Reaction times for hand movements made in response to visual versus vibratory cues.

Reaction times were determined for monkeys and humans who made wrist flexion and extension movements in response to vibratory and visual cues. Humans initiated movements approximately 50 msec sooner in response to vibratory as compared to visual cues. For monkeys, this difference was approximately 100 msec. Mean daily reaction times for monkeys and humans improved with practice until they reached a steady level of performance. Increased differences between vibratory and visual reaction times were weakly correlated with increased age of humans. The increase in the differences appeared to result from decreased reaction times by older subjects for vibratory-cued movements; reaction times for visually cued movements did not consistently vary across the age range of subjects tested (19-36 years). The results obtained using this novel paradigm suggest that it may be a useful tool for simultaneously testing behavioral performance or neurological function during somatosensorimotor and visuomotor tasks.