We are able to influence our sensory presence by influencing parts of the brain.
Here is fantastic text about the effects of sending distorted information to the brain:
Out-of-body experience recreated
Near-death events have triggered out-of-body experiences
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Two teams used virtual reality goggles to con the brain into thinking the body was located elsewhere.
The visual illusion plus the feel of their real bodies being touched made volunteers sense that they had moved outside of their physical bodies.
The researchers say their findings could have practical applications, such as helping take video games to the next level of virtuality so the players feel as if they are actually inside the game.
Clinically, surgeons might also be able to perform operations on patients thousands of miles away by controlling a robotic virtual self.
Teleported
For some, out-of-body experiences or OBEs occurs spontaneously, while for others it is linked to dangerous circumstances, a near-death experience, a dream-like state or use of alcohol or drugs.
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We feel that our self is located where the eyes are
UCL researcher Dr Henrik Ehrsson
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But the two teams, from University College London, UK, and the Swiss Federal Institute of Technology in Lausanne, believe there is a neurological explanation.
Their work suggests a disconnection between the brain circuits that process visual and touch sensory information may thus be responsible for some OBEs.
In the Swiss experiments, the researchers asked volunteers to stand in front of a camera while wearing video-display goggles.
Through these goggles, the volunteers could see a camera view of their own back - a three-dimensional "virtual own body" that appeared to be standing in front of them.
When the researchers stroked the back of the volunteer with a pen, the volunteer could see their virtual back being stroked either simultaneously or with a time lag.
The volunteers reported that the sensation seemed to be caused by the pen on their virtual back, rather than their real back, making them feel as if the virtual body was their own rather than a hologram.
Volunteers
Even when the camera was switched to film the back of a mannequin being stroked rather than their own back, the volunteers still reported feeling as if the virtual mannequin body was their own.
And when the researchers switched off the goggles, guided the volunteers back a few paces, and then asked them to walk back to where they had been standing, the volunteers overshot the target, returning nearer to the position of their "virtual self".
Dr Henrik Ehrsson, who led the UCL research, used a similar set-up in his tests and found volunteers had a physiological response - increased skin sweating - when they felt their virtual self was being threatened - appearing to be hit with a hammer.
Dr Ehrsson said: "This experiment suggests that the first-person visual perspective is critically important for the in-body experience. In other words, we feel that our self is located where the eyes are."
Dr Susan Blackmore, psychologist and visiting lecturer at the University of the West of England, said: "This has at last brought OBEs into the lab and tested one of the main theories of how they occur.
"Scientists have long suspected that the clue to these extraordinary, and sometimes life-changing, experiences lies in disrupting our normal illusion of being a self behind our eyes, and replacing it with a new viewpoint from above or behind."
Studies Report Inducing Out-of-Body Experience
Using virtual-reality goggles, a camera and a stick, scientists have induced out-of-body experiences — the sensation of drifting outside of one’s own body — in ordinary, healthy people, according to studies being published today in the journal Science.
Martin Boyer/EPFL
A representation of one of the scenarios that scientists used to study out-of-body experiences.
Nicolas Righetti for the New York Times
Professor Olaf Blanke, center, with his assistant and electronics engineer Tej Tadi and a mannequin nicknamed Estelle.
The research reveals that “the sense of having a body, of being in a bodily self,” is actually constructed from multiple sensory streams, said one expert on body and mind, Dr. Matthew M. Botvinick, an assistant professor of neuroscience at Princeton University.
Usually these sensory streams, which include vision, touch, balance and the sense of where one’s body is positioned in space, work together seamlessly, Dr. Botvinick said. But when the information coming from the sensory sources does not match up, the sense of being embodied as a whole comes apart.
The brain, which abhors ambiguity, then forces a decision that can, as the new experiments show, involve the sense of being in a different body.
The research provides a physical explanation for phenomena usually ascribed to otherworldly influences, said Peter Brugger, a neurologist at University Hospital in Zurich, who, like Dr. Botvinick, had no role in the experiments. In what is popularly referred to as near-death experience, people who have been in the throes of severe and sudden injury or illness often report the sensation of floating over their body, looking down, hearing what is said and then, just as suddenly, finding themselves back inside their body.
Out-of-body experiences have also been reported to occur during sleep paralysis, the exertion of extreme sports and intense meditation practices.
The new research is a first step in figuring out exactly how the brain creates this sensation, Dr. Brugger said.
The out-of-body experiments were conducted by two research groups using slightly different methods intended to expand the so-called rubber hand illusion.
In that illusion, people hide one hand in their lap and look at a rubber hand set on a table in front of them. As a researcher strokes the real hand and the rubber hand simultaneously with a stick, people have the vivid sense that the rubber hand is their own. When the rubber hand is whacked with a hammer, they wince and sometimes cry out.
The illusion shows that body parts can be “separated” from the whole body by manipulating a mismatch between touch and vision. That is, when a person’s brain sees the fake hand being stroked and feels the same sensation, the sense of being touched is misattributed to the fake.
The new experiments were designed to create a whole-body illusion with similar manipulations.
