Previous studies have provided evidence that the primary motor area (M1) is involved in actual execution of a motor program, while the premotor area (PreMA) and the supplementary motor area (SMA) play a role in its preparation. We have used the high temporospatial resolution of functional magnetic resonance imaging (fMRI) to study the relationship between stages of a motor program and activation of these motor-related cortical areas. Seven normal volunteers performed a delayed-motor task in which the preparation of finger movements was dissociated in time from movement execution, while event-related fMRI was obtained. The M1 and PreMA showed expected activation associated with execution and preparation stages, respectively. Within SMA, subregions with different temporal profiles of activation were identified: The anterior part became activated early in the preparation period, whereas the posterior part only with movement execution. This supports the notion that the classic SMA consists of the pre-SMA and SMA proper each with different functions.
Copyright 1999 Academic Press.