The road to sensory recovery after spinal cord injury is looking shorter thanks to revolutionary advancements in neural technologies by DARPA.
The latest feat, using an advanced prosthetic developed by the Applied Physics Laboratory at Johns Hopkins University, allowed a 28-year-old paralyzed man to feel physical sensations through the prosthetic hand that was connected to his brain.
“We’ve completed the circuit,” said DARPA program manager Justin Sanchez. “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 male participant, who has been paralyzed for more than a decade from a spinal cord injury, had electrode arrays placed on the sensory cortex and motor cortex, with wires attached to the mechanical hand. By linking the prosthetic to the motor cortex, the subject was able to control the hand with his thoughts.
In order to project a sense of touch, the prosthetic was equipped with torque sensors in the fingers that detected pressure. The sensors converted those sensations into electrical signals that reached the sensory cortex.
During testing, the participant was blindfolded while researchers gently touched each of the prosthetics’ fingers. The subject was able to identify with nearly 100% accuracy which finger was being touched, and described the feeling as if his own hand were being touched. The team also pressed two fingers at a time, after which, “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,” said Sanchez.
The findings, more of which are currently under peer review for publication, were presented by Sanchez at a DARPA future technology forum.