Scientists have taken another significant step toward restoring paralyzed patients the use of their limbs. On their latest experiment, detailed in the online journal Nature, they’ve managed to move a monkey’s paralyzed wrist by stimulating its brain cells with artificially routed electrical signals.

The procedure involved temporarily paralyzing a monkey’s wrist muscles with a local anesthetic, attaching electrodes for electrical stimulation to the muscles, and re-routing electrical signals from the brain to the paralyzed muscles.

The team of scientists at the University of Washington, Seattle, lead by Chet Moritz, conducted the experiment on two macaque monkeys, and re-routed the brain signals through an external circuit, to a computer. The signals were associated with a cursor on the screen, which the monkeys learned to move by using their brain.

Every electrode received signals from a single neuron, and as Moritz explained, all neurons were used equally, regardless of whether they had anything to do with the activity of the wrist muscles. “This dramatically expands the potential population of neurons that could be used to control a neural prosthesis,” Moritz said.

The neural prosthesis are artificial devices used in patients with an impaired nervous system, helping them regain or improve anything from visual, to auditory or motor functions. The biggest challenge for scientists at this point in neuroprosthetics is to help restore movement in paralyzed people, or in people with movement disabilities.

Neural prosthesis have been considered by the medical community to be not only useful, but also safe, and perhaps with the greatest potential to become effective ways of alleviating the lives of people with motor disabilities.

Moritz’s co-author of the study, Dr. Eberhard Fetz, explained that with the help of biofeedback, they saw the brain was able to control the stimulation of wrist muscles, which gives great hope for the future. The scientists believe that one day, they will be able to use stimulation in undamaged areas of the brain to help restore function lost from damage in other areas of the brain.

The researchers explained that in a practical approach to treating paralysis with artificial nerve connections, they also needed to increase the number of control signals from the brain in order to move muscle groups.

Furthermore, the scientists also need to address another issue, before neural prosthesis become applicable in patients with motor disabilities: the size of the devices, and the power source. “We could look into the possibilities of other power sources such as the radiofrequency transmission,” Fetz said.

Moritz’s study follows another major breakthrough in brain activity detailed by Andrew Schwartz, PhD., professor of neurobiology at the University of Pittsburg School Medicine, in May this year. Schwartz and his colleagues managed to train two monkeys in using their brain power to reach for food, by controlling a mechanical arm.

The experiment was based on the use of microelectrodes implanted in the brain, which redirected the brain signals to a computer, to further control the robotic arm. The researchers explained at the time that the monkeys considered the robotic arm as their own arm, which made it simple for them to learn how to control it to grab food.