A 28-year-old who has been paralyzed for more than a decade has become the first person to be able to “feel” physical sensations through a prosthetic hand directly connected to his brain, and even identify which mechanical finger is being gently touched.
The clinical work, made possible by DARPA’s Revolutionizing Prosthetics program, involved the placement of electrode arrays onto the paralyzed volunteer’s sensory cortex — the brain region 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.
To allow the subject to control the hand's movements with his thoughts, 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.
The APL hand contains sophisticated torque sensors that can detect when pressure is being applied to any of its fingers, and can convert the physical “sensations” into electrical signals. The team used wires to route those signals to the arrays on the volunteer’s brain.
In the very first set of tests, in which researchers gently touched each of the prosthetic hand’s fingers while the volunteer was blindfolded, he was able to report with nearly 100 percent accuracy which mechanical finger was being touched.
