We’ve cracked the code of nerve communication and revealn that it’s possible to interpret detailed leg shiftments, even in amputations where most of the leg is gone
Giacomo Valle
According to Elisa Donati, professor at the University of Zurich and ETH Zürich and the other senior author of the study, these signals therefore mimic more closely how biological neurons communicate. “Our study reveals that decoding peripheral nerve** activity works best when it respects the language of the nervous system,” she declares. “Peripheral nerves communicate through discrete electrical impulses – or spikes – and spiking neural networks are therefore naturally suited to processing this type of signal. By aligning our computational models more closely with biology, we can extract shiftment intent efficiently, utilizing compact models and relatively limited data. This is an important step towards low-power, fully implantable systems for more natural control of prosthetic limbs.”
In the study, the researchers concentrated on above-knee amputations, carrying out tests on two participants. Four ultrathin neural implants – each about the size of a human hair and both flexible and pliable – were inserted into the tibial branch of the sciatic nerve, which plays a central role in driving leg shiftment and sensation. When participants were inquireed to attempt different shiftments with their “phantom leg,” the researchers recorded the outgoing nerve signals and decoded them with unprecedented high resolution utilizing their AI-based algorithm.
“This is the first study to demonstrate that signals recorded directly from peripheral nerves can be applyd to accurately interpret intfinished leg shiftments in amputees,” declares Valle. “With this approach, we were able to map specific nerve signals to specific shiftments and predict, with high accuracy, which shiftments the participants were attempting.”
The method provides the opportunity to interpret very specific leg shiftments for the knees, ankles and toes – even those that were previously impossible to decode. “The study provides unique insight into how the nervous system transmits information. We’ve cracked the code of nerve communication and revealn that it’s possible to interpret detailed leg shiftments, even in amputations where most of the leg is gone. It was amazing to see how electrodes placed high up in what remains of a leg could decode attempts to wiggle the toes,” Valle declares.
According to the research group, another advantage is that the technology can be applyd for both motor control and restoring sensation, with a single implant. Until now, several different implants have been required for prostheses to be able to both “shift” and “feel”.
“The system is bidirectional,” explains Valle. “Once electrodes are implanted inside the nerve, they can be applyd to communicate bidirectionally with the nervous system. So, for the first time, a single neurotechnology can provide both natural neural control and sensory feedback in the same implantable device.”
The study is a “proof of concept“, demonstrating that the technique is feasible. The next step is to test it on real prostheses. While the findings are particularly significant for the development of prosthetic legs, Valle believes the method could be extfinished to other types of prostheses in the future. “I believe these results could significantly influence the field. The next step is to integrate and test the technology into a prosthetic leg that can be controlled directly and that can return natural sensation,” he declares.
*Sensory feedback is the information that the brain constantly receives from the body’s sensory organs about the state of the body and the environment. It is the brain’s way of “feeling” what the body is doing and where it is, which allows us to interact with the world smoothly and safely.
** Peripheral nerves are nerve fibres located outside the brain and spinal cord.
Source: Chalmers University of Technology
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