Large areas of the human motor cortex are devoted to the control of the contralateral hand and forearm. Just how activities scattered across these motor areas may be brought together in the execution of a given movement remains unclear. There is increasing evidence, largely from animal studies, suggesting that sensory integration involves the synchronization of activity between spatially distributed cortical sites. Here we review recent evidence that cortical activity becomes oscillatory and synchronized between spatially distributed sites during performance of a movement in humans. Cortico-cortical synchronization may occur with a precision in the millisecond range, is essentially limited to those cortical elements active in a given task, and changes in both its distribution and frequency in a task-related manner. Synchronization at specific frequencies may therefore link disparate cortical activities into the functional ensembles underlying voluntary movement in humans.
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