A team at the University of Pittsburgh is working to connect prosthetic arms and legs with the nervous system to give patients a sense of touch.
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Scientists want to make artificial limbs feel real. Scientists are developing bionic arms and legs that provide a sense of touch. NPR’s Jon Hamilton reports on work by researchers at the University of Pittsburgh.
JON HAMILTON, BYLINE: The group includes more than 80 people from 10 different labs. Lee Fisher is a bioengineer who runs one of those labs. He says their inspiration comes from Star Wars.
LEE FISHER: When Luke Skywalker has that amputation, they give him this new hand, and it – you can’t tell that it’s not his own hand.
HAMILTON: One reason – Luke’s prosthetic hand feels pressure and pain just like his natural one did. Fisher says we rely on a sense of touch for even simple tasks, like holding a cup of coffee. So the Pittsburgh scientists are finding ways to obtain tactile information from artificial limbs and transmit it to the user’s own nervous system. Fisher’s lab, for example, is using a device implanted in a person’s spine.
FISHER: It basically looks like – almost like a spaghetti noodle. They can be inserted through a needle.
HAMILTON: The device is designed to stimulate the nerves of people with chronic pain, but Fisher’s lab is using it to relay information from sensors on a prosthetic hand or foot. He says the trick is to stimulate the same nerve fibers that were once connected to the person’s own limb.
FISHER: The first thing we do is just try and understand, what does the stimulation feel like? So can we generate a sensation that feels like it’s coming from their missing hand or from their missing foot? Can we change how intense it feels?
HAMILTON: A study of four people suggests the answer is yes. Pat Bayne, whose right arm was amputated to stop an infection, described what the stimulation felt like in a video made by the university.
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PAT BAYNE: I know there’s no hand there, but I can feel it. They can make the palm of my hand feel like it’s the palm of my hand.
HAMILTON: Artificial legs and feet also work better with a sense of touch. Fisher says that’s because we rely on constant feedback from our feet just to stay upright.
FISHER: We’re basically like an upside down pendulum that you have to keep moving around to maintain that balance, and that sensory feedback from your feet is really what allows you to do that.
HAMILTON: Fisher says an experiment that added feedback from a prosthetic foot seemed to help at least one amputee.
FISHER: We saw what looks like improvements in her balance control during standing, her stability while she’s walking and also maybe some improvements in her confidence as well – so how comfortable she feels.
HAMILTON: A sense of touch can even help people whose limbs are paralyzed. For several years, the Pittsburgh group has been teaching paralyzed people to control a robotic arm using just their thoughts.
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HAMILTON: Jen Collinger, a rehabilitation scientist, says now they want to add a sense of touch to robotic arms, like this one named Kuka.
JEN COLLINGER: Kuka is an industrial robot. We selected it because it’s fast, and it also can be fairly flexible.
HAMILTON: In theory, Collinger says, robots could help a paralyzed person regain some independence.
COLLINGER: Being able to feed yourself – right? – being able to make a meal, to be able to get dressed, to game, to do anything, really, that you want to do.
HAMILTON: But tasks like that are difficult when a person has to rely solely on their eyes to know what a prosthetic arm is doing. Robert Gaunt, a biomedical engineer, says a sense of touch makes it much easier.
ROBERT GAUNT: It cuts in half the time that it takes somebody to pick up objects and move them around. And a lot of those trials actually get fast enough to be considered what we would call sort of able-bodied performance.
HAMILTON: So far, scientists can only provide a very basic sense of touch. Gaunt says it’s good enough to know when a foot has weight on it or a hand has encountered something.
GAUNT: Our ability to discriminate different types of objects, textures, surfaces – that’s a hard problem.
HAMILTON: Hard, he says, but not out of reach.
Jon Hamilton, NPR News.
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