Amputees often report that they can feel a “phantom limb” where theirs used to be. One of the great challenges is not just to create prosthetic replacements that the patient can control, but that also provide sensations as they are used. This closing of the feedback loop is key to the natural use of prosthetic limbs.
Researchers at Arizona State University (ASU) are making great strides in this area. In a recently published paper, they describe how they implanted a matrix of 96 electrodes in the arms of two amputees for a month. As these electrodes were stimulated, the patients reported on what they felt. By mapping the areas, they hope to be able to provide feedback from a prosthetic hand. They also mapped neural activity in the brain as the subjects thought about making different movements with their missing hands. They were able to decode these signals, and drive an animated robotic hand that was displayed on a screen.
The goal is to create a feedback loop that will enable a person to control a powered prosthetic, and then experience the hand’s operation through signals sent by sensors in the hand. They hope that this will make the prosthetic feel more “natural” and part of the subject’s own body. They expect to use virtual reality (VR) systems to help train subjects to control their prosthetic hands, and to interpret the sensations they receive as it moves. They hope to move to human trials soon, and then work toward creating affordable devices.