The magic touch: bringing sensory feedback to brain-controlled prosthetics

Researchers at the University of Chicago are leading a project to introduce the sense of touch to the latest brain-controlled prosthetic arms. Adding sensory feedback to already-complex neuroprosthetics is a towering task, but offers the chance to radically transform the lives of amputees and people living with paralysis.The future of prosthetics

Source of the Article: medicaldevice-network.com

A prosthetic that restores the sense of where your hand is

Source: Ecole Polytechnique Fédérale de Lausanne

Summary: Researchers have developed a next-generation bionic hand that allows amputees to regain their proprioception. The results of the study are the culmination of ten years of robotics research.

The next-generation bionic hand, developed by researchers from EPFL, the Sant’Anna School of Advanced Studies in Pisa and the A. Gemelli University Polyclinic in Rome, enables amputees to regain a very subtle, close-to-natural sense of touch. The scientists managed to reproduce the feeling of proprioception, which is our brain’s capacity to instantly and accurately sense the position of our limbs during and after movement — even in the dark or with our eyes closed.

The new device allows patients to reach out for an object on a table and to ascertain an item’s consistency, shape, position and size without having to look at it. The prosthesis has been successfully tested on several patients and works by stimulating the nerves in the amputee’s stump. The nerves can then provide sensory feedback to the patients in real time — almost like they do in a natural hand.

The findings have been published in the journal Science Robotics. They are the result of ten years of scientific research coordinated by Silvestro Micera, a professor of bioengineering at EPFL and the Sant’Anna School of Advanced Studies, and Paolo Maria Rossini, director of neuroscience at the A. Gemelli University Polyclinic in Rome.

Sensory feedback

Current myoelectric prostheses allow amputees to regain voluntary motor control of their artificial limb by exploiting residual muscle function in the forearm. However, the lack of any sensory feedback means that patients have to rely heavily on visual cues. This can prevent them from feeling that their artificial limb is part of their body and make it more unnatural to use.

Recently, a number of research groups have managed to provide tactile feedback in amputees, leading to improved function and prosthesis embodiment. But this latest study has taken things one step further.

“Our study shows that sensory substitution based on intraneural stimulation can deliver both position feedback and tactile feedback simultaneously and in real time,” explains Micera. “The brain has no problem combining this information, and patients can process both types in real time with excellent results.”

Intraneural stimulation re-establishes the flow of external information using electric pulses sent by electrodes inserted directly into the amputee’s stump. Patients then have to undergo training to gradually learn how to translate those pulses into proprioceptive and tactile sensations.

This technique enabled two amputees to regain high proprioceptive acuity, with results comparable to those obtained in healthy subjects. The simultaneous delivery of position information and tactile feedback allowed the two amputees to determine the size and shape of four objects with a high level of accuracy (75.5%).

“These results show that amputees can effectively process tactile and position information received simultaneously via intraneural stimulation,” says Edoardo D’Anna, EPFL researcher and lead author of the study.

Story Source:

Materials provided by Ecole Polytechnique Fédérale de Lausanne. Note: Content may be edited for style and length.


Journal Reference:

  1. Edoardo D’Anna, Giacomo Valle, Alberto Mazzoni, Ivo Strauss, Francesco Iberite, Jérémy Patton, Francesco M. Petrini, Stanisa Raspopovic, Giuseppe Granata, Riccardo Di Iorio, Marco Controzzi, Christian Cipriani, Thomas Stieglitz, Paolo M. Rossini, Silvestro Micera. A closed-loop hand prosthesis with simultaneous intraneural tactile and position feedback. Science Robotics, 2019; 4 (27): eaau8892 DOI: 10.1126/scirobotics.aau8892
Source of the Article: Ecole Polytechnique Fédérale de Lausanne. “A prosthetic that restores the sense of where your hand is.” ScienceDaily. ScienceDaily, 21 February 2019. <www.sciencedaily.com/releases/2019/02/190221110357.htm>.

