review on the role of the thalamus in aspects of
cognition and behavior, focusing on a summary of the topics
covered in a mini-symposium held at the Society for
Neuroscience meeting, 2014.},
Doi = {10.1523/jneurosci.3289-14.2014},
Key = {fds334800}
}
@article{fds334801,
Author = {Mueller, JK and Grigsby, EM and Prevosto, V and Petraglia, FW and Rao,
H and Deng, Z-D and Peterchev, AV and Sommer, MA and Egner, T and Platt,
ML and Grill, WM},
Title = {Simultaneous transcranial magnetic stimulation and
single-neuron recording in alert non-human
primates.},
Journal = {Nat Neurosci},
Volume = {17},
Number = {8},
Pages = {1130-1136},
Year = {2014},
Month = {August},
url = {http://dx.doi.org/10.1038/nn.3751},
Abstract = {Transcranial magnetic stimulation (TMS) is a widely used,
noninvasive method for stimulating nervous tissue, yet its
mechanisms of effect are poorly understood. Here we report
new methods for studying the influence of TMS on single
neurons in the brain of alert non-human primates. We
designed a TMS coil that focuses its effect near the tip of
a recording electrode and recording electronics that enable
direct acquisition of neuronal signals at the site of peak
stimulus strength minimally perturbed by stimulation
artifact in awake monkeys (Macaca mulatta). We recorded
action potentials within ∼1 ms after 0.4-ms TMS pulses and
observed changes in activity that differed significantly for
active stimulation as compared with sham stimulation. This
methodology is compatible with standard equipment in primate
laboratories, allowing easy implementation. Application of
these tools will facilitate the refinement of next
generation TMS devices, experiments and treatment
protocols.},
Doi = {10.1038/nn.3751},
Key = {fds334801}
}
@article{fds334804,
Author = {Prevosto, V and Sommer, MA},
Title = {Cognitive control of movement via the cerebellar-recipient
thalamus.},
Journal = {Frontiers in systems neuroscience},
Volume = {7},
Pages = {56},
Year = {2013},
Month = {October},
url = {http://dx.doi.org/10.3389/fnsys.2013.00056},
Abstract = {The cognitive control of behavior was long considered to be
centralized in cerebral cortex. More recently, subcortical
structures such as cerebellum and basal ganglia have been
implicated in cognitive functions as well. The fact that
subcortico-cortical circuits for the control of movement
involve the thalamus prompts the notion that activity in
movement-related thalamus may also reflect elements of
cognitive behavior. Yet this hypothesis has rarely been
investigated. Using the pathways linking cerebellum to
cerebral cortex via the thalamus as a template, we review
evidence that the motor thalamus, together with
movement-related central thalamus have the requisite
connectivity and activity to mediate cognitive aspects of
movement control.},
Doi = {10.3389/fnsys.2013.00056},
Key = {fds334804}
}
@article{fds334805,
Author = {Ashmore, RC and Sommer, MA},
Title = {Delay activity of saccade-related neurons in the caudal
dentate nucleus of the macaque cerebellum.},
Journal = {Journal of neurophysiology},
Volume = {109},
Number = {8},
Pages = {2129-2144},
Year = {2013},
Month = {April},
ISSN = {0022-3077},
url = {https://dl.dropboxusercontent.com/u/27738651/Publications/AshmoreSommer2013-CaudalDentateNucleus.pdf},
Abstract = {The caudal dentate nucleus (DN) in lateral cerebellum is
connected with two visual/oculomotor areas of the cerebrum:
the frontal eye field and lateral intraparietal cortex. Many
neurons in frontal eye field and lateral intraparietal
cortex produce "delay activity" between stimulus and
response that correlates with processes such as motor
planning. Our hypothesis was that caudal DN neurons would
have prominent delay activity as well. From lesion studies,
we predicted that this activity would be related to
self-timing, i.e., the triggering of saccades based on the
internal monitoring of time. We recorded from neurons in the
caudal DN of monkeys (Macaca mulatta) that made delayed
saccades with or without a self-timing requirement. Most
(84%) of the caudal DN neurons had delay activity. These
neurons conveyed at least three types of information. First,
their activity was often correlated, trial by trial, with
saccade initiation. Correlations were found more frequently
in a task that required self-timing of saccades (53% of
neurons) than in a task that did not (27% of neurons).
Second, the delay activity was often tuned for saccade
direction (in 65% of neurons). This tuning emerged
continuously during a trial. Third, the time course of delay
activity associated with self-timed saccades differed
significantly from that associated with visually guided
saccades (in 71% of neurons). A minority of neurons had
sensory-related activity. None had presaccadic bursts, in
contrast to DN neurons recorded more rostrally. We conclude
that caudal DN neurons convey saccade-related delay activity
that may contribute to the motor preparation of when and
where to move.},
Doi = {10.1152/jn.00906.2011},
Key = {fds334805}
}
@article{fds334806,
Author = {Smith, MA and Sommer, MA},
Title = {Spatial and temporal scales of neuronal correlation in
visual area V4.},
Journal = {The Journal of neuroscience : the official journal of the
Society for Neuroscience},
Volume = {33},
Number = {12},
Pages = {5422-5432},
Year = {2013},
Month = {March},
ISSN = {0270-6474},
url = {https://dl.dropbox.com/u/27738651/Publications/SmithSommer2013-SpatialTemporalCorrelationsV4.pdf},
Abstract = {The spiking activity of nearby cortical neurons is
correlated on both short and long time scales. Understanding
this shared variability in firing patterns is critical for
appreciating the representation of sensory stimuli in
ensembles of neurons, the coincident influences of neurons
on common targets, and the functional implications of
microcircuitry. Our knowledge about neuronal correlations,
however, derives largely from experiments that used
different recording methods, analysis techniques, and
cortical regions. Here we studied the structure of neuronal
correlation in area V4 of alert macaques using recording and
analysis procedures designed to match those used previously
in primary visual cortex (V1), the major input to V4. We
found that the spatial and temporal properties of
correlations in V4 were remarkably similar to those of V1,
with two notable differences: correlated variability in V4
was approximately one-third the magnitude of that in V1 and
synchrony in V4 was less temporally precise than in V1. In
both areas, spontaneous activity (measured during fixation
while viewing a blank screen) was approximately twice as
correlated as visual-evoked activity. The results provide a
foundation for understanding how the structure of neuronal
correlation differs among brain regions and stages in
cortical processing and suggest that it is likely governed
by features of neuronal circuits that are shared across the
visual cortex.},
Doi = {10.1523/jneurosci.4782-12.2013},
Key = {fds334806}
}
@article{fds334807,
Author = {Mayo, JP and Sommer, MA},
Title = {Neuronal correlates of visual time perception at brief
timescales.},
Journal = {Proc Natl Acad Sci U S A},
Volume = {110},
Number = {4},
Pages = {1506-1511},
Year = {2013},
Month = {January},
url = {https://dl.dropbox.com/u/27738651/Publications/MayoSommer2013-ReprintIncludingSupplInfo.pdf},
Abstract = {Successful interaction with the world depends on accurate
perception of the timing of external events. Neurons at
early stages of the primate visual system represent
time-varying stimuli with high precision. However, it is
unknown whether this temporal fidelity is maintained in the
prefrontal cortex, where changes in neuronal activity
generally correlate with changes in perception. One reason
to suspect that it is not maintained is that humans
experience surprisingly large fluctuations in the perception
of time. To investigate the neuronal correlates of time
perception, we recorded from neurons in the prefrontal
cortex and midbrain of monkeys performing a
temporal-discrimination task. Visual time intervals were
presented at a timescale relevant to natural behavior (<500
ms). At this brief timescale, neuronal adaptation--time-dependent
changes in the size of successive responses--occurs. We
found that visual activity fluctuated with timing judgments
in the prefrontal cortex but not in comparable midbrain
areas. Surprisingly, only response strength, not timing,
predicted task performance. Intervals perceived as longer
were associated with larger visual responses and shorter
intervals with smaller responses, matching the dynamics of
adaptation. These results suggest that the magnitude of
prefrontal activity may be read out to provide temporal
information that contributes to judging the passage of
time.},
Doi = {10.1073/pnas.1217177110},
Key = {fds334807}
}
@article{fds334811,
Author = {Shin, S and Sommer, MA},
Title = {Division of labor in frontal eye field neurons during
presaccadic remapping of visual receptive
fields.},
Journal = {Journal of neurophysiology},
Volume = {108},
Number = {8},
Pages = {2144-2159},
Year = {2012},
Month = {October},
url = {https://dl.dropbox.com/u/27738651/Publications/ShinSommer2012.pdf},
Abstract = {Our percept of visual stability across saccadic eye
movements may be mediated by presaccadic remapping. Just
before a saccade, neurons that remap become visually
responsive at a future field (FF), which anticipates the
saccade vector. Hence, the neurons use corollary discharge
of saccades. Many of the neurons also decrease their
response at the receptive field (RF). Presaccadic remapping
occurs in several brain areas including the frontal eye
field (FEF), which receives corollary discharge of saccades
in its layer IV from a collicular-thalamic pathway. We
studied, at two levels, the microcircuitry of remapping in
the FEF. At the laminar level, we compared remapping between
layers IV and V. At the cellular level, we compared
remapping between different neuron types of layer IV. In the
FEF in four monkeys (Macaca mulatta), we identified 27 layer
IV neurons with orthodromic stimulation and 57 layer V
neurons with antidromic stimulation from the superior
colliculus. With the use of established criteria, we
classified the layer IV neurons as putative excitatory (n =
11), putative inhibitory (n = 12), or ambiguous (n = 4). We
found that just before a saccade, putative excitatory
neurons increased their visual response at the RF, putative
inhibitory neurons showed no change, and ambiguous neurons
increased their visual response at the FF. None of the
neurons showed presaccadic visual changes at both RF and FF.
