In 2006, cognitive neuroscientist Olaf Blanke of the University of Geneva in Switzerland was testing a patient’s brain functions before her epilepsy surgery when he noticed something strange. Every time he electrically stimulated the region of her brain responsible for integrating different sensory signals from the body, the patient would look back behind her back as if a person was there, even when she knew full well that no one was actually present. Now, with the help of robots, Blanke and colleagues have not only found a neurological explanation for this illusion, but also tricked healthy people into sensing “ghosts,” they report online today in Current Biology. The study could help explain why schizophrenia patients sometimes hallucinate that aliens control their movements. [...] To pinpoint the brain regions responsible for such illusions, Blanke and colleagues compared brain damage in two groups of patients. The first group, mostly epilepsy patients, all reported feeling ghostly presences near them. The other group matched them in terms of the severity of their neurological illnesses and hallucinations, but didn’t perceive any ghostly presence. Brain imaging revealed that patients who sensed the “ghosts” had lesions in their frontoparietal cortex, a brain region that controls movements and integrates sensorimotor signals from the body—such as the “smack” and pain accompanying a punch—into a coherent picture. The researchers suspected that damage to this region could have disrupted how the brain integrates various sensory and motor signals to create a coherent representation of the body. That may have led the patients to mistakenly feel that someone else, not themselves, were creating sensations like touch.
Posted on: Thu, 06 Nov 2014 22:12:05 +0000
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