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A robotic arm with a sense of touch has allowed a man who is paralyzed to quickly perform tasks like pouring water in a cup. NPR's Jon Hamilton reports the arm provides sensory information directly to the man's brain.
JON HAMILTON, BYLINE: It's hard to hold on to something you can't feel, says Jen Collinger of the University of Pittsburgh.
JEN COLLINGER: Even something simple, like picking up a cup and trying to maintain the appropriate amount of pressure as you move it to another location, that relies a lot on the tactile feedback from your hand.
HAMILTON: Collinger is part of a team that's been looking for ways to add sensory feedback to a robotic arm and hand. The scientists have been working with Nathan Copeland, who is in his 30s and paralyzed. He has learned to control the device using just his thoughts. Collinger says the team began by finding a way to send electrical signals to the part of Copeland's brain that processes sensory information.
COLLINGER: It turned out that stimulating in the fingertip-related areas in the brain generated sensations that felt like they were coming from the participant's own hand.
HAMILTON: Next, the team figured out how to generate those signals when the robotic arm and hand made contact with something. Collinger says the final step was to have Copeland perform tasks like picking up a block or pouring water from one cup into another.
COLLINGER: With just visual feedback, his median time was about 20 seconds. With sensory feedback, he was able to complete it in 10.
HAMILTON: Not much slower than a person using their own hand, the team reports in the journal Science. And Copeland, who has been paralyzed since he was a teenager, says the results showed just how much people rely on a sense of touch.
NATHAN COPELAND: When I only had visual feedback, I could see that the hand had touched the object. But sometimes I would go to pick it up, and it would fall out.
HAMILTON: Copeland says that problem went away when he started receiving tactile feedback.
COPELAND: The sensation would actually change intensity based on how much force the hand was exerting on the object, so I could also tell if I had a firm grip on it or not.
HAMILTON: Copeland says adding a sense of touch also made using the robotic arm feel more natural.
COPELAND: The control is so intuitive that I'm basically just thinking about things as if I were moving my own arm.
HAMILTON: The results have implications beyond robotic arms. Jeremy Brown of Johns Hopkins University says high-tech prosthetic limbs also work better when they simulate a sense of touch. He says some do this by vibrating or providing some other form of what's known as haptic feedback.
JEREMY BROWN: You could build these arms. They operate just like our natural limbs do, right? But when you give somebody the ability to try and control this thing, until they have the haptics, it's clunky.
HAMILTON: Brown says touch tells us a lot more than just whether our hand has encountered an object.
BROWN: I feel the pressure. I feel the slip. I feel with the object is wet or dry. I can feel the texture of it. I know whether it's rough, whether it's smooth. I mean, we feel all of this the minute you come into contact with something.
HAMILTON: Scientists are just beginning to learn how to make artificial hands and fingers that can detect these features. Brown says the more information a prosthetic or robotic limb provides, the more useful it will be. But he says a sense of touch is about more than just increasing dexterity.
BROWN: It's not just the ability to reach in your pocket and grab your keys. It's also the ability to hold a loved one's hand and feel that emotional connection as well.
HAMILTON: Brown says that's something people miss after they lose an arm or a hand. He's hoping his own research will help bring that connection back. Jon Hamilton, NPR News.
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