Brain cell stimulates muscle to work, gives hope to humans

— -- In an advance scientists hope will one day benefit humans, new research has found that monkeys with electronic implants connected to single brain cells can learn to flex paralyzed muscles.

The study, published Wednesday in the journal Nature, opens a new path in neural prosthetics, the electronic links from brain to muscle that bypass spinal injuries. In this case, brain cells directly sent signals, unlike past computer-decoded efforts, to wrist muscles that had been paralyzed.

Researchers led by Chet Moritz of the University of Washington in Seattle used nerve blocks to paralyze the arms of two pig-tailed macaques. Electronic implants were attached to a random cell, and the cell firings were recorded during 90-minute sessions of the monkeys playing a wrist-controlled video game. Signals from the cells were transmitted by wires to electrodes implanted in the wrist muscles.

By a second session, the monkeys could tap into their newly enhanced brainpower to control the game without error, and they could move opposing muscles, ones needed for grasping, researchers found.

The findings raise the unexpected hope that neural prosthetics could work in a damaged brain by simply plugging implants into the motion-related area instead of the much more invasive procedure of identifying and attaching electrodes to cells solely devoted to moving specific muscles.

"We found, remarkably, that nearly every neuron (brain cell) we tested in the brain could be used to control this kind of stimulation," Moritz says.

It's exciting that the monkeys, determined to play the game, reprogrammed the individual neuron from whatever its original purpose was to control the wrist motion, says Joseph Pancrazio of the National Institute of Neurological Disorders and Stroke, which financed the study.

About 250,000 people nationwide have spinal cord injuries. Pancrazio predicts neural prosthetics in a human will be demonstrated within five years.

The study combines the two leading approaches to neural prosthetics: brain-machine interfaces that record signals from multiple brain cells and decode them to control artificial arms, and electronic stimulation devices that send signals to muscles in paralyzed limbs through eye blinks or other movements.