Commissural Fibers

What are Commissural Fibers?

Commissural fibers are white matter fiber tracts that cross the midline to connect structures on opposite sides of the nervous system. Cerebral commissures connect the two cerebral hemispheres; other commissures connect subcortical structures. These connections carry information used in cognitive, sensory, and motor functions.

Notable Commissural Fiber Tracts

• Corpus Callosum

  The corpus callosum is the largest and most prominent commissural fiber tract in the brain, containing approximately 200 million axons. It connects the left and right cerebral hemispheres and is involved in the transfer of information between the two sides, including sensory, motor, and cognitive processes.

• Anterior Commissure

  The anterior commissure is a smaller commissural fiber tract located near the front of the brain, connecting the temporal lobes of the two hemispheres. It plays a role in the integration of olfactory and emotional information, as well as the transfer of information related to memory and language.

• Posterior Commissure

  The posterior commissure is a small fiber bundle located near the back of the brain, connecting the two sides of the midbrain. It is involved in the coordination of eye movements and the integration of visual information.

Functions

• Interhemispheric Communication

  Cerebral commissural fibers exchange information between the left and right hemispheres, supporting sensory, motor, and cognitive coordination.

• Functional Integration

  By connecting regions across the midline, including corresponding and noncorresponding regions, commissural fibers contribute to the integration and coordination of various functions, such as language, memory, and emotional processing, across the two hemispheres.

Associated Disorders

• Split-Brain Syndrome

  Split-brain syndrome is a rare condition that occurs when the corpus callosum is surgically severed or damaged, often as a treatment for severe epilepsy. This results in a disruption of communication between the two hemispheres, leading to difficulties in the coordination of cognitive, sensory, and motor functions, as well as unusual perceptual experiences.

• Agenesis of the Corpus Callosum

  Agenesis of the corpus callosum is a congenital condition in which the corpus callosum is partially or completely absent. This can result in a range of neurological and developmental symptoms, such as cognitive impairments, motor difficulties, and social and communication challenges.

Sources and evidence

• OpenStax: Anatomy and Physiology 2e: The Central Nervous System. Describes white matter tracts and their connections.
• A. Goldstein, B. P. Covington, N. Mahabadi and F. B. Mesfin: Neuroanatomy, Corpus Callosum.