the corpus callosum is a region of white matter that
Corpus callosum 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[citation needed] 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.[1]
Anterior commissure The anterior commissure (also known as the precommissure) is a white matter tract (a bundle of axons) connecting the two temporal lobes of the cerebral hemispheres across the midline, and placed in front of the columns of the fornix. The great majority of fibers connecting the two hemispheres travel through the corpus callosum, which is over 10 times larger than the anterior commissure, and other routes of communication pass through the hippocampal commissure or, indirectly, via subcortical connections. Nevertheless, the anterior commissure is a significant pathway that can be clearly distinguished in the brains of all mammals.