A longitudinal study of reaction time performance in Long-Evans rats.

This study was undertaken to examine individual differences in the progression of age-related decline on a measure of sensorimotor function. Twenty-one adult rats were trained on a simple reaction time (RT) task and assessed every 6 weeks from 14.5 to 25 months of age. An overall slowing of RT latencies associated with chronological age was observed. However, some rats maintained a stable performance with age while others slowed considerably. Another measure within the RT task, accuracy of performance, appeared to represent a stable individual characteristic that was insensitive to the effects of age. However, no measure of performance on the RT task at 14.5 months of age predicted later impairment in RT latency. At the completion of longitudinal testing, spatial learning in the Morris water maze was assessed in these aged rats along with a young comparison group. The aged rats were impaired relative to young controls in locating the escape platform. Measures of cognitive function and sensorimotor function within the spatial task were, however, unrelated to slowing of RT latency.