Scientists report in the journal Nature the successful restoration of intentional walking movement in a pair of spinal cord-injured rhesus monkeys using a wireless “brain-spinal interface.”
The scientists—part of a collaboration between Ecole Polytechnique Federale Lausanne (EPFL) in Switzerland and Brown University, Medtronic and Fraunhofer ICT-IMM in Germany—note in a media release from Brown University that this work could contribute to the development of a similar system designed for humans with spinal cord injuries.
“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,” says David Borton, assistant professor of engineering at Brown and one of the study’s co-lead authors, in the release. “With the system turned on, the animals in our study had nearly normal locomotion.”
The brain-spinal interface used a pill-sized electrode array implanted in the brain to record signals from the motor cortex. A wireless neurosensory 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 release explains.
“Doing this wirelessly enables us to map the neural activity in normal contexts and during natural behavior,” Borton adds, per the release. “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 scientists then tested the system on two monkeys with lesions that spanned half the spinal cord in their thoracic spine, during the weeks immediately after the injury. When the system was turned on, the monkeys began spontaneously moving their legs while walking on a treadmill.
More work needs to be done before the system can be tested on humans, however, the scientists note. In addition, they note that this study has various limitations.
“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 states.
Despite the limitations, the research sets the stage for future studies in primates and, at some point, potentially as a rehabilitation aid in humans, per the release.
[Source(s): Brown University, Science Daily]