The internal capsule is a paired white matter structure, as a two-way tract, carrying ascending and descending fibers, to and from the cerebral cortex.

It also separates the caudate nucleus and the putamen in the dorsal striatum, a brain region involved in motor and reward pathways.

[1] The internal capsule is V-shaped in transection forming an anterior and posterior limb, with the angle between them called the genu.

Some fibers from the medial geniculate nucleus (which carry auditory information) also pass in the retrolenticular internal capsule, but most are in the sublenticular part.

The sublenticular part is beneath the lentiform nucleus, and contains fibers connecting with the temporal lobe.

[citation needed] Due to the orderly somatotropic arrangement of elements of the posterior limb of the internal capsule, small lesions can produce selective functional deficits.

[citation needed] The primary motor cortex sends its axons through the posterior limb of the internal capsule.