In Switzerland, Dr. Olaf Blanke, a neuroscientist at the École Polytechnique Fédérale in Lausanne, asked people to don virtual-reality goggles while standing in an empty room. A camera projected an image of each person taken from the back and displayed that image as if it were six feet in front of the subject, who thus saw an illusory image of himself.
Then Dr. Blanke stroked each person’s back for one minute with a stick while simultaneously projecting the image of the stick onto the illusory body.
When the strokes were synchronous, people reported the sensation of being momentarily within the illusory body. When the strokes were not synchronous, the illusion did not occur.
In another variation, Dr. Blanke projected a “rubber body” — a cheap mannequin bought on eBay and dressed in the same clothes as the subject — into the virtual-reality goggles. With synchronous strokes of the stick, people’s sense of self drifted into the mannequin.
A separate set of experiments was carried out by Henrik Ehrsson, an assistant professor of neuroscience at the Karolinska Institute in Stockholm.
Last year, when Dr. Ehrsson was “a bored medical student at University College London,” he wondered, he said, “what would happen if you ‘took’ your eyes and moved them to a different part of a room.”
“Would you see yourself where your eyes were placed?” he said. “Or from where your body was placed?”
To find out, he asked people to sit in a chair and wear goggles connected to two video cameras placed six feet behind them. The left camera projected to the left eye, the right camera to the right eye. As a result, people saw their own backs from the perspective of a virtual person sitting behind them.
Using two sticks, Dr. Ehrsson stroked each person’s chest for two minutes with one stick while moving the second stick just under the camera lenses, as if it were touching the virtual body.
Again, when the stroking was synchronous, people reported the sense of being outside their own bodies, in this case looking at themselves from a distance where their “eyes” were situated.
Then Dr. Ehrsson grabbed a hammer. While people were experiencing the illusion, he pretended to smash the virtual body by waving the hammer just below the cameras. Immediately, the subjects registered a threat response as measured by sensors on their skin. They sweated, and their pulses raced. They also reacted emotionally, as if they were watching themselves get hurt.
Participants in the experiments conducted by Dr. Blanke and Dr. Ehrsson reported having felt a sense of drifting out of their bodies, but not a strong sense of floating or rotating as is common in full-blown out-of-body experiences, the researchers said.
The next set of experiments, they said, will involve decoupling not just touch and vision but other aspects of sensory embodiment, including the sense of balance and the body’s position in space.
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Henrik Ehrsson / AP
An experiment in out-of-body experiences at the University College, London.
That is, of course, why out-of-body experiences have always been, well, out-of-body. People report such experiences after returning from the "brink of death," or being under the influence of mind-altering drugs — no doubt why the sensation has long been equated with spiritual awakening (and with crackpots). But, today, with new advances in neurology, scientists are better able than ever to locate the physical roots of these bizarre perceptions of self. For example, neurologists have studied amputees who can feel sensation where their missing limbs used to be; researchers think this phantom limb phenomenon has to do with rewiring in the brain's somatosensory cortex. And, in the lab, researchers have been able to make people feel that fake rubber hands are attached to their own bodies. (This was done simply enough, by touching the participants' real hands while having them watch the rubber hands be touched in the same way and the same time.) Now, there are the current Science experiments: the first where volunteers have relocated their entire "selves" — their minds, as it were — outside of their bodies.
In both studies, participants wore goggles hooked up to cameras planted behind them, so that participants had a view of their own backs. Then they were physically stimulated in ways that would enhance or reduce the feeling that their selves were located outside their bodies. For his paper, Ehrsson used a stick to poke the chest of each participant (out of view of the person being poked) while also poking the area below the camera where a chest would have been (which the person could see through the goggles). Sure enough, the participants reported that it felt like their vantage point was exactly the same as that of the camera. "You feel quite clearly that you are sitting in the corner of the room, and you see yourself sitting elsewhere. But it's not you," Ehrsson says. To be certain — and to get some harder data — he hooked up his participants to stress-monitoring devices, and then swung a hammer at the space where the illusory chest would have been. The readings showed signs of stress all right. Many participants also visibly flinched.
The second experiment was conducted at Ecole Polytechnique F�d�rale de Lausanne in Switzerland, by a team including neurologist Olaf Blanke, whose work with out-of-body experiences suggests that their neural underpinnings reside in the brain's temporo-parietal junction. Blanke and his colleagues had participants watch their own backs being stroked — either through a video feed coming live to their eyes or through one coming slightly out of synch. Afterward, the participants were blindfolded and asked to return to their original place in the room; on average, those who had had the in-synch physical stimuli — and, thus, the real feeling of an out-of-body experience — "drifted" toward where the illusion had been.
So, do these lab experiments really feel like a true out-of-body experience? "It's very vivid," says Ehrsson of his test. Participants say they really did feel like they were outside of their bodies. People in both sets of studies found the experience "weird." Some of Ehrsson's subjects described the experiment as "cool" and giggled, while some in Blanke's study called it "irritating." But the extent to which the experiments succeeded "depends what you mean by the full-blown out-of-body experience," says Ehrsson. "Of course you know that it's not real, that it's all due to the goggles. But you can't just think it away."
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