Identify the type of the fibre marked in the image of internal capsule:
A. Projection fibres
B. Short association fibres
C. Long association fibres
D. Commissural fibres
Answer A. Projection fibres
- Area of white matter in the brain that separates the caudate nucleus and the thalamus from the putamen and the globus pallidus.
- The internal capsule contains both ascending and descending axons.
- It consists of axonal fibres that run between the cerebral cortex and the pyramids of the medulla.
- The internal capsule is V-shaped when cut transversely (horizontally).
- When cut horizontally:
- the bend in the V is called the genu
- Anterior limb of the internal capsule.
- the posterior limb or crus posterius is the part behind the genu, between the thalamus and lenticular nucleus.
- the retrolenticular portion is caudal to the lenticular nucleus and carries optic tracts including the geniculocalcarine radiations.
- the sublenticular portion is beneath the lenticular nucleus and are tracts involved in the auditory pathway from medial geniculate nucleus to the primary auditory cortex (Brodmann Area 41).
- Gross motor strength is impaired with ischemia of the internal capsule.