Output structures of the basal ganglia

Both the substantia nigra and globus pallidus are splitted into two parts. The globus pallidus pars interna (GPi) of primates (equal to the entopeduncular nucleus in rodents) and the substantia nigra pars reticulata (SNpr) have very alike structures and are functionally equal. Both of them get inhibitory connections from the GABA/SP/DYN population of excitatory inputs and striatal neurons from the subthalamic nucleus, and both send GABAergic inhibitory outcomes to the thalamus. The thalamus in return projects to precise positions in the cerebral cortex. The GPi and SNpr make connections with numerous thalamic nuclei which plan to motor cortex, giving basal ganglia output for limb and facial movements. A portion of the SNpr is concerned with eye movements.

The globus pallidus pars externa (GPe) obtains its striatal connections from the GABA/ENK medium spiny neurons. The GPe neurons are GABAergic and plans generally to the subthalamic nucleus.