Capturing Touch for Prosthetic Limbs Through Artificial Skin

RESEARCH
Luke E. Osborn and Nitish V. Thakor

Those living with upper limb differences face numerous challenges, including lost limb movement and dexterity as well as missing sensory information during object manipulation. From a user’s perspective, upper limb prostheses still have several issues with control, general discomfort from the socket, and lack of sensory feedback 1. Significant efforts have resulted in sophisticated algorithms for decoding intended prosthesis movements along multiple degrees of freedom that have enabled amputees to regain more dexterous prosthesis control 2. Another seminal advancement is targeted muscle reinnervation surgery 3, which targets nerves to different intact muscle groups such as on the chest to provide a source of well differentiated myoelectric signals for prosthesis control.

Lack of sensory information and feedback has limited the perceptual capability of the amputees. Major advancements were made in 2014 when researchers used implanted stimulating electrodes to provide sensory information back to an upper limb amputee for detecting different objects during grasping 4, conveying pressure information to complete dexterous manipulation of a fragile object 5, and general tactile activation 6.

Touch Complexity

Sensory information, specifically touch, is an extremely complex and multifaceted percept that remains difficult to completely capture. Thousands of receptors in our hands work together to pass tactile information from our fingertips to the spinal cord and into the somatosensory regions of the cortex. For upper limb amputees, the peripheral nerves and feedback to the brain still exist, but these pathways are disrupted at the receptor level in the residual limb. Researchers can take advantage of the remaining intact neural pathways to provide some element of tactile information back to an amputee. One challenge is how to convey specific tactile information by stimulating remaining peripheral nerves either through the skin or directly. However, the disrupted distribution of the receptors in the amputee’s skin and their complex tactile encoding, both individually and as a population, make it hard to replicate complex touch sensations.

Tactile information is captured by various receptors in the skin. Mechanoreceptors are responsible for our ability to perceive sensations such as pressure, texture, vibration, and stretch whereas muscle spindles and Golgi tendons drives our innate ability to perceive position (i.e. proprioception). Thermoceptors convey sensations of temperature while nociceptors enable us to feel mechanical pain, such as a sharp prick or a cut 7. Researchers have been able to provide sensory percepts of pressure 4,5,8, vibrations 8, texture 9, illusory movements 10, and now even pain 11 to upper limb amputees. Extensive knowledge gained from studying skin receptor properties has spurred the development of artificial electronic skin (e-skin) and more specifically the electronic dermis (e-dermis).

Artificial Skin

Researchers have previously developed artificial electronic skins that take advantage of the developments in flexible electronics12,13 to produce e-skins. In one such implementation, the digital mechanoreceptor inspired sensor translates pressure into oscillatory spikes 14, and in another implementation the oscillatory output drives nerve stimulation of an artificial afferent in an invertebrate 15. Most advances in sensors and artificial skins are focused on materials and electronics and typically do not incorporate sensory feedback to a prosthesis or amputee. For upper limb prostheses, one challenge is translating the response of an artificial skin into meaningful sensory information to the user by mimicking the natural sensory encoding of touch.

E-dermis for Perception of Touch and Pain

Using biology as a model, we developed a multilayered electronic dermis (e-dermis) for capturing a range of tactile perceptions at the fingertips of a prosthetic hand. We implemented a neuromorphic model to transform the e-dermis measurements to biologically relevant spiking activity for nerve stimulation, which was then used for transcutaneous electrical nerve stimulation (TENS) to provide sensory feedback (Fig. 1A). A neuromorphic system is one that attempts to mimic components of a neural system through digital signals, in this case representing touch. The idea behind this implementation is to try and capture actual receptor characteristics to convey tactile information to an amputee.

The e-dermis mimics the skin and its receptors in several ways: it has an array of sensors (receptors); the sensors are arranged over multiple layers (Fig. 1B); it produces receptor like signals; and it encodes sensor information the manner encoded by nerves. The e-dermis was made up of piezoresistive fabric (Eeonyx), which was placed between intersecting conductive traces (LessEMF) to create pressure sensitive taxels. A 1-mm layer of silicone rubber (Dragon Skin 10, Smooth-On) was added between the epidermal and dermal layers of the e-dermis and a 2-mm rubber layer added protection and compliance to the fingertip e-dermis.

