Answer
The white matter of the cerebrum is composed of myelinated fibers. These are divided into three groups : the association fibers (tracts) , the commisural tracts ( commisures), and the projection fibers (tracts).
Work Step by Step
Association fibers carry impulses between gyri in the same hemisphere. Some examples of association tracts are arcuate, and urcinate fibers, and the cingulum. Commisures or commisural tracts transmit impulses between corresponding gyri in the opposite cerebral hemispheres. The largest commisure is the corpus callosum (CC). Others are the anterior, and posterior commisures.
The axons of projection tracts carry impulses from the cerebrum to lower (inferior) parts of the central nervous system (CNS)--thalamus, brainstem, and spinal cord. Examples of projection tracts are the internal capsule, and the corticospinal tracts.
