Dividing the Hemispheres Commisurotomy, the transection of the corpus callosum, is one possible treatment for patients with severe epilepsy. This procedure causes a complete split between the two hemispheres of the brain. As a result of this split, words presented to the patient's far left visual field cannot be read (alexia), and hidden objects placed into the left hand cannot be named (anomia). This is significant evidence for hemispheric specialization.