A research article published in the journal Current Biology by scientists of Department of Neuroscience at Karolinska Institutet in Stockholm, Sweden, attempted to study “out of body” experiences (OBE) by determining the active regions in the brain. The neuroscientists were able to create an “out of body” illusion by subjecting participants to functional Magnetic Resonance Imaging (fMRI). Subsequently, this illusion was used to “teleport” the participants by giving them the illusion that they were in a different location than they actually were. The scientists were able to monitor the participants’ brain activity to identify the regions that were involved in the perception of an out-of-body experience.
Out of body experiences have always intrigued mankind. There is some anecdotal evidence of people narrating such experiences. Some hospitals in the UK and the USA are attempting to test the validity of OBEs that occur in Emergency Rooms by hanging pictures that can only be viewed near the ceiling. If a person could see himself/herself from above, then he/she should be able to see the picture. To date, no one claiming to have had a near-death experience (NDE) in the Emergency Room has accurately described the picture.
In attempts to understand the phenomenon, numerous studies have illustrated that two cortices (the medial temporal and posterior parietal) of the brain create one’s spatial location and head direction. Experiments with rats have shown that specific regions of the brain contain GPS-like 'place cells' in the hippocampus that indicate the rat’s position in the room (this discovery was awarded the 2014 Nobel Prize in Physiology or Medicine). The current study attempted to answer the unknown; which brain parts create the sense of body ownership.
The researchers manipulated 15 healthy participants’ perception of “self-location, head direction, and sense of body ownership” by utilizing a “multisensory out-of-body illusion” and measured their responses with a high-resolution fMRI. The participants laid inside of an MRI scanner with their head tilted forward. They wore a “head-mounted display” (HMDs) system, which allowed them to experience the room through the eyes of a stranger. The stranger was placed in three different locations in the same room. The experimenters elicited the illusion of body ownership of the stranger’s body by applying touches to the participant (which was out of view) and the stranger (visible through the HMDs) at the same time (synchronous). As a control, participants and strangers were touched at different times (asynchronous), which reduced the illusion. With this experimental design, the researchers tested for alterations in brain activity that would suggest changes in the participants’ “feelings of body ownership, self-location, and the functional interplay between ownership and self-location.”
The scientists conducted different behavioral experiments to quantify “subjective and objective changes in the perceived self-location and body ownership”. The findings were:
- Self-location test: participants rated which position they most strongly perceived as themselves during the experiment. The data confirmed that synchronous touches, compared to the asynchronous, elicited a stronger ownership of the stranger’s body.
- Post-scan questionnaire: Participants confirmed feeling ownership of the stranger’s body during the “multisensory out-of-body illusion”.
- Skin conductance response (SCR): used to test body ownership. Threatening the stranger’s body significantly increased SCR in the synchronous versus the asynchronous condition. Suggests that the participants experienced the threat as though it was their own bodies
- Blood-oxygen-level-dependent (BOLD) responses: analyzed when the stranger or participant’s body was threatened. Responses affect regions of the brain involved in fear and anticipating pain. Similar results as in the SCR test.
“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,” says Arvid Guterstam, the lead author of the publication, to Karolinska Institutet (KI) News. “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.”
One of the brain regions involved in the illusion was the hippocampus, where the “place cells” are located. “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 at the Department of Neuroscience, Karolinska Institutet, to KI News.
The OBEs are more prevalent in patients suffering from schizophrenia and some forms of epilepsy. It would be interesting to find out if the hippocampal “place cells” are altered in any way in such patients.
Written by Monique Richards
Guterstam, A., Bjornsdotter, M., Gentile, G., & Ehrsson, H.H. (2015). Posterior Cingulate Cortex Integrates the Senses of Self-Location and Body Ownership. Current Biology,DOI: http://dx.doi.org/10.1016/j.cub.2015.03.059
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