commissural

Commissural is an anatomical term describing a commissure, a bundle of nerve fibers that connects structures on opposite sides of the body, most often within the nervous system. The word comes from Latin commissura, meaning a joining together.

In neuroanatomy, commissural tracts cross the midline to enable communication between the two sides of the brain or spinal cord. The largest and best known is the corpus callosum, a major pathway linking most cortical areas across the hemispheres. Other notable brain commissures include the anterior commissure, which connects parts of the temporal lobes and some olfactory structures; the posterior commissure, located in the dorsal midbrain and involved in coordinating certain reflexes; and the hippocampal commissure (part of the fornix) that connects the two hippocampi. In the spinal cord, the anterior white commissure contains crossing fibers that carry pain and temperature information from one side to the other.

Functionally, commissural pathways support bilateral integration of sensory and motor information and coordinate complex cognitive and perceptual processes that require cross-hemisphere communication. They also contribute to synchronized motor control and unified perception.

Developmentally, commissural tracts form as axons grow toward and across the midline under the influence of molecular guidance cues. Disruption of this process can lead to agenesis or hypoplasia of commissures, most commonly the corpus callosum, with a spectrum of neurodevelopmental outcomes.

Beyond neuroscience, the term commissural can describe similar midline-connecting structures in other organ systems, though in common usage it most often denotes neural commissures.