LONDON, England (CNN) -- It has perplexed and amazed those who claim to have experienced it, been the subject of rigorous debate among theologians and philosophers for centuries, and provided satirists and magicians with a rich seam of material for decades. But recent scientific research may at last be moving towards a more concrete understanding of the curious phenomena of the out-of-body experience (OBE).
Dr Henrik Ehrsson (centre) conducting his study into out-of-body experiences
OBEs have been reported in clinical conditions as a result of brain malfunction -- e.g. a stroke or epilepsy. Habitual users of recreational drugs sometimes report OBEs as do people who have experienced some form of life-threatening trauma -- e.g. a car accident.
They are a surprisingly common occurrence with around one in ten people claiming to have had an experience at some point during their lives. Yet the neuro-scientific basis of the phenomenon remains unclear.
Two recent scientific studies, however, have successfully created the illusion of an OBE and pave the way for a vastly improved understanding on the nature of consciousness.
Neuroscientist Dr Henrik Ehrsson devised an experimental method to induce an OBE in healthy participants and published his results in the journal Science last month.
Dr Ehrsson, who tested a total of 42 people, conducted his study at the Institute of Neurology at University College London. He was able to create the illusion of an OBE by setting up a relatively simple experiment.
Participants were asked to sit in a chair wearing a pair of head-mounted video displays (virtual reality goggles). The goggles had two small screens -- one for each eye -- which showed live film recorded by two video cameras, placed side by side, two meters behind the participant's head.
The image from the left video camera was presented on the left-eye display and images from the right camera fed to the right eye, allowing the person to see one stereoscopic (3D) image of their own image from behind.
In full view of the participant, Dr Ehrsson stood beside them and used two plastic rods to simultaneously touch the participant's actual chest out-of-view and the chest of the illusory body, moving the second rod towards where the illusory chest would be located, just below the camera's view.
"It was quite a vivid experience for most people," Dr Ehrsson told CNN. "Many of them giggled and said 'Wow, this is so weird!'. One of the people I tested had experienced an OBE before, and explained that the experiment had produced a very similar sensation."
An additional test was set up to measure the physiological response of volunteers. Ehrsson created a scenario where the illusory body was threatened - by swinging a hammer towards the virtual figure. Ehrsson calculated the amount that participants perspired - a common sign of fear. The results strongly indicated that the participants thought the threat was real.
There were a few people who didn't feel the illusion, but Ehrsson explained that this might have been due to the low-resolution on the virtual reality goggles which don't perfectly mimic human vision.
Dr Ehrsson believes that the invention of this illusion is an important step in understanding consciousness. "It reveals the basic mechanism that produces the feeling of being inside the physical body. This represents a significant advance because the experience of one's own body as the center of awareness is a fundamental aspect of self-consciousness," he said.
"I'm not really interested in out-of-body experiences," Dr Ehrsson told CNN, "I'm interested in the normal way we recognize our own bodies and how the brain distinguishes between the self and the environment."
Now based at the Karolinska Institute in Stockholm, Sweden, Dr Ehrsson told CNN that his study has already caught the eye of virtual reality researchers and video game developers. "Creating virtual reality avatars in games where you really feel it's you would give a much stronger feeling of presence in the virtual world."
He also pointed out other potential uses: "A surgeon could perform remote surgery, by controlling their virtual self from a different location," he said.
For Ehrsson this is only the beginning of a much broader study into the self-recognition and body ownership. "I will be doing a whole series of experiments," he explained. "We are now looking at motor responses and how they change when you feel that you are in a different place in a room."
A second study into OBEs -- also published in the journal Science -- was led by Dr Olaf Blanke at the Federal Polytechnic of Lausanne (EPFL) in Switzerland.
Like Dr Ehrsson's experiment, volunteers were fitted with stereoscopic headsets and were shown images of virtual figures -- this time the figures appeared in front of them. Participants either saw live footage of themselves, a mannequin or an inanimate black block.
Volunteers and the virtual figures were then stroked several times, sometimes simultaneously and sometimes not.
After one minute, subjects were then blindfolded and led two meters backwards. They were then asked to return to their original position.
Volunteers who had watched themselves or the mannequin being stroked overshot their original standing position by around 25 centimeters, suggesting that they had been drawn to the figure they had seen through the 3D goggles.
Dr Blanke concludes that a person can be tricked into subconsciously relocating their sense of self away from where it should have been. "The self was no longer within the body borders," he said. E-mail to a friend
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