for National Geographic News
Schizophrenics sometimes feel the presence of an unknown person behind them who mimics their movements. Now scientists have produced the same disturbing effect in a nonschizophrenic person by applying electric stimulation to a specific area of her brain.
The discovery could help scientists unravel the brain processes behind delusions of paranoia, persecution, and alien control.
Doctors unintentionally produced the delusion while evaluating a 22-year-old epileptic woman for possible surgery.
Though the woman had no history of psychological problems, she repeatedly perceived a "shadow person" hovering behind her when doctors electrically stimulated an area of her brain called the left temporoparietal junction.
"Our data most importantly show that paranoia might be related to disturbed processing of one's own body, [which] in some instances may become misrecognized as the body of somebody else," said Olaf Blanke, a neuroscientist at the Swiss Federal Institute of Technology in Lausanne.
The hallucinatory condition was temporary and ended when stimulations were stopped.
Too Close for Comfort
During her ordeal, the patient described sensing an unknown person standing just behind her, mimicking her body positions.
"He is behind me, almost at my body, but I do not feel it," she told doctors, who report their discovery in this week's issue of the journal Nature.
When asked to lean forward and grasp her knees, the patient reported that she felt as if the shadow person were embracing her—a sensation she described as disturbing.
When performing assigned activities, such as a language-testing card game, she said that the shadow tried to interfere.
"He wants to take the card," she told doctors. "He doesn't want me to read."
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