The commissural fibers or transverse fibers are coherent white matter structures that connect the two hemispheres of the brain. In contrast to commissural fibers, association fibers connect regions within the same hemisphere of the brain, and projection fibers connect each region to other parts of the brain or to the spinal cord.

Commissural fibers include anterior commissure, corpus callosum and fornix. Projection fibers are internal capsule and optic radiations ¹⁾.