Monkeys with spinal cord injuries leading to paralysis of one limb have regained their ability to walk thanks to a new wireless neuroimplant that re-establishes communication between the brain and spinal cord, scientists said Wednesday, Nov. 9.
This achievement marks another step forward in the rapidly evolving field of spinal cord injury treatment with the latest technology.
Over the past few years, scientists have created technologies to help humans and monkeys manipulate a robotic arm with literal power of thought, restored a paralyzed man's ability to use one hand through a microchip implanted in his brain, and used electrical nerve stimulation to make paralyzed rats walk.
The new system stands out among all these advances because it allows you to concentrate on your lower body and gives monkeys - probably humans in the near future - the ability to use a wireless system and not be tethered to a computer. The developers of this system used advances in neural activity mapping and neural stimulation. A computer is needed to decode brain signals and send them to the spinal cord, but computer technology has made it possible to create a portable device.
Grégoire Courtine, a spinal cord injury recovery specialist at the Swiss Federal Institute of Technology in Lausanne, says he hopes that the system he and his colleagues have developed can be used in 10 years to treat people by helping they go through the process of rehabilitation and "improve the quality of life."
However, as he emphasized, scientists set themselves the task of improving the rehabilitation process, and not inventing a fantastic cure for paralysis. “People won't be able to walk the streets with a brain-spine interface” in the near future, he added.
Andrew Jackson of the University of Newcastle, who studied upper body paralysis and was not involved in this study, believes it is "another key milestone" in the search for treatments for paralysis. Dr. Jackson wrote comments on this study in the journal Nature, which published the results of an experiment by Dr. Curtin, Marco Capogrosso, Tomislav Milekovic and others.
One of the reasons that this system should not be considered a miracle cure for paralysis is that the implant is capable of transmitting only those impulses that allow the limb to be stretched and flexed at the right time so that the animal can walk on four legs, but does not allow more complex movements, such as changing direction or avoiding obstacles. With people, things are even more complicated, because, for example, unlike four-legged animals, a person also has to maintain balance while walking.
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According to Dr. Curtin, they were doing the research in collaboration with Chinese experts because the restrictions on animal testing in Switzerland would have prevented them from completing the work. Now that their experiment was successful, he received permission to continue working in Switzerland.
Dr. Curtin wrote about the ethical side of such experiments with primates, stressing that it took him 10 years to experiment with rodents to get ready to work with monkeys. One of the reasons scientists have worked with only one paralyzed limb is that tetrapods are able to live relatively normally without using one leg, while maintaining control over the functions of the bladder and intestines, while a complete rupture of the spinal cord can have a devastating effect on the animal.
Moreover, as Dr. Curtin added, work on this project, which promises to help people with spinal cord injury in the future, cannot continue with human involvement until other primates have been experimented with. Reading signals from the brain and stimulating the spinal cord are performed using devices that are already used by humans for other purposes. However, signal decoding software has not yet been tested on humans.
David Borton of Brown University, one of the lead authors of the new report, developed the wireless sensor with his colleagues in the process of writing his doctoral dissertation, even before working with Dr. Curtin. Equipped with microelectrodes, this sensor records and transmits impulses to the part of the brain responsible for limb movement. One of the reasons the system can help with rehabilitation is because it strengthens the remaining neural connections between parts of the spinal cord and an injured limb, he said.
The device for recording brain signals has been complemented by an electrostimulation device placed outside the spinal cord, which transmits signals to the reflex system. The walking process is only partially controlled by the brain. The spinal cord has its own system capable of receiving and responding to information from the limbs. Most of the time, people don’t think about how they walk, and the walking process is not just controlled by the brain at a subconscious level. The main part of the load falls on the spinal cord and the reflex system.
Dr. Curtin has previously used electrical stimulation to train rats with spinal cord injuries to walk.
However, that work of his did not involve the brain, and one of the key components of these experiments was the time frame. “If the brain sends a signal to make a limb move, it only takes a few milliseconds for this connection to be established,” explained Dr. Borton.