Internal Capsule - Fibers

Fibers

Working anterior to posterior:

• The anterior limb of the internal capsule contains:

1) Frontopontine (corticofugal) fibers project from frontal cortex to pons;

2) Thalamocortical fibers (part of the thalamocortical radiations) connect the medial and anterior nuclei of the thalamus to the frontal lobes (these are severed during a prefrontal lobotomy).

• The genu contains corticobulbar fibers, which run between the cortex and the brainstem.

• The posterior limb of the internal capsule contains corticospinal fibers, sensory fibers (including the medial lemniscus and the anterolateral system) from the body and a few corticobulbar fibers.

Other fibers within the internal capsule

• The retrolenticular part contains fibers from the optic system, coming from the lateral geniculate nucleus of the thalamus. More posteriorly, this becomes the optic radiation. 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 contains fibers connecting with the temporal lobe. These include the auditory radiations and temporopontine fibers.