Normal functional imaging of the basal ganglia.

In non-human primates, all cortical projections into the striatum are topographically organized in discrete parallel circuits. These circuits are involved in distinct behavioral functions. In humans, functional imaging data support a similar organization of the striatum. The representation of the different elements of a motor act (such as movement learning, selection, mental representation, preparation and execution) are represented differentially along distinct cortico-basal ganglia circuits. Saccadic eye movements are predominantly represented in the caudate nucleus. Motivational processes are represented in the ventral part of the striatum. Thus, functional imaging data suggest that the human striatum is organized in parallel motor circuits similar to those found in animal studies.