Nav: Home

Researchers restore leg movement in primates using wireless neural interface

November 09, 2016

PROVIDENCE, R.I. [Brown University] -- An international team of scientists has used a wireless "brain-spinal interface" to bypass spinal cord injuries in a pair of rhesus macaques, restoring intentional walking movement to a temporarily paralyzed leg. The researchers, who describe their work in the journal Nature, say this is the first time a neural prosthetic has been used to restore walking movement directly to the legs of nonhuman primates.

The study was performed by scientists and neuroengineers in a collaboration led by Ecole Polytechnique Federale Lausanne (EPFL) in Switzerland, together with Brown University, Medtronic and Fraunhofer ICT-IMM in Germany. The work builds upon neural technologies developed at Brown and partner institutions, and was tested in collaboration with the University of Bordeaux, Motac Neuroscience and the Lausanne University Hospital.

"The system we have developed uses signals recorded from the motor cortex of the brain to trigger coordinated electrical stimulation of nerves in the spine that are responsible for locomotion," said David Borton, assistant professor of engineering at Brown and one of the study's co-lead authors. "With the system turned on, the animals in our study had nearly normal locomotion."

The work could help in developing a similar system designed for humans who have had spinal cord injuries.

"There is evidence to suggest that a brain-controlled spinal stimulation system may enhance rehabilitation after a spinal cord injury," Borton said. "This is a step toward further testing that possibility."

Grégoire Courtine, a professor at EPFL who led the collaboration, has started clinical trials in Switzerland to test the spine-part of the interface. He cautions: "There are many challenges ahead and it may take several years before all the components of this intervention can be tested in people."

Re-establishing communication

Walking is made possible by a complex interplay among neurons in the brain and spinal cord. 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.

Injury to the upper spine can cut off communication between the brain and lower spinal cord. Both the motor cortex and the spinal neurons may be fully functional, but they are unable to coordinate their activity. The goal of the study was to re-establish some of that communication.

The brain-spinal interface used a pill-sized electrode array implanted in the brain to record signals from the motor cortex. The sensor technology was developed in part for investigational use in humans by the BrainGate collaboration, a research team that includes Brown, Case Western Reserve University, Massachusetts General Hospital, the Providence VA Medical Center, and Stanford University. The technology is being used in ongoing pilot clinical trials, and was used previously in a study led by Brown neuroengineer Leigh Hochberg in which people with tetraplegia were able to operate a robotic arm simply by thinking about the movement of their own hand.

A wireless neurosensor, developed in the neuroengineering lab of Brown professor Arto Nurmikko by a team that included Borton, sends the signals gathered by the brain chip wirelessly to a computer that decodes them and sends them wirelessly back to an electrical spinal stimulator implanted in the lumbar spine, below the area of injury. That electrical stimulation, delivered in patterns coordinated by the decoded brain, signals to the spinal nerves that control locomotion.

To calibrate the decoding of brain signals, the researchers implanted the brain sensor and wireless transmitter in healthy macaques. The signals relayed by the sensor could then be mapped onto the animals' leg movements. They showed that the decoder was able to accurately predict the brain states associated with extension and flexion of leg muscles.

The ability to transmit brain signals wirelessly was critical to this work, Borton said. Wired brain-sensing systems limit freedom of movement, which in turn limits the information researchers are able to gather about locomotion.

"Doing this wirelessly enables us to map the neural activity in normal contexts and during natural behavior," Borton said. "If we truly aim for neuroprosthetics that can someday be deployed to help human patients during activities of daily life, such untethered recording technologies will be critical."

The researchers combined their understanding of how brain signals influence locomotion with spinal maps, developed by Courtine's lab at EPFL, which identified the neural hotspots in the spine responsible for locomotor control. That enabled the team to identify the neural circuits that should be stimulated by the spinal implant.

With these pieces in place, the researchers then tested the entire system on two macaques with lesions that spanned half the spinal cord in their thoracic spine. Macaques with this type of injury generally regain functional control of the affected leg over a period of a month or so, the researchers said. The team tested their system in the weeks following the injury, when there was still no volitional control over the affected leg.

The study showed that with the system turned on, the animals began spontaneously moving their legs while walking on a treadmill. Kinematic comparisons with healthy controls showed that the lesioned macaques, with the aid of brain-controlled stimulation, were able to produce nearly normal locomotor patterns.

