Neuronal activity in circuits between the basal ganglia (BG) and motor cortical areas is abnormally synchronized and rhythmic. The oscillatory activity prevails at 8-30 Hz in untreated Parkinson's Disease (PD) and its amplitude at both subthalamic and cortical levels inversely correlates with motor impairment. Moreover, these different levels in BG-cortical loops are coherent in this frequency band. The 8-30 Hz activity is suppressed by treatment following treatment with dopaminergic drugs and is partially suppressed prior to and during voluntary movements. An unanswered question is how do BG-cortical loops become so prominently engaged in this oscillatory activity? One possible explanation is that the resonance frequencies of the loops fall in the 8-30 Hz band in the untreated state, so that oscillations in this band are transmitted particularly well. So we hypothesize loop resonances in the 8-30 Hz frequency band at rest, which should be suppressed during movement and following dopaminergic therapy.