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    Quadriplegic walks again thanks to device connecting his brain to his muscles



    Gert-Jan, at the hospital of the University of Lausanne (Switzerland), on March 2, 2023. This patient, who became quadriplegic after an accident, is testing the brain-machine interface to move around.

    A bicycle accident left Gert-Jan (his surname has not been given) quadriplegic 10 years ago, completely unable to walk. Today, the 40-year-old has regained natural control of his leg movement, can stand and even climb stairs. This incredible feat has been achieved thanks to a brain-machine interface that allows him to transform his thoughts into concrete actions – the result of a collaboration between Swiss and French researchers.

    After successfully helping paraplegic patients to walk with the help of electrical stimulation of the spinal cord, activated using remote controls, a new step has been taken by the teams working with Jocelyne Bloch and Grégoire Courtine. Both professors at the University of Lausanne, the Federal Polytechnic School of Lausanne and the University Hospital of Vaud, they worked with their colleagues at the Swiss research center NeuroRestore and from the Clinatec research center, in Grenoble. Their case study, published on Wednesday, May 24, in the newspaper Natureshows how a wireless digital bridge between the brain and spinal cord allows decoded movement intentions to be transmitted from brain recordings and then converted into electrical stimulation that activates leg muscles.

    “In our previous trials, the way the muscles were stimulated could be compared to an ‘on-off’ system,” explained Courtine. “Now, their activation is controlled by the patient. This is why walking is much smoother, more fluid.” “With the previous technology, it was for example very complicated to climb stairs,” added Bloch. “Now, thinking about making a movement longer or with a greater amplitude makes it possible to walk in a way that adapts to the environment voluntarily. To achieve this result, we had to add layers of essential technology.”

    Brain signals decoded by a laptop computer

    The system includes, on the one hand, an implant that was placed on the spinal cord. This consists of a neurostimulator connected to a field of electrodes allowing control of leg movement. On the other hand, two wireless electronic recording devices, 5 centimeters in diameter and composed of 64 electrodes each, were implanted in the patient’s head. They are placed under the skin, in the place of a part of the cranium at the level of the motor cortex, the area that is dedicated to the control of the voluntary movements of the body.

    When the device is activated, Gert-Jan wears a helmet adapted to the location of his implants, in which two antennas are integrated, one feeding the implanted electronics by induction, the other transferring the signals generated by the brain to a computer processing the data in near real-time, with a time lag of only 300 to 500 milliseconds. Placed on a walker, or in a backpack if walking with crutches, the computer decodes the brain signals and then creates a stimulation of the spinal cord by means of implants located in the abdomen and under the vertebrae.

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