Final answer:
The corpus callosum would be severed to stop interhemispheric communication in Desmond's brain to control his seizures, which could result in split-brain syndrome.
Step-by-step explanation:
The doctors would sever the corpus callosum to stop the communication between the two hemispheres of Desmond's brain. This structure is a bundle of neural fibers that connects the left and right hemispheres of the brain, allowing them to communicate with each other. Cutting the corpus callosum is a treatment method used in cases of severe epilepsy when other treatments, such as antiseizure medication, are not effective. While this surgical intervention can prevent seizures from spreading between the hemispheres, it can result in a condition known as split brain, where the two halves of the brain can no longer communicate directly. Patients with split brain may exhibit unique behaviors, such as being unable to name objects in their left visual field because the speech center is generally located in the left hemisphere, but they can still pick up objects with their left hand guided by the right hemisphere.