the corpus callosum is a region of white matter that
The corpus callosum (/ ˈkɔːrpəs kəˈloʊsəm /; Latin for "tough body"), also callosal commissure, is a wide commissure, a flat bundle of commissural fibers, about 10 cm long beneath the cerebral cortex in the brains of placental mammals. It spans part of the longitudinal fissure, connects the left and right cerebral hemispheres, and enables communication between the hemispheres. It is the largest white matter structure in the human brain, consisting of 200 -- 250 million axonal projections.