Currently people who break their backs or suffer a spinal trauma are unable to stand or move even though their legs still work, because the signal which connects their brains to their muscles is disconnected.
Two monkeys who were temporarily paralysed in one leg were able to walk again instantly using the technique, which could be available for humans within a decade.
“For the first time, I can imagine a completely paralysed patient able to move their legs through this brain-spine interface, said neurosurgeon Jocelyne Bloch of the Lausanne University Hospital.
Humans are able to move because electrical signals originating in the brain’s motor cortex travel down to the lumbar region in the lower spinal cord, where they activate motor neurons that coordinate the movement of muscles responsible for extending and flexing the leg.
But injury to the upper spine can cut off communication between the brain and lower spinal cord.
To create a device which mimicked the natural communication of the brain and muscles, scientists needed to decode signals from the motor cortex and turn them into electronic signals which could fire electrodes and stimulate nerves in the spine.
It was tested on two macaque monkeys with lesions that spanned half the spinal cord and who could not walk on one leg. When turned on, the animals began spontaneously moving their legs while walking on a treadmill.
“With the system turned on, the animals in our study had nearly normal locomotion,” said Dr David Borton, assistant professor of engineering at Brown and one of the study’s co-lead authors.
Previous studies have shown that it is possible to use signals decoded from the brain to control movement of a robotic or prosthetic hands but it has never been shown to help stimulate muscles directly.
The researchers say not only could it help paralysed people to walk again, but in the long term may even encourage the regrowth of damaged circuits.
“There’s an adage in neuroscience that circuits that fire together wire together,” added Dr Borton.
“The idea here is that by engaging the brain and the spinal cord together, we may be able to enhance the growth of circuits during rehabilitation. That’s one of the major goals of this work and a goal of this field in general.”
“It is an important step forward in our understanding of how we could improve motor recovery in patients affected by spinal cord injury by using brain-spinal interface approaches,” said Prof Simone Di Giovanni, Chair in Restorative Neuroscience, Imperial College London.
“In principle this is reproducible in human patients. The issue will be how much this approach will contribute to functional recovery that impacts on the quality of life. This is still very uncertain.”
Dr Andrew Jackson, of the Movement Laboratory at the Institute of Neuroscience, Newcastle University, added: “The idea of using electronic implants to bypass damaged neural pathways dates back to the 1970s but the twenty-first century has seen remarkable progress in this field.
“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.”
The research was published in the journal Nature Neuroscience.