Question

Identify the type of the fibre marked in the image of the internal capsule.

• A. Projection fibres
• B. Short association fibres
• C. Long association fibres
• D. Commissural fibres

Hint:

The internal capsule carries cortex-to-cord axons, which are projection fibres.

Answer 1

The Correct Option is A

Step 1: The marked tract is the internal capsule, an area of white matter that separates the caudate nucleus and thalamus from the putamen and globus pallidus.
Step 2: The internal capsule contains both ascending and descending axons that run between the cerebral cortex and lower structures such as the pyramids of the medulla. These are projection fibres.
Step 3: Projection fibres connect the cortex with subcortical and spinal targets. The internal capsule is V-shaped when cut horizontally, with the bend forming the genu, an anterior limb, and a posterior limb.
Step 4: Commissural fibres (such as the corpus callosum) link the two hemispheres, and association fibres link regions within one hemisphere. The internal capsule does neither, so the marked fibres are projection fibres.