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Wrist research might one day help the paralyzed

Monkeys taught to play a computer game were able to overcome wrist paralysis with an experimental device that might lead to new treatments for patients with stroke and spinal cord injury.

Remarkably, the monkeys regained use of paralyzed muscles by learning to control the activity of just a single brain cell.

The result is “an important step forward,” said Dawn Taylor of Case Western Reserve University in Cleveland, who studies the concept of using brain signals to overcome paralysis. She wasn't involved in the new work.

The device monitored the activity of a brain cell and used that as a cue to stimulate wrist muscles electrically. Researchers found it could even use brain cells that normally had nothing to do with wrist movement, said study co-author Chet Moritz.

So a large untapped pool of brain cells may be available for letting paralyzed people do things like grasping a coffee cup or brushing teeth, Moritz said. But he stressed the approach is years, if not decades, away from use in people.

Moritz and his colleagues at the University of Washington report the results in a paper published online Wednesday by the journal Nature.

Taylor, who also works with the Cleveland VA Medical Center, said the study illustrates the potential of the approach and the flexibility of brain cells.

Lee Miller, a researcher at Northwestern University who has done similar work, said any demonstration of a device using brain signals to make paralyzed limbs move is “an important new development.”

Miller used the pattern of activity in about 100 brain cells to predict the kind of wrist movement a monkey wanted to make. Moritz said focusing on the output of an individual brain cell instead may turn out to work better for overcoming paralysis.

The research is an example of what scientists call functional electrical stimulation, or FES, which involves stimulating muscles by applying electrical current. Partially paralyzed people use FES devices now to let them stand, walk, use their arms and hands, and do other things. But they control those devices by flicking a switch, moving joints or tensing a muscle – even, say, the muscle that enables them to wiggle an ear.

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