Early onset of post-movement beta electroencephalogram synchronization in the supplementary motor area during self-paced finger movement in man.

A voluntary finger movement is accompanied by an event-related desynchronization followed by a short burst of beta oscillations or event-related synchronization. These beta bursts are dominant over the contralateral hand representation area, but also appear over the midcentral area overlaying the supplementary motor area (SMA) and the foot representation area. We show that the induced midcentral beta oscillations following movement-offset display not only slightly higher frequency components, but have also a significantly earlier onset. These beta oscillations arise likely from the SMA. Assuming that the short-lasting beta synchronizations at frequencies below 35 Hz after termination of a movement reflect a state of localized cortical inhibition, we propose that the induced midcentral oscillations reflect the inhibition of networks within the SMA. This assumed resetting or inhibitory process within the SMA precedes that of the networks within the primary motor hand area.