WIKIMEDIA, ALFONSOPAZIf an experimenter touches a subject’s hand, which is hidden from view, while simultaneously touching the same location on a rubber hand that is left in sight, the subject will “adopt” the rubber hand as his own. This bizarre effect has to do with the brain’s maps of the body, called schema, originally proposed more than 100 years ago by neurologist Henry Head, who suggested that they might extend beyond the physical body to include tools and other objects. Now, research published today (August 26) in Proceedings of the National Academy of Sciences points to a neurologic mechanism behind the phenomenon.
Solaiman Shokur of L'Ecole Polytechnique Fédérale de Lausanne (EPFL) in Switzerland and his colleagues worked with two macaques in a variation of the rubber-hand experiment described above. One at a time, the researchers strapped the monkeys into a special chair that hid their arms from view while presenting two virtual arms on a large screen. The team used a brush to stroke the monkeys’ real arms while the screen depicted a ball touching the virtual arms—sometimes in synchrony with the real touches and in corresponding places on the arms, sometimes in different places and at different times. Meantime, the researchers recorded the activities of individual neurons in the somatosensory cortex, which processes sensory input, and in the motor cortex, which sends signals that control the ...
