A new brain implant can control a monkey's paralyzed hand by completely bypassing the spinal cord, giving new hope that paralysis from spinal damage may be overcome, according to research released Wednesday.
The neurologists administered a nerve blocker to temporarily paralyze the monkey's arm, rendering unable to lift the ball. Once researchers switched on the implant to mimick the brain impulses of picking up a ball, however, the monkey completed the task almost 80 percent of the time, according to the study.
This gives the monkey voluntary control of his hand that is not possible with the current clinical prostheses, Lee Miller, lead researcher and professor of neuroscience at Northwestern University, said in a statement.
While promising, critics said in a real patient, many more muscles would be involved, making the process much more difficult.
In a truly paralyzed arm, many more muscles would have to be activated, Andrew Schwartz, a neuroscientist at the University of Pittsburgh, told ScienceNow. To achieve more natural behaviors, complex combinations of muscles would need to be activated, and this kind of control is much more complex than what was shown in this demonstration.
To overcome the paralysis, neurologists found the brain patterns that signal picking up a ball then relayed the signal back into a monkey's brain.
The neuroprosthetic implant listens in to the natural electrical signals that the brain sends to the arm to tell it how to move and intercepts them, sending those signals directly to the muscles instead of directing them through the spinal cord. The process takes less than 40 milliseconds to complete.
Some people with spinal cord injuries cannot move one or more of their limbs because the signal never reaches the body part, even though the part is technically fully functional, researchers said. By bypassing the spinal cord, patients should be able to regain movement.
Approximately 200,000 people currently live with spinal cord injuries, according to the Centers for Disease Control and Prevention. Medical care for spinal cord injury costs between $15,000 and $30,000 annually, and over the course of a lifetime could reach $3 million, depending on the severity of the injury.
The monkey's control was slightly clumsy, but researchers said that with time and practice, it should be able to use it almost as well as it did before it was paralyzed.
The monkey won't use his hand perfectly, but there is a process of motor learning that we think is very similar to the process you go through when you learn to use a new computer mouse or a different tennis racquet, Miller said. Things are different and you learn to adjust to them.
Researchers said they will continue to work on mapping electrical signals and muscle movement. They will also test whether they can stimulate nerves directly, which would allow for much more dexterity.
The journal Nature published the study on Wednesday.