Covert movements trigger repetition suppression of electroencephalography in sensorimotor cortex.

'Repetition suppression' (RS) denotes the decrease of neural responses to repeated external sensory stimuli. We showed that RS can be also triggered by internal processes alone. When individuals perform repetitive covert movements, that is, motor imagery or quasi-movements, both of which are associated with pericentral cortical activity without muscle activations, there was a significant recovery of electroencephalographic oscillations over sensorimotor cortices back to resting baseline level. After 58 s of task performance only 20% of α and 5% of β suppressions remained (overt movements: 34% remaining in α, complete recovery in β). This result suggests that various, possibly all, repeated cerebral activations are associated with RS, presumably reflecting the adaptation to stereotyped activation in neural networks.