In contrast, neurons in layer V showed full remapping (at
both the RF and FF). Our data suggest that elemental signals
for remapping are distributed across neuron types in early
cortical processing and combined in later stages of cortical
microcircuitry.},
Doi = {10.1152/jn.00204.2012},
Key = {fds334811}
}
@article{fds334808,
Author = {Mayo, JP and DiTomasso, A and Sommer, M and Smith,
MA},
Title = {An improved method for mapping neuronal receptive fields in
prefrontal cortex},
Journal = {Journal of Vision},
Volume = {12},
Number = {9},
Pages = {81-81},
Publisher = {Association for Research in Vision and Ophthalmology
(ARVO)},
Year = {2012},
Month = {August},
url = {http://dx.doi.org/10.1167/12.9.81},
Doi = {10.1167/12.9.81},
Key = {fds334808}
}
@article{fds334810,
Author = {Middlebrooks, PG and Sommer, MA},
Title = {Neuronal correlates of metacognition in primate frontal
cortex.},
Journal = {Neuron},
Volume = {75},
Number = {3},
Pages = {517-530},
Year = {2012},
Month = {August},
ISSN = {08966273},
url = {https://dl.dropbox.com/u/27738651/Publications/MiddlebrooksSommer2012-MetacogNeurons-TextSupplPreview.pdf},
Abstract = {Humans are metacognitive: they monitor and control their
cognition. Our hypothesis was that neuronal correlates of
metacognition reside in the same brain areas responsible for
cognition, including frontal cortex. Recent work
demonstrated that nonhuman primates are capable of
metacognition, so we recorded from single neurons in the
frontal eye field, dorsolateral prefrontal cortex, and
supplementary eye field of monkeys (Macaca mulatta) that
performed a metacognitive visual-oculomotor task. The
animals made a decision and reported it with a saccade, but
received no immediate reward or feedback. Instead, they had
to monitor their decision and bet whether it was correct.
Activity was correlated with decisions and bets in all three
brain areas, but putative metacognitive activity that linked
decisions to appropriate bets occurred exclusively in the
SEF. Our results offer a survey of neuronal correlates of
metacognition and implicate the SEF in linking cognitive
functions over short periods of time.},
Doi = {10.1016/j.neuron.2012.05.028},
Key = {fds334810}
}
@article{fds334809,
Author = {Crapse, TB and Sommer, MA},
Title = {Frontal eye field neurons assess visual stability across
saccades.},
Journal = {The Journal of neuroscience : the official journal of the
Society for Neuroscience},
Volume = {32},
Number = {8},
Pages = {2835-2845},
Year = {2012},
Month = {February},
ISSN = {0270-6474},
url = {https://dl.dropbox.com/u/27738651/Publications/CrapseSommer2012.pdf},
Abstract = {The image on the retina may move because the eyes move, or
because something in the visual scene moves. The brain is
not fooled by this ambiguity. Even as we make saccades, we
are able to detect whether visual objects remain stable or
move. Here we test whether this ability to assess visual
stability across saccades is present at the single-neuron
level in the frontal eye field (FEF), an area that receives
both visual input and information about imminent saccades.
Our hypothesis was that neurons in the FEF report whether a
visual stimulus remains stable or moves as a saccade is
made. Monkeys made saccades in the presence of a visual
stimulus outside of the receptive field. In some trials, the
stimulus remained stable, but in other trials, it moved
during the saccade. In every trial, the stimulus occupied
the center of the receptive field after the saccade, thus
evoking a reafferent visual response. We found that many FEF
neurons signaled, in the strength and timing of their
reafferent response, whether the stimulus had remained
stable or moved. Reafferent responses were tuned for the
amount of stimulus translation, and, in accordance with
human psychophysics, tuning was better (more prevalent,
stronger, and quicker) for stimuli that moved perpendicular,
rather than parallel, to the saccade. Tuning was sometimes
present as well for nonspatial transaccadic changes (in
color, size, or both). Our results indicate that FEF neurons
evaluate visual stability during saccades and may be general
purpose detectors of transaccadic visual
change.},
Doi = {10.1523/jneurosci.1320-11.2012},
Key = {fds334809}
}
@article{fds334813,
Author = {Basso, MA and Sommer, MA},
Title = {Exploring the role of the substantia nigra pars reticulata
in eye movements.},
Journal = {Neuroscience},
Volume = {198},
Pages = {205-212},
Year = {2011},
Month = {December},
url = {http://dx.doi.org/10.1016/j.neuroscience.2011.08.026},
Abstract = {Experiments that demonstrated a role for the substantia
nigra in eye movements have played an important role in our
understanding of the function of the basal ganglia in
behavior more broadly. In this review we explore more recent
experiments that extend the role of the substantia nigra
pars reticulata from a simple gate for eye movements to
include a role in cognitive processes for eye movements. We
review recent evidence suggesting that basal ganglia nuclei
beyond the substantia nigra may also play a role in eye
movements and the cognitive events leading up to the
production of eye movements. We close by pointing out some
unresolved questions in our understanding of the
relationship of basal ganglia nuclei and eye
movements.},
Doi = {10.1016/j.neuroscience.2011.08.026},
Key = {fds334813}
}
@article{Sommer2009,
Author = {Middlebrooks, PG and Sommer, MA},
Title = {Metacognition in monkeys during an oculomotor
task.},
Journal = {Journal of experimental psychology. Learning, memory, and
cognition},
Volume = {37},
Number = {2},
Pages = {325-337},
Year = {2011},
Month = {March},
ISSN = {0278-7393},
url = {https://dl.dropbox.com/u/27738651/Publications/MiddlebrooksSommer2011-MetacognitionInMonkeys.pdf},
Abstract = {This study investigated whether rhesus monkeys show evidence
of metacognition in a reduced, visual oculomotor task that
is particularly suitable for use in fMRI and
electrophysiology. The 2-stage task involved punctate visual
stimulation and saccadic eye movement responses. In each
trial, monkeys made a decision and then made a bet. To earn
maximum reward, they had to monitor their decision and use
that information to bet advantageously. Two monkeys learned
to base their bets on their decisions within a few weeks. We
implemented an operational definition of metacognitive
behavior that relied on trial-by-trial analyses and signal
detection theory. Both monkeys exhibited metacognition
according to these quantitative criteria. Neither external
visual cues nor potential reaction time cues explained the
betting behavior; the animals seemed to rely exclusively on
internal traces of their decisions. We documented the
learning process of one monkey. During a 10-session
transition phase, betting switched from random to a
decision-based strategy. The results reinforce previous
findings of metacognitive ability in monkeys and may
facilitate the neurophysiological investigation of
metacognitive functions.},
Doi = {10.1037/a0021611},
Key = {Sommer2009}
}
@article{fds334816,
Author = {Mayo, JP and Sommer, MA},
Title = {Shifting attention to neurons.},
Journal = {Trends Cogn Sci},
Volume = {14},
Number = {9},
Pages = {389},
Year = {2010},
Month = {September},
url = {http://dx.doi.org/10.1016/j.tics.2010.06.003},
Doi = {10.1016/j.tics.2010.06.003},
Key = {fds334816}
}
@article{fds334814,
Author = {Crapse, T and Sommer, M},
Title = {Translation of a visual stimulus during a saccade is more
detectable if it moves perpendicular, rather than parallel,
to the saccade},
Journal = {Journal of Vision},
Volume = {10},
Number = {7},
Pages = {521-521},
Publisher = {Association for Research in Vision and Ophthalmology
(ARVO)},
Year = {2010},
Month = {August},
url = {http://dx.doi.org/10.1167/10.7.521},
Doi = {10.1167/10.7.521},
Key = {fds334814}
}
@article{fds334815,
Author = {Shin, S and Sommer, MA},
Title = {Activity of neurons in monkey globus pallidus during
oculomotor behavior compared with that in substantia nigra
pars reticulata.},
Journal = {Journal of neurophysiology},
Volume = {103},
Number = {4},
Pages = {1874-1887},
Year = {2010},
Month = {April},
ISSN = {0022-3077},
url = {https://dl.dropbox.com/u/27738651/Publications/ShinSommer2010.pdf},
Abstract = {The basal ganglia are a subcortical assembly of nuclei
involved in many aspects of behavior. Three of the nuclei
have high firing rates and inhibitory influences: the
substantia nigra pars reticulata (SNr), globus pallidus
interna (GPi), and globus pallidus externa (GPe). The SNr
contains a wide range of visual, cognitive, and motor
signals that have been shown to contribute to saccadic eye
movements. Our hypothesis was that GPe and GPi neurons carry
similarly diverse signals during saccadic behavior. We
recorded from GPe, GPi, and SNr neurons in monkeys that made
memory-guided saccades and found that neurons in all three
structures had increases or decreases in activity
synchronized with saccade generation, visual stimulation, or
reward. Comparing GPe neurons with GPi neurons, we found
relatively more visual-related activity in GPe and more
reward-related activity in GPi. Comparing both pallidal
samples with the SNr, we found a greater resemblance between
GPe and SNr neurons than that between GPi and SNr neurons.
As expected from a known inhibitory projection from GPe to
SNr, there was a general reversal of sign in activity
modulations between the structures: bursts of activity were
relatively more common in GPe and pauses more common in SNr.
We analyzed the response fields of neurons in all three
structures and found relatively narrow and lateralized
fields early in trials (during visual and saccadic events)
followed by a broadening later in trials (during reward).
