What is the large white matter structure located in subcortical structures that functions as a communication pathway?

• A. Corpus callosum
• B. Internal capsule
• C. Thalamus
• D. Cerebral peduncle

Answer: (B)

The main idea is recognizing the major white matter bundle that serves as the primary communication highway between the cortex and deeper brain structures. The internal capsule fits this role perfectly: it’s a large, compact tract of white matter in the subcortical region that carries the major projection fibers between the cortex and the brainstem (and spinal cord), including the corticospinal and thalamocortical pathways. This bundle effectively routes motor commands from the cortex down to the body and brings sensory information back up to the cortex.

By comparison, the corpus callosum is a commissural pathway connecting the two cerebral hemispheres, not a subcortical highway; the thalamus is gray matter that relays information rather than forming a broad white matter tract; and the cerebral peduncle is a midbrain structure that contains many descending motor fibers but is not the large subcortical white matter communication highway described.