Steady-state movement-related potentials evoked by fast repetitive movements

We investigated steady-state movement-related cortical potentials elicited by fast repetitive movements (1/sec) with 50-channel EEG. The experimental design comprised a comparison (a) between unilateral movements of the digit s and the toes and (b) between metronome-paced and self-paced initiation of the movements. A distinct biphasic pattern of electrical activity followin g movement onset was observed, namely a frontal negative peak at a latency of 90ms (post-MP100) and a frontal positive peak at a latency of 310 ms (po st-MP300). Pacing exerted its effects mainly on the amplitude and on the la tency of the post-MP300. Source analysis revealed that both peaks could be modelled by a single source. The source locations were highly reproducible across the metronome-paced and self-paced conditions, and, they followed th e expected somatotopic organisation.