Scientists have discovered how to control the limbs of a completely paralysed rat in real time to help it walk again. With plans for tests in human patients underway, the team behind the new technology believes it could help improve the lives of people with spinal cord injuries.
By electrically stimulating the severed part of the spinal cord in a completely paralysed rat, scientists at École Polytechnique Fédérale de Lausanne (EPFL) can control in real-time how the rat moves forward and how high it lifts its limbs, enabling it to walk over obstacles and climb stairs.
“We’re really excited about these discoveries, because we have now established all the technology that will allow us to test the exact same stimulation protocol in paraplegic people,” says EPFL neuroscientist Grégoire Courtine in a video accompanying a press release. Courtine is the senior author of a report detailing the results, published in the latest issue of Science Translational Medicine.
A new research laboratory at Lausanne University Hospital will extend the technology to human patients next summer. Bringing together new monitoring and rehabilitation technology, the ‘Gait Platform’ will take the European Project NEUWalk a big step closer to clinical trials.
“My team and I are aware that we have not found a cure for spinal cord injury. But we have now gathered all the knowledge and technology to extend this treatment developed in rats to spinal cord injured people using this innovative Gait Platform,” Courtine says in the video.
Stimulating the nervous system
The human body needs electricity to function. The electrical output of the human brain, for instance, is about 30 watts. When the circuitry of the nervous system is damaged, the transmission of electrical signals is impaired, often leading to devastating neurological disorders like paralysis.
Electrical stimulation of the nervous system can help relieve these neurological disorders. Deep brain stimulation is used to treat tremors related to Parkinson’s disease, for example. Electrical signals can be engineered to stimulate nerves and recover the sense of touch in the missing limb of amputees. And electrical stimulation of the spinal cord can restore movement control in spinal cord injury.
But can electrical signals be engineered to help a paraplegic walk naturally? The answer is yes – for rats, at least.
How does it work?
“We have complete control of the rat’s hind legs,” Courtine says in the press release. “The rat has no voluntary control of its limbs, but the severed spinal cord can be reactivated and stimulated to perform natural walking. We can control in real-time how the rat moves forward and how high it lifts its legs.”
The scientists studied rats whose spinal cords were completely severed in the middle-back, so signals from the brain were unable to reach the lower spinal cord. That’s where they surgically implanted flexible electrodes. Sending electric current through the electrodes, they could stimulate the spinal cord.
The researchers then discovered a direct relationship between the frequency of the electrical stimulation and how high the rat lifted its limbs. Based on this and careful monitoring of the rat’s walking patterns – its gait – they tailored the electrical stimulation to adapt to the rat’s stride in anticipation of upcoming obstacles, such as barriers or stairs.
“Simple scientific discoveries about how the nervous system works can be exploited to develop more effective neuroprosthetic technologies,” says co-author and neuroengineer Silvestro Micera. “We believe that this technology could one day significantly improve the quality of life of people confronted with neurological disorders.”
Adapted from EPFL Mediacom