Neuronal circuitry and synaptic connectivity of the basal ganglia.

The concept of organization of the basal ganglia has changed markedly over the last 10 years. These developments have led to the introduction of a schematic model of the functional circuitry of the basal ganglia that accounts for normal and abnormal basal ganglia functions. The recent introduction of powerful techniques for the analysis of neuronal networks has led to many new developments in our understanding of the anatomic and synaptic organization of the basal ganglia. The objective of this article is to go from the established model of the basal ganglia connectivity to new anatomic findings that lead to reconsideration and refinement of some aspects of the models.