Prosthetic arm restores paralyzed man’s sense of touch

A new robotic arm has enabled a victim of a spinal cord injury to regain motion and sensation— a technological breakthrough that offers promise for a patient population with few successful therapeutic options. In this case, the 28-year-old man, who was not named, regained those abilities 10 years after his injury.

Military research agency Defense Advanced Research Project Agency (DARPA) developed the arm and said the man is the first-ever patient to be able to sense when the prosthetic fingers were being stimulated. The artificial limb’s sensors are connected to the brain.

The work shows the potential for seamless biotechnological restoration of near-natural function, researchers said.

“We’ve completed the circuit,” DARPA program manager Justin Sanchez said in a news release on Friday. “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.”

Researchers placed electrode arrays onto the area of the paralyzed volunteer’s brain that’s responsible for identifying tactile sensations, such as pressure. Arrays were also placed on the volunteer’s motor cortex, which directs body movements. The mechanical hand and the arrays on the motor cortex were connected by wires, allowing him to control the hand’s movements with his thoughts.

The mechanical hand, developed by the Applied Physics Laboratory (APL) at Johns Hopkins University, contains sophisticated torque sensors able to detect when pressure is being applied to any of the fingers. It then can convert the physical “sensations” into electrical signals that were routed by wires to the arrays in the patient’s brain.

While blindfolded, the volunteer was able to report with nearly 100 percent accuracy, which mechanical finger was being touched — in the very first set of tests.

“At one point, instead of pressing one finger, the team decided to press two without telling him,” Sanchez, who oversees the Revolutionizing Prosthetics program, said in the news release. “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.”

According to Tech Times, the prosthetic hand does not cover the whole hand, and it is not sensitive to temperature and other factors like a real hand.

The findings were presented September 10 at “What What? A Future Technology Forum” hosted by DARPA.