Implanted electrodes created "shadow" feeling
When electrodes were used to stimulate the temporoparietal junction (TPL) of an epilepsy patient, she suddenly had the feeling that a man was playing her shadow, mimicking all her movements. This brain region is known for linking visual and self-perceptual information.
Olaf Blanke from the Polytechnic University of Lausanne and his colleagues had implanted electrodes in the young woman in order to find out the centers of epileptic seizures before an operation. When they gently stimulated the left TPL, the patient explained that she felt someone imitating her - sitting behind her or lying down next to her. The shadow even seemed to want to take the piece of paper away from her when she was supposed to be taking a language test, and when she was asked to bend forward and grab her knees, she felt clutched from behind.
This "shadow" phenomenon could perhaps help in schizophrenia research, Blanke explains. Here self-perception disorders occur more frequently in that patients perceive their body as that of another person. Perhaps the area also plays a role in out-of-body experiences - when people perceive themselves to be floating above their bodies, for example.