Scientists, carrying out a neurological study on macaque monkeys at the University of Washington say their findings show that an electronic connection between the brain and muscles – artificial motor nerves in essence – could help millions regain mobility from paralysis due to spinal injury, stroke and brain disease. The study was published yesterday in Nature Magazine.

The study was done on macaques that were taught beforehand, in return for food, to play a simple targeting game on a computer screen which involved moving a cursor on a screen and ‘catch’ targets using only their brain activity. This was done through electrodes implanted in the motor cortex of the monkeys. After the monkeys had learnt the game, scientists injected a neural blocking anaesthetic in their wrist muscles so that they could not move them. They then output the brain electrodes which had controlled the computer signals for the game, and inserted them to directly stimulate wrist muscles.

It took the macaques all of an hour to learn to learn to move their wrists using these neurons, which had nothing to do with wrist movement originally, instead of their normal neural pathways which were blocked by the drug.

The interesting thing that scientists discovered is that it doesn’t really matter what function the neuron previously had, it can be trained to perform a different one regardless.

"All neurons could be used equally well, regardless of whether that neuron was originally related to the activity of these muscles. This dramatically expands the potential population of neurons that could be used to control a neural prosthesis," says Chet Moritz, head of the study.

Andrew Schwartz, a neurobiologist at the University of Pittsburgh who published a study earlier this year on using the brain to control robotic arms, remarks upon the "amazing flexibility in the way that the system can learn," as the monkeys control over their muscles in the new way improved manifold with practice.

Clinical uses of the discovery, says Moritz, may still be many years away, as the incipient technology is still too crude to use with humans subjects. He goes on to say that while using a single neuron to control one muscle was relatively simple to achieve, multiple actions which require coordinated movements are a whole different thing altogether. "Multi-joint movement is orders of magnitude more complicated than this demonstration," says the scientist.

The technology, given time to develop will mark a significant improvement over current robotic prosthetics, which requires rather cumbersome computers which decode signals from the brain and pass them to the limb. They have been getting smaller with the years, but this discovery will bring about an even greater degree of miniaturization. "We already have electronics that are small enough to be worn in a shirt pocket, or hopefully in several years implanted under the skin like a pacemaker," says Moritz.