Publications [#70612] of Ruey-Kuang Cheng

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1. Meck, W.H., Scott, A.C., Williams, C.L., & *Cheng, R.K. (November 6, 2007). Effects of prenatal choline supplementation on modality differences in timing and temporal memory as a function of age. (Poster presentation given at the 37th annual meeting of the Society for Neuroscience, San Diego, CA.).
   (last updated on 2008/06/18)

   Abstract:
   Timing and time perception for durations in the seconds-to-minutes range is influenced by attention and memory, both of which change over the lifespan. In the current study young (6 mo - n=15) and old (20 mo - n=12) male Sprague Dawley rats were trained on a duration bisection procedure using auditory and visual stimuli. Half of the older rats were exposed during embryonic days 12-17 to choline sufficiency/control (CON: 7.9 mmol/kg choline chloride) and the remaining older rats were exposed to choline supplementation (SUP: 35.6 mmol/kg choline chloride) through the pregnant dam’s drinking water. Rats were first trained to classify “short” (2 s) and “long” (8 s) standard durations of an auditory (white noise) or a visual (house light) signal presented in random order with equal probability during the same session by pressing either the left (2 s) or the right (8 s) lever for food reinforcement. In order to obtain a psychophysical function relating signal duration to the probability of a “long” response rats were later tested with a range of 5 log-spaced intermediate durations for which left or right response classifications were unreinforced. Following steady-state performance the intensity of the auditory and visual signals were varied from “low” to “high” in a counter-balanced design in blocks of 5 sessions in order to observe the interactions among the classification of the signal durations as a function of the auditory/visual intensity combinations (e.g., Low-Noise/High-Light; High-Noise/High-Light; High-Noise/Low-Light; Low-Noise/Low-Light). All groups reproduced the classic finding that “sounds are judged longer than lights”, but this effect was greater for the older rats than for the young rats. Psychophysical functions were analyzed using the Sample Known Exactly-Mixed Memory quantitative bisection model of Scalar Timing Theory. Results indicate that the relative difference in clock speed between auditory and visual signals increases with age and that 20-mo old CON rats show an exaggerated tendency to judge visual signals as “short” and are less affected by the differences in auditory/visual stimulus intensities than the 20-mo old SUP rats. These findings support suggestions that prenatal choline supplementation is able to protect the representations of visual stimuli relative to auditory stimuli in long-term memory as a function of age.