Our data reinforce an emerging, new consensus that the GPe
and GPi, in addition to the SNr, contribute to oculomotor
behavior.},
Doi = {10.1152/jn.00101.2009},
Key = {fds334815}
}
@article{fds334817,
Author = {Sommer, MA},
Title = {How the visual system monitors where the eyes will
move},
Journal = {Journal of Vision},
Volume = {9},
Number = {14},
Pages = {13-13},
Publisher = {Association for Research in Vision and Ophthalmology
(ARVO)},
Year = {2009},
Month = {December},
url = {http://dx.doi.org/10.1167/9.14.13},
Doi = {10.1167/9.14.13},
Key = {fds334817}
}
@article{fds334818,
Author = {Sommer, MA},
Title = {Corollary discharge circuits for stabilizing visual
perception},
Journal = {PSYCHOPHYSIOLOGY},
Volume = {46},
Pages = {S9-S9},
Publisher = {WILEY-BLACKWELL PUBLISHING, INC},
Year = {2009},
Month = {September},
Key = {fds334818}
}
@article{fds334819,
Author = {Mayo, JP and Sommer, MA},
Title = {Monkey and human performance in a chronostasis task suitable
for neurophysiology},
Journal = {Journal of Vision},
Volume = {9},
Number = {8},
Pages = {406-406},
Publisher = {Association for Research in Vision and Ophthalmology
(ARVO)},
Year = {2009},
Month = {August},
url = {http://dx.doi.org/10.1167/9.8.406},
Doi = {10.1167/9.8.406},
Key = {fds334819}
}
@article{Crapse2009,
Author = {Crapse, TB and Sommer, MA},
Title = {Frontal eye field neurons with spatial representations
predicted by their subcortical input.},
Journal = {The Journal of neuroscience : the official journal of the
Society for Neuroscience},
Volume = {29},
Number = {16},
Pages = {5308-5318},
Year = {2009},
Month = {April},
ISSN = {0270-6474},
url = {https://dl.dropbox.com/u/27738651/Publications/CrapseSommer2009_JNeurosci.pdf},
Abstract = {The frontal eye field (FEF) is a cortical structure involved
in cognitive aspects of eye movement control. Neurons in the
FEF, as in most of cerebral cortex, primarily represent
contralateral space. They fire for visual stimuli in the
contralateral field and for saccadic eye movements made to
those stimuli. Yet many FEF neurons engage in sophisticated
functions that require flexible spatial representations such
as shifting receptive fields and vector subtraction. Such
functions require knowledge about all of space, including
the ipsilateral hemifield. How does the FEF gain access to
ipsilateral information? Here, we provide evidence that one
source of ipsilateral information may be the opposite
superior colliculus (SC) in the midbrain. We physiologically
identified neurons in the FEF that receive input from the
opposite SC, same-side SC, or both. We found a striking
structure-function relationship: the laterality of the
response field of an FEF neuron was predicted by the
laterality of its SC inputs. FEF neurons with input from the
opposite SC had ipsilateral fields, whereas neurons with
input from the same-side SC had contralateral fields. FEF
neurons with input from both SCs had lateralized fields that
could point in any direction. The results suggest that
signals from the two SCs provide each FEF with information
about all of visual space, a prerequisite for higher level
sensorimotor computations.},
Doi = {10.1523/jneurosci.4906-08.2009},
Key = {Crapse2009}
}
@article{Crapse2008a,
Author = {Crapse, TB and Sommer, MA},
Title = {Corollary discharge circuits in the primate
brain.},
Journal = {Current opinion in neurobiology},
Volume = {18},
Number = {6},
Pages = {552-557},
Year = {2008},
Month = {December},
ISSN = {0959-4388},
url = {https://dl.dropbox.com/u/27738651/Publications/CrapseSommer_CurrOpinionNeurobiology2008.pdf},
Abstract = {Movements are necessary to engage the world, but every
movement results in sensorimotor ambiguity. Self-movements
cause changes to sensory inflow as well as changes in the
positions of objects relative to motor effectors (eyes and
limbs). Hence the brain needs to monitor self-movements, and
one way this is accomplished is by routing copies of
movement commands to appropriate structures. These signals,
known as corollary discharge (CD), enable compensation for
sensory consequences of movement and preemptive updating of
spatial representations. Such operations occur with a speed
and accuracy that implies a reliance on prediction. Here we
review recent CD studies and find that they arrive at a
shared conclusion: CD contributes to prediction for the sake
of sensorimotor harmony.},
Doi = {10.1016/j.conb.2008.09.017},
Key = {Crapse2008a}
}
@article{Mayo2008a,
Author = {Mayo, JP and Sommer, MA},
Title = {Neuronal adaptation caused by sequential visual stimulation
in the frontal eye field.},
Journal = {J Neurophysiol},
Volume = {100},
Number = {4},
Pages = {1923-1935},
Year = {2008},
Month = {October},
ISSN = {0022-3077},
url = {https://dl.dropbox.com/u/27738651/Publications/MayoSommer2008-FEFadaptation.pdf},
Abstract = {Images on the retina can change drastically in only a few
milliseconds. A robust description of visual temporal
processing is therefore necessary to understand visual
analysis in the real world. To this end, we studied
subsecond visual changes and asked how prefrontal neurons in
monkeys respond to stimuli presented in quick succession. We
recorded the visual responses of single neurons in the
frontal eye field (FEF), a prefrontal area polysynaptically
removed from the retina that is involved with higher level
cognition. For comparison, we also recorded from small
groups of neurons in the superficial superior colliculus
(supSC), an area that receives direct retinal input. Two
sequential flashes of light at varying interstimulus
intervals were presented in a neuron's receptive field. We
found pervasive neuronal adaptation in FEF and supSC. Visual
responses to the second stimulus were diminished for up to
half a second after the first stimulus presentation.
Adaptation required a similar amount of time to return to
full responsiveness in both structures, but there was
significantly more neuronal adaptation overall in FEF.
Adaptation was not affected by saccades, although visual
responses to single stimuli were transiently suppressed
postsaccadically. Our FEF and supSC results systematically
document subsecond visual adaptation in prefrontal cortex
and show that this adaptation is comparable to, but stronger
than, adaptation found earlier in the visual
system.},
Doi = {10.1152/jn.90549.2008},
Key = {Mayo2008a}
}
@article{Crapse2008b,
Author = {Crapse, TB and Sommer, MA},
Title = {Corollary discharge across the animal kingdom.},
Journal = {Nature reviews. Neuroscience},
Volume = {9},
Number = {8},
Pages = {587-600},
Year = {2008},
Month = {August},
ISSN = {1471-0048},
url = {https://dl.dropbox.com/u/27738651/Publications/CrapseSommer_CDReview2008.pdf},
Abstract = {Our movements can hinder our ability to sense the world.
Movements can induce sensory input (for example, when you
hit something) that is indistinguishable from the input that
is caused by external agents (for example, when something
hits you). It is critical for nervous systems to be able to
differentiate between these two scenarios. A ubiquitous
strategy is to route copies of movement commands to sensory
structures. These signals, which are referred to as
corollary discharge (CD), influence sensory processing in
myriad ways. Here we review the CD circuits that have been
uncovered by neurophysiological studies and suggest a
functional taxonomic classification of CD across the animal
kingdom. This broad understanding of CD circuits lays the
groundwork for more challenging studies that combine
neurophysiology and psychophysics to probe the role of CD in
perception.},
Doi = {10.1038/nrn2457},
Key = {Crapse2008b}
}
@article{Mayo2008b,
Author = {Mayo, JP and Sommer, MA},
Title = {Neuronal adaptation: Delay compensation at the level of
single neurons?},
Journal = {Behavioral and Brain Sciences},
Volume = {31},
Number = {2},
Pages = {210-212},
Publisher = {Cambridge University Press (CUP)},
Year = {2008},
Month = {April},
ISSN = {0140-525X},
url = {https://dl.dropbox.com/u/27738651/Publications/MayoSommer2008-BBScommentary.pdf},
Abstract = {Saccades divide visual input into rapid, discontinuous
periods of stimulation on the retina. The response of single
neurons to such sequential stimuli is neuronal adaptation; a
robust first response followed by an interval-dependent
diminished second response. Adaptation is pervasive in both
early and late stages of visual processing. Given its
inherent coding of brief time intervals, neuronal adaptation
may play a fundamental role in compensating for visual
delays. © 2008 Cambridge University Press
2008.},
Doi = {10.1017/S0140525X08003944},
Key = {Mayo2008b}
}
@article{Sommer2008a,
Author = {Sommer, MA and Wurtz, RH},
Title = {Brain circuits for the internal monitoring of
movements.},
Journal = {Annual review of neuroscience},
Volume = {31},
Pages = {317-338},
Year = {2008},
Month = {January},
ISSN = {0147-006X},
url = {https://dl.dropbox.com/u/27738651/Publications/SommerWurtz_AnnualRevNeurosci2008.pdf},
Abstract = {Each movement we make activates our own sensory receptors,
thus causing a problem for the brain: the spurious,
movement-related sensations must be discriminated from the
sensory inputs that really matter, those representing our
environment. Here we consider circuits for solving this
problem in the primate brain. Such circuits convey a copy of
each motor command, known as a corollary discharge (CD), to
brain regions that use sensory input. In the visual system,
CD signals may help to produce a stable visual percept from
the jumpy images resulting from our rapid eye movements. A
candidate pathway for providing CD for vision ascends from
the superior colliculus to the frontal cortex in the primate
brain. This circuit conveys warning signals about impending
eye movements that are used for planning subsequent
movements and analyzing the visual world. Identifying this
circuit has provided a model for studying CD in other
primate sensory systems and may lead to a better
understanding of motor and mental disorders.},
Doi = {10.1146/annurev.neuro.31.060407.125627},
Key = {Sommer2008a}
}
@article{Sommer2008b,
Author = {Sommer, MA and Wurtz, RH},
Title = {Visual perception and corollary discharge.},
Journal = {Perception},
Volume = {37},
Number = {3},
Pages = {408-418},
Year = {2008},
Month = {January},
ISSN = {0301-0066},
url = {https://dl.dropbox.com/u/27738651/Publications/SommerWurtz2008-Perception.pdf},
Abstract = {Perception depends not only on sensory input but also on the
state of the brain receiving that input. A classic example
is perception of a stable visual world in spite of the
saccadic eye movements that shift the images on the retina.
A long-standing hypothesis is that the brain compensates for
the disruption of visual input by using advance knowledge of
the impending saccade, an internally generated corollary
discharge. One possible neuronal mechanism for this
compensation has been previously identified in parietal and
frontal cortex of monkeys, but the origin of the necessary
corollary discharge remained unknown. Here, we consider
recent experiments that identified a pathway for a corollary
discharge for saccades that extends from the superior
colliculus in the midbrain to the frontal eye fields in the
cerebral cortex with a relay in the medial dorsal nucleus of
the thalamus. We first review the nature of the evidence
used to identify a corollary discharge signal in the
complexity of the primate brain and show its use for guiding
a rapid sequence of eye movements. We then consider two
experiments that show this same corollary signal may provide
the input to the frontal cortex neurons that alters their
activity with saccades in ways that could compensate for the
displacements in the visual input produced by saccadic eye
movements. The first experiment shows that the corollary
discharge signal is spatially and temporally appropriate to
produce the alterations in the frontal-cortex neurons. The
second shows that this signal is necessary for this
alteration because inactivation of the corollary reduces the
compensation by frontal-cortex neurons. The identification
of this relatively simple circuit specifies the organization
of a corollary discharge in the primate brain for the first
time and provides a specific example upon which
consideration of the roles of corollary activity in other
systems and for other functions can be evaluated.},
Doi = {10.1068/p5873},
Key = {Sommer2008b}
}
@article{fds334831,
Author = {Crapse, TB and Sommer, MA},
Title = {The frontal eye field as a prediction map.},
Journal = {Progress in brain research},
Volume = {171},
Pages = {383-390},
Editor = {C. Kennard and R. J. Leigh},
Year = {2008},
Month = {January},
ISSN = {0079-6123},
url = {https://dl.dropbox.com/u/27738651/Publications/CrapseSommer_ProgressBrainRes2008.pdf},
Abstract = {Predictive processes are widespread in the motor and sensory
areas of the primate brain. They enable rapid computations
despite processing delays and assist in resolving noisy,
ambiguous input. Here we propose that the frontal eye field,
a cortical area devoted to sensorimotor aspects of eye
movement control, implements a prediction map of the
postsaccadic visual scene for the purpose of constructing a
stable percept despite saccadic eye movements.},
Doi = {10.1016/s0079-6123(08)00656-0},
Key = {fds334831}
}
@article{Sommer2007a,
Author = {Sommer, MA},
Title = {Microcircuits for attention.},
Journal = {Neuron},
Volume = {55},
Number = {1},
Pages = {6-8},
Year = {2007},
Month = {July},
ISSN = {0896-6273},
url = {https://dl.dropbox.com/u/27738651/Publications/Sommer2007-NeuronCommentary.pdf},
Abstract = {Researchers who study the neuronal basis of cognition face a
paradox. If they extract the brain, its cognitive functions
cannot be assessed. On the other hand, the brain's
microcircuits are difficult to study in the intact animal.
