Which structure is the largest bundle of axons providing communication between the cerebral hemispheres?

• A. Hippocampus
• B. Amygdala
• C. Thalamus
• D. Corpus Callosum

Answer: (D)

The corpus callosum is the primary interhemispheric bridge, a thick bundle of axons that directly connects the left and right cerebral cortices. It contains hundreds of millions of fibers, making it the largest white matter structure in the brain, and it spans the midline to link corresponding areas across both hemispheres. This extensive cross-midline wiring enables rapid coordination of motor, sensory, and cognitive processes between the two sides, which is why disruption of this pathway—such as in split-brain cases—can lead to a separation of hemispheric function.

The other structures serve different roles. The hippocampus is central to memory formation and is connected within a hemisphere via the fornix to limbic structures; it’s not the major conduit for cross-hemisphere communication. The amygdala is involved in emotion processing and also isn’t the main highway between hemispheres. The thalamus acts as a relay station for sensory and motor information within each hemisphere and to the cortex, rather than serving as the large cross-hemisphere connector.