The basal ganglia are gray matter masses buried deep in both cerebral hemispheres and are the main structures that make up the extrapyramidal system. It mainly consists of the caudate nucleus, the plexiform nucleus (shell nucleus and pallidum), the pallidum, and the amygdala. This concept can be broken down into four parts: (i) located deep in both cerebral hemispheres, (ii) a gray matter mass, (iii) the main structure that makes up the extrapyramidal system, which serves the function of controlling and regulating movement together with the cerebral cortex and cerebellum, and (iv) mainly including the nucleus accumbens, the caudate nucleus, the nucleus accumbens, and the amygdala. In contrast, the internal and external capsule (which is the white matter conduction bundle) and the thalamus (which belongs to the mesencephalon) are not part of the basal ganglia, despite their close relationship with the basal ganglia.