Using Brainpower to Control Paralyzed Limbs

Researchers at Northwestern University in Evanston, Illinois are developing systems to translate brain activity into real time muscle movements. Combining functional electrical stimulation (FES) and a neural implant, the new system could allow people paralyzed because of spinal cord damage to directly control intact nerves in their arms or legs and potentially return significant levels of function to these limbs.
 A diagram showing the different elements of the FES/implant system (Source: Northwestern University)
A diagram showing the different 
elements of the FES/implant system 
(Source: Northwestern University)

Researchers at Case Western Reserve University have previously used FES, or the direct electronic stimulation of nerves bypassing the spinal cord and normal neural pathways, to redirect one motion into another. For example, they have redirected the shoulder shrugging motion to initiate hand grasping in some patients. However, the range of motion and complexity of sequenced motions is limited.

Post-graduate student Christian Ethier, a member of the Miller Laboratory of Limb Control at Northwestern, is expanding the CWRU design to add neural implants to control the motion and greatly increase the complexity of motions that can be performed. Early versions of his system have been successfully tested on monkeys who, after given local anasthetics to temporarily paralyze an arm, were able to pick up a ball and place it in a target 77% of the time (compared to 100% before the anasthetic was applied and 10% with the anasthetic and without the help of Ethier’s device). Further tests are planned to test reaching instead of grasping motions. Ethier and his colleagues hope to eventually support a full range of complex motions in both arms and legs.

Cortical implants similar to that used by Ethier are already approved and in use in human subjects, but a newer model that’s fully wireless and completely internal is under development at Brown University. Ethier intends to wait for the Brown implant before starting human testing of his system.

TFOT has previously reported on assistive technology designed to help paralyzed or mobility impaired individuals walk including mind controlled bionic limbs that use implants and algorithms similar to those used by Ethier in his system, Honda’s Stride Management Assist and Bodyweight Support Assist devices designed to help people with mobility difficulties walk, lift, and crouch better, the HAL robot suit designed to directly stimulate muscles and help rehabilitate severely injured individuals, and the ReWalk motorized suit designed to give wheelchair bound individuals with full upper body mobility some ability to walk again.

Read more about the current experiments on grasping at this Northwestern research page. Read more about the original Case Western research forming the starting point for Ethier’s approach at Dr. Robert Kircsh’s research page.