In this issue of Neuron, Mitchell et al. make use of a
promising approach based on waveform analysis to reveal new
details about neuronal interactions during visual
attention.},
Doi = {10.1016/j.neuron.2007.06.022},
Key = {Sommer2007a}
}
@article{Sommer2007b,
Author = {Sommer, MA},
Title = {The feeling of looking.},
Journal = {Nature neuroscience},
Volume = {10},
Number = {5},
Pages = {538-540},
Year = {2007},
Month = {May},
ISSN = {1097-6256},
url = {https://dl.dropbox.com/u/27738651/Publications/Sommer2007-FeelingOfLooking.pdf},
Abstract = {Sensory cortex area 3a contains a map of the body. A new
paper reports the location of eye position signals in this
map which should allow researchers to test the functions of
eye position signals and visual gain fields in more detail.
© 2007 Nature Publishing Group.},
Doi = {10.1038/nn0507-538},
Key = {Sommer2007b}
}
@article{Sommer2006,
Author = {Sommer, MA and Wurtz, RH},
Title = {Influence of the thalamus on spatial visual processing in
frontal cortex.},
Journal = {Nature},
Volume = {444},
Number = {7117},
Pages = {374-377},
Year = {2006},
Month = {November},
ISSN = {0028-0836},
url = {https://dl.dropbox.com/u/27738651/Publications/SommerWurtz2006_Nature_Reprint.pdf},
Abstract = {Each of our movements activates our own sensory receptors,
and therefore keeping track of self-movement is a necessary
part of analysing sensory input. One way in which the brain
keeps track of self-movement is by monitoring an internal
copy, or corollary discharge, of motor commands. This
concept could explain why we perceive a stable visual world
despite our frequent quick, or saccadic, eye movements:
corollary discharge about each saccade would permit the
visual system to ignore saccade-induced visual changes. The
critical missing link has been the connection between
corollary discharge and visual processing. Here we show that
such a link is formed by a corollary discharge from the
thalamus that targets the frontal cortex. In the thalamus,
neurons in the mediodorsal nucleus relay a corollary
discharge of saccades from the midbrain superior colliculus
to the cortical frontal eye field. In the frontal eye field,
neurons use corollary discharge to shift their visual
receptive fields spatially before saccades. We tested the
hypothesis that these two components-a pathway for corollary
discharge and neurons with shifting receptive fields-form a
circuit in which the corollary discharge drives the shift.
First we showed that the known spatial and temporal
properties of the corollary discharge predict the dynamic
changes in spatial visual processing of cortical neurons
when saccades are made. Then we moved from this correlation
to causation by isolating single cortical neurons and
showing that their spatial visual processing is impaired
when corollary discharge from the thalamus is interrupted.
Thus the visual processing of frontal neurons is
spatiotemporally matched with, and functionally dependent
on, corollary discharge input from the thalamus. These
experiments establish the first link between corollary
discharge and visual processing, delineate a brain circuit
that is well suited for mediating visual stability, and
provide a framework for studying corollary discharge in
other sensory systems.},
Doi = {10.1038/nature05279},
Key = {Sommer2006}
}
@article{fds334835,
Author = {Wurtz, RH and Sommer, MA},
Title = {A corollary discharge for perceptual stability},
Journal = {PERCEPTION},
Volume = {35},
Pages = {10-11},
Publisher = {SAGE PUBLICATIONS LTD},
Year = {2006},
Month = {January},
Key = {fds334835}
}
@article{fds334836,
Author = {Wurtz, RH and Sommer, MA and Cavanaugh, J},
Title = {Drivers from the deep: the contribution of collicular input
to thalamocortical processing.},
Journal = {Progress in brain research},
Volume = {149},
Pages = {207-225},
Year = {2005},
Month = {January},
ISSN = {0079-6123},
url = {https://dl.dropbox.com/u/27738651/Publications/WurtzSommerCavanaugh_ProgrBrainRes2005.pdf},
Abstract = {A traditional view of the thalamus is that it is a relay
station which receives sensory input and conveys this
information to cortex. This sensory input determines most of
the properties of first order thalamic neurons, and so is
said to drive, rather than modulate, these neurons. This
holds as a rule for first order thalamic nuclei, but in
contrast, higher order thalamic nuclei receive much of their
driver input back from cerebral cortex. In addition, higher
order thalamic neurons receive inputs from subcortical
movement-related centers. In the terminology popularized
from studies of the sensory system, can we consider these
ascending motor inputs to thalamus from subcortical
structures to be modulators, subtly influencing the activity
of their target neurons, or drivers, dictating the activity
of their target neurons? This chapter summarizes relevant
evidence from neuronal recording, inactivation, and
stimulation of pathways projecting from the superior
colliculus through thalamus to cerebral cortex. The study
concludes that many inputs to the higher order nuclei of the
thalamus from subcortical oculomotor areas - from the
superior colliculus and probably other midbrain and pontine
regions - should be regarded as motor drivers analogous to
the sensory drivers at the first order thalamic nuclei.
These motor drivers at the thalamus are viewed as being at
the top of a series of feedback loops that provide
information on impending actions, just as sensory drivers
provide information about the external environment.},
Doi = {10.1016/s0079-6123(05)49015-9},
Key = {fds334836}
}
@article{fds334838,
Author = {Sommer, MA and Wurtz, RH},
Title = {What the brain stem tells the frontal cortex. II. Role of
the SC-MD-FEF pathway in corollary discharge.},
Journal = {Journal of neurophysiology},
Volume = {91},
Number = {3},
Pages = {1403-1423},
Year = {2004},
Month = {March},
url = {http://dx.doi.org/10.1152/jn.00740.2003},
Abstract = {One way we keep track of our movements is by monitoring
corollary discharges or internal copies of movement
commands. This study tested a hypothesis that the pathway
from superior colliculus (SC) to mediodorsal thalamus (MD)
to frontal eye field (FEF) carries a corollary discharge
about saccades made into the contralateral visual field. We
inactivated the MD relay node with muscimol in monkeys and
measured corollary discharge deficits using a double-step
task: two sequential saccades were made to the locations of
briefly flashed targets. To make second saccades correctly,
monkeys had to internally monitor their first saccades;
therefore deficits in the corollary discharge representation
of first saccades should disrupt second saccades. We found,
first, that monkeys seemed to misjudge the amplitudes of
their first saccades; this was revealed by systematic shifts
in second saccade end points. Thus corollary discharge
accuracy was impaired. Second, monkeys were less able to
detect trial-by-trial variations in their first saccades;
this was revealed by reduced compensatory changes in second
saccade angles. Thus corollary discharge precision also was
impaired. Both deficits occurred only when first saccades
went into the contralateral visual field. Single-saccade
generation was unaffected. Additional deficits occurred in
reaction time and overall performance, but these were
bilateral. We conclude that the SC-MD-FEF pathway conveys a
corollary discharge used for coordinating sequential
saccades and possibly for stabilizing vision across
saccades. This pathway is the first elucidated in what may
be a multilevel chain of corollary discharge circuits
extending from the extraocular motoneurons up into cerebral
cortex.},
Doi = {10.1152/jn.00740.2003},
Key = {fds334838}
}
@article{fds334839,
Author = {Sommer, MA and Wurtz, RH},
Title = {What the brain stem tells the frontal cortex. I. Oculomotor
signals sent from superior colliculus to frontal eye field
via mediodorsal thalamus.},
Journal = {Journal of neurophysiology},
Volume = {91},
Number = {3},
Pages = {1381-1402},
Year = {2004},
Month = {March},
url = {http://dx.doi.org/10.1152/jn.00738.2003},
Abstract = {Neuronal processing in cerebral cortex and signal
transmission from cortex to brain stem have been studied
extensively, but little is known about the numerous feedback
pathways that ascend from brain stem to cortex. In this
study, we characterized the signals conveyed through an
ascending pathway coursing from the superior colliculus (SC)
to the frontal eye field (FEF) via mediodorsal thalamus
(MD). Using antidromic and orthodromic stimulation, we
identified SC source neurons, MD relay neurons, and FEF
recipient neurons of the pathway in Macaca mulatta. The
monkeys performed oculomotor tasks, including
delayed-saccade tasks, that permitted analysis of signals
such as visual activity, delay activity, and presaccadic
activity. We found that the SC sends all of these signals
into the pathway with no output selectivity, i.e., the
signals leaving the SC resembled those found generally
within the SC. Visual activity arrived in FEF too late to
contribute to short-latency visual responses there, and
delay activity was largely filtered out in MD. Presaccadic
activity, however, seemed critical because it traveled
essentially unchanged from SC to FEF. Signal transmission in
the pathway was fast ( approximately 2 ms from SC to FEF)
and topographically organized (SC neurons drove MD and FEF
neurons having similarly eccentric visual and movement
fields). Our analysis of identified neurons in one pathway
from brain stem to frontal cortex thus demonstrates that
multiple signals are sent from SC to FEF with presaccadic
activity being prominent. We hypothesize that a major signal
conveyed by the pathway is corollary discharge information
about the vector of impending saccades.},
Doi = {10.1152/jn.00738.2003},
Key = {fds334839}
}
@article{fds334837,
Author = {Wurtz, RH and Sommer, MA},
Title = {Identifying corollary discharges for movement in the primate
brain.},
Journal = {Progress in brain research},
Volume = {144},
Pages = {47-60},
Year = {2004},
Month = {January},
ISSN = {0079-6123},
url = {https://dl.dropbox.com/u/27738651/Publications/WurtzSommer_ProgBrainRes2004.pdf},
Abstract = {The brain keeps track of the movements it makes so as to
process sensory input accurately and coordinate complex
movements gracefully. In this chapter we review the brain's
strategies for keeping track of fast, saccadic eye
movements. One way it does this is by monitoring copies of
saccadic motor commands, or corollary discharges. It has
been difficult to identify corollary discharge signals in
the primate brain, although in some studies the influence of
corollary discharge, for example on visual processing, has
been found. We propose four criteria for identifying
corollary discharge signals in primate brain based on our
experiences studying a pathway from superior colliculus, in
the brainstem, through mediodorsal thalamus to frontal eye
field, in the prefrontal cortex. First, the signals must
originate from a brain structure involved in generating
movements. Second, they must begin just prior to movements
and represent spatial attributes of the movements. Third,
eliminating the signals should not impair movements in
simple tasks not requiring corollary discharge. Fourth,
eliminating the signals should, however, disrupt movements
in tasks that require corollary discharge, such as a
double-step task in which the monkey must keep track of one
saccade in order to correctly generate another. Applying
these criteria to the pathway from superior colliculus to
frontal eye field, we concluded that it does indeed convey
corollary discharge signals. The extent to which cerebral
cortex actually uses these signals, particularly in the
realm of sensory perception, remains unknown pending further
studies. Moreover, many other ascending pathways from
brainstem to cortex remain to be explored in behaving
monkeys, and some of these, too, may carry corollary
discharge signals.},
Doi = {10.1016/s0079-6123(03)14403-2},
Key = {fds334837}
}
@article{fds334841,
Author = {Sommer, MA},
Title = {The role of the thalamus in motor control.},
Journal = {Current opinion in neurobiology},
Volume = {13},
Number = {6},
Pages = {663-670},
Year = {2003},
Month = {December},
url = {http://dx.doi.org/10.1016/j.conb.2003.10.014},
Abstract = {Two characteristics of the thalamus--its apparently simple
relay function and its daunting multinuclear structure--have
been customarily viewed as good reasons to study something
else. Yet, now that many other brain regions have been
explored and neurophysiologists are turning to questions of
how larger circuits operate, these two characteristics are
starting to seem more attractive. First, the relay nature of
thalamic neurons means that recording from them, like
tapping into a wire, can reveal the signals carried by
specific circuits. Second, the concentration of like relay
neurons into nuclei means that inactivating or stimulating
them can efficiently test the functions of the circuits.
