'Double neural bypass' restores hand use and some sensation in a person with complete tetraplegia

What happened

The "double neural bypass" joins an intracortical brain–computer interface to targeted, patterned stimulation of the spinal cord and the cortex. Brain signals that reflect the intention to move drive the user's own hand in real time, while the stimulation is designed to promote lasting recovery.

The system uses recurrent neural networks and reinforcement learning for fine grasp control, together with patterned spinal cord stimulation and a form of intracortical microstimulation the authors call "cortical mirroring". In one participant with chronic C4 sensory and C5 motor complete tetraplegia, it enabled self-feeding and the handling of delicate objects. It also produced significant, persistent improvements in elbow flexion and in tactile sensation at the wrist, which remained when the system was switched off.

Why it matters

Most neuroprostheses either substitute for a lost function while switched on or aim at rehabilitation. This one attempts both, and reports lasting recovery of some function in an injury classed as complete.

Caveats

This is a report of a single participant, and the paper is indexed as a case report. This entry is based on the abstract, which does not quantify the improvements or say how long they lasted. The approach requires implants in the brain and stimulation of the spinal cord.