ABSTRACT
Extrapyramidal motor system consists of the basal nuclei, substantia nigra, red nucleus, subthalamic nucleus, and reticular formation. The basal nuclei (Figures 21.1 through 21.6) are a collection of subcortical nuclei embedded in the white matter of the cerebral hemispheres, which include the globus pallidus, caudate nucleus, and putamen that collectively form the corpus striatum. Some authors have extended the conventional definition of the basal nuclei to also include the subthalamic nucleus and the substantia nigra. The basal nuclei regulate stereotyped movements and mediate control of saccadic eye movements via reciprocal connections to the
frontal eyefield and via their projections to the superior colliculus. They also coordinate orientation-associated memory and behavior via the bidirectional connections to the prefrontal and orbitofrontal cortices. This diverse origin and connections may account for the important role that the basal nuclei play in regulating motor activity and higher cognitive functions.
