Cortical representation of self-paced finger movement.

We compared the cortical fields activated by simple, self-paced index-finger flexions with those activated during visually triggered movement and rest using PET. Of 12 fields detected during self-paced movement compared to rest, three were located in the classically defined motor areas: primary motor area (M1), premotor cortex (PM) and supplementary motor area (SMA). The latter extended into the cingulate motor area (CMA). Four corresponding clusters were also found when triggered movement was subtracted from self-paced movement. The change in regional cerebral blood flow (rCBF) was greater in SMA than in PM during self-paced movement compared with either control. We conclude that repetitive, self-paced index-finger flexions can activate SMA, PM and CMA, and that this movement activates SMA more strongly than PM.