Connections of the Basal Ganglia

This schematic shows the major connections of the basal ganglia and associated structures. Excitatory connections are shown as black lines; inhibitory connections are shown as red lines. Many connections, such as the inputs to the substantia nigra, are omitted for clarity. Two regions that have been targets of stereotaxic surgery for Parkinson’s disease—the internal division of the globus pallidus and the subthalamic nucleus—are outlined in gray. Damage to these regions reduces inhibitory input to the thalamus and facilitates movement. Deep brain stimulation of these regions produces similar effects.