Rewiring the Sense of Touch Doctors have rewired the nerves of two amputees to restore the sensation of touch to their missing hands. The amputees now experience an object touching their chest in two ways at the same time — the expected feeling of being touched on the chest, and the sensation of being touched on a missing hand.

Rewiring the Sense of Touch

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Up first this hour, hopeful news for people who have suffered amputations. Doctors working with two-arm amputees say they rerouted the nerves that went to the now-missing hands and moved them into the chest muscle. The nerves took, so to speak, and the amputees say they can feel their missing hands when certain spots on the chest are touched. Why would that be a good thing? Why would research want to do that?

Joining me now to talk about this is Todd Kuiken, he's director of the Neural Engineering Center for Artificial Limbs at the Rehabilitation Institute of Chicago, and he joins me by phone.


Dr. TODD KUIKEN (Director, Neural Engineering Center for Artificial Limbs, Rehabilitation Institute of Chicago): Good morning.

FLATOW: Hi, Dr. Kuiken. How are you?

Dr. KUIKEN: I'm fine. Thank you for having me on your show today.

FLATOW: We actually have some video of the kind of work that you're doing that has led to this procedure. Now, our listeners can go to iTunes and search for SCIENCE FRIDAY and look for our video podcast there of the kind of work you're doing to reroute the nerves into the chest. Tell us what the object here - what you did.

Dr. KUIKEN: Well, one of the challenges with artificial arms is how do you tell them what to do. You lose your muscle and your bones, but the nerves are still there, and the nerves carry all the information, they carry the commands from the brain and they carry the sensation signals from the arm to the - back to the brain. So we've taken those nerves, which we're calling data cables, and moved them to spare muscle on the chest.

The amputee - these amputees have no arms, so the muscles that used to go to it are not doing anything, and we've let these nerves grow in the new muscles on the chest and on the chest skin. So now, when the patient thinks close their hand, a piece of the chest muscle contracts. The brain doesn't know it's going to the wrong muscle, but a piece of the chest muscle contracts. We can pick up that signal and tell the artificial hand to close. In this way, we can control an arm in a much more natural and fluid way.

And the flipside of it is that the hand sensation nerves grew into the chest skin, so now when you touch that chest skin, the patient feels as if you're touching the missing hand.

And we at the Rehabilitation Institute of Chicago are very excited about this because this is a portal into the nervous system, the sensory nervous system, and our goal is to put sensors in a prosthetic hand, so that when it touches something, we can measure how hard it's touching and squeezing, and we can feed that information back to devices that we put over this new skin called tactors, so that the tactor presses on the skin and, thus, the amputee will touch something with their artificial hand and feel it in their own missing hand. And that would be a very powerful feedback for them. And it's also, you know, very powerful psychologically. You touch something and it feels like it's your own hand.

FLATOW: Have you actually been able to create prosthesis that can actually feel these sensors yet?

Dr. KUIKEN: Yes, we've done early experiments in the lab where we've had sensors in the fingers and fed that information back onto the chest. And it's - I would say it's a crude sensation right now, but something's better than nothing, and we have a lot of room for improvement.

FLATOW: 1-800-989-8255 is our number. Also, if you're in the "Second Life," you can find our folks at "Second Life" there in the SciLand in Science School.

And a question from Lawrence(ph) in "Second Life" says, can the wire - the nerves detect heat, can they detect heat also?

Dr. KUIKEN: Yes. Actually, our patients are able to detect hot and cold within near normal levels as if it were in their missing hand. And the touch that they feel is very exquisite. They can feel, like, one gram of force pushing against the skin, and they feel it as if it's in their own hand.

FLATOW: Mm-hmm. Now, a video we have up and running on iTunes actually shows a demonstration of the chest muscles moving. And you're saying - and you have an image of somebody who actually has artificial limbs on, he's controlling those just by thinking…

Dr. KUIKEN: That's right.

FLATOW: …about moving the - moving his limbs.

Dr. KUIKEN: Yes, sir. So he thinks to move his elbow or move his hands or move his wrist and the sensors on the skin pick up the signals of the muscles. The muscles are actually acting like a biological amplifier, if you would, of the nerve signals. So we're getting lots of data that we can then process and use to control an artificial arm in a very natural way.

FLATOW: Do the people find - you know, the people who you're testing this at on, do they find the sensation disconcerting that you could feel your missing arm by touching your chest?

Dr. KUIKEN: Well, I think it's a little bit different, and it was actually quite a surprise the first time it developed. But for the most part, patients have enjoyed it. They liked to be able to feel their missing arm, and no one has complained that it's uncomfortable. I think when it first started re-growing in, it was kind of sensitive for a little while, but that…


Dr. KUIKEN: …even that sensitivity kind of went away, and it - and our patients have enjoyed having the sensation.

FLATOW: Now, when you reroute the nerves to the chest, let's say, nerves from the hand, can you know which part of the hand shows up in which part of the chest?

Dr. KUIKEN: To some extent, yes. My colleague, Dr. Greg Dumanian at Northwestern Memorial Hospital, did the surgery, and there's four main nerves that go to your arm, and each of those nerves go to the sensation of different parts of your hand. For example, the median nerve innervates the thumb, first finger and second finger, so we can put that to one section. And the fourth - ring finger and pinky finger are innervated by another nerve, so we can make that go to a different section.

FLATOW: Let's go to the phones. To Eric(ph) in Jerseyville, Illinois. Hi, Eric.

ERIC (Caller): How are you?