Limitations and future work

While demonstrating that the system works in a nonhuman primate is an important step, the researchers stressed that much more work must be done to begin testing the system in humans. They also pointed out several limitations in the study.

For instance, while the system used in this study successfully relayed signals from the brain to the spine, it lacks the ability to return sensory information to the brain. The team was also unable to test how much pressure the animals were able to apply to the affected leg. While it was clear that the limb was bearing some weight, it wasn't clear from this work how much.

"In a full translational study, we would want to do more quantification about how balanced the animal is during walking and measure the forces they're able to apply," Borton said.

Despite the limitations, the research sets the stage for future studies in primates and, at some point, potentially as a rehabilitation aid in humans.

"There's an adage in neuroscience that circuits that fire together wire together," Borton said. "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."
-end-
The research was funded by European Community's Seventh Framework Program (CP-IP 258654, NeuWALK), International Foundation for Research in Paraplegia Starting Grant from the European Research Council (ERC 261247, Walk Again), The Wyss Centre in Geneva Marie Curie Fellowship (331602, e-WALK), Marie Curie COFUND EPFL fellowships, Medtronic Morton Cure Paralysis Fund fellowship, NanoTera.ch Programme (SpineRepair), National Centre of Competence in Research in Robotics Sinergia program (CRSII3_160696), Sino-Swiss Science and Technology Cooperation (IZLCZ3_156331) and the Swiss National Science Foundation.

Brown University

Related Spinal Cord Articles:

Neurological signals from the spinal cord surprise scientists
With a study of the network between nerve and muscle cells in turtles, researchers from the University of Copenhagen have gained new insight into the way in which movements are generated and maintained.
An 'EpiPen' for spinal cord injuries
An injection of nanoparticles can prevent the body's immune system from overreacting to trauma, potentially preventing some spinal cord injuries from resulting in paralysis.
From spinal cord injury to recovery
Spinal cord injury disconnects communication between the brain and the spinal cord, disrupting control over part of the body.
Transplanting adult spinal cord tissues: A new strategy of repair spinal cord injury
Spinal cord injury repair is one of the most challenging medical problems, and no effective therapeutic methods has been developed.
Gene medication to help treat spinal cord injuries
The two-gene medication has been proven to recover motor functions in rats.
Spinal cord is 'smarter' than previously thought
New research from Western University has shown that the spinal cord is able to process and control complex functions, like the positioning of your hand in external space.
The lamprey regenerates its spinal cord not just once -- but twice
Marine Biological Laboratory (MBL) scientists report that lampreys can regenerate the spinal cord and recover function after the spinal cord has been severed not just once, but twice in the same location.
Timing could mean everything after spinal cord injury
Moderate damage to the thoracic spinal cord causes widespread disruption to the timing of the body's daily activities, according to a study of male and female rats published in eNeuro.
New approach could jumpstart breathing after spinal cord injury
A research team at the Krembil Research Institute in Toronto has developed an innovative strategy that could help to restore breathing following traumatic spinal cord injury.
Dr. Jekyll, Mr. Hyde: Study reveals healing mesenchymal cells morph and destroy muscles in models of spinal cord injury, ALS and spinal muscular atrophy
Scientists at Sanford Burnham Prebys Medical Discovery Institute (SBP), in collaboration with the Fondazione Santa Lucia IRCCS in Rome, have discovered a new disease-specific role in FAP cells in the development of muscle tissue wasting, indicating a potential new avenue for treating motor neuron diseases including spinal cord injury, ALS and spinal muscular atrophy.
More Spinal Cord News and Spinal Cord Current Events

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Rethinking Anger
Anger is universal and complex: it can be quiet, festering, justified, vengeful, and destructive. This hour, TED speakers explore the many sides of anger, why we need it, and who's allowed to feel it. Guests include psychologists Ryan Martin and Russell Kolts, writer Soraya Chemaly, former talk radio host Lisa Fritsch, and business professor Dan Moshavi.
Now Playing: Science for the People

#538 Nobels and Astrophysics
This week we start with this year's physics Nobel Prize awarded to Jim Peebles, Michel Mayor, and Didier Queloz and finish with a discussion of the Nobel Prizes as a way to award and highlight important science. Are they still relevant? When science breakthroughs are built on the backs of hundreds -- and sometimes thousands -- of people's hard work, how do you pick just three to highlight? Join host Rachelle Saunders and astrophysicist, author, and science communicator Ethan Siegel for their chat about astrophysics and Nobel Prizes.