Wires bypass spinal cord

Aided by external wires that re-routed signals from their brains, two monkeys regained control of their paralyzed wrists and played a simple video game, scientists said Wednesday.

The study published in the journal Nature could lead to devices that allow people to regain some limb control after suffering spinal cord injuries and other forms of paralysis, scientists said.

Beneath the monkeys’ skulls, scientists had implanted electrodes into an area of the motor cortex responsible for hand and wrist movements. As the monkeys played, the electrodes recorded signals from individual brain cells so scientists could determine a firing rate.

Once the monkeys had learned the game, scientists implanted wires that ran from the electrodes into the muscles of each monkey’s forearm. Researchers used an anesthetic to immobilize the animals’ wrists temporarily.

A small battery-operated device used the firing rate to convert brain signals into electrical stimulation to the monkeys’ muscles. Thus, the animals continued to play the target practice game using their otherwise paralyzed wrists to move the cursors.

Researchers said they learned that only a single neuron was needed to control a pair of muscles, such as wrist flexors and extensors, and that cells anywhere in the motor cortex were capable of stimulating activity.

Clinical applications for the technology are at least a decade away, said Eberhard E. Fetz, a professor of physiology and biophysics at the University of Washington and an author.