The DS is comprised of the caudate nucleus and putamen, which are separated in primates by the internal capsule. The rostroventral border of the caudate nucleus and putamen merge with the dorsal nucleus accumbens, making the region ventral to the internal capsule continuous. Caudally the putamen merges to varying degrees with the tail of the caudate. The nucleus accumbens and the rostroventral-most aspects of the caudate and putamen form the VS. The VS includes the ventral extension of the putamen, which reaches the surface of the brain in the region of the anterior perforated space. This ventral region, which had been included in the substantia innominata, is now considered part of the VS on the basis of its histochemistry and connections. In addition, the olfactory tubercle and the rostrolateral portion of the anterior perforated space adjacent to the lateral olfactory tract in primates are also included in the VS.
