Due to their proximity, these two structures were formerly considered one, however, the two are separated by a thin layer of white matter—the external medullary lamina—and are functionally and connectionally distinct.

[1] The lentiform nucleus is a large, lens-shaped mass of gray matter just lateral to the internal capsule.

When divided horizontally, it exhibits, to some extent, the appearance of a biconvex lens, while a coronal section of its central part presents a somewhat triangular outline.

[citation needed] The lentiform nucleus is involved in the pathology of Wilson's disease as it is one of the neuroanatomical locations of copper deposition.

[citation needed] The name comes from Latin and means lens-shaped, probably referring to the appearance of the nucleus from the side.