Monkey Studies Could Help Paralyzed Humans

RENEE MONTAGNE, Host:

Scientists are reporting progress in the effort to restore movement in paralyzed limbs. The researchers at the University of Washington worked with monkeys. They used electrodes to connect individual brain cells to muscles in the arms of the animals. The monkeys were able to use those brain cells to move their hands. NPR's Dan Charles has more.

DAN CHARLES: Researcher Chet Moritz says the monkeys in these experiments are a little bit like some people.

CHET MORITZ: These are adolescent male monkeys, and one of their favorite things is actually to play video games, as you can imagine.

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CHARLES: But Moritz and his colleagues took away that pleasure temporarily. They injected the monkey's arms with anesthetic so the limbs were paralyzed. The drug broke the communication links between brain and hand. But the researchers set up an alternate link.

MORITZ: We surgically implanted electrodes that are about the thickness of a hair, about 50 micrometers in diameter, down into the brain in order to record the activity from single neurons.

CHARLES: The electrodes picked up that brain cell activity and sent it back outside the body to a small computer. The computer translated the nerve impulses into electrical signals and sent them down a wire that was connected to a muscle in the monkey's wrist. The monkeys didn't know all that, but they did realize they could clench and unclench the muscle. It wasn't much, but it was enough to play a really simple version of their favorite video game. Moritz says the experiment showed dramatically how quickly the brain can find new ways to do something.

MORITZ: One of the most interesting findings of the study was that it didn't matter whether the nerve cell in the brain that we recorded from was previously related to these movements in the wrists.

CHARLES: Somehow, the monkey's brain figured out it now could use this new neuron to move that muscle. There's a lot riding on this sort of experiment. Ultimately, scientists are hoping people who are paralyzed could someday walk again. And half a dozen laboratories are trying slightly different approaches. Scientists have inserted electrodes into the brains of paralyzed humans, for instance. Those people have been able to move a cursor around a computer screen just by thinking about it. And Lee Miller at Northwestern University also restored movement to paralyzed monkey muscles. But he monitored a whole array of nerve cells and used powerful computers to analyze the activity of the neurons. In this case, the computers decided how to activate the monkey's muscles.

LEE MILLER: What we're trying to do is figure out what those neurons really were trying to do and get us close to that as we can.

CHARLES: Miller thinks this approach may be more likely to restore a monkey's or a person's ability to perform complicated tasks like picking something up or walking. Chet Moritz, who got his monkeys playing video games, is betting that the brain doesn't need that big computer. He's hoping it's enough just to create a connection between mind and body.

MORITZ: And let the nervous system learn to co-op with this connection, to use this connection in order to restore functional movements after paralysis.

CHARLES: But real help for paralyzed humans may still be a long way off. Moritz estimates at least five to 15 years. Scientists haven't yet used these artificial connections to control complicated movements. Also, they'd have to develop a reliable way to tap into brain activity over long periods of time without opening the door for infections. Dan Charles, NPR News, Washington. Transcript provided by NPR, Copyright NPR.