So he thinks he's walking. Gert-Jan Oskam, a 38-year-old Dutchman, estimated that he would never be able to stand up and move forward again after a serious accident more than 10 years ago. But an implant in his brain allowed this chronic quadriplegic to regain the use of his legs, details the Swiss team of scientists behind this therapeutic breakthrough, in an article published Wednesday, May 24 in the journal Nature.
Gert-Jan Oskam was able to move several times, including climbing stairs, thanks to the device imagined by these researchers. "I was able to get up for the first time in 10 years to go for a drink with my friends. It's pretty cool," he told The Guardian.
A "digital bridge"
"Our concept of a 'digital bridge' between the brain and spinal cord heralds a new era in the treatment of motor deficits caused by neurological disorders," enthuse these scientists led by the Swiss Jocelyne Bloch and the French Grégoire Courtine, two leading figures in their field.
This "digital bridge" consists of two implants: one placed on the surface of the brain and the other at the level of the spinal cord "under the lesion", says Henri Lorach, brain-spinal cord interface project manager at the École polytechnique fédérale de Lausanne and member of the team that carried out the operation.
These two boxes are connected wirelessly and can communicate with each other live. "In the case of a spinal cord injury, the natural connection with the brain is broken, and the purpose of this bridge is to restore it by measuring brain activity and then transmitting stimuli to the spinal cord," says Lorach.
Easier said than done. The implant must first recognize the electrical impulses in the brain that correspond to the commands to walk, then it must decode them, and then transmit the right information to the spinal cord.
The team of Jocelyne Bloch and Grégoire Courtine has been working on these brain-machine interactions for therapeutic purposes for several years and they "are recognized as precursors in the field," says Camille Jeunet-Kelway, a specialist in brain-machine interfaces at the Institute of Cognitive and Integrative Neuroscience of Aquitaine (INCIA), a joint research laboratory of the CNRS and the University of Bordeaux.
These Swiss-based neuroscientists had already made a big leap forward in 2018. They had identified the right electrical impulses that corresponded, at the level of the brain, to the commands to walk and had succeeded in creating a program capable of reproducing them in order to transmit the necessary stimuli to the spinal cord.
Gert-Jan Oskam was able to benefit from the improved version of this device. The big difference is that "everything is done this time in real time," says Henri Lorach. The patient wants to walk and the device understands it and executes. "This is a big step forward in the field of natural walking for these individuals," admits Camille Jeunet-Kelway.
A pinch of AI
How does the implant manage to "read" thoughts? It is the result of a training phase. "They used a statistical method to accumulate evidence during the calibration phase," explains Camille Jeunet-Kelway. Concretely, for several weeks, Gert-Jan Oskam had to think about moving so that the algorithm used to assist the patient correctly isolates the electrical impulses corresponding to the different movements.
After this training, the AI used will, thanks to what it has learned, "predict which cervical data to decode and transmit," explains Henri Lorach.
The result is impressive in more ways than one. The device "decodes reliably and there are few false positives," notes Camille Jeunet-Kelway. The implant not only decodes the right signals, but also correctly interprets the intensity of the command to be transmitted. Otherwise, the legs may make movements too wide or too discreet to advance or climb stairs.
Finally, the scientists found that this work with the implants also had a beneficial effect on the patient's healing... once the device is removed. "Victims of this type of neurological injury usually experience a therapeutic plateau after a certain period of rehabilitation. In this case, the patient appeared to have reached it, but after using the implant, his general condition improved and he passed the plateau. So the implant seems not only to compensate for the handicap but also to help heal," notes Camille Jeunet-Kelway.
>> Read also: Elon Musk's brain implants, science or science fiction?
This is therefore a very promising step forward, but the results of which have yet to be confirmed. The experiment, although successful, involved only one individual. "The spinal cord injuries were severe but only partial, and we don't yet know if the device will work with patients with deeper lesions or in other locations," the authors of the paper acknowledge in Nature.
There are also limits related to "the autonomy of the device", acknowledges Henri Lorach. If the device breaks down while its user is running, the consequences could be serious.
The effort to walk again after years of enforced immobility is also intense. As a result, "we must also take into account fatigue that requires sessions limited in time," notes Henri Lorach. One of the ways is to succeed in miniaturizing the entire device - including the laptop that decodes brain signals - in order to make it less cumbersome.
Very different from Elon Musk's implant
In any case, brain-machine interfaces are on the rise. The day after the publication of the article of these neuroscientists, the whimsical multibillionaire Elon Musk announced that the US authorities had given him the green light to test his implant - developed by his company Neurolink - on humans.
In 2019, the wealthy boss of Tesla, SpaceX, Twitter and Neurolink had specified that his implant would help millions of people with neurological disorders.
Will the scientists at the École Polytechnique de Lausanne have to compete with one of the richest men in the world? The two projects have, in fact, little in common. The Neurolink implant must be inserted directly into the cortex as close as possible to the neurons. "Our method is less invasive, because the electrodes are placed on the surface of the brain [but still under the skull, editor's note]. It's more acceptable to the patient," Lorach said.
Second, Neurolink sees its mission as more than merely therapeutic goals. Elon Musk thinks that his implant will also allow you to learn languages directly, control your smartphone by thought, etc. "In fact we do not yet really know what it should be used for," summarizes Camille Jeunet-Kelway. "There is a difference in philosophy, Elon Musk proposes to increase the human even healthy, while our goal is only to help patients with neurological disorders," summarizes Henri Lorach.
A more limited field of action but which nevertheless opens many doors. Walking is only the first step. The next objective "is to restore the movements of the arms in those who have lost the use," says Henri Lorach.
And that's another matter. "The number of degrees of freedom [of movement] to take into account is much greater than for the legs, where it is essentially hip, knees, feet. Especially if you take into account hands and fingers," explains Camille Jeunet-Kelway.
In addition, much greater precision is needed in the analysis of signals and information. For example, having a drink and drinking requires the right range of motion to aim right, and enough pressure but not too much to hold the glass without breaking it...
This implant that helps the patient live can also be useful beyond the case of quadriplegic or paraplegic patients. "From a medical point of view, when it comes to rehabilitation of motor functions, this type of implant can be useful," says Camille Jeunet-Kelway. The accompaniment of other diseases that cause a reduction in motor skills - such as Parkinson's disease - could also benefit from these implants.
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