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Out-of-body experience
« on: 2002-09-19 07:35:44 » |
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Electrodes trigger out-of-body experience
Stimulating brain region elicits illusion often attributed to the paranormal.
Source: Nature
Author: Helen Pearson
Dated: 2002-09-19
Activity in one region of the brain could explain out-of-body experiences. Researchers in Switzerland have triggered the phenomenon using electrodes1.
People describe out-of-body experiences as feeling that their consciousness becomes detached from their body, often floating above it. Because these lucid states are popularly linked to the paranormal, "a lot of people are reluctant to talk about them", says neurologist Olaf Blanke of Geneva University Hospital in Switzerland.
Blanke found that electrically stimulating one brain region -- the right angular gyrus -- repeatedly triggers out-of-body experiences. Blanke and his team were using electrodes to excite the brain of a woman being treated for epilepsy.
The right angular gyrus integrates visual information -- the sight of your body -- and information that creates the mind's representation of your body. This is based on balance and feedback from your limbs about their position in space.
"It makes perfect sense," agrees Peter Brugger of University Hospital, Zurich, in Switzerland, who studies the phenomenon. "We have representations of our entire body that can be dissociated from our real body," he says. But this is an isolated case, he points out.
With gentle stimulation, the woman, who could speak during the operation, felt she was falling or growing lighter. As the intensity increased she told them: "I see myself lying in bed, from above."
When asked to look at her raised arm, she thought it was coming to punch her. This observation suggests that 'alien hand syndrome' -- when people feel that a limb is foreign -- or 'phantom' limbs that people can feel after amputations could be related to out-of-body experiences, says Blanke.
Weird science
Out-of-body experiences are incredibly common, says clinical neurologist John Marshall of the Radcliffe Infirmary in Oxford, UK. Some are part of near-death experiences.
Some believe that the events have religious or spiritual causes, or that a person really leaves their physical body behind. They may, for example, interpret them as evidence that the physical and spiritual body can separate again after death.
The new experiments cannot disprove such ideas, says Marshall: "It doesn't show that people with paranormal beliefs are wrong" - it simply demonstrates one way that the experience can be stimulated. Nevertheless, "I think it would give great comfort to patients" who, he says, frequently question their own sanity.
Thrill-seekers will be hard-pushed to artificially create their own out-of-body experiences, adds Brugger. "You can't stimulate that precisely without opening up the skull," he says.
References
1. Blanke, O., Ortigue, S., Landis, T., Seeck, M. Stimulating own-body perceptions. Nature, 419, 269 - 270, (2002).
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rhinoceros
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Re:Out-of-body experience
« Reply #1 on: 2002-09-21 11:03:15 » |
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Stress Cited in 'Out-of-Body' Claims
Source: Washington Post (from Associated Press)
Author: Joseph B. Verrengia, AP Science Writer
Dated: 2002-09-19
A study suggests the oft-reported sensation of leaving the body during a brush with death may have a simple explanation in the body itself.
These "out-of-body" and "near-death" experiences -- in which people resuscitated on the operating table speak of being drawn toward a brilliant light, or looking down on their own bodies -- may be influenced by a portion of the brain misfiring under stress, the study suggests.
The paper describes one patient's visions while she was being evaluated for epilepsy and does not wrestle with issues of the soul. And researchers noted that the brain-mapping results may not entirely explain the phenomenon.
The study focuses on a processing center in the brain known as the angular gyrus, thought to play an important role in the way the brain analyzes sensory information to give us a perception of our own bodies. When it misfires, they speculate, the result can be visions of floating outside of ourselves.
The findings were published in Thursday's issue of the journal Nature.
"We do not fully understand the neurological mechanism that causes OBEs," conceded the study's lead researcher, neurologist Dr. Olaf Blanke at the University Hospitals of Geneva and Lausanne in Switzerland.
Skeptics of out-of-body experiences said the experiment goes a long way toward providing a scientific explanation for what some believe is a paranormal phenomenon, even if the study is based on only one patient.
"It's another blow against those who believe that the mind and spirit are somehow separate from the brain," said psychologist Michael Shermer, director of the Skeptic Society, which seeks to debunk alien abductions and other paranormal claims. "In reality, all experience is derived from the brain."
Other researchers described the experiment as modest but interesting.
Neurologist Dr. Bruce Greyson of the University of Virginia said the experiment does not necessarily prove that all out-of-body experiences are illusions.
"We cannot assume from the fact that electrical stimulation of the brain can induce OBE-like illusions that all OBEs are therefore illusions," Greyson said.
The Swiss researchers mapped the brain activity of a 43-year old woman who had been experiencing seizures for 11 years. They implanted electrodes to stimulate portions of her brain's right temporal lobe.
The temporal lobe, which includes the angular gyrus structure, is associated with perception of sound, touch, memory and speech.
Blanke suspects that the right angular gyrus integrates signals from the visual system, as well as information on touch and balance.
When electrical stimulation was applied, the patient reported seeing herself "lying in bed, from above, but I only see my legs and lower trunk." She also described herself as "floating" near the ceiling.
Millions of people have reported OBEs, but relatively few have been clinically analyzed.
Last December, the British medical journal Lancet published a Dutch study in which 344 cardiac patients were resuscitated from clinical death. About 12 percent reported seeing light at the end of a tunnel, or speaking to dead relatives.
Other researchers have suggested that OBEs occur as brain cells die from lack of oxygen, or when the brain releases pain-reducing chemicals called endorphins.
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