The researchers were able to replicate that ghostly feeling in a lab by interfering with the sensorimotor input of participants’ brains. When confronted with conflicting sensory-motor signals, some of the participants said they felt up to four ghosts. Some were so disturbed that they asked the experiment to be stopped.
Participants were blindfolded and asked to perform movements with their hands in front of their bodies while a robotic device reproduced their movements and touched their backs. When a delay was introduced between the movement and the robotic touch, it created a distorted spatial perception that led to the ghost illusion, the researchers said.
An MRI analysis confirmed that the participants’ brains were undergoing interference with the three regions associated with self-awareness and sense of spatial position.
“Our experiment induced the sensation of a foreign presence in the laboratory for the first time,” Olaf Blanke, head of the Laboratory of Cognitive Neuroscience at EPFL in Switzerland, said in a press release. “It shows that it can arise under normal conditions, simply through conflicting sensory-motor signals.”
The sensation can occur in patients with mental disorders as well as in healthy individuals placed in extraordinary circumstances, he said.
“Our brain possesses several representations of our body in space,” said lead researcher Giulio Rognini. “Under normal conditions, it is able to assemble a unified self-perception of the self from these representations. But when the system malfunctions because of disease — or, in this case, a robot — this can sometimes create a second representation of one’s own body, which is no longer perceived as ‘me’ but as someone else, a ‘presence’.”
From Discovery News
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