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When Gyorgy Levay lost parts of the four extremities, including most of his left arm, to meningitis in 2010, he resolved to make the best of a bad situation.
He mastered his replacement advanced prosthesis. He has changed the focus of his graduate studies from electrical engineering to biomedical engineering. The native Hungarian found it interesting to see how he continued to feel the sensations of the hand that he no longer possessed.
But like most amputees, he felt that something was missing. Because his prostheses had no sense of touch, they seemed to him extraterrestrial attachments.
Through a team of researchers from Johns Hopkins University, he learned what they might feel if they were part of him. Levay was the main volunteer subject in a two-year university study that endowed an artificial limb with the ability to feel pressure and pain.
Led by Luke Osborn and Nitish Thakor, a graduate student and professor of biomedical sciences from Johns Hopkins engineering department, the team developed a form of "electronic skin" that records the touch of the same way that the human body.
Wearing this "skin", a fabric and rubber sheath with sensors that the team called "e-dermis," on the fingertips of his prosthetic left hand, Levay picked up several small rounded objects, then did the same thing with a sharp object.
While picking up rounded objects, he felt different levels of physical pressure; holding the object pointed, he felt pain.
For Levay, it was as if a lifeless appendage – his left hand and his arm – was reborn.
"Normally, my" hand "looks a bit like a hollow shell," he said in a telephone interview from his hometown of Budapest. "When these electronic stimulations began to take hold to produce, it was as if one filled a glove with water, almost as if it was filling with life. "
The experiment showed the first time that an amputee could feel a range of benign physical pressures a prosthesis – and the first time anyone felt pain
"For the first time, a prosthesis can provide a range of perceptions, from fine touch to harmful touch , to an amputee, and that sounds a lot more like human hand, "said Thakor, the co-founder of Infinite Biomedical Technologies, a small Baltimore-based company that provided the prosthetic equipment for the study.
An article on the study appeared in the journal Science Robotics recently.
Progress is the latest in a field of research that has expanded rapidly over the last decade and a half, thanks in large part to the work done at Johns Hopkins.
About four years ago, however, Case Western Reserv researchers from the University of Cleveland and elsewhere began to take steps to implant dentures with touch.
These researchers achieved their results by affixing electronic sensors to prosthetic limbs. These tiny devices could record touch, translate it into electronic signals, and send signals across a set of wires to the appropriate locations in what was left of user members.
Every pioneering experience has its limits, and these were no exception. The process required invasive surgery – electrodes had to be implanted in the residual limbs to receive the signals and transmit them through the nervous system – and the work provided only a narrow range of pressure sensations [19659017]. menu of sensations provided, up to and including pain – a category of feeling that, although still unpleasant, serves a crucial survival function. "Pain is a sensation we use to protect our bodies," Osborn said. "We can take it for granted, and we certainly do not always like it, but it serves as a warning system, helping us avoid harmful events."
The team, which included members of the Johns Hopkins Departments of Electrical Engineering The sensory receptor cells of human skin, they observed, are actually at different levels, those responsible for pain sensations (nociceptors) being mainly close to the surface of the skin. and those responsible for detecting the pressure (mechanoreceptors) put deeper.
To replicate this system, they designed e-dermis to have sensors arranged in two layers, instead of one as the previous engineers
"The sensors in each layer to generate the appropriate sensations to this layer
Again, they turned to biology.
The team studied the frequencies, amplitudes, and wavelengths of signals that the body normally sends out. Then, they calibrated the sensory device to mimic these variables.
Osborn developed this "neuromorphic" approach, ie creating a new one. technology that mimics biological patterns
as well as impulses that transmit pressure information, texture, and so on, "he said." We created similar impulses and compared them to what the subjects actually perceive. "[19659002] The next challenge was to make sure the system was spatially accurate – that is, if the contact occurred on the prosthetic index, the brain perceives it as they are there. reached through "sensory mapping" – probing each square centimeter of the subject's residual limb and noting where the subject "felt" each of these keys on his "ghost" hand
allowed Osborn and the company to wire the sensor on the index, for example, directly to the nerve in the residual limb that would normally connect to the actual index.
"The nerves that went to your hand are still there, they are no longer connected to the hand," Osborn said. "By stimulating each of these nerves, we activate the location in the brain that says" pink finger, "" index, "or" thumb, "and the sensation should ideally feel like it would before amputation . " [19659002] After mapping the nerve patterns so precisely, the team was able to avoid requiring invasive implantation of metal electrodes in the residual limb.
They attached prosthesis wires to appropriate places on the limb, but they did the surface of the skin, a process that is much easier on the subject.
Levay said that he enjoyed it on many levels.
He was studying Biomedical Engineering on a Fulbright Scholarship at Johns Hopkins when Thakor and Osborn started their research in 2015.
Because he was interested on a personal and professional level, and physically nearby, he made the ideal topic for the study, which was funded by grants from Johns Hopkins Applied Physics Laboratory and the National Institute of Biomedical Imaging and Engineering, a division of the National Institutes of Health, among other sources.
The group worked with a number of amputee volunteers during the course of the study, but because it was still available for several months, Levay emerged as the central, nameless subject of the study. 39, article, entitled "Prosthesis with neuromorphic multi-layered e-dermis perceives touch and pain."
The experiments were painful at first, Levay says with a laugh, as Osborn looked for the right match between the shocks that he caused and the sensations felt by Levay.
The more they worked together, the closer the correlation became, until the only pain felt during the sessions came when he took the sharp object, signaling that the experience "
That, he said, was a pain that he was too happy to feel.
"The E-dermis still does not work perfectly," said Levay, "but it's definitely a step closer in achieving its return to the hand. "
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