Neuroscientists investigating a young woman with epilepsy believe they have stumbled on an explanation why some people feel a ghostly presence nearby or develop paranoia or persecution.
The 22-year-old woman was being assessed for brain surgery for epilepsy but was otherwise psychologically healthy.
Part of this evaluation was to pinpoint the area needed for surgery, using thin electrodes implanted into a region of the brain.
Reporting the case in tomorrow’s issue of Nature, the weekly British science journal, the doctors said that when they sent a small current to the woman’s left temporoparietal junction, she said she had the impression there was somebody behind her.
The person was a “shadow”, young and of indeterminate sex and did not speak, she said.
The doctors slightly increased the current and changed the woman’s position from lying down to seated, and got her to hug her knees.
She then said she felt the creepy presence of man who was also sitting and who was clasping her unpleasantly in his arms.
The current was slightly increased further and the woman, this time seated, carried out a language test, reading from a card held in her right hand. She reported the presence of a sitting “person,” this time displaced behind her to her right, who tried to interfere with the test.
“He wants to take the card… he doesn’t want me to read,” she said.
The sensation was so real that at no time did the woman realise that it was an illusion generated by her own mind, said the Swiss authors of the case sudy.
The temporoparietal junction is used for social reasoning – to assess oneself and distinguish oneself from others.
“Our findings may be a step towards understanding the mechanisms behind psychiatric manifestations such as paranoia, persecution and alien control,” the authors said.
Hat tip: Somnilista