Recent studies implementing these principles have revealed
pathways through the thalamus that contribute to generating
movements and to monitoring one's own actions (corollary
discharge).},
Doi = {10.1016/j.conb.2003.10.014},
Key = {fds334841}
}
@article{fds334840,
Author = {Sommer, MA and Wurtz, RH},
Title = {The frontal eye field sends predictively remapped visual
signals to the superior colliculus},
Journal = {Journal of Vision},
Volume = {3},
Number = {9},
Pages = {146-146},
Publisher = {Association for Research in Vision and Ophthalmology
(ARVO)},
Year = {2003},
url = {http://dx.doi.org/10.1167/3.9.146},
Abstract = {We perceive a stable visual world even though saccades often
move our retinas. One way the brain may achieve a stable
visual percept is through predictive remapping of visual
receptive fields: just before a saccade, the receptive field
of many neurons moves from its current location ("current
receptive field") to the location it is expected to occupy
after the saccade ("future receptive field"). Goldberg and
colleagues found such remapping in cortical areas, e.g. in
the frontal eye field (FEF), as well as in the intermediate
layers of the superior colliculus (SC). In the present study
we investigated the source of the SC's remapped visual
signals. Do some of them come from the FEF? We identified
FEF neurons that project to the SC using antidromic
stimulation. For neurons with a visual response, we tested
whether the receptive field shifted just prior to making a
saccade. Saccadic amplitudes were chosen to be as small as
possible while clearly separating the current and future
receptive fields; they ranged from 5-30 deg. in amplitude
and were directed contraversively. The saccadic target was a
small red spot. We probed visual responsiveness at the
current and future receptive field locations using a white
spot flashed at various times before or after the saccade.
Predictive remapping was indicated by a visual response to a
probe flashed in the future receptive field just before the
saccade began. We found that many FEF neurons projecting to
the SC exhibited predictive remapping. Moreover, the
remapping was as fast and strong as any previously reported
for FEF or SC. It is clear, therefore, that remapped visual
signals are sent from FEF to SC, providing direct evidence
that the FEF is one source of the SC's remapped visual
signals. Because remapping requires information about an
imminent saccade, we hypothesize that remapping in FEF
depends on corollary discharge signals such as those
ascending from the SC through MD thalamus (Sommer and Wurtz
2002).},
Doi = {10.1167/3.9.146},
Key = {fds334840}
}
@article{fds334842,
Author = {Sommer, MA and Wurtz, RH},
Title = {A pathway in primate brain for internal monitoring of
movements.},
Journal = {Science (New York, N.Y.)},
Volume = {296},
Number = {5572},
Pages = {1480-1482},
Year = {2002},
Month = {May},
ISSN = {0036-8075},
url = {https://dl.dropbox.com/u/27738651/Publications/SommerWurtz2002.pdf},
Abstract = {It is essential to keep track of the movements we make, and
one way to do that is to monitor correlates, or corollary
discharges, of neuronal movement commands. We hypothesized
that a previously identified pathway from brainstem to
frontal cortex might carry corollary discharge signals. We
found that neuronal activity in this pathway encodes
upcoming eye movements and that inactivating the pathway
impairs sequential eye movements consistent with loss of
corollary discharge without affecting single eye movements.
These results identify a pathway in the brain of the primate
Macaca mulatta that conveys corollary discharge
signals.},
Doi = {10.1126/science.1069590},
Key = {fds334842}
}
@article{fds334845,
Author = {Sommer, MA and Wurtz, RH},
Title = {Frontal eye field sends delay activity related to movement,
memory, and vision to the superior colliculus.},
Journal = {Journal of neurophysiology},
Volume = {85},
Number = {4},
Pages = {1673-1685},
Year = {2001},
Month = {April},
url = {http://dx.doi.org/10.1152/jn.2001.85.4.1673},
Abstract = {Many neurons within prefrontal cortex exhibit a tonic
discharge between visual stimulation and motor response.
This delay activity may contribute to movement, memory, and
vision. We studied delay activity sent from the frontal eye
field (FEF) in prefrontal cortex to the superior colliculus
(SC). We evaluated whether this efferent delay activity was
related to movement, memory, or vision, to establish its
possible functions. Using antidromic stimulation, we
identified 66 FEF neurons projecting to the SC and we
recorded from them while monkeys performed a Go/Nogo task.
Early in every trial, a monkey was instructed as to whether
it would have to make a saccade (Go) or not (Nogo) to a
target location, which permitted identification of delay
activity related to movement. In half of the trials (memory
trials), the target disappeared, which permitted
identification of delay activity related to memory. In the
remaining trials (visual trials), the target remained
visible, which permitted identification of delay activity
related to vision. We found that 77% (51/66) of the FEF
output neurons had delay activity. In 53% (27/51) of these
neurons, delay activity was modulated by Go/Nogo
instructions. The modulation preceded saccades made into
only part of the visual field, indicating that the
modulation was movement-related. In some neurons, delay
activity was modulated by Go/Nogo instructions in both
memory and visual trials and seemed to represent where to
move in general. In other neurons, delay activity was
modulated by Go/Nogo instructions only in memory trials,
which suggested that it was a correlate of working memory,
or only in visual trials, which suggested that it was a
correlate of visual attention. In 47% (24/51) of FEF output
neurons, delay activity was unaffected by Go/Nogo
instructions, which indicated that the activity was related
to the visual stimulus. In some of these neurons, delay
activity occurred in both memory and visual trials and
seemed to represent a coordinate in visual space. In others,
delay activity occurred only in memory trials and seemed to
represent transient visual memory. In the remainder, delay
activity occurred only in visual trials and seemed to be a
tonic visual response. In conclusion, the FEF sends diverse
delay activity signals related to movement, memory, and
vision to the SC, where the signals may be used for saccade
generation. Downstream transmission of various delay
activity signals may be an important, general way in which
the prefrontal cortex contributes to the control of
movement.},
Doi = {10.1152/jn.2001.85.4.1673},
Key = {fds334845}
}
@article{fds334843,
Author = {Wurtz, RH and Sommer, MA and Paré, M and Ferraina,
S},
Title = {Signal transformations from cerebral cortex to superior
colliculus for the generation of saccades.},
Journal = {Vision research},
Volume = {41},
Number = {25-26},
Pages = {3399-3412},
Year = {2001},
Month = {January},
ISSN = {0042-6989},
url = {https://dl.dropbox.com/u/27738651/Publications/WurtzSommerPareFerraina2001.pdf},
Abstract = {The ability of primates to make rapid and accurate saccadic
eye movements for exploring the natural world is based on a
neuronal system in the brain that has been studied
extensively and is known to include multiple brain regions
extending throughout the neuraxis. We examined the
characteristics of signal flow in this system by recording
from identified output neurons of two cortical regions, the
lateral intraparietal area (LIP) and the frontal eye field
(FEF), and from neurons in a brainstem structure targeted by
these output neurons, the superior colliculus (SC). We
compared the activity of neurons in these three populations
while monkeys performed a delayed saccade task that allowed
us to quantify visual responses, motor activity, and
intervening delay activity. We examined whether delay
activity was related to visual stimulation by comparing the
activity during interleaved trials when a target was either
present or absent during the delay period. We examined
whether delay activity was related to movement by using a
Go/Nogo task and comparing the activity during interleaved
trials in which a saccade was either made (Go) or not
(Nogo). We found that LIP output neurons, FEF output
neurons, and SC neurons can all have visual responses, delay
activity, and presaccadic bursts; hence in this way they are
all quite similar. However, the delay activity tended to be
more related to visual stimulation in the cortical output
neurons than in the SC neurons. Complementing this, the
delay activity tended to be more related to movement in the
SC neurons than in the cortical output neurons. We conclude,
first, that the signal flow leaving the cortex represents
activity at nearly every stage of visuomotor transformation,
and second, that there is a gradual evolution of signal
processing as one proceeds from cortex to
colliculus.},
Doi = {10.1016/s0042-6989(01)00066-9},
Key = {fds334843}
}
@article{fds334844,
Author = {Sommer, M and Wurtz, R},
Title = {A subcortical source of visual input to the frontal eye
field},
Journal = {Journal of Vision},
Volume = {1},
Number = {3},
Pages = {259-259},
Publisher = {Association for Research in Vision and Ophthalmology
(ARVO)},
Year = {2001},
url = {http://dx.doi.org/10.1167/1.3.259},
Abstract = {Many neurons in the frontal eye field (FEF) exhibit visual
responses and are thought to play important roles in
visuosaccadic behavior. The FEF, however, is far removed
from striate cortex. Where do the FEF's visual signals come
from? Usually they are reasonably assumed to enter the FEF
through afferents from extrastriate cortex. Here we show
that, surprisingly, visual signals also enter the FEF
through a subcortical route: a disynaptic, ascending pathway
originating in the intermediate layers of the superior
colliculus (SC). We recorded from identified neurons at all
three stages of this pathway (n=30-40 in each sample): FEF
recipient neurons, orthodromically activated from the SC;
mediodorsal thalamus (MD) relay neurons, antidromically
activated from FEF and orthodromically activated from SC;
and SC source neurons, antidromically activated from MD. We
studied the neurons while monkeys performed delayed saccade
tasks designed to temporally resolve visual responses from
presaccadic discharges. We found, first, that most neurons
at every stage in the pathway had visual responses,
presaccadic bursts, or both. Second, we found marked
similarities between the SC source neurons and MD relay
neurons: in both samples, about 15% of the neurons had only
a visual response, 10% had only a presaccadic burst, and 75%
had both. In contrast, FEF recipient neurons tended to be
more visual in nature: 50% had only a visual response, none
had only a presaccadic burst, and 50% had both a visual
response and a presaccadic burst. This suggests that in
addition to their subcortical inputs, these FEF neurons also
receive other visual inputs, e.g. from extrastriate cortex.
