Two brains are better than one. At least that is the rationale for the close - sometimes too close - relationship between the human body's two brains, the one at the top of the spinal cord and the hidden but powerful brain in the gut known as the enteric nervous system.

For Dr. Michael Gershon, the author of "The Second Brain" and the chairman of the department of anatomy and cell biology at Columbia University, the connection between the two can be unpleasantly clear.

"Every time I call the National Institutes of Health to check on a grant proposal," Gershon said, "I become painfully aware of the influence the brain has on the gut."

In fact, anyone who has ever felt butterflies in the stomach before giving a speech, a gut feeling that flies in the face of fact or a bout of intestinal urgency the night before an examination has experienced the actions of the dual nervous systems.