MOVEMENT-RELATED POTENTIALS ASSOCIATED WITH MOTOR INHIBITION AS DETERMINED BY USE OF A STOP SIGNAL PARADIGM IN HUMANS

The motor inhibition process was examined in humans by monitoring reaction times, electromyograms, and movement-related potentials. Four subjects performed a simple visual Stop Signal Paradigm. The results were as follows. (1) The EEG waveform pattern was remarkably consistent among subjects. NO-GO-specific negative-positive potentials were observed under all experimental conditions. (2) The timing of the onset and the peak latency of the negative potential relative to the second stimulus, S2, were constant (about 200-210 ms and 250-260 ms for each) regardless of changes in the S2 delay. The time interval between the initial onset of the negative potential and its peak latency was constant (about 50 ms). (3) By contrast, the peak-to-peak time between the negative potential and the positive potential became smaller as the S2 delay was increased. It is suggested, therefore, that the motor inhibition process might consist of different sub-processes and that some part of the inhibition process might be of constant and specific duration.