Functional segregation of movement-related rhythmic activity in the human brain.

Multiple synaptic interconnections in the human brain support concerted rhythmic activity of a large number of cortical neurons, typically close to 10 and 20 Hz. Our present neuromagnetic data provide evidence for distinct functional roles of these spectral components in the somatomotor cortex. The sites of suppression during movement and the subsequent rebound of the 20-Hz rhythm followed, along the motor cortex, the representation of fingers, toes, and mouth, as opposed to the stable origin of the 10-Hz rhythms close to the hand somatosensory cortex. The 20-Hz activity appears to be a signature of active immobilization following movement, whereas the reactive 10-Hz signals likely reflect lack of relevant sensory input from the important upper limbs.