Scientists at the Swedish medical university Karolinska Institutet have now come up with a technique that recreates this sensation in fully conscious healthy volunteers. They hope that this technique will enable them to study the relationship between the body and the 'self' in the laboratory environment.
“The idea for the study came to me several years ago”, says Dr Henrik Ehrsson, research leader in the Department of Clinical Neuroscience. “I wondered what would happen if you moved a person’s eyes to somewhere else in the room. It has been found that the visual perspective is crucial in determining how the ego is experienced.”
The experiments involve the scientists connecting two video cameras placed side by side - like robot eyes - to a display on the volunteer's head, one camera for each eye. The cameras are positioned behind the volunteers and aimed at them. The volunteers then see themselves from outside, as if they were someone else looking at them.
But to be able to induce an out-of-body experience it is also necessary for the volunteers to sense their self outside their physical body. The scientist can induce such a sensation by standing in front of the cameras and poking a point just below them, that is to say the chest of the “phantom body” – the illusory body the volunteers perceive outside their physical body – while the actual chest is touched without the volunteers seeing that this is being done.
“The brain then responds to the hand that touches the illusory body, whereupon the volunteer has a powerful experience of being several metres outside their actual body”, says Dr Ehrsson. “The self has thus moved two metres in space and left the actual body, which instead feels like an empty shell, a doll.”
To prove the illusion scientifically, Dr Ehrsson hit the phantom body of the twelve volunteers with a hammer, and measured and degree of skin sweating in response to the provocation. It was found that the volunteers exhibited the same physiological stress response as when someone's real body is threatened, but only during the periods when the volunteers were actually experiencing the out-of-body illusion.
The new tool in the laboratory environment means that it is possible for the first time to undertake scientific research on what we call the self, both fundamental research and applied research, for example in computer science.
“In the future it may be possible not just to control a person in a virtual environment but to become the virtual person, that is to say one's self will be able to move to virtual persons,” says Dr Ehrsson.
Karolinska Institutet is one of the leading medical universities in Europe. Through research, education and information, Karolinska Institutet contributes to improving human health. Each year, the Nobel Assembly at Karolinska Institutet awards the Nobel Prize in Physiology or Medicine.
Katarina Sternudd | alfa
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