In the Duke experiment, the two monkeys observed a realistic, computer-generated image of a monkey arm on a screen being touched by a virtual ball. At the same time, the monkeys' arms were touched, triggering a response in their somatosensory and motor cortical areas.
The monkeys then observed the ball touching the virtual arm without anything physically touching their own arms. Within a matter of minutes, the researchers saw the neurons located in the somatosensory and motor cortical areas begin to respond to the virtual arm alone being touched.
The responses to virtual touch occurred 50 to 70 milliseconds later than physical touch, which is consistent with the timing involved in the pathways linking the areas of the brain responsible for processing visual input to the somatosensory and motor cortices. Demonstrating that somatosensory and motor cortical neurons can respond to visual stimuli suggests that cross-functional processing occurs throughout the primate cortex through a highly distributed and dynamic process.
"These findings support our notion that the brain works like a grid or network that is continuously interacting," Nicolelis said. "The cortical areas of the brain are processing multiple streams of information at the same time instead of being segregated as we previously thought."
The research has implications for the future design of neuroprosthetic devices controlled by brain-machine interfaces, which hold promise for restoring motor and somatosensory function to millions of people who suffer from severe levels of body paralysis. Creating neuroprostheses that become fully incorporated in the brain's sensory and motor circuitry could allow the devices to be integrated into the brain's internal image of the body. Nicolelis said he is incorporating the findings into the Walk Again Project, an internatio
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Duke University Medical Center