We all know that a damaged or severed spinal cord often leads to paralysis, as the spinal cord is the necessary means by which the brain tells the arms and legs to move. Right now, there are few ways to reanimate a person’s limbs once the damage is done. One neural prosthesis currently available allows a patient to perform a very limited number of hand movements, such as opening and closing a hand, but these are triggered by a series of shoulder shrugs, so the patient still has to have movement in their shoulder.
At Northwestern University in Illinois, neuroscientists have found a way for patients to perform these basic hand movements, and possibly more, without the need of a properly functioning spinal cord. And, these activities are activated the way nature intended to – by simply thinking.
The researchers describe the process as “eavesdropping” on the brain. Neural signals from the brain that correspond with a basic limb movement, such as grasping an object, are recorded with a special electrode array in the brain. Neuroscientists use these recordings to develop an algorithm that processes the neural signals and predicts patterns of muscle activity. The processed signals are sent in less than 40 milliseconds to a modified functional electrical stimulation (FES) system in the arm, which in turn causes the relevant muscles to contract.
Researchers tested the system on rhesus monkeys, experimenting to see whether they could utilize the neuroprosthesis implant to pick up and move a ball. With a local anesthetic to block nerve activity in the elbow to temporarily simulate the loss of motor control in a situation such as paralysis, the monkeys were successfully able to pick up the ball and complete the task nearly as well as they did before.
It wasn’t perfect, though; the neuroprosthesis only decodes activity from about 100 neurons out of the millions involved in even simple movements, and some of the neural activity was likely lost in the decoding process. But it was a result that researchers think could theoretically improve over time through learning, much in the same way that we learn new dance moves or how to use a new tool. More importantly, the result showed that it is possible to extract neural signals from the brain and redirect them from the spinal cord directly to the paralyzed limbs.
News article from Northwestern University: New Brain-Machine Interface Moves a Paralyzed Hand…
Journal Abstract from Nature: Restoration of grasp following paralysis through brain-controlled stimulation of muscles
(hat tip: MSNBC)