DARPA’s Revolutionizing Prosthetics program is breaking new ground with a prosthetic hand that provides a sense of touch to the person who is wearing it. This research builds upon an earlier experiment in which a volunteer with paralysis was able to control a prosthetic hand using only his thoughts. After its success with movement, the researchers wanted to add touch to the artificial hand, making it possible for those with paralysis to perform precise movements that require both movement and touch feedback.
In its most recent experiment, researchers placed a series of electrode arrays onto both the sensory cortex and the motor cortex of a volunteer’s brain. The sensory cortex is the region of the brain responsible for sensing touch while the motor cortex manages the movement. This direct motor cortex connection was used by a volunteer to control a prosthetic hand with his thoughts in an earlier, groundbreaking DARPA experiment.
Using the knowledge gleaned from their motor cortex work, DARPA scientists wired the sensory connection in the volunteer’s brain to torque sensors in the artificial hand. These hand sensors translated the physical touch of an object to electrical signals that the brain can read. The connection and translation process allowed a 28-year-old volunteer, who was paralyzed following a spinal injury, to sense touch. The volunteer reported feeling a near natural sensation “as if his own hand were being touched.”
The sense of touch was very noticeable to the volunteer, who was able to report with near 100 percent accuracy which finger on the prosthetic hand was being touched. The researchers even tried to fool the volunteer by touching two fingers without telling him and he responded by asking”whether somebody was trying to play a trick on him.”
Neurotechnology advances won’t eliminate paralysis, however, the scientists at DARPA hope the knowledge gained from the Revolutionizing Prosthetics program will provide a tangible benefit for those living with paralysis. DARPA presented its initial findings on its touch prosthetic hand at the recent Wait, What? A Future Technology Forum with a detailed report to be released following peer review and publication in a scientific journal.