Does post-movement beta synchronization reflect an idling motor cortex?

After the completion of a voluntary movement, a synchronization of cortical beta rhythms is recorded over the contralateral central region, which is a ssumed to reflect the termination of the motor command. In order to test th is hypothesis, we compared in eight healthy subjects the synchronization of EEG beta rhythms following active and passive index extension. The passive movement was also performed after deafferentation by ischaemic nerve block in three subjects. Beta synchronization was present in all subjects after both active and passive movements, and disappeared under ischaemia in all t hree subjects. Post-movement beta synchronization can not solely be explain ed by an idling motor cortex. It may also, at least in part, reflect a move ment-related somatosensory processing. NeuroReport 12:3859-3863 (C) 2001 Li ppincott Williams & Wilkins.