Steady-state movement-related cortical potentials: a new approach to assessing cortical activity associated with fast repetitive finger movements.

Traditionally, studies of movement-related cortical potentials have focused on the preparation of single self-paced movements performed slowly. We studied MRCPs elicited by metronome-paced, fast repetitive finger movements (2/s) with 28-channel (10 normal subjects) and 122-channel (two subjects) EEG. EMG-locked averaging of 500 ms time windows (300 ms before to 200 ms after each EMG onset) produced a distinct pattern of phasic MRCPs (steady-state MRCPs). The main components were a pre-movement peak (pre-MP), 57 ms before EMG onset, and a post-movement peak (post-MP), 93 ms after EMG onset. From timing information and topographic mapping results, we propose that the pre-MP is largely generated by a tangential source in the anterior bank of the central sulcus and reflects precentral motor processing, whereas the post-MP is generated in the posterior bank of the central sulcus and represents post-central feedback processing. Steady-state MRCPs require actual recording times of less than 10 min, and show excellent inter-session reproducibility. These characteristics may make them convenient for studying sensorimotor cortex activity experimentally and clinically.