Anatomy, physiology, and pharmacology of the basal ganglia.

The basal ganglia consist of five interconnected nuclei in the basal forebrain that influence cortical control of voluntary movement. Synaptic information travels through the basal ganglia using distinct pathways from the input structure, the striatum, to the output nuclei, the substantia nigra pars reticulata and the globus pallidus internal segment. The activity of the striatal output pathways is influenced by glutamatergic input from the cerebral cortex, dopaminergic input from the substantia nigra pars compacta, and cholinergic interneurons. Since the basal ganglia output nuclei tonically inhibit the motor nuclei of the thalamus, the basal ganglia facilitate motor activity by disinhibiting the thalamus.