The corpus callosum is a structure consisting of nerve fibers that are located deep in the cleft (longitudinal fissure) between the right and left hemispheres of the brain , and provide communication between the two hemispheres. Axons and dendrites of neurons in the corpus callosum make connections with symmetrical points in the opposite hemisphere. For this reason, electrical stimulation given to a point in one hemisphere of the brain usually causes a response at the symmetrical point on the opposite side. Nerve fibers in the corpus callosum are surrounded by a myelin sheath and isolated so that signals can be transmitted rapidly. It is the largest white matter structure in the human brain. It is about 10 centimeters long and contains 200-300 million axon fibers.
The corpus callosum is subdivided into genu, rostrum, trunk, and splenium according to the location of the nerve bundles connecting different parts of the brain. The thin part between the trunk and the splenium is called the isthmus. The genu is the anterior folded portion close to the frontal lobes. The genu tapers down by bending backwards; This thin part is called the rostrum. The posterior part of the corpus callosum close to the cerebellum is the splenium, its thickest part. The trunk is the place between the splenium and the genu.
The corpus callosum partially forms the roof of the lateral ventricles. It is separated from the cingulate fold by a cleft called the collosal sulcus.
One of the diseases affecting the corpus callosum is Marchiafava-Bignami disease. In this disease associated with excessive alcohol consumption, corpus callosum neurons lose their myelin sheath. Vitamin B1 (thiamine) deficiency may be effective in the development of the disease. Symptoms such as irritability, depression, paralysis (hemiparesis), ataxia, apraxia, loss of consciousness, and coma can be seen.
Partial or complete lack of development of the corpus callosum during the embryonic period causes corpus callosum agenesis. It is one of the most common types of developmental disorders affecting the human brain. It can cause severe symptoms that are noticed from infancy or have mild effects. In some people, it may be asymptomatic enough to cause it to be detected by chance. Infants may have symptoms such as seizures, feeding problems, holding their head, sitting, standing, walking, delayed mental development, hand-eye coordination disorder, visual and auditory memory impairment. Many children with agenesis of the corpus callosum continue their lives normally and have average intelligence. However, in detailed mental tests, some minor differences can be detected in higher cognitive functions with peers of the same age group and education. While “agenesis” describes the absence of the corpus callosum, its partial formation is described with the terms “hypogenesis”, incorrect development “dysgenesis”, insufficient development (such as too thin) “hypoplasia”. Thin corpus callosum can cause attention deficit and hyperactivity disorder.
The corpus callosum has an important role in explaining the specific functions of each hemisphere. It has been observed that the cerebral hemispheres of people whose corpus callosum has been cut for the treatment of epilepsy work largely independently of each other. As a result of these observations, it has been determined that the right brain has more proficiency in language than is thought.
Corpus callosum problems also play a role in the formation of diseases such as foreign hand syndrome, akinetic mutism, anomic aphasia, and split brain syndrome.