Which structure is the largest bundle of white matter in the brain and forms the roof of the lateral ventricles?

• A. Cingulate Gyrus
• B. Corpus Callosum
• C. Fornix
• D. Internal Capsule

Answer: (B)

White matter bundles are the wiring that connects different parts of the brain, and the largest of these is the corpus callosum. It’s a broad, C-shaped tract that carries the major commissural fibers linking homologous areas of the left and right hemispheres, enabling quick interhemispheric communication. Its position sits above the lateral ventricles, and along its inferior surface it forms the roof of these ventricles, outlining their superior boundary. That combination of being the largest white matter bundle and physically forming the roof of the lateral ventricles makes it the best answer. The fornix is a smaller limbic tract, the internal capsule is a deep projection pathway, and the cingulate gyrus is grey matter cortical tissue, not a large white matter bundle.