Predictive encoding of motor behavior in the supplementary motor area is disrupted in parkinsonism

Many studies suggest that Parkinson's disease (PD) is associated with changes in neuronal activity patterns throughout the basal ganglia-thalamocortical motor circuit. There are limited electrophysiological data, however, describing how parkinsonism impacts the pre-supplementary motor area (pre-SMA) and SMA proper (SMAp), cortical areas known to be involved in movement planning and motor control. In this study, local field potentials (LFPs) were recorded in the pre-SMA/SMAp of a non-human primate during a visually cued reaching task. Recordings were made in the same subject in both the naive and parkinsonian state using the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) model of parkinsonism. We found that in the naive animal, well before a go cue providing instruction of reach onset and direction was given, LFP activity was dynamically modulated in both high (20-30 Hz) and low-beta (10-20 Hz) bands, and the magnitude of this modulation correlated linearly with reaction time (RT) on a trial-to-trial ...