People who’ve stared death in the face and lived to tell about it—mountain climbers who’ve made a harrowing descent, say, or survivors of the World Trade Center attacks—sometimes report that just when their situation seemed impossible, a ghostly presence appeared. People with schizophrenia and certain types of neurological damage sometimes report similar experiences, which scientists call, aptly, “feeling of presence.”
Now a team of neuroscientists says it has identified a set of brain regions that seems to be involved in generating this illusion. Better yet, they’ve built a robot that can cause ordinary people to experience it in the lab.
The team was led by Olaf Blanke, a neurologist and neuroscientist at the Swiss Federal Institute of Technology in Lausanne. Blanke has a long-standing interest in creepy illusions of bodily perception. Studying these bizarre phenomena, he says, could point to clues about the biology of mental illness and the mechanisms of human consciousness.
In 2006, for example, Blanke and colleagues published a paper in Nature that had one of the best titles you’ll ever see in a scientific journal: “Induction of an illusory shadow person.” In that study, they stimulated the brain of a young woman who was awaiting brain surgery for severe epilepsy. Surgeons had implanted electrodes on the surface of her brain to monitor her seizures, and when the researchers passed a mild current through the electrodes, stimulating a small region at the intersection of the temporal and parietal lobes of her brain, she experienced what she described as a shadowy presence lurking nearby, mimicking her own posture.