How Swedish researchers triggered out-of-body experience in laboratory model
MOST of us have heard of an out-of-body experience – the idea that a person’s consciousness can travel and exist outside the physical body. Some of you may have even had such an experience.
Now, researchers from the Karolinska Institutet in Sweden reveal how they induced an out-of-body illusion in healthy study participants. What is more, the researchers were able to use this illusion to perceptually “teleport” these participants to various locations in a room, indicating that the location of where we believe our physical body to be can be interpreted from specific brain patterns.
Lead author Arvid Guterstam and colleagues publish their findings in the journal Current Biology. The researchers explain that in order for a person to determine the exact location of their body within a certain environment, the brain must constantly draw information from the different senses.
Previous research in rats has shown that certain regions of the brain contain “place cells,” which act like a GPS to indicate a rats’ exact position within their environment.
But according to Guterstam and colleagues, exactly how the human brain works to give us an accurate sense of where we are located in a specific space is unclear.
Do we have place cells in the same brain regions as those identified in rats? And if so, are they responsible for our perception of self-location? Perceived self-location decoded from brain activity in temporal and parietal lobes For their study, 15 healthy participants were placed inside a brain scanner while wearing a head-mounted display, on which the participants were able to view themselves inside the brain scanner from another area in the room.
The head-mounted display then showed each participant the body of a stranger standing in front of their body in the brain scanner. To trigger an out-of-body illusion, a researcher touched the participant’s actual body with an object, while the display showed the stranger receiving identical touches in synchrony.
“In a matter of seconds, the brain merges the sensation of touch and visual input from the new perspective, resulting in the illusion of owning the stranger’s body and being located in that body’s position in the room, outside the participant’s physical body,” explains Guterstam.
The researchers then used this out-of-body illusion to “teleport” the participants to different locations in the room while monitoring their brain activity via pattern recognition techniques.
From this, the researchers found they were able to interpret participants’ perceived location from specific activity patterns that occurred in the temporal and parietal lobes of the brain.
What is more, the team detected a link between the information present in these activity patterns and the extent to which participants felt their out-of-body illusion was real.
One brain region from which participants’ perceived location could be interpreted was the hippocampus – an area in which place cells have been identified in rats.
“This finding is particularly interesting because it indicates that place cells are not only involved in navigation and memory encoding, but are also important for generating the conscious experience of one’s body in space,” says principal investigator Henrik Ehrsson, professor in the Department of Neuroscience at Karolinska Institutet.
Speaking about the relevance of their findings, Guterstam says: “The sense of being a body located somewhere in space is essential for our interactions with the outside world and constitutes a fundamental aspect of human self-consciousness.
Our results are important because they represent the first characterization of the brain areas that are involved in shaping the perceptual experience of the bodily self in space.”