Researchers Stimulate Hand Movements in Paralyzed Monkeys

Researchers at Northwestern University’s Feinberg School of Medicine have restored complex hand movements in paralyzed monkeys.

The study, funded by the National Institutes of Health and reported in the journal Nature, explores the use of a neuroprosthesis, a device that replaces lost or impaired nervous system function. The two-part device consists of a multi-electrode array that is implanted directly into the brain and a functional electrical stimulation (FES) device. The array enables researchers to detect and decipher the brain signals for arm and hand movements, while the FES stimulates the paralyzed muscles with electrical currents. The brain array activates the FES device directly and bypasses the spinal cord.

To test the device, researchers used an anesthetic to cause temporary paralysis below the elbow in monkeys. Both monkeys in the study were able to regain movement with the use of the neuroprosthesis. The team also performed grip strength tests and discovered that their system restored precision grasping ability.

The team hopes that the new research might someday help patients with spinal cord injury perform activities of daily living and gain more independence.

Currently, FES devices are being used to address foot drop, a condition in which weak or paralyzed muscles cause the toes to catch on the ground while walking. FES devices can be activated with shoe sensors or coordinated with walking movements to stimulate muscles and lift the toes at the appropriate time during a step. Other FES devices are being used in prosthetics, including a sensor built into the shoulder that activates via a shrugging motion to stimulate the muscles that open and close the hand in patients with partial motion.

The researchers cautioned that the temporary nerve block used in the monkeys does not replicate the chronic changes that occur after prolonged brain and spinal cord injuries.