recovered to baseline, demonstrated increased activation in the right premotor cortex, left supplementary motor area, and bilateral cingulate motor areas (Figure 8). Thus, recovery of task performance was associated with increased activity in multiple other cortical regions. These compensatory increases in activity were not seen when subjects performed a control motor task that did not involve the left premotor cortex, and these changes were also not seen when rTMS was applied to primary motor cortex, suggesting that the observed changes were occurring in a task- and region-specific manner. To show that this compensatory activity in right premotor cortex is behaviorally relevant, TMS was then also applied to the right premotor cortex. TMS to the right premotor cortex alone had no effect on task performance, suggesting that right premotor cortex is usually not critical for task performance. However, if right premotor cortex was stimulated after rTMS of left premotor cortex, task performance was impaired. Thus, the results suggest that the compensatory increase in right premotor activity seen after inhibitory rTMS of left premotor cortex is causally involved in behavioral recovery, a finding with significant clinical implications for motor recovery after stroke.
