The microcircuitry of primate subthalamic nucleus.

Single-cell labeling experiments in cynomolgus monkeys have revealed that the subthalamic nucleus (STN) harbors several subtypes of projection neurons, each endowed with a highly patterned set of axon collaterals. This organizational feature allows single STN neurons to act directly upon the two major output structures of the basal ganglia--the substantia nigra pars reticulata and the internal pallidum--and, at the same time, to exert a multifarious effect upon the external pallidum with which the STN is reciprocally connected. These findings have clarified the role of the STN in basal ganglia organization and led to the elaboration of more accurate computational models of deep brain stimulation, a therapeutic approach currently used to alleviate the motor symptoms of Parkinson's Disease.