[Movement-related potentials associated with motor inhibition during different types of stop signal paradigm in humans].

The motor inhibition process was examined in humans by monitoring reaction times, electromiograms, and movement-related potentials. Four subjects performed two types of visual stop signal paradigm. In one type, they were required to push a button (GO) or not to push it (NOGO), in another type, to release the button (GO) or to keep pushing it (NOGO). The results were summarized as follows; (1) The EEG waveform pattern was remarkably consistent among subjects. NO-GO-specific negative-positive potentials were observed under both tasks without significant background EMG activity changes in agonist and antagonist muscles. (2) The timing of the onset and the peak latency of the negative potential relative to the second stimulus, S 2, were constant (about 180-200 ms and 230-250 ms for each) in both tasks. The time interval between the initial onset of the negative potential and its peak latency was also constant (about 50 ms) in both tasks. The amplitude of the negative potentials was maximum at FCz (supposed to be around supplementary motor area) and their distribution was invariant among tasks. Constant features of NO-GO-specific potentials during both task performance suggested the temporally and spatially same inhibition process might specifically suppress the new motor program regardless of the existence of ongoing motor program.