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When Gyorgy Levay lost parts of the four extremities, including most of his left arm, to meningitis in 2010, he decided to make the best of a bad situation.
He mastered his state-of-the-art prosthetic replacements. He has changed the focus of his graduate studies from electrical engineering to biomedical engineering. The native Hungarian even found interesting 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 in the Department of Biomedical Engineering at Johns Hopkins, the team developed a form of "electronic skin" that records touch in the same way as the body human.
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 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 born again.
"Normally, my" hand "looks a bit like an empty shell," he said in a telephone interview from his hometown of Budapest. "When these electronic stimulations began to occur, it was like filling a glove with water, almost as if it was filling with life."
The experiment showed the first time that an amputee could feel a whole range of benign physical pressures a prosthetic appliance – and the first time anyone felt pain.
Luke Osborn began researching e-dermis with Nitish Thakor in 2015. – Johns Hopkins University / TNS
"For the first time, a prosthesis can provide a range of perceptions, from the fine touch to the harmful touch, to an amputee, and it looks much more like a human hand," said Thakor, the co-founder of 39; Infinite Biomedical Technologies, a small Baltimore-based company that provided prosthetic equipment for the study.
An article on the study appeared in the journal Science Robotics recently
Advances are the latest in a field of research that has developed rapidly over the last decade and a half, largely thanks to the work of Johns Hopkins.
However, there are about four years, the che The researchers at Case Western Reserve University in Cleveland and elsewhere have begun to take steps to implant dentures to the 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.
The Hopkins team undertook to expand the menu of sensations provided, up to and including pain, a category of feelings that, though still unpleasant, fulfilled a crucial survival function.
"Pain is a sensation we use to protect our body," 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, Computer Engineering and Neurology, turned to biology for its model.
The sensory receptor cells of human skin, they observed, are located at various levels, those responsible for the pain sensations (nociceptors) mainly near the surface of the skin and those responsible for the pressure (mechanoreceptors) deeper .
To replicate this system, they designed e-dermis to have sensors arranged in two layers, instead of one as the previous engineers.
The challenge was then to "learn" the sensors in each layer to generate the appropriate sensations for that layer.
Again, they turned to biology.
The team studied the frequencies, amplitudes, and wavelengths of signals that the body normally sends when it generates pressure and pain sensations. Then they calibrated the sensory device to mimic these variables.
Osborn developed this "neuromorphic" approach – that is, the creation of a technology that mimics biological patterns.
"We knew what an electrical pulse was like for pain, as well as impulses that convey information about pressure, texture, and so on," he said. "We created similar impulses and compared them to what the subjects actually perceive."
The next challenge was to ensure that the system was spatially accurate – that is, if the contact occurred on the prosthetic index, the brain perceives it as coming from this place.
They achieved this through "sensory mapping" – by probing each square centimeter of the subject's residual limb and noting where the subject "felt" each of these keys on his "ghost" hand.
The process 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.
"Those nerves that once 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 nervous patterns so accurately, 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 it on the surface of the skin, a process that is much easier on the subject.
Levay says that he enjoyed this on several levels.
He studied 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 close, he has made the volunteer an ideal subject of study, which has been funded by grants from the 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 study, but because it was still available for several months, Levay emerged as the central and anonymous topic of the article , entitled "Prosthesis with multi-layer neuromorphic e- the dermis perceives touch and pain".
The experiences were painful at first, said Levay laughing, while Osborn was looking for the right fit between the shocks he was delivering 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 experiment had reached its goal .
It was, he says, a pain that he was too happy to feel.
"E-dermis does not work yet perfectly," said Levay, "but it's certainly a step closer to bringing back the sensations to the hand." – The Baltimore Sun / Tribune News Service
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