Reconnecting the Brain and Legs

Incredibly, we may be a mere decade away from giving paraplegics back their walking legs.

Scientists recently enabled paralyzed monkeys to walk again. They devised a brain-computer interface or BCI along with a spinal implant that worked together to once again allow the brain's motor cortex to send electrical signals to the legs.

The first thing they did was to get around the complex mechanism of walking. Rather than map all the commands responsible for each movement and sending them to the correct muscles, scientists decided to let the spinal cord handle some of that task. They can do so because research for the past century has shown that circuits embedded in the lumbar segments of the spine, the five vertebrae between the last rib and the pelvis, can produce coordinated leg movements without input from the brain. The answer is a device called epidural electrical stimulation or EES.

So. the researchers spent a decade recording spinal nerve activities in monkeys in order to build a model of their spine along with the nerves for leg movements. This information allowed them to build an EES with wires for attaching to the nerves responsible for walking and implanted it in the spines of two paralyzed monkeys. They then placed a wireless BCI in their brains which would detect walking signals and send them to the EES to initiate movements for walking. Within days one monkey walked and the other did so in two weeks.

The implants have already been placed in two human patients. Six more people will be added to the study. If it works, it will be an unprecedented accomplishment.