Internal capsule

Internal capsule & related structures dissected from the lateral side

Horizontal section through the internal capsule & related structures

Detail of horizontal section through the internal capsule & related structures

Internal capsule regions & related structures in horizontal section

Major pathways passing through the internal capsule in horizontal section

About the internal capsule / Internal capsule further information

This is a small area of the cerebral hemispheres through which almost all tracts enter or leave the cerebrum. It lies between the lentiform nucleus laterally and the thalamus and head of the caudate nucleus medially. Its full name is the internal capsule of the lentiform nucleus, but it is customarily shortened to just “internal capsule”. In horizontal section it is shaped like a shallow letter V, but dissection shows it to be fan-like, with ascending fibres radiating out above it (the corona radiata) towards and from the different cortical areas.

Functionally different tracts run in different parts of the internal capsule, including those carrying somato-sensation, voluntary motor commands, motor control connections (with basal ganglia and cerebellum), vision. Also present in and hearing as well as those associated with mood, memory and cognitive functions.

Somato-sensory and motor axons serving the head pass through the genu, while other parts of the body contain axons serving the rest of the body, arranged as though it was lying with the feet most posteriorly placed in the posterior limb of the internal capsule.

Because of the concentration of different tracts in this confined region, small lesions to the internal capsule give rise to major functional deficits including:

SEE ALSO: Blood supply of internal capsule; effects of lesions to internal capsule (opens in a new window/tab).