LONDON: Ever felt like watching yourself from the sidelines? Scientists have just replicated that feeling in the lab. Neuroscientists have created an out-of-body illusion in people placed inside a br8ain scanner and used that illusion to perceptually ‘teleport’ the participants to different locations in a room.

Scientists from Sweden’s Karolinska Institutet have shown that the perceived location of the bodily self can be decoded from activity patterns in specific brain regions. Studies in rats have shown that specific regions of the brain contain GPS-like ‘place cells’ that signal the rat’s position in the room – a discovery that was awarded the 2014 Nobel Prize in physiology or medicine.

To date, however, it remains unknown how the human brain shapes our perceptual experience of being a body somewhere in space, and whether the regions that have been identified in rats are involved in this process.

In a study published in the scientific journal Current Biology, the scientists created an out-of-body illusion in fifteen healthy participants placed inside a brain scanner. In the experiment, the participants wore head-mounted displays and viewed themselves and the brain scanner from another part of the room.

From the new visual perspective, the participant observes the body of a stranger in the foregr8ou8nd while their physical body is visible in the background, protruding from the bore of the brain scanner.

To elicit the illusion, the scientist touches the participant’s body with an object in synchrony with identical touches being delivered to the stranger’s body, in full view of the participant. “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,” said Arvid Guterstam, lead author of the study.

In the most important part of the study, the scientists used the out-of-body illusion to perceptually ‘teleport’ the participants between different places in the scanner room. They then employed pattern recognition techniques to analyse the brain activity and show that the perceived self-location can be decoded from activity patterns in specific areas in the temporal and parietal lobes.

The scientists could demonstrate a systematic relationship between the information content in these patterns and the participants’ perceived vividness of the illusion of being located in a specific out-of-body position.

“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,” Guterstam said.

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