ERIC: Hey, I had a question for you. I am a below-elbow amputee and this happened back in 1998. And since then, I have had some really weird sensations, like below my elbow with some nerves, and I guess they call it phantom, I don't know, phantom pain or phantom feelings or something to that effect. But I was - they tried to fit me for a myoelectric arm. And when they fit to this myoelectric arm, they were reading - I guess, they're taking readings from off of my stump. And how would this pertain with these readings since they can never pin them down and they can never make them work right? How could this help me, you know, in my situation? Sorry, I'm really nervous.

FLATOW: That's okay. You did fine.

ERIC: You guys (Unintelligible).

FLATOW: We understand the question; it's a good one.

Dr. KUIKEN: Oh, that's fine. So the prostheses that we're using now really are myoelectric prostheses in that they're using the muscle signals much like the one they tried with you. We do pretty well with the myoelectric prostheses in most people with below-the-elbow amputations because all the muscles that control the hand, or many of the muscles that control the hand, are still there in your residual limb up by your elbow, and we can use those signals to tell a hand to open and close in a natural way. Right now, our research is looking at helping people with higher level of amputations. So they've lost all those muscles and their amputation is above the shoulder…

ERIC: Yeah.

Dr. KUIKEN: …or at the shoulder. But we are actually just starting to look at people with below-elbow amputations to see if we can use the same technique to get more information to allow people to control a wrist or even a hand that has different hand grasp patterns as…

ERIC: Oh, wow.

Dr. KUIKEN: …opposed just open and close, like the one you have.

ERIC: Yeah, there is massive trauma to the arm itself, So there's a lot of scar tissue left around; they can never pin down a nerve to control it, so they said, you know, I wasn't really eligible.

Dr. KUIKEN: Yeah, you…

ERIC: So that is something that's really neat.

FLATOW: Thanks for…

Dr. KUIKEN: Yeah. You have to have some good muscle for us to work with, and I'm sorry that that didn't work for you.

FLATOW: Thanks for calling. 1-800-989-8255.

Let's go to Phil(ph) in Fort Lauderdale. Hi, Phil.

PHIL (Caller): Hi. How are you doing?

FLATOW: Hi, there.

PHIL: I had kind of a piggyback question with the last caller. The first part of my question was regarding whether this would alleviate phantom limb pain for, say, a double amputee. But then the second part dealing with the emotional aspect of amputations - if this was a way to get around kind of that sense of loss of ability to embrace a loved one or whatever if you have that sensation of touch. If a loved one were to put their hand on your chest, would someone feel like they were holding someone's hand or holding their loved one?

FLATOW: Good question. Let's go to the last one first.

Dr. KUIKEN: Well, you know, the sense of touch is very important in our interactions, and there's nothing more wonderful than holding loved one's hand or picking up your child. The sense of touch that we get with this procedure is real as if it's touching a hand. But it's still, I'd say, kind of crude. My one patient describes it as, well, it feels like you're touching my hand, but I've got to stick glove on my hand.

So it's not as exquisite a sensation as your real hand, but there is kind of a neat connection to the fact that it is going to hand sensation, which is what we use when we touch our loved ones most of the time.


Dr. KUIKEN: So I think there's a potential to help with that part of the emotional adjustment, and emotional adjustment to amputation is a huge issue.

FLATOW: Is it - is there a phantom pain? Is that gone?

Dr. KUIKEN: Well, phantom pain is a different phenomenon. It's more - something to do with the brain and having it signal sensation go away. The kind of brain does something that causes sensation and pain. Whereas, what we've done is provide a real sensation. I had hoped that it would help phantom limb sensation by giving the nerves something to do. But, in fact, we found - it really hasn't changed much. I've had patients who had severe phantom limb pain before this procedure and they've had it afterwards. And I've had patients with no phantom limb pain or sensation to speak up before this procedure and none after. So it doesn't seem to affect that much.

FLATOW: We've got about a minute left. Could this also be a bionic arm control? Can you - for people who are not amputees, is this a way to maybe control remotely arms across the Internet or on other parts of places?

Dr. KUIKEN: I mean, the signals could be hooked up to robotic arms anywhere, but for normal able-bodied people going to the muscle to get signals for control would be a step backwards. It's really - we'd want to use our hands and our fingers and thumbs…

FLATOW: Right.

Dr. KUIKEN: …because we get a lot of other types of sensory feedback and much better control.

FLATOW: One last question from Muslima(ph) in "Second Life." Is this technology also help those that lost their lower limbs?

Dr. KUIKEN: Well, that's an exciting possibility, and we're just starting to study the idea of creating a neural interface like this at the Rehab Institute of Chicago for people with lower limb loss and using powered artificial legs. So that's something we're just starting and very excited about.

FLATOW: And that's where you're headed, a new area now?

Dr. KUIKEN: Yes, that's a new area we've just started in the last year.

FLATOW: Well, Dr. Kuiken, I want to thank you to talking time to be with us.

Dr. KUIKEN: Thank you very much.

FLATOW: You're welcome.

Todd Kuiken is director of the Neural Engineering Center for Artificial Limbs at the Rehabilitation Institute of Chicago talking about the - his new sensors. He's rerouted nerve impulses into the chest. If you want to see photos of some of his work, you can go to iTunes and look at that SCIENCE FRIDAY podcast. We now have video podcast on that.

We're going to take a short break and talk about stress. Oh, yeah, holidays - stress time. You know what I'm talking about. We'll try to give you some hints about how to deal with it, maybe if we stress you a little bit this Friday. Take a deep breath. We'll be back after this break.

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