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MCAT Question A Day - 6/27/13 - Answer!

One technique previously used to reduce the effects of massive epileptic seizures in the cerebrum was to sever the corpus callosum. What result would you expect from such a procedure?

A.  The seizure would be limited to one half of the cerebrum.
B.  The seizure would be limited to the cerebral cortex only.
C.  The patient would not feel any pain after the procedure.
D.  Future seizures would involve sensory systems or motor systems but not both.

The correct answer is (A). The corpus callosum is the tract that connects the right and left cerebral hemispheres. There is no particular pathway that could separate the entire cerebral cortex from other parts of the cerebrum (choice B). Pain (choice C) can be experienced on either side of the brain (somatic sensory area) whether or not the two cerebral hemispheres are connected. Both cerebral hemispheres contain somatic sensory and motor areas (choice D). Therefore, a seizure confined to either half could still affect both sensory and motor functions.