The Brain Continues To Keep Contact With Disabled Limb : Shots - Health News A neurologist who wanted to know how the brain changes in response to a physical disability put his arm in a pink cast for two weeks to find out.

A Scientist's Pink Cast Leads To Discovery About How The Brain Responds To Disability

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MARY LOUISE KELLY, HOST:

A scientist put his arm in a pink cast, and then stuck his head in a brain scanner. The result - a discovery about how the brain adapts and maintains connections to an unused limb. NPR's Jon Hamilton reports.

JON HAMILTON, BYLINE: Dr. Nico Dosenbach of Washington University in St. Louis says he often prescribes an odd treatment to young patients who have an arm that is partially paralyzed.

NICO DOSENBACH: You put their good arm, their more functional arm, in a full-arm cast all the way down to the fingertips to force them to use the other side.

HAMILTON: It's called constraint-induced movement therapy, and scientists think it works by strengthening the connections between brain and arm. But that's just a hypothesis. So Dosenbach says one day, a colleague made a suggestion.

DOSENBACH: You know, Nico, you should do this to yourself, and we should scan you to find out, you know, how the brain reorganizes in that situation.

HAMILTON: Dosenbach encased his arm in a full-length fiberglass cast. Why pink?

DOSENBACH: My daughter at the time was 2, and I didn't want to frighten her.

HAMILTON: Dosenbach wanted to maximize the effect on his brain, so for two weeks he kept doing all the things he'd done before, like buckling a belt and putting away dishes.

DOSENBACH: The whole goal was that I wouldn't cut myself any slack. And so, yeah, I got pretty good at changing diapers with a fiberglass cast on.

HAMILTON: And every day at 5 a.m., he went in for a brain scan. Dosenbach says those scans showed that almost immediately his brain began disconnecting the circuits that controlled his immobilized arm.

DOSENBACH: The brain can be very stable - is very stable - unless it has to change, and then it can change at a rate and a scale that I would have never thought possible until the results from the study.

HAMILTON: All that disconnecting could have meant that the brain was about to abandon the idle arm and concentrate on the one he was still using. But Dosenbach says his team noticed that as the old motor circuits faded, his brain began to generate a new signal.

DOSENBACH: We start seeing in the disused motor circuitry, but not anywhere else, we start seeing these pulses of spontaneous activity that are very large that actually seem to maintain the connections.

HAMILTON: The pulses weren't telling his arm to do anything. They were just keeping the lines of communication open. Dosenbach repeated the experiment on two colleagues. One got a purple cast. The other got blue. And the results, which appear in the journal Neuron, were the same. Lynne Gauthier of UMass, Lowell, says the rapid brain changes are consistent with what she sees in patients who get constraint-induced movement therapy. Gauthier says she and her research team have patients play a video game that tests their less-functional arm - the one that's not constrained.

LYNNE GAUTHIER: So we're able to track the trajectory of the recovery over time. And we can see that a lot of the recovery happens in a very short period of time.

HAMILTON: Gauthier says those spontaneous pulses in the brain should be reassuring to professionals who use constraint therapy on young patients.

GAUTHIER: Therapists have expressed concern that - what's going to happen if you restrain that stronger arm for two weeks? Is that going to affect their normal development? And what this study shows is that it probably won't.

HAMILTON: But Gauthier says it's unclear whether the pulses Dosenbach back found can help patients whose brain circuits have been disrupted by a major stroke or severe traumatic brain injury.

GAUTHIER: Those pulses may go through in a normal brain, but if you have a damaged brain, those pulses may not be happening. We just don't know.

HAMILTON: And finding out will take more than a scientist who puts his own arm in a cast.

Jon Hamilton, NPR News.

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