Lateral globus pallidus
The lateral globus pallidus (or external, GPe) receives a strong glutamatergic projection from the subthalamic nucleus. The two form a particular system: a coupled pacemaker. The axons of the external globus pallidum go essentially to the subthalamic nucleus. They go also to other elements of the basal ganglia system, the striatum, the substantia nigra pars reticulata, and the internal globus pallidus, where they release the neurotransmitter GABA. GPe is particular in comparison to the other elements of the set by the fact that it does not work as an output base of the basal ganglia (not sending axons to the thalamus) but as the main regulator of the basal ganglia system. It is sometimes used as a target for deep brain stimulation as a treatment for Parkinson's disease.