Last week we reported on a new technology which uses biopolymer scaffolding to treat acute spinal cord injuries. In tests of that technology, animals that had undergone acute spinal cord injuries regained the ability to move their legs again.
ScienceNOW, a leading general science journal, reports that a new study has demonstrated a way to re-establish the links between the brain and the muscles that move limbs after they have been severed. In this study, scientists implanted electrodes in the brain’s movement control center and wired them to muscles in the arm. These electrodes allowed the researchers to restore movement to monkeys that had temporarily lost the ability to move their hand.
During the study, researchers injected the monkeys with a nerve-blocking drug to temporarily cause hand paralysis. After the shot, the science publication explained the monkeys were unable to do “a simple task they’d previously learned, picking up a rubber ball and dropping it into a tube to earn a reward of juice.” However, once these electrodes were switched on, they regained much of their lost ability, succeeding with this task about 80 percent of the time.
This study represents the combination of two approaches which make up the emerging field of neuroprosthetics. This field combines prosthetics, which help paralyzed patients interact with the world, with methods that have recently been developed to “decode signals from electrodes implanted in the brain so that a paralyzed person can control a cursor on a computer screen or manipulate a robotic arm with their thoughts alone.”
Although the article notes that the brain implant technology remains experimental and few have received it, it explains that “several hundred patients have received a different kind of neural prosthetic that uses residual shoulder movement or nerve activity to stimulate arm muscles, allowing them to grasp objects with their hands.”
With this new study, scientists have effectively joined these two techniques. After implanting “electrode grids into the primary motor cortex of two monkeys,” the scientists were able to record the electrical activity of about 100 neurons that control the hand. They then implanted electrodes in the arm muscles used for making the hand grasp objects.
“By recording simultaneously from the brain and muscle electrodes as the monkeys gripped various objects,” the researchers were able to develop “computerized decoding algorithms that predicted how signals from the brain translated into electrical activity in each of the three muscles,” the article explains. With the use of these algorithms, the researchers interpreted the brain commands from the paralyzed monkeys’ brains needed to stimulate the right muscles to produce the intended movement.
According to one of the researchers, Neuroscientist Lee Miller, Ph.D., of the Northwestern University Feinberg School of Medicine in Chicago, Illinois, with their system they are “going back to the brain and eavesdropping on the signals that normally occur.” With this technology, Miller hopes paralyzed individuals will soon be able to move their hand with just a thought, instead of using “current muscle-stimulating prostheses, which rely on residual movement in other body parts and require patients to learn unnatural movements such as moving a shoulder up and down to grasp and release.”
Although Miller explains there are not many “technical hurdles” to experimenting with this technology in humans, getting approval and recruiting patients will take several years. Furthermore, many spinal injuries cause more widespread paralysis in patients than seen with these test monkeys, which would require a greater number of muscles to be stimulated.
Nevertheless, Miller remains optimistic about their chances of achieving the dexterity needed in humans. Another approach he and his team are looking into is the stimulation of the nerves controlling muscles in the arm and hand, rather than the muscles themselves.