It turns out your teachers were being a little hasty when they said there are only five senses. For instance, there’s proprioception, which is essentially the brain’s ability to take stock of where your limbs are in relation to the rest of your body, without seeing or touching anything. Even floating in a pool with your eyes shut, you don’t have to check to know where your arms and legs are.
This, of course, gets a bit complicated when you lose an arm or leg. In 80% of patients, the result, at least for a little while, is a condition called phantom limb syndrome: a burning or tingling perceived in the area of the former extremity, which scientists theorize may be the nerve endings attempting to make sense of the sudden disconnect. Previously, we wrote about an experimental phantom limb treatment involving a VR headset.
However, now a new solution may be on the horizon, created by EPFL, the Sant’Anna School of Advanced Studies in Pisa and the A. Gemelli University Polyclinic in Rome. They’ve developed a prosthetic hand, but far from being a simple facsimile of a palm and five fingers, it is instead a complex piece of robotics designed to stimulate the nerves of the user’s stump. It’s the result of ten years of research—and it shows.
Current robotic prosthetics on the market allow the user to control their new hand using the remaining muscles of the forearm. That said, the only feedback the user gets is visual. If the user wants to pick something up, the only way to get the sensory information of “I’m touching this item, now I’m holding it,” is to watch it happen. That disconnect can make it harder for the user to integrate the prosthesis as part of their body.
Research groups have been studying how to give amputees that all-important tactile feedback, but this recent study represents another big step forward. Not only does this new “intraneural stimulation” approach allow for tactile feedback, but positional feedback as well, meaning these are prosthetics that will provide the all-important sense of proprioception for that hand. “The brain has no problem combining this information, and patients can process both types in real time with excellent results,” Silvestro Micera told the press.
This process doesn’t happen overnight. Electrodes are placed on the amputee’s stump, and the patient must then go through a special course to train their brains to convert electrical pulses into the sense of touching something, or moving the hand through space. Although trials so far have been very limited, thus far, two amputees were able to regain proprioception of the hand, and to determine the size and shape of objects touched with slightly over 75% accuracy.
No headset required.