By Amielle Moreno
In Current Biology this month, a paper titled “Neurological and Robot-Controlled Induction of an Apparition” features neuroscientists exploring a sensation that’s ubiquitous among humans in every culture; the feeling or chilling sensation that someone is behind you when no one is present. Feeling of Presence, or FoP, is a phenomena present in both healthy individuals and those with psychotic disorders, such as schizophrenia. But like most sensory experiences, this one has its roots in neuroscience and not the occult or divine.
First author Olfe Blake and senior author Giulio Rognini, both out of Switzerland, conducted this study using mostly epileptic patients, who frequently experience this body delusion, to determine which brain location is commonly affected. They determined that the frontoparietal lobe was specifically associated with FoP. Responsible for the integration of sensory stimuli, these researchers suggest that the parietal lobe is the location responsible for that creepy feeling we all get when we turn out the lights in the basement, and then we have to walk up the stairs in the dark, and we swear there’s a monster behind us, and we run up the stairs and slam the door behind us, and we realize we’re breathing heavily and crying just a little bit, but we’re not embarrassed at all because this is totally something everybody does.
To experimentally replicate this sensation in a healthy population, the researchers designed a robot whose movements were guided by the fingers of study participants. Blindfolded and in a room alone, the participants would control the robot, making it touch their back. One group controlled the robot in real time, the other group had robots that would mimic their movements, but with a time delay. Subjects in the time delay group reported the experience to be more like another person was in the room with them, touching their back. This method induced FoP in some participants and made a smaller subset feel so uncomfortable that they had to stop the experiment! In this way the asynchronous robot stimulation was capable of simulated FoP in healthy participants. Scientists failed to control for the possibility that actual ghosts were present in the room during the experiment.
Blanke et al. concluded that they were able to create “a conflict between proprioceptive-motor signals and tactile feedback” that is similar to the FoP experience. Shining light on the cause of this sensation, researches believe that “abnormal integration of sensorimotor signals” is responsible for ghosts, I mean, FoP. So the experience of an unknown “other” just behind you and out of sight is simply a confusion between the brain’s sensation of the “self” and the “other.”
The researchers went further, suggesting that schizophrenics have deficits in the integration of sensory inputs, and this causes these individuals to be more likely to attribute “self-generated” sounds or touch as being “other-generated.” The authors hope that this study will have applications to schizophrenic individuals who experience this specific delusion. As the phenomenology behind the feeling of presence is explained, science puts another nail in the coffin of the “supernatural.”
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