The corpus callosum is a bundle of nerve fibers connecting the two hemispheres of the brain that facilitates the transfer of information from one hemisphere to the other. It is composed of 200 to 250 million axons, and it is the brain's largest white-matter structure.
The corpus callosum integrates the cognitive, motor and sensory functions of the brain's right and left hemispheres. It allows the brain to interpret the visual field as a unified whole by integrating sensory information from the eyes.
Full or partial absence of the corpus callosum, a congenital disorder known as agenesis of the corpus callosum, is usually diagnosed in the first two years of life and generally results in seizures, delays in mental and physical development and problems with hand-eye coordination. However, the condition is rarely fatal, and with treatment many sufferers can go on to lead normal lives and have average intelligence, though motor-function impairment is often evident. The savant Kim Peek, who was the basis for Dustin Hoffman's character in the movie "Rain Man," was found to have agenesis of the corpus callosum. In some cases, the surgical severing of the corpus callosum has been shown to reduce the symptoms of refractory epilepsy.