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Luke Skywalkers Robotic Hand No Longer Fiction Thanks To New Brain To Prosthesis Connections

A US research team attaching thought-controlled arms that allow amputees to touch and feel again sees its goal of off-the-shelf Luke Skywalker arms as within its grasp.

Associate Professor Gregory Clark, 67, from the Department of Biomedical Engineering in the University of Utah’s College of Engineering spoke to Real Press in an exclusive interview about how the collaborative effort to mimic human arms with synthetic replacements is reaching new heights.

He, and a team of specialists have been creating cutting-edge methods to attach robotic arms to amputees at the University of Utah’s Center for Neural Interfaces.

Picture is Keven Walgamott plucking grapes with the LUKE arm in a lab test. (University of Utah Center for Neural Interfaces/Real Press)

“We are basically trying to do the Luke Skywalker thing so people have a pre-prepared notion of what we are trying to accomplish,” says Professor Clark. “We want to take this advanced, dexterous, sensitised arm and attach it to the users own neuromuscular system, and that way the person can move the arm just by thinking about it, and importantly, they can also get the sense of touch and movement back from the arm – and with those feelings ideally maybe begin to feel whole again.”

The University of Utah team inspired the Skywalker association two years ago with their first success in connecting an advanced prosthetic device named the LUKE arm to study participants via embedded electrodes, but since then their work has tuned initial concepts into a more everyday reality.

Prior to this advance, prosthetics with motor functions used simpler external stimuli to operate, but the team’s use of a surgically-embedded device called the Utah Slanted Electrode Array made thought control possible via an on-board computer.

Picture is a live subject using the arm outside in normal activities for the first time. (University of Utah Center for Neural Interfaces/Real Press)

Professor Clark says there are many advantages of using surgically embedded electrodes over contemporary prosthetic systems that use exterior sensors triggered by muscle movement: “One of the advantages of kicking it up that notch is stability, and another is high resolution.”

The “high resolution” is achieved through exponentially more electrodes capable of creating fine signals for individual muscles. This gives users a much more agile range of movements than the comparably blunt reactions of external muscle-triggered signals.

Professor Clark explains: “Our nerve electrodes go in and are capable of having very intimate conversations with a very small set of motor fibres that control just one part of one muscle, or to talk back to just one pixel of this one type of information on this one spot on a finger.

Picture is student Jacob George and Associate Professor Gregory Clark working with the LUKE arm. (University of Utah Center for Neural Interfaces/Real Press)

“The nerves in our arms are like biological wires that communicate bidirectionally between our body and our brain. And so, what we basically did was wiretap into those biological wires to record and interpret the signals so that the person can more effortlessly, intuitively and dextrously.”

He describes the myriad of sensory processes involved in merely selecting ripe fruit: “Imagine going to the grocers and picking up a plum. It is hard to tell whether it is ripe or not, so I’ve got to do the squeeze thing.

“You pick it up and then you have got to keep your pressure steady, and then you put it down, but you can’t release until after you put it down.

Picture is Keven Walgamott touching his wife for the first time with his touch-sensitive arm. (University of Utah Center for Neural Interfaces/Real Press)

“When you pick it up there is a little vibration and when you put it down there is a little vibration, and those transitions are very important.

“We use our hands to not only manipulate the environment but also to explore it.”

Though the team have yet to perfectly mimic the biological signals, the digital pulse codes they use are now very similar to natural ones allowing the brain to understand it almost perfectly.

Picture is Keven Walgamott plucking grapes with the LUKE arm in a lab test. (University of Utah Center for Neural Interfaces/Real Press)

He describes the signals the team are now able to send as “almost biofidelic”.

But this is no small feat. Though we may talk of humans possessing only five senses, the reality is that what we group into the one label of ‘sense of touch’ is in fact a collective web of many sub-components that maintain our perception of an array of individual factors such as temperature, pressure, acceleration, velocity and more.

“Part of the magic of the brain,” says Professor Clark. “Is that it takes all these individual components and puts them together into one percept.

Picture is Associate Professor Gregory Clark and student, Jacob George, in a scene from a university promotion video about their work with the LUKE arm. (University of Utah/Real Press)

“Out here in your hand there is little pixels of information and your brain will look at all those pixels and merge them together into this unified percept.”

But before that can happen the team have to fine tune the connections they create.

All people have very similar nerve fibres but they are so intricate and fine that it is a complex process to connect electrodes to the correct fibre, and so a complex “psychophysics” process is used to patch newly connected electrodes with the correct perceptions from the recipient’s brain.

Picture is Associate Professor Gregory Clark and student, Jacob George, in a scene from a university promotion video about their work with the LUKE arm. (University of Utah/Real Press)

The brain adjusts and learns to manipulate the new arm effectively over a short amount of time, but Professor Clark explains that that is not the end result the team is looking for: “Our goal is to make it so that the hand moves exactly the way your biological hand moved. If we could do the perfect decode of the signals coming down and translate that perfectly into moving the hand the person wouldn’t have to learn anything new. We are not there but that is what we are shooting for.”

But for now, the connection between the LUKE arm and the recipient is becoming incredibly close to biologically perfect, and recipients are engaging in dexterous movement within a remarkably short training time – for both the recipient and for the onboard computer that translates signals between the arm and the person.

And every case presents a different set of conditions. Amputations occur at different places on the arm leaving differing amounts of muscle bulk retained, not to mention compensating for the subjective translations of pulse codes that vary between recipients.

Picture is a video clip of sensory feedback tests with a live subject operating the LUKE arm in typical daily use scenarios. (Vince Horiuchi/University of Utah College of Engineering/Real Press)

The LUKE arm is made by DEKA Research & Development, a company created by Segway inventor Dean Kamen, and it currently holds only 19 sensors.

But the embedded array the team is implanting has 300 electrodes – although not all of these connect successfully in the attachment procedure.

Having this many possible connections goes a long way toward mimicking a living human hand that possesses thousands of sensors, and when technological advances enable the LUKE arm to include more, the intricacy of signals being passed back to a person will increase many times.

Picture is a video clip of sensory feedback tests with a live subject operating the LUKE arm in typical daily use scenarios. (Vince Horiuchi/University of Utah College of Engineering/Real Press)

Since the first results of the study were published, the team has been able to hone their work through a new study participant who was undergoing elective amputation of a damaged hand.

This ability to be there at the beginning of the process where neural memory is still strong has made for many advances in the science, and the participant was able to keep the implants for almost one and a half years, furnishing the team with many more real-world insights into the process.

Recent regulatory advances in approval from the US Food and Drug Administration (FDA) now allows people to keep the implants longer and take the prosthetic home to use unsupervised.

Picture is a video clip of a live subject using the LUKE arm outside in normal activities. (University of Utah College of Engineering/Real Press)

This has allowed test subjects to incorporate the prosthesis into their own body image and become far more comfortable with the device as a permanent part of themselves.

A new round of test subjects will now be able to extend the amount of knowledge the team gains on long-term use.

And so, the dream of synthetic arms as perfect biological replacements draws closer.

Picture is a video clip from a promotion for the university’s work on the LUKE arm. (Vince Horiuchi/University of Utah College of Engineering/Real Press)

“We hope to restore not only these somewhat potentially prosaic senses of touch or the ability to move, but even the sense of self,” says Professor Clark. “One of our participants once remarked that losing your hand is like losing a family member that you loved except you are reminded of it every day, and so if we could bring their hand back to life it will have that kind of impact as if a key part of them was gone but has now returned.”

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