Internal capsule
- A band of white matter in the cerebral hemispheres through which almost all tracts enter or leave the cerebral cortex.
- It lies between the lentiform nucleus laterally and the thalamus and head of the caudate nucleus medially.
- In horizontal section the internal capsule 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 the different cortical areas, and descending fibres collecting at its base to enter the midbrain.
- Functionally different tracts are arranged from anterior to posterior, including somato-sensory, voluntary motor, motor control, vision and hearing as well as those associated with mood, memory and cognitive functions.
- Because of the concentration of different tracts, small lesions to the internal capsule give rise to major functional deficits including paralysis, anaesthesia, loss of motor control, cognitive and memory deficits etc.
