ghost phenomenon
November 7, 2014

Ghost In The Machine: Study Probes Causes Of ‘Feeling Of Presence’ Phenomenon

Chuck Bednar for redOrbit.com - Your Universe Online

Call them ghosts, specters, apparitions, guardian angels or phantoms, but tales of that strange sensation people experience when they think they feel someone nearby reach across cultures and time periods. Now, however, researchers have attempted to replicate this eerie phenomenon.

A team of researchers led by Olaf Blanke of the Swiss Federal Institutes of Technology (EPFL) analyzed 12 patients suffering from various neurological conditions in search of the origins of this so-called “feeling of a presence” (FoP), then developed a robot capable of instilling this same sensation in otherwise healthy men and women.

Writing in the November 6 edition of the journal Current Biology, Blanke and his colleagues reported that their data indicated that FoP was “an illusory own-body perception with well-defined characteristics that is associated with sensorimotor loss and caused by lesions in three distinct brain regions: temporoparietal, insular, and especially frontoparietal cortex.”

By combining those findings with the recent experimental advances in the field of multisensory own-body illusions, they developed a robotic system that was capable of generating the same feeling by sending mixed-up sensorimotor signals to the brains of healthy individuals. This FoP sensation, they said, is “caused by misperceiving the source and identity of sensorimotor (tactile, proprioceptive, and motor) signals of one’s own body.”

According to CNET’s Michelle Starr, Blanke’s team focused the initial part of their study on a dozen patients who suffered from neurological conditions such as epilepsy, stroke, tumors or migraines, each of whom had previously reported experiencing FoP for a period of at least several seconds. They traced the experiences to damage in one of the three aforementioned regions of the brain, all of which are involved with self-awareness, movement and spatial positioning.

However, Starr noted that brain damage wasn’t necessarily determined to be the cause of the experiences. Upon examining each patient’s symptoms further, Blanke’s team came to the conclusion that, in addition to lesions, FoP could be caused by confusion over the source of sensorimotor signals (meaning that they mistake their own body movements as belonging to something else). Using this knowledge, they created a robot designed to intentionally make it so that healthy brains could no longer recognize that these signals belonged to their own bodies.

They then recruited volunteers to take part in an experiment which mixed up their movements and brain signals according to Sarah Knapton, Science Editor for The Telegraph. During the experiment, the scientists made it seem as though the subjects saw as many as four phantoms standing around them. The subjects were even made to believe that the ghosts were touching their backs with invisible fingers.

“To manifest their ghosts, the scientists set up a robot device that allowed volunteers to control the movements of a jointed mechanical arm with their index fingers. The movements were relayed to another robot arm behind them which touched their backs,” Knapton said. “When both the finger-pushing and back-touching occurred at the same time, it created the illusion that the volunteers were caressing their own backs.”

“That felt weird enough to the blindfolded participants. But something a lot stranger happened when the back-touching was delayed and about 500 milliseconds out of sync with the finger movements,” she added. “Suddenly the volunteers felt as if they were being watched, and touched, by one or more ghostly presences. At the same time, they had the disconcerting sensation of drifting backwards, towards the unseen hand.”

At the conclusion of the experiments, several of the study participants reported feeling a strong sensation of invisible people being close to them, counting an average of two and as many as four at a time, according to Knapton. Two participants even reported being so disturbed by the experience that they actually asked Blanke and his colleagues to halt the experiment, she added.

“Our experiment induced the sensation of a foreign presence in the laboratory for the first time. It shows that it can arise under normal conditions, simply through conflicting sensory-motor signals,” Blanke explained in a statement. “The robotic system mimics the sensations of some patients with mental disorders or of healthy individuals under extreme circumstances. This confirms that it is caused by an altered perception of their own bodies in the brain.”

“In addition to explaining a phenomenon that is common to many cultures, the aim of this research is to better understand some of the symptoms of patients suffering from schizophrenia,” the EPFL added. “Such patients often suffer from hallucinations or delusions associated with the presence of an alien entity whose voice they may hear or whose actions they may feel. Many scientists attribute these perceptions to a malfunction of brain circuits that integrate sensory information in relation to our body’s movements.”

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