Engineering news
The École Polytechnique Fédérale de Lausanne (EPFL) in Switzerland has developed a neuroprosthetic system called the ‘brain-spine interface’, that has enabled a primate with spinal cord injury to regain control of its paralysed leg by restoring communication between the brain and the region of the spinal cord.
EPFL is collaborating with Lausanne University Hospital to conduct clinical trials on humans that evaluate the therapeutic potential of this spinal cord stimulation technology, without the brain implant, to improve walking with partial spinal cord injury affecting the lower limbs.
The interface decodes brain activity associated with walking movements and relays this information to the spinal cord through electrodes that stimulate the neural pathways that activate leg muscles during natural locomotion.
Grégoire Courtine, a neuroscientist involved in the study at EPFL, said: “This is the first time that neurotechnology restores locomotion in primates. But there are many challenges ahead and it may take several years before all the components of this intervention can be tested in people.”
The brain-spine interface bridges the spinal cord injury, in real-time and wirelessly. The neuroprosthetic system decodes spiking activity from the brain’s motor cortex and then relays this information to a system of electrodes located over the surface of the lumbar spinal cord, below the injury. Electrical stimulation of a few volts, delivered at precise locations in the spinal cord, modulates distinct networks of neurons that can activate specific muscles in the legs.
Courtine added: “To implement the brain-spine interface, we developed an implantable, wireless system that operates in real-time and enabled a primate to behave freely, without the constraint of tethered electronics. We understood how to extract brain signals that encode flexion and extension movements of the leg with a mathematical algorithm. We then linked the decoded signals to the stimulation of specific hotspots in the spinal cord that induced the walking movement.”
The study showed that the primate regained control of its paralysed leg immediately upon activation of the brain-spine interface, without any physiotherapy or training. The interface should also work for more severe injuries of the spinal cord with the aid of pharmacological agents, according to the scientists.
Information is processed in the brain by transmitting spikes of electricity from one neuron to the next. This electrical spiking gives rise to brain signals that can be measured and interpreted. The lumbar region of the spinal cord also contains complex networks of neurons that activate leg muscles to walk. Bundles of nerves coming from the brain carry the relevant information to the spinal cord about the intended activation of leg muscles. The signals travel down the spinal cord, reach the neural networks located in the lumbar region, and these in turn activate muscles in the legs to produce walking movements.
Spinal cord injuries partly or completely prevent these signals from reaching the neurons that activate leg muscles, leading to paralysis.
Earlier in the year, other technologies emerged with the aim to tackle paralysis. The University of Melbourne developed a brain machine interface with a stent-based electrode that is implanted in a blood vessel in the brain and records signals that are transmitted to the exoskeleton that control limb mobility.
Duke University in North Carolina developed a robotic exoskeleton, where the brain machine interface used implanted electrodes to detect brain signals and translate them into demands.
Doctors in Ohio implanted a computer chip into a paralysed man’s brain that was connected to his sleeve through computers in the lab. The chip can decode brain signals and match them to specific movements. Through intensive mental will and strenuous practice, the man was able to regain restricted mobility in one of his hands.
The results of the study conducted by EPFL have been published in Nature.