We conclude that visual activity in the FEF results not only
from cortical afferents but also from subcortical inputs.
Intriguingly, this implies that some of the visual signals
in FEF are pre-processed by the SC.},
Doi = {10.1167/1.3.259},
Key = {fds334844}
}
@article{fds334849,
Author = {Port, NL and Sommer, MA and Wurtz, RH},
Title = {Multielectrode evidence for spreading activity across the
superior colliculus movement map.},
Journal = {Journal of neurophysiology},
Volume = {84},
Number = {1},
Pages = {344-357},
Year = {2000},
Month = {July},
url = {http://dx.doi.org/10.1152/jn.2000.84.1.344},
Abstract = {The monkey superior colliculus (SC) has maps for both visual
input and movement output in the superficial and
intermediate layers, respectively, and activity on these
maps is generally related to visual stimuli only in one part
of the visual field and/or to a restricted range of saccadic
eye movements to those stimuli. For some neurons within
these maps, however, activity has been reported to spread
from the caudal SC to the rostral SC during the course of a
saccade. This spread of activity was inferred from averages
of recordings at different sites on the SC movement map
during saccades of different amplitudes and even in
different monkeys. In the present experiments, SC activity
was recorded simultaneously in pairs of neurons to observe
the spread of activity during individual saccades. Two
electrodes were positioned along the rostral-caudal axis of
the SC with one being more caudal than the other, and 60
neuron pairs whose movement fields were large enough to see
a spread of activity were studied. During individual
saccades, the relative time of discharge of the two neurons
was compared using 1) the time difference between peak
discharge of the two neurons, 2) the difference between the
"median activation time" of the two neurons, and 3) the
shift required to align the two discharge patterns using
cross-correlation. All three analysis methods gave
comparable results. Many pairs of neurons were activated in
sequence during saccade generation, and the order of
activation was most frequently caudal to rostral. Such a
sequence of activation was not observed in every neuron
pair, but over the sample of neuron pairs studied, the
spread was statistically significant. When we compared the
time of neuronal activity to the time of saccade onset, we
found that the caudal neuronal activity was more likely to
be before the saccade, whereas the rostral neuronal activity
was more likely to be during the saccade. These results
demonstrate that when individual pairs of neurons are
examined during single saccades there is evidence of a
caudal to rostral spread of activity within the monkey SC,
and they confirm the previous inferences of a spread of
activity drawn from observations on averaged neuronal
activity during multiple saccades. The functional
contribution of this spread of activity remains to be
determined.},
Doi = {10.1152/jn.2000.84.1.344},
Key = {fds334849}
}
@article{Tehovnik2000,
Author = {Tehovnik, EJ and Sommer, MA and Chou, IH and Slocum, WM and Schiller,
PH},
Title = {Eye fields in the frontal lobes of primates.},
Journal = {Brain research. Brain research reviews},
Volume = {32},
Number = {2-3},
Pages = {413-448},
Year = {2000},
Month = {April},
ISSN = {0165-0173},
url = {https://dl.dropbox.com/u/27738651/Publications/TehovnikEtAl-2000_EyeFieldsInFrontalCortex-Review.pdf},
Abstract = {Two eye fields have been identified in the frontal lobes of
primates: one is situated dorsomedially within the frontal
cortex and will be referred to as the eye field within the
dorsomedial frontal cortex (DMFC); the other resides
dorsolaterally within the frontal cortex and is commonly
referred to as the frontal eye field (FEF). This review
documents the similarities and differences between these eye
fields. Although the DMFC and FEF are both active during the
execution of saccadic and smooth pursuit eye movements, the
FEF is more dedicated to these functions. Lesions of DMFC
minimally affect the production of most types of saccadic
eye movements and have no effect on the execution of smooth
pursuit eye movements. In contrast, lesions of the FEF
produce deficits in generating saccades to briefly presented
targets, in the production of saccades to two or more
sequentially presented targets, in the selection of
simultaneously presented targets, and in the execution of
smooth pursuit eye movements. For the most part, these
deficits are prevalent in both monkeys and humans.
Single-unit recording experiments have shown that the DMFC
contains neurons that mediate both limb and eye movements,
whereas the FEF seems to be involved in the execution of eye
movements only. Imaging experiments conducted on humans have
corroborated these findings. A feature that distinguishes
the DMFC from the FEF is that the DMFC contains a
somatotopic map with eyes represented rostrally and
hindlimbs represented caudally; the FEF has no such
topography. Furthermore, experiments have revealed that the
DMFC tends to contain a craniotopic (i.e., head-centered)
code for the execution of saccadic eye movements, whereas
the FEF contains a retinotopic (i.e., eye-centered) code for
the elicitation of saccades. Imaging and unit recording data
suggest that the DMFC is more involved in the learning of
new tasks than is the FEF. Also with continued training on
behavioural tasks the responsivity of the DMFC tends to
drop. Accordingly, the DMFC is more involved in learning
operations whereas the FEF is more specialized for the
execution of saccadic and smooth pursuit eye
movements.},
Doi = {10.1016/s0165-0173(99)00092-2},
Key = {Tehovnik2000}
}
@article{fds334848,
Author = {Sommer, MA and Wurtz, RH},
Title = {Composition and topographic organization of signals sent
from the frontal eye field to the superior
colliculus.},
Journal = {Journal of neurophysiology},
Volume = {83},
Number = {4},
Pages = {1979-2001},
Year = {2000},
Month = {April},
url = {http://dx.doi.org/10.1152/jn.2000.83.4.1979},
Abstract = {The frontal eye field (FEF) and superior colliculus (SC)
contribute to saccadic eye movement generation, and much of
the FEF's oculomotor influence may be mediated through the
SC. The present study examined the composition and
topographic organization of signals flowing from FEF to SC
by recording from FEF neurons that were antidromically
activated from rostral or caudal SC. The first and most
general result was that, in a sample of 88 corticotectal
neurons, the types of signals relayed from FEF to SC were
highly diverse, reflecting the general population of signals
within FEF rather than any specific subset of signals.
Second, many neurons projecting from FEF to SC carried
signals thought to reflect cognitive operations, namely
tonic discharges during the delay period of a
delayed-saccade task (delay signals), elevated discharges
during the gap period of a gap task (gap increase signals),
or both. Third, FEF neurons discharging during fixation were
found to project to the SC, although they did not project
preferentially to rostral SC, where similar fixation neurons
are found. Neurons that did project preferentially to the
rostral SC were those with foveal visual responses and those
pausing during the gap period of the gap task. Many of the
latter neurons also had foveal visual responses, presaccadic
pauses in activity, and postsaccadic increases in activity.
These two types of rostral-projecting neurons therefore may
contribute to the activity of rostral SC fixation neurons.
Fourth, conduction velocity was used as an indicator of cell
size to correct for sampling bias. The outcome of this
correction procedure suggested that among the most prevalent
neurons in the FEF corticotectal population are those
carrying putative cognitive-related signals, i.e., delay and
gap increase signals, and among the least prevalent are
those carrying presaccadic burst discharges but lacking
peripheral visual responses. Fifth, corticotectal neurons
carrying various signals were biased topographically across
the FEF. Neurons with peripheral visual responses but
lacking presaccadic burst discharges were biased laterally,
neurons with presaccadic burst discharges but lacking
peripheral visual responses were biased medially, and
neurons carrying delay or gap increase signals were biased
dorsally. Finally, corticotectal neurons were distributed
within the FEF as a function of their visual or movement
field eccentricity and projected to the SC such that
eccentricity maps in both structures were closely aligned.
We conclude that the FEF most likely influences the activity
of SC neurons continuously from the start of fixation,
through visual analysis and cognitive manipulations, until a
saccade is generated and fixation begins anew. Furthermore,
the projection from FEF to SC is highly topographically
organized in terms of function at both its source and its
termination.},
Doi = {10.1152/jn.2000.83.4.1979},
Key = {fds334848}
}
@article{Sommer1999,
Author = {Sommer, MA and Tehovnik, EJ},
Title = {Reversible inactivation of macaque dorsomedial frontal
cortex: effects on saccades and fixations.},
Journal = {Experimental brain research},
Volume = {124},
Number = {4},
Pages = {429-446},
Year = {1999},
Month = {February},
ISSN = {0014-4819},
url = {https://dl.dropbox.com/u/27738651/Publications/SommerTehovnik1999-DMFCinactivation.pdf},
Abstract = {Neural recording and electrical stimulation results suggest
that the dorsomedial frontal cortex (DMFC) of macaque is
involved in oculomotor behavior. We reversibly inactivated
the DMFC using lidocaine and examined how saccadic eye
movements and fixations were affected. The inactivation
methods and monkeys were the same as those used in a
previous study of the frontal eye field (FEF), another
frontal oculomotor region. In the first stage of the present
study, monkeys performed tasks that required the generation
of single saccades and fixations. During 15 DMFC
inactivations, we found only mild, infrequent deficits. This
contrasts with our prior finding that FEF inactivation
causes severe, reliable deficits in performance of these
tasks. In the second stage of the study, we investigated
whether DMFC inactivation affected behavior when a monkey
was required to make more than one saccade and fixation. We
used a double-step task: two targets were flashed in rapid
succession and the monkey had to make two saccades to
foveate the target locations. In each of five experiments,
DMFC inactivation caused a moderate, significant deficit.
Both ipsi- and contraversive saccades were disrupted. In two
experiments, the first saccades were made to the wrong place
and had increased latencies. In one experiment, first
saccades were unaffected, but second saccades were made to
the wrong place and had increased latencies. In the
remaining two experiments, specific reasons for the deficit
were not detected. Saline infusions into DMFC had no effect.
