A 28-year-old who has been paralyzed for more than a decade has become the first person to “feel” physical sensations through a prosthetic hand that’s directly connected to his brain, the U.S. Department of Defense announced last week. He was even able to figure out which of his new mechanical fingers was being touched.

“We’ve completed the circuit,” Justin Sanchez of the Defense Advanced Research Projects Agency (DARPA) says in a statement. “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 mechanical hand, developed by the Applied Physics Laboratory at Johns Hopkins University, contains sensors that detect when pressure is being applied to the fingers. This “touch” is then converted into electrical signals that are routed to electrode arrays in the wearer’s brain using wires. These arrays were placed in the sensory cortex, which is responsible for identifying tactile sensations, as well as the motor cortex, which directs movement. As a result, the volunteer, who became paralyzed after a spinal cord injury, was able to control the hand’s movements with his thoughts.

Furthermore, when the researchers touched the mechanical fingers, the blindfolded man was able to accurately identify which finger was being touched nearly 100% of the time. He said it felt like his own hand was being touched. “At one point, instead of pressing one finger, the team decided to press two without telling him,” Sanchez says. “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.”

This piece of neurotechnology was developed under DARPA’s Revolutionizing Prosthetics program. The basic findings were described at Wait, What? A Future Technology Forum in St. Louis last week. More details will become available when the work is published in a peer-reviewed journal.

Image in text: Johns Hopkins University