Your Brain on Dreams

A century after Sigmund Freud pioneered the field of dream analysis, scientists are only now decoding the biology of how we manufacture dreams.

At the Sleep Neuroimaging Research Program at the University of Pittsburgh Medical Center, researcher Eric Nofzinger, MD, delves into the brains of sleeping subjects using PET scans normally employed to detect cancer and other diseases. By injecting subjects with mildly radioactive glucose, he's traced the source of dreams to the limbic system, a primitive part of the brain that controls emotions. During dreaming, the limbic system explodes like fireworks with neural activity, suffusing our dreams with drama.

"That's why so many dreams are emotional events," says Nofzinger, "where we're running from danger or facing an anxious situation. The part of the brain that controls dreams also orchestrates our instincts, drives, sexual behavior and fight-or-flight response." Meanwhile, the frontal lobes of the brain that govern logic disengage, explaining why dreams are often bizarre combinations of events and people.