Tags: prosthetics, amputation, rehabilitation

Feb 9, 2015 — Greg Clark, PhD, associate professor of bioengineering at the University of Utah is working with a team to develop a prosthetic hand that amputees can move with their thoughts, and that allows them to feel sensation. He talks about what will be capable with the new technology, how it works, and the emotional impact of providing patients with a prosthetic that feels like a part of their body. Learn more about the research


Interviewer: Amputees move prosthetic hands with their thoughts. Up next, on The Scope.

Announcer: Examining the latest research and telling you about the latest breakthroughs. The Science and Research Show is on The Scope.

Interviewer: I'm talking with Dr. Greg Clark, Associate Professor of Bioengineering at the University of Utah. Dr. Clark, I love you work because you're turning what sounds like science fiction into reality. Tell us what you're doing.

Dr. Clark: One example of what we're trying to do is to restore sensory function and motor function back to people who may have lost their hands and long term amputations. So one of the limitations with present prostheses is having enough control over them. The limitation isn't simply in making a hand. That's an engineering challenge for sure, and a very real one. But even if you have that hand, the problem is how does the user control it? Especially if they've lost a lot of their limb, they don't have very many muscles left. So what do they use?
And one idea is to plug that hand right into the user's own nervous system. The brain thinks about moving, just as it normally does with a normal hand. The signals come flying down the nerve, just as they normally would. And if we could wiretap into that nerve, and capture those signals, and translate them, and send them into the artificial hand, the hand would move just as it always did. So one of the beautiful aspects of that approach is that the person doesn't have to learn anything new. They don't have to learn anything counter intuitive.

Interviewer: Well, and I think one of the amazing things is that this has gone beyond the planning stages. I mean, you've actually been able to try parts of this with people, correct?

Dr. Clark: Yes, and we're not the only ones. This actually builds on a pioneering technology and set of studies here done a long time ago, or a decade ago at the University of Utah, by one of my present colleagues Dr. Douglas Hutchinson and Ken Horchin, and others. And they showed that, perhaps surprisingly, the nerves that used to be attached to the hand still work after the hand is lost. And that opens up lots of possibilities both for capturing motor signals, but also talking back to the user and providing sensory experiences.

Interviewer: And that's another interesting aspect of it. Is that the user will not only be able to just move their hand, like you said, they can also feel the hand. What will they be able to feel? Just pressure, or pain, or...?

Dr. Clark: We're hoping to not activate pain, if that's your question. So there's really two important aspects of this, and the best way to think about this is to imagine yourself picking up an object. So imagine picking up, say, a Styrofoam cup filled with water. Close your eyes, reach out, grab that cup. Pick it up, and you know what it is. That's almost self-evident, but think about what it means.
So in our brains, without our even being consciously aware of it, we take all of this type of sensory information and build this mental image. So, although we call it a sense of touch, it's actually conveys lots of information about pressure. That's one example. About vibration when we first hit it. About where our hand is in space. The shape of our hand, both from stretch receptors in our skin, and also from joint receptors that tell us what our joint angle is, and also from muscle receptors that tell us how we're contracting our muscles.

So the two basic types of sensory experience we want to be able to restore are the sense of touch, and the sense of movement so that the person can move his or her own hand through space and know where it is, without having to watch it, but actually feel it. And in the end, we hope that this very rich sensory experience will allow the person to integrate the hand into their own body image, and so the hand will feel like part of themselves.

Interviewer: So you're really sort of the technology behind this ability to move things with their thoughts, and to feel, and...

Dr. Clark: There's many aspects to that technology, and one is actually developing the electrodes, the actually interface that will plug into the nervous system. But if you think about it just a moment more, there's other aspects about that that are very challenging and extraordinarily important. And one reason this is a huge multidisciplinary project is that all of these have to work in order for it to work together.
So for example, suppose I had the perfect electrode technology and I could record the neural signals coming down the nerve, I still have to know how to interpret those, and then send them to the muscle.

So a big part of our project is doing what's called the decode. That is the interpretation of the signals. Another aspect of it is talking back to the nervous system so that the user can understand that the hand has just touched something, or that it's moving through space. And that's called the encode problem. That is sending information into the brain in such a way that the user understands what's out there in the real world. And then there's the whole clinical aspect of it, and then we also have testing the user's ability to use a real physical hand. And so the real benchmark is how well does this prosthetic hand compare with a real biological hand?

Interviewer: This must have an incredible kind of emotional, or psychological impact on the person who's using it.

Dr. Clark: Indeed it does. Today we've done four human subjects. They've been able to control an advanced prosthetic hand on, in virtual realities. That is on a computer screen, and they've also been able to get a sense of touch and movement back from that virtual hand. And it truly is as emotional as you say. One user describes it as, "The loss of hand is like losing a family member, except you're reminded of it every day of your life." And so, as he sat there using it for the first time, it turned out that we provided movement back to him 21 years to the day after he lost his hand, and he could watch it and see it move again.
And one time we began to also provide sensory feedback to it. He could feel his hand, and he described what he had been through. He had been through some 10 surgeries, and after his hand was first damaged they tried to save his thumb, and it didn't quite work. And he went back again, over and over again, 10 times, to try to save his hand. And ultimately it didn't work, and he said, "Just please it out. Take it away." And that day it woke up again for the first time and he could feel it and he could move it, and it was truly overwhelming experience for him. And that's we hope to be able to do. To restore a sense of touch and motion back to individuals, included wounded warriors who have given their, literally their arms for our country, but also we hope this technology to disseminate into the larger community.

Interviewer: What was your reaction when you saw this technology work with a real person?

Dr. Clark: One of the truly poignant aspects is that you do get to know them. We work together with them, and they become truly a part of the team. They tell us what it's like, and what they like and what they don't like, and we try to incorporate that into present work and future designs. And, to be honest, they win your heart as well as your mind. And when you begin to restore some of that sensation and motion back to them, and see how important it is to them, you share a little bit in that joy.

Announcer: Interesting, informative, and all in the name of better health. This is the Scope Health Science Radio.