Scientists in the U.K. have restored hand motion in a pair of paralyzed macaque monkeys. This is the first time this has ever been achieved. Their work could lead to treatments that restore movement in the upper limbs of human patients who have suffered damage to the spinal cord.
Brain-machine interfaces allow scientists to perform previous impossible feats of medical engineering, such as restoring arm and leg motion in paralyzed people or allowing patients to move prosthetic arms with only their thoughts. But this is the first time scientists have restored not only feeling in the hands but also the ability to grasp objects.
For the experiments, the team led by Newcastle University's Andrew Jackson and Jonas Zimmerman used a drug that wore off in an hour or two to temporarily paralyze macaques. Those primates had electrodes under the skin to stimulate their muscles just as the nervous system would. Researchers also installed neural implants to detect the monkeys' brain activity and look for the patterns associated with hand motion.
Finally, connections wired between the brain and arm allowed the neural signals to trigger the electrical impulses and move the hands even while the animals were otherwise paralyzed. As Jackson explains in the video (below), the brain in a paralyzed monkey or person still fires in a way that signals the intention to move -- it's just that the message isn't getting through to the muscles because of nervous system damage. His team's circuitry acts as a new pathway that restores the connection.
In the clip, you can see a macaque do what it's been trained to do: try to pull on a spring-loaded handle. When the paralysis drug sets in, brain activity spikes but the monkey can't squeeze its fingers. When Jackson's team activates the electric stimulation, it can grasp.
The team cautions that there are hurdles to making this technology work in humans beyond the differences in human and macaque brains. For example, when a back or spinal injury limits a person's motion, sometimes their brain organization changes. Different parts of the brain could become responsible for movement, which would complicate the design of a brain-machine interface.
Still, Jackon says in a press release: "I think within five years we could have an implant which is ready for people. And what is exciting about this technology is that it would not just be useful for people with spinal injuries but also people who have suffered from a stroke and have impaired movement due to that."
The work appears in Frontiers of Neuroscience this week.
[Via Newcastle University]
Image: Newcastle University