Neuroscience: Paralysed monkeys walk this way

A new device that restores movement of a paralysed leg in monkeys as early as six days after spinal cord injury is reported in a paper published in Nature this week. The implantable, wireless brain-spine interface uses components that have been approved for research in humans, and is a step towards clinical trials to test the efficacy of this approach in people with paraplegia.

Previous studies have shown that it is possible to use signals decoded from brain areas involved in planning and executing movement to control movement of a robotic or prosthetic hand and, in one case, the patient’s own paralysed hand. However, whether this approach can be used to restore the complex leg muscle activation patterns and coordination involved in walking has not previously been investigated.

Gregoire Courtine and colleagues developed a brain-spine interface that decodes signals from the part of the motor cortex that orchestrates leg movements to stimulate electrodes implanted in ‘hotspots’ in the lower spinal cord that modulate the flexion and extension of the leg muscles. The authors tested the interface in two rhesus monkeys each having one leg paralysed by a partial spinal cord lesion. One of the monkeys regained some use of its paralysed leg within the first week after injury, without training, both on a treadmill and on the ground; the other monkey took two weeks to recover to the same point.

In an accompanying News & Views article, Andrew Jackson suggests that, given the rapid translation of other neural interfaces from monkeys to humans in recent years, “it is not unreasonable to speculate that we could see the first clinical demonstrations of interfaces between the brain and spinal cord by the end of the decade.”