Corpus callosotomy (or less frequently, callotomy) is a surgical procedure that disconnects the cerebral hemispheres resulting in a condition which is called split-brain.
Most modern callosotomies involve only the anterior portion of the corpus callosum, reflecting the fact that the frontal and temporal lobes are the most commonly involved in the genesis of seizures. The deficits from this modified procedure are milder; side effects have not been found in some patients (although it is very unlikely that none exist).
The corpus callosum is usually severed in order to stop epileptic seizures. Once the corpus callosum is cut, the human brain is no longer capable of sending messages between its left and right hemispheres. This does not have any major effect in everyday circumstances but when tested in particular situations, it is obvious that information does not transfer from one hemisphere to the other.