Grégoire Courtine has been commuting between his lab at the Swiss Federal Institute of Technology in Lausanne and a lab in Beijing, China, for more than a decade in order to carry out research on monkeys with spinal-cord injuries.
Now, for the first time ever, partially-paralysed primates have been able to walk again. Published in the science journal Nature, Courtine’s research used wireless implants that stimulate electrodes in the leg in order to bypass the injured nerves and restore locomotion. This neuroprosthetic, or “brain-spine”, interface enabled a resus macaque to walk only six days after it was paralysed in its hind legs.
“It was a big surprise for us,” commented Courtine. “The gait was not perfect, but it was almost like normal walking. The foot was not dragging and it was fully weight bearing.”
Paralysis occurs when a spinal cord lesion prevents transmission of signals from the motor cortex in the brain to neurons that control muscle movement. Since nerves do not heal spontaneously, these debilitating injuries are often for life. Courtine’s approach, which involves four major components, may hold the key to future treatment. The first component is a brain implant, which records the activity of 50 to 100 neurons between the monkey’s legs and the brain and beams it wirelessly in real time. A computer decodes the signals and passes them onto a pulse generator. The pulses are then transmitted to a second implant at the base of the monkey’s spine, which stimulates nerves and allows specific leg muscles to contract and the monkeys to walk.
By re-establishing a link between the brain and the spinal cord, researchers hope that eventually, the implant could help remaining nerves to regain control of lost functions and allow recovery of movement in people.
Jocelyne Bloch, a neurosurgeon at Lausanne University Hospital in Switzerland, said: “For the first time, I can imagine a completely paralysed patient able to move their legs through this brain-spine interface.”