Scientists develop technique to induce out-of-body experiences
|Friday, 24th of August, 2007 05:47:59 PM|
|Scientists have induced the age-old phenomenon of out-of-body experiences in healthy volunteers for the first time.|
The technique, which uses a virtual-reality-style set up of cameras linked to a head-mounted video display, will help researchers understand how the brain assimilates sensory information to determine the position of its body.
The technique could also improve virtual reality games and remote surgery by creating the illusion that a person is somewhere other than in their own body.
Out-of-body experiences are defined as those where a person who is awake sees their own body from somewhere outside themselves. The experiences have been reported in situations where brain function has been damaged through a stroke, epilepsy or drug abuse. The most common cases occur in traumatic situations such as car accidents or on operating tables.
"Out-of body-experiences have fascinated mankind for millennia - their existence has raised fundamental questions about the relationship between human consciousness and the body, and has been much discussed in theology, philosophy and psychology," said Henrik Ehrsson, who carried out his experiments at University College London and is now based at the Karolinska Institute in Stockholm.
"Although out-of-body experiences have been reported in a number of clinical conditions, the neuro-scientific basis of this phenomenon remains unclear."
One idea is that these experiences could be explained by errors in how the brain assimilates the visual, tactile and other sensory information coming in from the body. Normally the brain uses the information to construct an idea of the body's position in space. By mixing up the sensory inputs Dr Ehrsson wanted to see if the brain could be tricked into believing its body was somewhere else.
In his experiment participants wore goggles containing a video screen for each eye. Each screen was fed images from a separate camera behind the participant and, because the two images were combined by the brain into a single image, they saw a 3D image of their own back.
Dr Ehrsson then moved a plastic rod towards a location just below the cameras while the participant's real chest was simultaneously touched in the corresponding position. The participants reported feeling that they were located back where the cameras had been placed, watching a body that belonged to someone else.
Olaf Blanke of Ecole Polytechique Fédérale de Lausanne carried out a similar experiment but added another exercise after the virtual reality section, blindfolding the volunteers and guiding them a few steps backwards. When the volunteers were asked to return to their original position, he found they were confused, always overshooting their actual start position in the direction of their virtual body.
"This is a part of what people with spontaneous out of body experiences have, the self is not within the bodily borders," said Professor Blanke. "This is some aspect of an out-of-body experience we have reproduced in a mechanistic way."
Volunteers did not overshoot their original position if they just saw a black screen or a plain box in their goggles.
Both research groups, who published their results today in Science, concluded that confusion between the senses was a key mechanism in the explanation of out- of-body experiences.
As well as providing scientists with a way to examine out-of-body experiences further in a lab setting, the experiments could have industrial applications. "This is essentially a means of projecting yourself, a form of teleportation," said Dr Ehrsson. "If we can project people into a virtual character, so they feel and respond as if they were really in a virtual version of themselves, just imagine the implications.
"The experience of playing video games could reach a whole new level, but it could go much beyond that. A surgeon could perform remote surgery, by controlling their virtual self from a different location."