Motor performance and sensory-evoked potentials

Abstract

Averaged evoked potentials (EP) to tones were determined for fifteen subjects in three tasks which were designed to evaluate the effects of motor response, of withholding a response and of different response latencies. With the influence of eye movement minimized, it was found that the various deflections of the sensory EPs were affected differently as follows: 1. 1. Withholding a response produced a significantly larger P 3 deflection. The amplitude of this deflection was negatively correlated with reaction time (RT). 2. 2. Stimuli to which overt motor responses were subsequently made produced a negative shift in deflections N 1, P 2 and N 2, but there were no significant changes in deflections P 1, P 3 and N 3. 3. 3. No effects which could be ascribed to specific time characteristics of the tasks ( e.g., simple versus choice RT) were found and no effects could be attributed to the overt motor response or its immediately preceding EMG activity. The data were interpreted to mean that the negative shift in N 1, P 2 and N 2 is related to the development of an excitatory state associated with the intention to respond to the stimulus and that increased positivity in P 3 is uniquely related to the act of withholding a response to the stimulus when rapid action is required. No effects on the averaged EP were observed that could be attributed unequivocally to occurrence of overt motor response itself.