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Brain Divide

February 27, 2007

A listener asks: Why does each half of the brain control the opposite side of the body?


The brain-body connection. I’m Bob Hirshon and this is Science Update.

Michael of Traverse City, Michigan, asks why each half of the brain controls the opposite side of the body. Well, Michael, it is true that nerve fibers from the right side of the brain cross over to the left side of the body and vice versa. But according to neuroscientist Michael Gazzaniga of the University of California, Santa Barbara, that doesn’t mean one brain side totally controls the opposite side of the body.

MICHAEL GAZZANIGA (University of California, Santa Barbara):
Everything seems more distributed and the actual ways information comes together to effect a motor response seems to involve both sides of the brain in many kinds of tasks.

As to why nerves from the brain cross to the other side of the body, that’s still a mystery. If you have a science question, call us at 1-800-why-isit. If we use it on the air, you’ll win a Science Update mug. I’m Bob Hirshon for AAAS, The Science Society.