Which structure is the main tract that connects the two hemispheres?

• A. Corpus callosum
• B. Anterior commissure
• C. Foramen of Monro
• D. Medial lemniscus

Answer: (A)

Interhemispheric communication relies primarily on a large bundle of nerve fibers that crosses the brain’s midline to connect corresponding areas in the two cerebral hemispheres. This major tract is the corpus callosum, a vast bridge of axons spanning from the frontal region all the way to the occipital lobe and organized into parts that connect different cortical areas (rostrum, genu, body, and splenium). Because it is the primary conduit for exchanging sensory, motor, and higher-order information between the hemispheres, it is the best answer to identifying the main tract that links the two sides of the brain.

The anterior commissure is a smaller cross-hemispheric pathway, mainly linking parts of the temporal lobes and limbic structures, so it does contribute to interhemispheric communication but not as the principal highway. The foramen of Monro is a ventricular passage and not a neural tract. The medial lemniscus is a brainstem sensory pathway that carries touch and proprioception to the thalamus, without connecting the hemispheres.