An artificial connection between the brain and muscles can restore complex hand movements in monkeys following paralysis, according to a study funded by the National Institutes of Health. In an April report published in the journal Nature, researchers describe how they combined a brain-computer interface (BCI) and functional electrical stimulation (FES) to create a neuroprosthesis. The BCI, which allows researchers to detect the activity of about 100 brain cells and decipher the signals that generate arm and hand movements, activates the FES device directly, bypassing the spinal cord to allow intentional, brain-controlled muscle contractions and restore movement.
The research team was led by Lee E. Miller, PhD, professor of physiology/physical medicine and rehabilitation at Northwestern University’s Feinberg School of Medicine, Chicago, Illinois. Prior to testing the neuroprosthesis, Miller’s group recorded the brain and muscle activity of two healthy monkeys as the animals performed a task requiring them to reach out, grasp a ball, and release it. The researchers then used the data from the brain-controlled FES device to determine the patterns of muscle activity predicted by the brain activity.
To test the device, the researchers gave monkeys an anesthetic to block local nerve activity at the elbow, causing temporary paralysis of the hand. With the aid of the neuroprosthesis, both monkeys regained movement in the paralyzed hand, could pick up and move the ball in a nearly routine manner, and complete the task as before. Miller’s research team also performed grip-strength tests, and found that their system restored precision grasping ability. The device allowed voluntary and intentional adjustments in force and grip strength, which are keys to performing everyday tasks naturally and successfully.
This new research moves beyond earlier work from Miller’s group, which showed that a similar neuroprosthesis restores monkeys’ ability to flex or extend the wrist despite paralysis.
“With these neural engineering methods, we can take some of the important basic physiology that we know about the brain, and use it to connect the brain directly to muscles,” Miller said. “This connection from brain to muscles might someday be used to help patients paralyzed due to spinal cord injury perform activities of daily living and achieve greater independence.”
The temporary nerve block used in the current study is a useful model of paralysis, but it does not replicate the chronic changes that occur after prolonged brain and spinal cord injuries, Miller cautioned. He said the next steps include testing this system in primate models of long-term paralysis and studying how the brain changes as it continues to use this neuroprosthesis.