Corpus callosum

In the human brain, the corpus callosum (Latin for "tough body"), or callosal commissure, is a wide, thick nerve tract, consisting of a flat bundle of commissural fibers, located beneath the cerebral cortex. It is present in placental mammals, and is related to handedness and laterality. It spans part of the longitudinal fissure, connecting the left and right cerebral hemispheres, enabling communication between them. It is the largest white matter structure in the human brain, about 10 cm (3.9 in) in length and consisting of 200–300 million axonal projections.

A number of separate nerve tracts, classed as subregions of the corpus callosum, connect different parts of the hemispheres. The main ones are known as the genu, the rostrum, the trunk or body, and the splenium.