A man who was paralysed due to spinal cord injury can now walk naturally using his thoughts. Yes, you heard that correctly. The thought-controlled walk is possible due to a brain computer interface established using a special device.
The device is a wireless digital bridge, which helps re-establish the communication between the brain and spinal cord that is disrupted following a spinal cord injury. The study describing the findings was published May 24 in the journal Nature.
Meet the man who could use his thoughts to walk
The man, Gert-Jan, suffered a spinal cord injury following a bicycle accident. The mishap left him paralysed. Gert-Jan had chronic tetraplegia, which refers to paralysis in the upper and lower body.
Neuroscientists and neurosurgeons from the Swiss Federal Institute of Technology Lausanne (EPFL), Lausanne University Hospital (CHUV), and the University of Lausanne, Switzerland, and other institutes contributed to the efforts which allowed the man to walk naturally again.
How the brain and spinal cord help us walk
In order to walk, the brain delivers executive commands to the neurons present in the lumbosacral spinal cord, which consists of five large vertebrae, and five fused vertebrae, the study said.
Why is a person paralysed after a spinal cord injury?
According to the authors, a spinal cord injury interrupts the communication between the brain and the region of the spinal cord that produces walking, leading to paralysis. While the majority of spinal cord injuries do not directly damage the neurons in the lumbosacral spinal cord, the disruption of descending pathways due to spinal cord injuries interrupts the brain-derived commands that are important for the neurons to produce walking. Eventually, people with spinal cord injuries become paralysed.
How the brain computer interface helped the man walk using his thoughts
The authors restored Gert-Jan's brain-spinal cord communication with a digital bridge between the brain and spinal cord, enabling him to stand and walk naturally in community settings. The digital bridge between the brain and spinal cord would enable volitional (relating to one's will) control over the timing and amplitude of muscle activity, and restore more natural and adaptive control of standing and walking in people with paralysis due to spinal cord injury, the authors suggested.
The digital bridge has been named the brain-spine interface.
In a statement released by the Swiss Federal Institute of Technology Lausanne, Grégoire Courtine, a professor of neuroscience, said the interface transforms thought into action.
According to the study, the brain-spine interface consists of fully implanted recording and stimulation systems that establish a direct link between cortical signals and the analogue modulation of epidural electrical stimulation, an experimental therapy which has the potential to help individuals with spinal cord injuries, to regain movement and control, and involves implanting a small device over the protective coating of the spinal cord.
The authors established the bridge by integrating two fully implanted systems that enable recording of cortical activity and the stimulation of the lumbosacral spinal cord wirelessly in real time, the study said.
One type of electronic implant was fitted into the brain, while the other was implanted on the spinal cord. In the statement, Jocelyn Bloch, a neurosurgeon, explained that the researchers implanted the devices, called WIMAGINE, above the region of the brain that is responsible for controlling leg movements, and decodes electrical signals generated by the brain when one thinks about walking. She explained that the researchers also positioned a neurostimulator connected to an electrode array over the region of the spinal cord that controls leg movement.
Therefore, the devices compensate for the disrupted communication between the brain and spinal cord due to a spinal cord injury by decoding the electrical signals generated when one thinks about walking, and using these signals to stimulate the regions of the spinal cord that control walking, standing and climbing stairs. The signals activate leg muscles to help the person in whom the devices have been implanted move with their thoughts.
By establishing this direct link between signals from the cortex and the epidural electrical stimulation, the device targets the spinal cord regions involved in the production of walking, the study said.
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How long did the digital bridge remain stable for the participant?
The authors noted that a highly reliable brain-spine interface is calibrated within a few minutes, and this reliability in Gert-Jan remained stable for over a year, including during independent use at home.
According to the authors, Gert-Jan reported that the brain-spine interface enables natural control over the movements of his legs to stand, walk, climb stairs and even traverse complex terrains.
Thus, the brain-spine interface provided neurorehabilitation, which improved neurological recovery.
The researchers saw that Gert-Jan's sensory perceptions and motor skills improved remarkably, even when the brain-spine interface was switched off. Gert-Jan was able to walk with crutches, even when the digital bridge was turned off, the study said.
This suggests that the digital repair of the spinal cord has helped develop new nerve connections, according to the Swiss Federal Institute of Technology Lausanne.
The researchers aim to test the digital bridge for arm and hand restoration functions, and intend to apply it to other clinical conditions such as paralysis due to stroke.
The authors concluded that this digital bridge establishes a framework to restore natural control of movement after paralysis.