Systems coordinating the sense of self may break down, the researchers say
WEDNESDAY, Oct. 31 (HealthDay News) -- New research is taking a little of the mystery out of the phenomenon known as the "out-of-body" experience.
A team of Belgian scientists have linked the sense of disembodiment central to the experience -- the feeling of leaving one's body and then floating outside it -- to abnormal activity in a specific region of the brain.
This activity appears to short-circuit the processing of sensory information and the ability to locate oneself in time and space, the team said.
"Self-perception is nothing else but a creation of your brain," explained study lead author and neurosurgeon Dr. Dirk De Ridder, of the neurosurgical department at Antwerp University. "We found a key spot in the brain in which different areas are normally activated whenever stimulus comes in, so you can relate that stimulus to yourself, which helps create a unified perception of ourselves."
"The 'total perception of self,' " he added, "is built out of different parts. And one of these parts is that your consciousness belongs within your body."
"But when something goes wrong in that brain area so that the integration of all the incoming information -- sight, sound, smell, the senses -- is not happening as it should, then you can feel that you're not in your body," De Ridder said. "You can get an out-of-body experience. You're perfectly conscious. But you just feel as if you're not actually sitting in your body."
His team reported its finding in the Nov. 1 issue of the New England Journal of Medicine.
De Ridder's team discovered what they believe is a hardwired connection between the out-of-body experience and specific abnormal brain activity. They did so while observing the unanticipated side-effects of a treatment offered to a 63-year-old Belgian patient suffering from tinnitus, more commonly known as "ringing in the ears."
To alleviate his condition, doctors had implanted electrodes in a region in the right side of the man's brain known as the temporoparietal junction.
Unfortunately, stimulation of the electrodes failed to halt the ear-ringing. However, in the process of doing so, the attending physicians found that the patient repeatedly experienced what he described as an out-of-body experience.
By monitoring the use of a patient-controlled button pressed at the start and end of each experience, researchers found that within one second following electrode stimulation to the brain, out-of-body experiences were provoked -- each lasting from 15 to 21 seconds an episode.
While at no time causing any alteration in his sense of consciousness, during each episode, the patient consistently reported feeling disembodied to a specific location -- namely about 20 inches behind his body and to the left. The perception remained the same, regardless of whether the patient was standing or lying down during electrode stimulation.
At no time did the patient report the sense that he was watching his actual body from another place -- a phenomenon known as autoscopy. Rather, he said that throughout each out-of-body episode, he visually perceived the world as usual -- from the vantage point of his actual body. At the same time, however, he continued to feel as if his body was located elsewhere.
During repeated actual and false (placebo) stimulations, the researchers conducted 12 PET scans of the patient's brain.
The scans revealed that throughout each out-of-body episode, brain activity spiked in two areas surrounding the electrode implant: a small area where the angular gyrus meets the supramarginal gyrus, and in the rear section of the superior temporal cortex.
The former area is known for being associated with integrating sensory stimulus -- such as sight, sound, and touch -- in order to establish head and body orientation in space.
The latter area is known to be integral to the forming of a so-called "map" of self-perception -- a key ingredient in establishing self-consciousness.
The researchers concluded that electrode stimulation of these two areas seems to alter a person's spatial self-perception, while leaving global self-consciousness -- the ability to perceive the surrounding world -- untouched. The result: an out-of-body experience.
However, they cautioned that while epileptics, patients suffering from migraines and tinnitus, and those undergoing a near-death experience have all been known to spontaneously experience out-of-body episodes, it remains unclear whether pro-actively stimulating the two identified cranial areas -- which don't normally activate in unison -- would induce a similar experience in healthy individuals.
"It's fairly rare," said De Ridder. "It might be possible to trigger this experience -- and even likely -- in a normal brain, and mess up the normal integration of the functions, the senses. But we're not sure yet."
"It's fascinating," commented Paul Sanberg, a distinguished university professor and director of the Center of Excellence for Aging and Brain Repair with the University of South Florida's College of Medicine in Tampa.
"This gives a physiological mechanism for out-of-body experiences under different conditions," he said. "And, it points out that our sense of self isn't just our cognitive abilities and our emotions, but it's also our sense of time and space."
"So, I imagine if you can stimulate a part of the brain that has been found to control where we are in space and orientation and our sense of body, it could give a sense of being out of our body," he said. "It could give us a sense that we are somewhere else. Perhaps not a real out-of-body experience. But a perceptual experience, nonetheless."
For more on the brain and sensory perception, visit the Howard Hughes Medical Institute.
SOURCES: Dirk De Ridder, M.D., neurosurgeon, neurosurgical department, Antwerp University, Belgium; Paul Sanberg, Ph.D., distinguished university professor and director, Center of Excellence for Aging and Brain Repair, University of South Florida, College of Medicine, Tampa; Nov. 1, 2007, New England Journal of Medicine
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