Inactivation of FEF caused a larger double-step deficit than
did inactivation of DMFC. The FEF inactivation impaired
contraversive first or second saccades of the sequence. In
conclusion, our results suggest that the DMFC makes an
important contribution to generating sequential saccades and
fixations but not single saccades and fixations. Compared
with the FEF, the DMFC has a weaker, less directional, more
task-dependent oculomotor influence.},
Doi = {10.1007/s002210050639},
Key = {Sommer1999}
}
@article{Chou1999,
Author = {Chou, IH and Sommer, MA and Schiller, PH},
Title = {Express averaging saccades in monkeys.},
Journal = {Vision research},
Volume = {39},
Number = {25},
Pages = {4200-4216},
Year = {1999},
Month = {January},
ISSN = {0042-6989},
url = {https://dl.dropbox.com/u/27738651/Publications/ChouEtAl1999-ExpressAveragingSaccades.pdf},
Abstract = {When monkeys are presented simultaneously with multiple
stimuli, they can make one of two types of response. Either
they make averaging saccades, that land at intermediate
locations between the targets, or target-directed saccades,
that land close to one of the targets. The two types of
saccades occur at different latencies and are thought to
reflect different processes; fast reflexive averaging and
slower target selection. We investigated the latency of
averaging saccades in five monkeys, with particular emphasis
on 'express' latency saccades, which are thought to be
inhibited by target selection. Express averaging saccades
were made prolifically by the two monkeys that made both
express and regular latency saccades, but only when no
specific instruction was given regarding the saccade target.
When these monkeys had to choose one of the targets, on the
basis of its color, they still made averaging saccades.
However, the endpoints formed two distributions close to the
targets as opposed to one single distribution centered
between the targets, as was the case when targets were
identical; also, express saccades were almost entirely
absent. We conclude that express averaging saccades are a
form of spatial and temporal optimization of gaze
shifting.},
Doi = {10.1016/s0042-6989(99)00133-9},
Key = {Chou1999}
}
@article{fds334853,
Author = {Sommer, MA and Wurtz, RH},
Title = {Frontal eye field neurons orthodromically activated from the
superior colliculus.},
Journal = {Journal of neurophysiology},
Volume = {80},
Number = {6},
Pages = {3331-3335},
Year = {1998},
Month = {December},
url = {http://dx.doi.org/10.1152/jn.1998.80.6.3331},
Abstract = {Frontal eye field neurons orthodromically activated from the
superior colliculus. J. Neurophysiol. 80: 3331-3333, 1998.
Anatomical studies have shown that the frontal eye field
(FEF) and superior colliculus (SC) of monkeys are
reciprocally connected, and a physiological study described
the signals sent from the FEF to the SC. Nothing is known,
however, about the signals sent from the SC to the FEF. We
physiologically identified and characterized FEF neurons
that are likely to receive input from the SC. Fifty-two FEF
neurons were found that were orthodromically activated by
electrical stimulation of the intermediate or deeper layers
of the SC. All the neurons that we tested (n = 34)
discharged in response to visual stimulation. One-half also
discharged when saccadic eye movements were made. This
provides the first direct evidence that the ascending
pathway from SC to FEF might carry visual- and
saccade-related signals. Our findings support a hypothesis
that the SC and the FEF interact bidirectionally during the
events leading up to saccade generation.},
Doi = {10.1152/jn.1998.80.6.3331},
Key = {fds334853}
}
@article{fds334852,
Author = {Nichols, AM and Ruffner, TW and Sommer, MA and Wurtz,
RH},
Title = {A screw microdrive for adjustable chronic unit recording in
monkeys.},
Journal = {Journal of neuroscience methods},
Volume = {81},
Number = {1-2},
Pages = {185-188},
Year = {1998},
Month = {June},
ISSN = {0165-0270},
url = {https://dl.dropbox.com/u/27738651/Publications/NicholsRuffnerSommerWurtz_JNeuroscienceMethods1998.pdf},
Abstract = {A screw microdrive is described that attaches to the grid
system used for recording single neurons from brains of
awake behaving monkeys. Multiple screwdrives can be mounted
on a grid over a single cranial opening. This method allows
many electrodes to be implanted chronically in the brain and
adjusted as needed to maintain isolation. rights
reserved.},
Doi = {10.1016/s0165-0270(98)00036-3},
Key = {fds334852}
}
@article{Tehovnik1997a,
Author = {Tehovnik, EJ and Sommer, MA},
Title = {Electrically evoked saccades from the dorsomedial frontal
cortex and frontal eye fields: a parametric evaluation
reveals differences between areas.},
Journal = {Experimental brain research},
Volume = {117},
Number = {3},
Pages = {369-378},
Year = {1997},
Month = {December},
ISSN = {0014-4819},
url = {https://dl.dropbox.com/u/27738651/Publications/TehovnikSommer1997.pdf},
Abstract = {Using electrical stimulation to evoke saccades from the
dorsomedial frontal cortex (DMFC) and frontal eye fields
(FEF) of rhesus monkeys, parametric tests were conducted to
compare the excitability properties of these regions. Pulse
frequency and pulse current, pulse frequency and train
duration, and pulse current and pulse duration were varied
to determine threshold functions for a 50% probability of
evoking a saccade. Also a wide range of frequencies were
tested to evoke saccades, while holding all other parameters
constant. For frequencies beyond 150 Hz, the probability of
evoking saccades decreased for the DMFC, whereas for the FEF
this probability remained at 100%. To evoke saccades readily
from the DMFC, train durations of greater than 200 ms were
needed; for the FEF, durations of less than 100 ms were
sufficient. Even though the chronaxies of neurons residing
in the DMFC and FEF were similar (ranging from 0.1 to 0.24
ms) significantly higher currents were required to evoke
saccades from the DMFC than FEF. Thus the stimulation
parameters that are optimal for evoking saccades from the
DMFC differ from those that are optimal for evoking saccades
from the FEF. Although the excitability of neurons in the
DMFC and FEF are similar (due to similar chronaxies), we
suggest that the density of saccade-relevant neurons is
higher in the FEF than in the DMFC.},
Doi = {10.1007/s002210050231},
Key = {Tehovnik1997a}
}
@article{Sommer1997b,
Author = {Sommer, MA},
Title = {The spatial relationship between scanning saccades and
express saccades.},
Journal = {Vision research},
Volume = {37},
Number = {19},
Pages = {2745-2756},
Year = {1997},
Month = {October},
ISSN = {0042-6989},
url = {https://dl.dropbox.com/u/27738651/Publications/Sommer1997-ScanningAndExpressSaccades.pdf},
Abstract = {When monkeys interrupt their saccadic scanning of a visual
scene to look at a suddenly appearing target, saccades to
the target are made after an "express" latency or after a
longer "regular" latency. The purpose of this study was to
analyze the spatial patterns of scanning, express, and
regular saccades. Scanning patterns were spatially biased.
Express saccade patterns were biased, too, and were directly
correlated with scanning patterns. Regular saccade patterns
were more uniform and were not directly correlated with
scanning patterns. Express saccades, but not regular
saccades, seemed to be facilitated by preparation to scan.
This study contributes to a general understanding of how
monkeys examine scenes containing both unchanging and
suddenly appearing stimuli.},
Doi = {10.1016/s0042-6989(97)00078-3},
Key = {Sommer1997b}
}
@article{Sommer1997a,
Author = {Sommer, MA and Tehovnik, EJ},
Title = {Reversible inactivation of macaque frontal eye
field.},
Journal = {Experimental brain research},
Volume = {116},
Number = {2},
Pages = {229-249},
Year = {1997},
Month = {September},
ISSN = {0014-4819},
url = {https://dl.dropbox.com/u/27738651/Publications/SommerTehovnik1997.pdf},
Abstract = {The macaque frontal eye field (FEF) is involved in the
generation of saccadic eye movements and fixations. To
better understand the role of the FEF, we reversibly
inactivated a portion of it while a monkey made saccades and
fixations in response to visual stimuli. Lidocaine was
infused into a FEF and neural inactivation was monitored
with a nearby microelectrode. We used two saccadic tasks. In
the delay task, a target was presented and then
extinguished, but the monkey was not allowed to make a
saccade to its location until a cue to move was given. In
the step task, the monkey was allowed to look at a target as
soon as it appeared. During FEF inactivation, monkeys were
severely impaired at making saccades to locations of
extinguished contralateral targets in the delay task. They
were similarly impaired at making saccades to locations of
contralateral targets in the step task if the target was
flashed for < or =100 ms, such that it was gone before the
saccade was initiated. Deficits included increases in
saccadic latency, increases in saccadic error, and increases
in the frequency of trials in which a saccade was not made.
We varied the initial fixation location and found that the
impairment specifically affected contraversive saccades
rather than affecting all saccades made into head-centered
contralateral space. Monkeys were impaired only slightly at
making saccades to contralateral targets in the step task if
the target duration was 1000 ms, such that the target was
present during the saccade: latency increased, but increases
in saccadic error were mild and increases in the frequency
of trials in which a saccade was not made were
insignificant. During FEF inactivation there usually was a
direct correlation between the latency and the error of
saccades made in response to contralateral targets. In the
delay task, FEF inactivation increased the frequency of
making premature saccades to ipsilateral targets. FEF
inactivation had inconsistent and mild effects on saccadic
peak velocity. FEF inactivation caused impairments in the
ability to fixate lights steadily in contralateral space.
FEF inactivation always caused an ipsiversive deviation of
the eyes in darkness. In summary, our results suggest that
the FEF plays major roles in (1) generating contraversive
saccades to locations of extinguished or flashed targets,
(2) maintaining contralateral fixations, and (3) suppressing
inappropriate ipsiversive saccades.},
Doi = {10.1007/pl00005752},
Key = {Sommer1997a}
}
@article{Tehovnik1997b,
Author = {Tehovnik, EJ and Sommer, MA},
Title = {Effective spread and timecourse of neural inactivation
caused by lidocaine injection in monkey cerebral
cortex.},
Journal = {Journal of neuroscience methods},
Volume = {74},
Number = {1},
Pages = {17-26},
Year = {1997},
Month = {June},
ISSN = {0165-0270},
url = {https://dl.dropbox.com/u/27738651/Publications/TehovnikSommer1997-LidocaineInactivation.pdf},
Abstract = {We studied the effective spread of lidocaine to inactivate
neural tissue in the frontal cortex of the rhesus monkey.
Injections of 2% lidocaine at 4 microl/min were made while
units were recorded 1 or 2 mm away. To inactivate units 1 mm
away from the injection site 100% of the time, 7 microl of
lidocaine had to be injected. To inactivate units 2 mm away
from the injection site 100% of the time, 30 microl of
lidocaine were required. Units were maximally inactivated
around 8 min after the start of a lidocaine injection, and
they gradually recovered, regaining most of their initial
activity by around 30 min after the start of an injection.
The volume of lidocaine required to inactivate neurons > 90%
of the time could be estimated by the spherical volume
equation, V = 4/3 pi (r)3. To prolong the inactivation, a
slower infusion of lidocaine subsequent to an initial bolus
was effective. Saline control injections had no effect.
