Spinal implant allows paralysed primate to walk

The implant, developed after a decade of research on rats, works by bypassing the injured portion the spinal column, sending signals directly from the brain to the intact nerves below the injury.

The researchers, led by EPFL neuroscientist Gregoire Courtine, call the implant the "brain-spine interface". It consists of several components, and takes advantage of the fact that even when spinal-cord injury causes paralysis, the motor sections of the brain remain intact and still produce the signals which is an uninjured vertebrate would order muscles to flex and relax; the nerves and muscles in the paralysed limb are also generally intact but merely are unable to communicate with the brain because of the spinal injury.

"To implement the brain-spine interface, we developed an implantable, wireless system that operates in real time and enabled a primate to behave freely, without the constraints of tethered electronics," Courtine explained.

The interface has two implants, one which attaches to the region of the motor cortex responsible for producing signals that control the leg; the other, a network of electrodes attached directly to nerve fibres is implanted on the surface of the spinal cord in the lumbar region, beyond the lesion which caused the monkey’s paralysis. The brain implant picks up the electrical signals produced by the cortex's nerve cells and transmits them to an external computer, which decodes the electrical spikes and send signals, again wirelessly, to the lumbar implant ordering the previously-inactive muscles to contract. The signals are only of the order of a few volts.