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.