– John Williams, San Diego

ANSWER: Despite their New Age mystique and association with certain substances consumed by hippies, out-of-body experiences are reported by many people, particularly those who suffer from migraines and neurological conditions. Studies of out-of-body experiences have recently been published in highly respected journals, including Science and Nature.

These studies do not tie the phenomenon to alternate universes, though. The existence of multiple parallel universes is predicted by the complicated mathematics of quantum physics. Even if these alternative universes exist, physicists say it is not possible to access or even perceive them.

Instead, the study of out-of-body experiences is the purview of psychologists and neuroscientists. Out-of-body experiences have been accidentally induced in patients undergoing focused electrical stimulation of the brain during epilepsy treatment. One patient described a sensation of floating above the bed during electrical stimulation of a brain region called the angular gyrus.

The angular gyrus is on the surface of the brain, toward the rear, and it receives input about vision, hearing and touch. The angular gyrus is also close to the vestibular cortex, which processes sensory information to maintain the sense of balance. The brain stimulation research suggests that out-of-body experiences may be caused by the dissociation of information coming simultaneously from two or more senses.

This hypothesis is supported by studies that used head-mounted video displays to give people visual information that placed them in a different location. The visual information on its own did not give people the feeling of being outside their bodies. But when they saw their virtual body being touched at the same time as their real body was being touched, they felt as if the virtual body was their own body. Then when a hammer was swung so that it appeared to hit the virtual body, measurements of skin conductance – a sign of stress – indicated the hammer was registered as a threat, although it posed no real danger.

The studies show that information from the senses can modify the brain's representation of the body. The research provides insight into consciousness, since the feeling of being within one's physical body is a foundation for the concept of self.

Sherry Seethaler is a UCSD science writer and educator. Send scientific questions to her at Quest, The San Diego Union-Tribune, P.O. Box 120191, San Diego, CA 92112-0191. Or e-mail sseethaler@ucsd.edu. Please include your name, city of residence and phone number.