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Researchers in the US have for the first time connected a person's brain to a prosthetic hand, enabling them to directly experience physical sensations.
The experiment, which was carried out on a 28-year-old who has been paralysed for more than a decade because of a spinal cord injury, enabled him to “feel” physical sensations and identify which of the mechanical fingers is being gently touched.
Justin Sanchez, the manager of Darpa's Revolutionizing Prosthetics programme, said: “We’ve completed the circuit. Prosthetic limbs that can be controlled by thoughts are showing great promise, but without feedback from signals traveling back to the brain it can be difficult to achieve the level of control needed to perform precise movements.
“By wiring a sense of touch from a mechanical hand directly into the brain, this work shows the potential for seamless bio-technological restoration of near-natural function.”
The researchers placed electrode arrays onto the paralysed volunteer’s sensory cortex, the region of the brain responsible for identifying tactile sensations such as pressure. In addition, the team placed arrays on the volunteer’s motor cortex, the part of the brain that directs body movements.
Wires were run from the arrays on the motor cortex to a mechanical hand developed by the Applied Physics Laboratory (APL) at Johns Hopkins University, giving the volunteer the capability to control the hand's movements with his thoughts.
The APL hand features torque sensors to detect when pressure is being applied to any of its fingers, and converts this data into electrical signals. Researchers used wires to route those signals to the arrays on the volunteer’s brain.
In the first set of tests each of the prosthetic hand’s fingers where touched while the volunteer was blindfolded. He reported 100% accurately which mechanical finger was being touched. The feeling, he reported, was as if his own hand were being touched.
“At one point, instead of pressing one finger, the team decided to press two without telling him,” said Sanchez. “He responded in jest asking whether somebody was trying to play a trick on him. That is when we knew that the feelings he was perceiving through the robotic hand were near-natural.”
The findings were released at a Darpa event in St Louis in the US last week and are pending peer review.
The restoration of sensation with implanted neural arrays is one of several neurotechnology-based projects being conducted by Darpa, US defence research agency said. Other projects include work to restore function to individuals living with memory loss or traumatic brain injury.
Sanchez said: “Our investments in neurotechnologies are helping to open entirely new worlds of function and experience for individuals living with paralysis and have the potential to benefit people with similarly debilitating brain injuries or diseases.”