These results allow both a prediction of the timecourse of
neural inactivation and an estimate of the spread of neural
inactivation following injection of lidocaine into the
monkey cerebral cortex.},
Doi = {10.1016/s0165-0270(97)02229-2},
Key = {Tehovnik1997b}
}
@article{Tehovnik1996,
Author = {Tehovnik, EJ and Sommer, MA},
Title = {Compensatory saccades made to remembered targets following
orbital displacement by electrically stimulating the
dorsomedial frontal cortex or frontal eye fields of
primates.},
Journal = {Brain research},
Volume = {727},
Number = {1-2},
Pages = {221-224},
Year = {1996},
Month = {July},
ISSN = {0006-8993},
url = {https://dl.dropbox.com/u/27738651/Publications/TehovnikSommer1996.pdf},
Abstract = {If the eye-position signal during visually-evoked saccades
is dependent on the dorsomedial frontal cortex (DMFC), one
would expect that saccades generated to briefly presented
visual targets would be disrupted after displacement of the
eyes via electrical stimulation of this cortical area.
Compared are compensatory saccades evoked to brief targets
following stimulation of the DMFC and frontal eye fields
(FEF). Compensatory saccades produced to brief targets
following perturbation via the DMFC were not affected.
Accordingly, electrical stimulation of the DMFC does not
disrupt the eye-position signal during the execution of
visually-evoked saccades.},
Doi = {10.1016/0006-8993(96)00475-1},
Key = {Tehovnik1996}
}
@article{SOMMER1994,
Author = {Sommer, MA},
Title = {Express saccades elicited during visual scan in the
monkey.},
Journal = {Vision research},
Volume = {34},
Number = {15},
Pages = {2023-2038},
Year = {1994},
Month = {August},
ISSN = {0042-6989},
url = {https://dl.dropbox.com/u/27738651/Publications/Sommer1994.pdf},
Abstract = {Monkeys trained to saccade to visual targets can develop
separate "express" and "regular" modes in their distribution
of saccadic latencies. The purpose of this study was to
determine whether this occurs under more natural viewing
conditions, when targets are suddenly presented in a
structured visual field during visual scan. It was found
that scanning saccades stopped appearing 60 msec after a
target's onset, and subsequent saccades, which were directed
toward the suddenly appearing target, had a bimodal
distribution of latencies. Express saccades were more likely
to occur as the target was presented later in a fixation.
Regular mode saccades were more likely to occur with longer
target durations. Scanning saccades made to stimuli of the
structured visual field always had unimodal inter-saccadic
interval distributions. All these effects were apparent
after only 2-3 days of training. These findings, taken
together with recent physiological results, suggest that the
visuomotor cells of the superior colliculus mediate latency
bimodality.},
Doi = {10.1016/0042-6989(94)90030-2},
Key = {SOMMER1994}
}
@article{RICHARDS1994,
Author = {Richards, W and Wilson, HR and Sommer, MA},
Title = {Chaos in percepts?},
Journal = {Biological cybernetics},
Volume = {70},
Number = {4},
Pages = {345-349},
Year = {1994},
Month = {January},
ISSN = {0340-1200},
url = {https://dl.dropbox.com/u/27738651/Publications/RichardsWilsonSommer1994_BiologicalCybernetics.pdf},
Abstract = {Multistability in perceptual tasks has suggested that the
mechanisms underlying our percepts might be modeled as
nonlinear, deterministic systems that exhibit chaotic
behavior. We present evidence supporting this view,
obtaining an estimate of 3.5 for the dimensionality of such
a system. A surprising result is that this estimate applies
for a rather diverse range of perceptual
tasks.},
Doi = {10.1007/bf00200331},
Key = {RICHARDS1994}
}
@article{fds334862,
Author = {Sommer, MA and Schiller, PH and McPeek, RM},
Title = {What neural pathways mediate express saccades?},
Journal = {Behavioral and Brain Sciences},
Volume = {16},
Number = {3},
Pages = {589-590},
Publisher = {Cambridge University Press (CUP): STM Journals},
Year = {1993},
Month = {September},
url = {http://dx.doi.org/10.1017/S0140525X00031824},
Doi = {10.1017/S0140525X00031824},
Key = {fds334862}
}
@article{fds334863,
Author = {Sommer, MA and Forno, LS and Smith, ME},
Title = {EAE cerebrospinal fluid augments in vitro phagocytosis and
metabolism of CNS myelin by macrophages.},
Journal = {Journal of neuroscience research},
Volume = {32},
Number = {3},
Pages = {384-394},
Year = {1992},
Month = {July},
ISSN = {1097-4547},
url = {https://dl.dropbox.com/u/27738651/Publications/SommerFornoSmith_JNeurosciRes1992.pdf},
Abstract = {Previous studies from this laboratory have shown that CNS
myelin is phagocytized and metabolized by cultured rat
macrophages to a much larger extent when myelin is
pretreated with serum containing antibodies to myelin
constituents than when it is left untreated or pretreated
with non-specific serum. In this study the effect of
cerebrospinal fluid (CSF) from rabbits with experimental
allergic encephalomyelitis (EAE) in promoting myelin
phagocytosis was examined. Fourteen rabbits were immunized
with purified myelin in Freund's complete adjuvant, seven of
which developed clinical EAE symptoms. Serum and CSF were
collected from EAE and control rabbits, and the CSF was
centrifuged to remove cells. Sera and CSF from these rabbits
and from Freund's adjuvant-immunized controls and untreated
controls were measured for IgG content by radial diffusion
assay, their myelin antibody characteristics were analyzed
by immunoblots, and the ability of these serum and CSF
samples to promote myelin phagocytosis when used for myelin
opsonization was examined. The ability of a CSF sample to
enhance radioactive myelin uptake and phagocytosis by
cultured macrophages as measured by the appearance of
radioactive cholesterol ester was linearly proportional to
its total IgG titer, and correlated approximately both with
clinical symptoms of the animal and the presence of antibody
against the myelin constituents myelin basic protein,
proteolipid protein, and galactocerebroside. The cholesterol
esterification activities of EAE sera correlated to a lesser
extent with IgG levels and clinical symptoms.(ABSTRACT
TRUNCATED AT 250 WORDS)},
Doi = {10.1002/jnr.490320310},
Key = {fds334863}
}
@article{fds334864,
Author = {Smith, ME and Sommer, MA},
Title = {Association between cell-mediated demyelination and
astrocyte stimulation.},
Journal = {Progress in brain research},
Volume = {94},
Pages = {411-422},
Year = {1992},
Month = {January},
url = {http://dx.doi.org/10.1016/s0079-6123(08)61768-9},
Doi = {10.1016/s0079-6123(08)61768-9},
Key = {fds334864}
}
@article{fds334866,
Author = {Sadler, RH and Sommer, MA and Forno, LS and Smith,
ME},
Title = {Induction of anti-myelin antibodies in EAE and their
possible role in demyelination.},
Journal = {Journal of neuroscience research},
Volume = {30},
Number = {4},
Pages = {616-624},
Year = {1991},
Month = {December},
ISSN = {1097-4547},
url = {https://dl.dropbox.com/u/27738651/Publications/SadlerSommerFornoSmith_JNeurosciRes1991.pdf},
Abstract = {Experimental allergic encephalomyelitis is characterized by
invasion of lymphocytes and macrophages into the central
nervous system resulting in inflammation, edema, and
demyelination. Sera from Lewis rats from 7-95 days after
immunization with purified guinea pig CNS myelin were
examined with respect to their ability to opsonize myelin.
This was correlated with the appearance of antibody
components and the relative amounts of antibody to myelin
basic protein (MBP) and proteolipid protein (PLP). Sera from
rats 10-95 days after immunization preincubated with
purified myelin induced phagocytosis of myelin by cultured
macrophages with the resulting production of cholesterol
ester. This opsonization activity as measured by the
percentage of cholesterol esterified reached a peak at 26-27
days after immunization but remained significantly elevated
up to 95 days post-immunization compared to the activity of
serum from the Freund's adjuvant-injected controls.
Immunoblots of the sera revealed a gradual increase in
antibody activity against myelin components. ELISA assays
for MBP and PLP antibody showed a similar pattern. Antibody
to galactocerebroside (GC) was not detected by immunostains
nor by the ELISA assay. Areas of demyelination were observed
histologically by luxol-fast blue stained spinal cords up to
60 days post-immunization. These results indicate that
antibodies to myelin protein when given access to myelin
through or within the blood brain barrier could initiate or
enhance the phagocytic response by peripheral or resident
macrophages.},
Doi = {10.1002/jnr.490300404},
Key = {fds334866}
}
@article{fds334865,
Author = {Hrushesky, WJ and Fader, DJ and Berestka, JS and Sommer, M and Hayes, J and Cope, FO},
Title = {Diminishment of respiratory sinus arrhythmia foreshadows
doxorubicin-induced cardiomyopathy.},
Journal = {Circulation},
Volume = {84},
Number = {2},
Pages = {697-707},
Year = {1991},
Month = {August},
ISSN = {00097322},
url = {https://dl.dropbox.com/u/27738651/Publications/HrusheskyFaderBerestkaSommerHayesCope_Circulation1991.pdf},
Abstract = {<h4>Background</h4>The development of a microcomputer-based
device permits quick, simple, and noninvasive quantification
of the respiratory sinus arrhythmia (RSA) during quiet
breathing.<h4>Methods and results</h4>We prospectively and
serially measured the radionuclide left ventricular ejection
fraction and the RSA amplitude in 34 cancer patients
receiving up to nine monthly bolus treatments with
doxorubicin hydrochloride (60 mg/m2). Of the eight patients
who ultimately developed symptomatic doxorubicin-induced
congestive heart failure, seven (87.5%) demonstrated a
significant decline in RSA amplitude; five of 26 subjects
without clinical symptoms of cardiotoxicity (19.2%) showed a
similar RSA amplitude decline. On average, significant RSA
amplitude decline occurred 3 months before the last planned
doxorubicin dose in patients destined to develop clinical
congestive heart failure.<h4>Conclusion</h4>Overall, RSA
amplitude abnormality proved to be a more specific predictor
of clinically significant congestive heart failure than did
serial resting radionuclide ejection fractions.},
Doi = {10.1161/01.cir.84.2.697},
Key = {fds334865}
}
@article{fds334867,
Author = {Sommer Marc and A and Berestka John and B},
Title = {RSA -- Respiratory Sinus Arrhythmia: A new measure of
cardiac health},
Journal = {Medical Electronics},
Pages = {112-114},
Year = {1987},
Month = {April},
ISSN = {0149-9734},
url = {https://dl.dropbox.com/u/27738651/Publications/SommerBerestka_MedElectronics1987.pdf},
Key = {fds334867}
}
| |
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