Dysfunctional cortico-basal ganglia (BG) processing can result in severely disrupted movement control as observed in Parkinson’s disease, Huntington’s disease and dystonia. Simple ballistic movements are accompanied by increased synchronization at relatively high frequencies (gamma = 60-90 Hz) while slower beta-rhythmic activity (13-30 Hz) is suppressed. Gamma and beta oscillations thus have been conceptualized to represent pro-kinetic and anti-kinetic processes, respectively. To uncover how the cortico-BG network supports more complex actions we recorded EEG activity and subthalamic nucleus (STN) local field potentials in Parkinson’s patients in the following two tasks: Rapid stopping of a continuous finger tapping movement and smooth transitions between stable muscle contractions
During rapid stopping of the ongoing tapping movement, STN gamma oscillations increased, transforming the previously held view of gamma oscillations being predominantly pro-kinetic. At the same time, phase coupling between STN and cortical gamma activity rapidly dropped, which may reflect a gating mechanism that can either facilitate movement by promoting network propagation of gamma activity or rapidly cancel it. During smooth stabilization of muscle contractions when performing gradual adjustments, beta oscillations dominated, suggesting that when neural dynamics need to be stabilized, the cortico-BG network relies on beta synchronization.