Summary
This brain structure consists of a bundle of over 200 million axons that connect the right and left hemispheres. These nerve tracts ensure that both hemispheres can communicate with each other. The term corpus callosum literally means "hard body", referring to its tough structure. It is not the only, but by far the most important connection between the two hemispheres.

Split-brain patients
A rigorous rarely used intervention in epilepsy patients is the cutting of the corpus callosum. This prevents an epileptic seizure from spreading from one half of the brain to the other. Patients who have undergone such an operation are called split-brain patients. This procedure leads to interesting neuroscientific insights. Remarkably, at first glance this procedure does not have much effect on daily functioning. Changes only become apparent when one of the brain hemispheres is deprived of information, for example when patients wear special lenses that ensure that information only enters one brain hemisphere. In this way, the right field of vision, for example, can be blocked, allowing information to enter only the right hemisphere of the brain. For example, if a spoon is presented in such a case, the patient will recognise the spoon but will not be able to name it. The patient can point to the spoon, but cannot tell what this utensil is called. This is because language functions are located in the left hemisphere of most people. Without the lenses, this does not cause any problems for split-brain patients, because both the left and right hemispheres can "see" the spoon. With the lenses in, however, the left hemisphere remains devoid of information and the patient cannot use this hemisphere to link the utensil to the word "spoon".

Author: Bart Aben (translated by Pauline van Gils)

Image: Marcel Loeffen