Striatum: Part of the basal ganglia of the brain. The basal ganglia are interconnected masses of gray matter located in the interior regions of the cerebral hemispheres and in the upper part of the brainstem.
The striatum is also called the striate body. It includes the caudate nucleus and the lentiform nucleus. The term striatum (striate) refers to the layered appearance of bands of gray matter that course from one of these nuclei to the other and represent the connections between them.