Medical

Ghost in the machine: Scientists recreate "phantom presence" perception in the lab

EPFL researchers succeeded in recreating the feeling of a "ghostly presence" in the laboratory (Photo: Shutterstock)
EPFL researchers succeeded in recreating the feeling of a "ghostly presence" in the laboratory (Photo: Shutterstock)
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Researchers have artificially recreated the sensation of a "ghostly presence" in healthy subjects by interfering with the proprioception and tactile feedback mechanisms (Image: Alain Herzog/EPFL)
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Researchers have artificially recreated the sensation of a "ghostly presence" in healthy subjects by interfering with the proprioception and tactile feedback mechanisms (Image: Alain Herzog/EPFL)
Delaying touch feedback caused hallucination of up to 4 external entities (Image: Alain Herzog/EPFL)
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Delaying touch feedback caused hallucination of up to 4 external entities (Image: Alain Herzog/EPFL)
Analysis of lesion overlap between 12 subjects who experienced apparitions, on the left, with a control group, on the right (Image: Current Biology)
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Analysis of lesion overlap between 12 subjects who experienced apparitions, on the left, with a control group, on the right (Image: Current Biology)
A robotic arm mirrors the movement of the front arm controlled by the subject (Image: Alain Herzog/EPFL)
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A robotic arm mirrors the movement of the front arm controlled by the subject (Image: Alain Herzog/EPFL)
The participant, blindfolded, moves a robotic arm with his hands; the movements are mirrored on his back, providing tactile feedback with a short delay (Image: Current Biology)
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The participant, blindfolded, moves a robotic arm with his hands; the movements are mirrored on his back, providing tactile feedback with a short delay (Image: Current Biology)
EPFL researchers succeeded in recreating the feeling of a "ghostly presence" in the laboratory (Photo: Shutterstock)
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EPFL researchers succeeded in recreating the feeling of a "ghostly presence" in the laboratory (Photo: Shutterstock)

Mountain climbers facing extreme climatic conditions, patients affected by schizophrenia or neurological disorders and athletes facing severe exhaustion have all reported experiencing an invisible and yet persistent "presence" that is often felt just outside their field of view. Researchers at the École polytechnique fédérale de Lausanne (EPFL) have now recreated the same sensations in perfectly healthy subjects, inducing ghostly hallucinations in a matter of minutes.

The "Speech Jammer" is a silly little tool that can easily turn even the most eloquent of speakers into a babbling mess. It works by listening to your own words and then repeating them back to you with a very slight delay. A difference of a few tenths of a second is enough to trip up the feedback loop between your voice and your ears – with some hilarious results.

The EPFL experiment suggests that similarly "jamming" the feedback loop between your body awareness and your sense of touch can have drastic consequences too – you may start to feel the presence of up to four people other than yourself.

Researcher Giulio Rognini and colleagues began by analyzing the brains of 12 patients with neurological disorders who have reported experiencing such "apparitions" (curiously, all coming from behind). By comparing their MRI brain scans with a control group they confirmed that the apparitions were a result of lesions in the frontoparietal cortical region of the brain, associated with bodily self-consciousness and sensorimotor skills.

Analysis of lesion overlap between 12 subjects who experienced apparitions, on the left, with a control group, on the right (Image: Current Biology)
Analysis of lesion overlap between 12 subjects who experienced apparitions, on the left, with a control group, on the right (Image: Current Biology)

The scientists used these results to set up an experiment designed to send conflicting signals to this area of the brain and create the feeling of a presence even in healthy subjects, in a matter of minutes.

The system they came up with was a robot comprised of two parts: a front arm that is moved around by the subject, and a second one that recreates exactly the same movements of the first, but touching the subject’s back as he or she is blindfolded.

As Rognini and team found out, introducing a slight delay in the back arm "jammed" the feedback loop between body positioning and sense of touch, distorting perception and creating the impression, in healthy subjects, that up to four people separate from themselves had materialized near them.

The participant, blindfolded, moves a robotic arm with his hands; the movements are mirrored on his back, providing tactile feedback with a short delay (Image: Current Biology)
The participant, blindfolded, moves a robotic arm with his hands; the movements are mirrored on his back, providing tactile feedback with a short delay (Image: Current Biology)

"Our brain possesses several representations of our body in space," says Rognini. "Under normal conditions, it is able to assemble a unified self-perception of the self from these representations. But when the system malfunctions because of disease  –  or, in this case, a robot  –  this can sometimes create a second representation of one’s own body, which is no longer perceived as 'me' but as someone else, a 'presence'."

This could help understand the symptoms of schizophrenia, suggesting that these patients are perceiving their own sounds and movements as being generated by someone else. And, say the researchers, it could also help explain why ghosts are present in so many cultures throughout the world.

The researchers describe their work in a paper published on the journal Current Biology, and in the video below.

Source: EPFL

Neuroscientists awaken ghosts… hidden in our cortex

6 comments
Nomad Red
That's ridiculous. I hardly think, the phenomenon experienced by people suffering from exhaustion or exposure, first of all would have any relationship to the group of individuals suffering from Schizophrenia, and secondly that the optimistic conclusion of these scientists, that the experience is even slightly representative of what either group actually experiences on a personal level, can be replicated based on pretty colors from a scan and a "Fun for all the family" robotic palor trick. I find it completely insensitive and immature to be making light of such serious experiences. I find the line, "...suggesting that these patients are perceiving their own sounds and movements as being generated by someone else." to be an exact example of how ignorant and removed the scientific community is from understanding, albeit, even capable of empathising with their "subjects". I mean really? Did they actually think that when a mentally ill patient says that they are hearing voices, they actually considered the idea that the voices may actually be coming from somewhere other than the patients head???. Science is no more than religion, except for the much cleverer way in how the scripture is presented with "evidence" as opposed to "faith".
lwesson
Hilarious. I am not sure how to share this with the ghostly occupants of our 1925 house, but it is more than likely to get a rise out of them, like laughter, which I have heard upon discussing with the Missus, about my novel... and she heard it too. The Life Challenged seem to have grasp for humor. Of course, the playful antics of moving items, ringing a disconnected door bell, and responding to a query with said door bell, I am certain that Scientists will start out with a certain diamond hard assumption, and try to concoct some reasonable explanation. This is the haughty foundation that some Scientists operate from. Give them computer stats, and the stats can be manipulated to get the desired results. Humm? I bet that never ever happens. OK ghosts, I am waiting... Really, they left some time ago, I think. Kind of lonely here now.
Layne Nelson
How about a cure for Idiopathic Pulmonary Fibrosis?
warren52nz
@Nomad Red "Science is no more than religion" That's pretty funny. :-)
rocketride
@ Nomad Red I'm pretty sure that you either missed the point or are being deliberately obtuse. They're trying to figure out how a brain sometimes generates spurious sensations and why it sometimes can neither integrate them into normal perception nor weed them out -- leaving hallucinations. One good way to get a handle on how brains sometimes go off the rails without any help is to figure out a way to cause them to do it.
Slowburn
Being caught in a blizzard and walking to exhaustion I had the presence behind me. Can these scientist explain why the motivation that kept me moving after I gave up came from him.