Background: Although it has long been recognized that the basal ganglia play a major role in motor control, their precise functions remain unclear. As patients with Parkinson's disease (PD) have difficulties initiating movement, the basal ganglia may be involved in movement preparation. The subthalamic nucleus (STN) is particularly suited to play a role in movement preparation because it receives direct input from the supplementary motor area through the corticosubthalamic pathway.
Methods: Taking advantage of the electrodes surgically implanted in the STN for deep brain stimulation (DBS) treatment in 13 PD patients, we recorded from the DBS electrodes and the scalp simultaneously while the patients were performing self-paced wrist extension movements.
Results: Scalp recordings showed a slow, negative movement-related potential (MRP) in all patients studied (onset 1,690 +/- 336 milliseconds before electromyography onset). STN recordings showed premovement MRP in 11 of 13 patients. The STN activity occurred with both ipsilateral and contralateral hand movement. The onset time for STN MRP (contralateral 2,095 +/- 1,005 milliseconds, ipsilateral 2,020 +/- 920 milliseconds) was not significantly different from that for cortical MRP.
Conclusion: The STN or nearby structures are active before self-paced movement in humans.