The white matter of the cerebrum consists of the axons of these cell bodies, which lie beneath the gray matter. The white matter of the cerebrum broadly make up three types of axonal tracts - commissural, association and projection tracts. Commissural Tracts Commissural tracts are bundles of axons that run between the two hemispheres and, therefore, serve as communication link between the two hemispheres.
Commissural tracts connect a region in one hemisphere with a region in the opposite hemisphere.
Corpus callosum is the largest and the most important of the commissural tracts. This half-moon shaped bundle of myelinated axons on the medial aspect of the two cerebral hemispheres consist of four parts. The fibers of the corpus callosum establish communication between the corresponding areas of the two hemispheres. The body of the corpus callosum link the parietal lobes and the posterior portions of the frontal lobes. The occipital and temporal lobes of the two hemispheres communicate with each other by way of the splenium.