Simple stimulation of the brain can cause the mind to play complex and creepy tricks on itself, neurologists have discovered. They found that, by inserting electrodes into a specific part of the brain, they could induce a patient to sense that an illusory ‘shadow person’ was lurking behind her and mimicking her movements.
Doctors treating the patient, a 22-year-old woman with epilepsy, found that when they stimulated a brain region called the left temporoparietal junction, the patient sensed the presence of a sinister figure behind her who copied her actions. They suspect that the effect is due to the mind projecting its own movements onto a phantom figure conjured up by the brain, an effect that is seen in some patients with serious psychiatric conditions.
“It was quite astonishing — she definitely realized the ‘person’ was taking the same posture as she did, but she didn’t make the connection,” says Olaf Blanke of the École Polytechnique Fédérale de Lausanne in Switzerland, who led the research. “To her it remained a different person, an alien — exactly what you find in schizophrenics.”