 The subthalamic nucleus is a diencephalic gray matter portion of the basal ganglia, and the only portion of the ganglia that produces an excitatory neurotransmitter, glutamate.The role of the subthalamic nucleus is to stimulate the SNr-GPi complex and it is part of the indirect pathway.The subthalamic nucleus receives inhibitory input from the external part of the globus pallidus and sends excitatory input to the GPi.