Cognitive motor control in human pre-supplementary motor area studied by subdural recording of discrimination/selection-related potentials

To clarify the functional role of human pre-supplementary motor area (pre-S MA) in 'cognitive' motor control as compared with other non-primary motor c ortices (SMA-proper and lateral premotor areas) and prefrontal area, we rec orded epicortical field potentials by using subdural electrodes in five epi leptic patients during presurgical evaluation, whose pre-SMA, SMA-proper, p refrontal and lateral premotor areas were defined by electric cortical stim ulation and recent anatomical orientations according to the bicommissural p lane and callosal grid system. An S1-Go/NoGo choice and delayed reaction ta sk (S1-choice paradigm) and a warned choice Go/NoGo reaction task (S2-choic e paradigm) with inter-stimulus intervals of 2 s were employed. The results showed (i) transient potentials with onset and peak latencies of about 200 and 600 ms, respectively, after S1 in the S1-choice paradigm mainly at pre -SMA and to a lesser degree at the prefrontal and lateral premotor areas, b ut not in the S2-choice paradigm. At SMA-proper, a similar but much smaller potential was seen after S1 in both S1- and S2-choice paradigms and (ii) s low sustained potentials between S1 and S2 in both S1- and S2-choice paradi gms in all of the non-primary motor areas investigated (pre-SMA, SMA-proper and lateral premotor areas) and prefrontal area. It is concluded that pre- SMA plays a more important role in cognitive motor control which involves s ensory discrimination and decision making or motor selection for the action after stimuli, whereas SMA-proper is one of the main generators of Bereits chaftspotential preceding self-paced, voluntary movements. In the more gene ral anticipation of and attention to the forthcoming stimuli, non-primary m otor cortices including pre-SMA, SMA-proper and lateral premotor area, and the prefrontal area are commonly involved.