What Is A Commissural Fiber In Neuroscience

What are Commissural Fibers?

Commissural fibers are a type of white matter fiber tracts in the brain that connect the two cerebral hemispheres, allowing for communication and integration of information between the left and right sides of the brain. These axonal connections play a crucial role in the coordination of various 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.


  • Interhemispheric Communication

    Commissural fibers facilitate the exchange of information between the left and right cerebral hemispheres, enabling the brain to process and integrate sensory, motor, and cognitive information from both sides.

  • Functional Integration

    By connecting homologous regions of the brain, 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.


Commissural fibers, such as the corpus callosum, anterior commissure, and posterior commissure, are critical for the integration and coordination of information between the left and right cerebral hemispheres. Disorders affecting these fiber tracts can have significant consequences for cognitive, sensory, and motor functions, as well as overall quality of life.

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