The corpus callosum is the brain’s largest commissure connecting matching areas of the two cerebral hemispheres.
It is a broad band of white matter made of millions of axons that cross the longitudinal fissure. These fibers allow information to be exchanged between left and right cortical regions, supporting coordinated perception, movement, and cognition.
The corpus callosum is commonly divided into named parts, including the rostrum, genu, body, and splenium. Different portions connect broadly corresponding regions, although the arrangement is not a simple one-to-one wiring diagram.
Other commissures also cross the midline, such as the anterior commissure and hippocampal commissure, but they are much smaller or more specialized. Surgical section of the corpus callosum, once used for some severe epilepsy cases, can reduce the spread of abnormal electrical activity and has contributed to research on hemispheric specialization.