The basal ganglia are a group of nuclei located in the deep portion of the brain. Along with the cerebellum, the basal ganglia have a major role in controlling human voluntary movements, and their dysfunction is apparently responsible for various involuntary movements. Although the exact mechanism of how the basal ganglia control movements has yetto be clarified, the model of focused selection (through the direct pathway) and tonic inhibition (via the indirect pathway) is proposed to be a principal functional model of the basal ganglia. Parkinson
