How a New Prosthetic Leg Restores Natural Sensations

Restoring Natural Sensory Feedback Results in Functional and Cognitive Benefits for Leg Prosthesis Users

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Restoring natural sensory feedback leads to practical and cognitive advantages for leg prosthesis users. Credit: Pietro Comaschi

A couple of years back, a group of scientists working under Professor Stanisa Raspopovic at the ETH Zurich Neuroengineering Lab got around the world attention when they revealed that their prosthetic legs had actually allowed amputees to feel feelings from this synthetic body part for the very first time. Unlike industrial leg prostheses, which merely supply amputees with stability and assistance, the ETH scientists’ prosthetic gadget was linked to the sciatic nerve in the guinea pig’ thigh through implanted electrodes.

This electrical connection allowed the neuroprosthesis to interact with the client’s brain, for instance communicating info on the consistent modifications in pressure identified on the sole of the prosthetic foot when strolling. This provided the guinea pig higher self-confidence in their prosthesis– and it allowed them to stroll substantially quicker on difficult surfaces. “Our experimental leg prosthesis succeeded in evoking natural sensations. That’s something current neuroprostheses are mainly unable to do; instead, they mostly evoke artificial, unpleasant sensations,” Raspopovic states.

This is most likely due to the fact that today’s neuroprosthetics are utilizing time-constant electrical pulses to promote the nerve system. “That’s not only unnatural, but also inefficient,” Raspopovic states. In a just recently released paper, he and his group utilized the example of their leg prostheses to highlight the advantages of utilizing naturally motivated, biomimetic stimulation to establish the next generation of neuroprosthetics.

Model mimics the activation of nerves in the sole

To produce these biomimetic signals, Natalija Katic– a doctoral trainee in Raspopovic’s research study group– established a computer system design called FootSim. It is based upon information gathered by partners in Canada, who tape-recorded the activity of natural receptors, called mechanoreceptors, in the sole of the foot while touching various points on the feet of volunteers with a vibrating rod.

The design mimics the vibrant habits of great deals of mechanoreceptors in the sole of the foot and produces the neural signals that soar the nerves in the leg towards the brain– from the minute the heel strikes the ground and the weight of the body begins to move forward to the beyond the foot up until the toes press off the ground prepared for the next action. “Thanks to this model, we can see how sensory receptors from the sole, and the connected nerves, behave during walking or running, which is experimentally impossible to measure,” Katic states.

Information overload in the spine

To evaluate how carefully the biomimetic signals computed by the design represent the signals given off by genuine nerve cells, Giacomo Valle– a postdoc in Raspopovic’s research study group– dealt with associates in Germany, Serbia, and Russia on try outs felines, whose nerve system processes motion in a comparable method to that of human beings. The experiments happened in 2019 at the Pavlov Institute of Physiology inSt Petersburg and were performed in accordance with the appropriate European Union standards.

The scientists implanted electrodes, linking some to the nerve in the leg and some to the spine to find how the signals are sent through the nerve system. When the scientists used pressure to the bottom of the feline’s paw, consequently stimulating the natural neural action that takes place when a feline takes an action, the strange pattern of activity tape-recorded in the spine did certainly look like the patterns that were generated in the spine when the scientists promoted the leg nerve with biomimetic signals.

By contrast, the traditional method of time- consistent stimulation of the sciatic nerve in the feline’s thigh generated a considerably various pattern of activation in the spine. “This clearly shows that the commonly used stimulation methods cause the neural networks in the spine to be flooded with information,” Valle states. “This information overload could be the reason for the unpleasant sensations or paraesthesia reported by some users of neuroprosthetics,” Raspopovic includes.

Learning the language of the nerve system

In their medical trial with leg amputees, the scientists had the ability to reveal that biomimetic stimulation transcends to time-constant stimulation. Their work plainly showed how the signals that simulated nature produced much better outcomes: not just were the guinea pig able to climb up actions quicker, they likewise made less errors in a job that needed them to climb up the very same actions while spelling words backwards. “Biomimetic neurostimulation allows subjects to concentrate on other things while walking,” Raspopovic states, “so we concluded that this type of stimulation is more naturally processed and less taxing on the brain.”

Raspopovic, whose laboratory kinds part of the ETH Institute of Robotics and Intelligent Systems, thinks that these brand-new findings are not just appropriate to the limb prostheses he and his group have actually been dealing with for over half a years. He argues that the requirement to move far from abnormal, time-constant stimulation towards biomimetic signals likewise uses to an entire series of other help and gadgets, consisting of back implants and electrodes for brain stimulation. “We need to learn the language of the nervous system,” Raspopovic states. “Then we’ll be able to communicate with the brain in ways it really understands.”

Reference: “Biomimetic computer-to-brain communication enhancing naturalistic touch sensations via peripheral nerve stimulation” by Giacomo Valle, Natalija Katic Secerovic, Dominic Eggemann, Oleg Gorskii, Natalia Pavlova, Francesco M. Petrini, Paul Cvancara, Thomas Stieglitz, Pavel Musienko, Marko Bumbasirevic and Stanisa Raspopovic, 20 February 2024, < period class ="glossaryLink" aria-describedby ="tt" data-cmtooltip ="<div class=glossaryItemTitle>Nature Communications</div><div class=glossaryItemBody>&lt;em&gt;Nature Communications&lt;/em&gt; is a peer-reviewed, open-access, multidisciplinary, scientific journal published by Nature Portfolio. It covers the natural sciences, including physics, biology, chemistry, medicine, and earth sciences. It began publishing in 2010 and has editorial offices in London, Berlin, New York City, and Shanghai.&nbsp;</div>" data-gt-translate-attributes="[{"attribute":"data-cmtooltip", "format":"html"}]" tabindex ="0" function ="link" >NatureCommunications
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