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Amputees Reconnecting

Scientists are discovering new ways to help amputees reconnect with the functionality of their missing limbs. Tom Bearden reports on this cutting-edge technology.

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  • TOM BEARDEN:

    Jesse Sullivan is on the cutting edge of a revolution that may change the whole lifestyle of disabled persons. His brain is directly controlling his mechanical hand. Two years ago, Sullivan lost both his arms in a power line accident in his hometown of Dayton, Tenn. He has two prostheses. The one on his right shoulder is the old technology. Sullivan can use chin switches and others inside the vest to operate the mechanical limb, but the device on his left shoulder is very different.

  • JESSE SULLIVAN:

    I guess in my mind, my hand is still there, so I use my hand as … my elbow as the control to it. When I open that, I'm literally … opened my hand. And when I close it, I literally close my hand.

  • TOM BEARDEN:

    That kind of control is possible because of a new technique pioneered by Dr. Todd Kuiken and his colleagues at the Rehabilitation Institute of Chicago. Surgeons took the severed ends of the nerves that once controlled Sullivan's arm, and rerouted them to muscles in his chest. The nerves grew into the muscles, and as a result of the new connection, Sullivan's brain could now move them instead. Dr. Kuiken says Sullivan is the first person to receive such a nerve-muscle graft and use it to control an artificial limb.

  • DR. TODD KUIKEN:

    So now, when he thought "close hand" for instance, the nerve that used to close his hand made a little slip of his chest muscle contract, and we can detect that chest muscle contracting because every time a muscle contracts, it emits an electrical potential. So we had two little antennas over that muscle, and we could tell when it contracted and then tell the artificial hand to close. So he thinks "close hand," muscle contracts, artificial hand closes.

  • TOM BEARDEN:

    It sounds like you almost rewired him.

  • DR. TODD KUIKEN:

    Exactly. We rewired him. We're using his muscle as a biological amplifier of his nerve signal, is what we're doing.

  • TOM BEARDEN:

    Like the switches on his mechanical arm, the antennas are inside the supporting vest. The device senses the movement and translates it into mechanical motion of the pincer and the elbow. It isn't perfect. Sullivan was in Chicago for a kind of tune-up of the fitting. Nevertheless, it has dramatically improved his outlook on life because he is now able to do many more things on his own.

  • JESSE SULLIVAN:

    Well, I can pick up objects with the electric side, like a quarter. I can pick it flat up off the floor or a table. I can get it with this one, but it's difficult. I have to wrestle with it. The hook will pick up smaller objects, and I can do it a little quicker because it's manual. But with the non-electric side, I can pick up an object like a round ball or something like that, I can actually snatch it up in a short time. And anything that's got a little weight to it, the hook has a hard time lifting, because at certain points you exceed the lifting capacity of the … of the hook, and then the hook will open and drop whatever you're trying to lift. So it, you know … whereas this one won't.

  • TOM BEARDEN:

    Dr. Kuiken thinks the basic idea can be developed and improved.

  • DR. TODD KUIKEN:

    Right now, we're just using one nerve to one segment of muscle to get … try and get one control signal. Potentially, if you think about it, the nerve that used to go to the hand closes all the fingers individually, closes the thumb. It does a lot more than just open and close. So perhaps with some advanced signal processing techniques, we could get better control than we are right now. We're, we're thrilled with what we've got so far, but there's potential, by applying some other people's research, to do even better.

  • TOM BEARDEN:

    Some of the most innovative research is being done by Miguel Nicolelis, a neurologist at Duke. He has bypassed the muscle system entirely. His experiments are based on directly reading the firing of neurons in the brains of monkeys. Neurosurgeons implanted an electrode with tiny wires into the surface of an animal's brain, and then connected them to a computer.

  • DR. MIGUEL NICOLELIS:

    This microchip that you see here is plugged into the electrodes inserted in the animal's brain.

  • TOM BEARDEN:

    The electrodes measured electrical activity in a limited number of brain cells and sent that information through more wires to a computer. Then the monkeys were trained to play simple video games, and the computer recorded what their brains were doing.

  • DR. MIGUEL NICOLELIS:

    Like any kid, or any of us would learn, basically by using a joystick to play the game. So the monkeys enjoyed that a lot. It's a great, you know, playtime for them, so they learn to use their hands to control a joystick. And the joystick controls a little computer cursor that is continuously tracking targets that appear on the screen. So the moment the target appears, the animal has to move the joystick so that the cursor will intersect that target and basically grab the target.

  • TOM BEARDEN:

    The computer established the correlation between what the monkey's brain was doing and how its hand was moving the joystick. That was difficult to do because a brain doesn't have specific cells that control specific movements. Such activity is distributed throughout the brain, the so-called motor system.

  • DR. MIGUEL NICOLELIS:

    There's no central single location in the brain where this information is stored or this information is computed. And that's the image that, until very recently, you could not get: How a brain circuit operates in real time.

  • TOM BEARDEN:

    Software translated that information into computer commands that would control a robotic arm in the same way as the joystick. The big moment came when they disconnected the joystick. At first, the monkey continued to move it with its arm, but quickly realized the cursor was no longer responding. And then the monkey began to move the cursor only with its mind. Nicolelis and his colleagues were stunned at how quickly it happened.

  • DR. MIGUEL NICOLELIS:

    That was a day, we were just tired, looking at monitors, and all of a sudden, she's playing, and she stops moving, but the game continues. We couldn't speak because it was one of these … it almost looks like a movie, the main part of the movie when you were just looking at something extraordinary. She basically stopped playing with the joystick, but you could see that the game was still going on and she was still winning.

  • TOM BEARDEN:

    So in a sense, the monkey is using its mind to control a computer which is controlling the robotic arm?

  • DR. MIGUEL NICOLELIS:

    Yes. And at that point, the motions of the robotic arm control the displacement of the cursor on the screen, so the monkey's seeing, now, the outcome of the robotic arm performance. And it's only if the robotic arm can reach the target and grab a virtual object that the monkey can accomplish the goal of completing the video game. So to get the reward now, he has to basically … the animals have to basically utilize the robotic arm as the actuator, instead of their own arms. And the surprising result was at that point, they stopped moving their own arms. They realized that that was a waste of time.

  • TOM BEARDEN:

    Nicolelis says it was a remarkable moment for him and his team.

  • DR. MIGUEL NICOLELIS:

    It was very satisfying because this involves almost 20 years of work, you know, many, many people, not only in our laboratory, in many groups all over the world, you know. And that's why science is so wonderful. You know, you have lots of people working all over the world, and it's a common language. It's just a few minutes, seeing something or doing something that has never happened before. I think that's what any scientist lives for, that kind of moment.

  • TOM BEARDEN:

    Nicolelis thinks the technique, using implanted electrodes, may someday help severely disabled patients. Those with spinal cord injuries, for example, might use miniature wireless devices to control artificial limbs with their minds.

  • DR. MIGUEL NICOLELIS:

    What we want to do is to try to produce a prosthetic device that would get signals from these healthy brain areas, the code for the intention of movement, and allow these signals to be controlling a variety of actuators: Robotic arms, wheelchairs, appliances — a spectrum of devices that would be used to restore basic motor behaviors that these patients have lost, behaviors that would allow them to be more independent, to communicate to the external world, to achieve basic tasks that they cannot any longer achieve without the help of someone else.

  • TOM BEARDEN:

    But Nicolelis doesn't want to raise false hopes. He cautioned it will be at least two years before he begins clinical trials with human subjects. Neuroprosthetic research is also continuing at other universities and biotech companies, as all struggle to find ways to help hundreds of thousands of disabled people regain greater control over their environment.