Our goal was to model the skin and its receptors, and to mimic the range of perceptions from light touch to noxious, or painful. To detect pressure and pain, we treated the epidermal (upper) layer of the e-dermis as a nociceptor and the sensing elements in the dermal (bottom) layer as mechanoreceptors. The neuromorphic output from the e-dermis was then used as the stimulation signal for sensory feedback.

To understand the sensory perceptions perceived by an amputee during nerve stimulation. We performed sensory mapping of the phantom hand of one amputee as well as a quantification of the various sensory perceptions, including discomfort resulting from stimulation at a noxious level produced by controlling different stimulation parameters. Additional details can be found in 11.

To evaluate the ability of the amputee wearing the prosthesis to differentiate between tactile pressure and pain, we used 3 objects of varying curvature for a simple prosthesis grasping task (Fig. 2A). The prosthesis was able to reliably detect pain when grasping the sharpest item (Fig, 2B). Indeed, the prosthesis responded with a reflex to drop the object, similar to what happens in biology when we experience pain (i.e. withdrawal reflex). In another experiment where the user’s vision was occluded from the object being grasped, the sharper object was perceived by the user as being more painful (Fig. 2C).

One question that should be addressed: why pain? Our perception of pain is valuable because it protects our bodies by conveying information on things in our environment that are potentially damaging or harmful. A prosthetic arm doesn’t have this ability. Our recent research investigated how the idea of sensing pain could potentially benefit a prosthesis user. Because a prosthesis doesn’t have the ability to heal itself, we created a prosthesis pain reflex to compliment the sensory information being sent back to the user. In a way, this additional sensation of pain enables the prosthesis itself to become a little more lifelike and “self-aware” in its ability to understand the environment. At the same time, the tactile information being sent back to the user hopefully helps create a more realistic and feature-rich sensation of touch.

The combination of the biologically inspired e-dermis with neuromorphic stimulation models attempts to capture some of the nuanced characteristics of natural receptors, specifically those that convey innocuous and noxious signals. As upper limb prostheses continue to advance we turn to the human body as a template for developing sophisticated sensors and techniques for making these prosthetic devices more lifelike. Recreating the complex sensation of touch requires continued research of how nerve stimulation is perceived by a prosthesis user as well as how we can more accurately convey artificial neural signals that can be perceived as natural sensations.

Acknowledgements

This work was partially funded by the Space@Hopkins funding initiative through Johns Hopkins University. The results of this study were published in the June 2018 edition of Science Robotics:

Osborn, L. E., Dragomir, A., Betthauser, J. L., Hunt, C. L., Nguyen, H. H., Kaliki, R. R., & Thakor, N. V. Prosthesis with neuromorphic multilayered e-dermis perceives touch and pain. Science Robotics, 2018;3(19):eaat3818. DOI: 10.1126/scirobotics.aat3818.

References

  1. Biddiss, E., Beaton, D., and Chau, T. Consumer design priorities for upper limb prosthetics. Disability and Rehabilitation: Assistive Technology. 2007;2(6):346-57. DOI: 10.1080/17483100701714733.
  2. Farina, D. et al. Man/machine interface based on the discharge timings of spinal motor neurons after targeted muscle reinnervation. Nature Biomedical Engineering. 2017;1(2):25. DOI: 10.1038/s41551-016-0025.
  3. Kuiken, T. A. et al. Targeted reinnervation for enhanced prosthetic arm function in a woman with a proximal amputation: a case study. Lancet. 2007;369(9559):371-80. DOI: 10.1016/S0140-6736(07)60193-7.
  4. Raspopovic, S. et al. Restoring natural sensory feedback in real-time bidirectional hand prostheses. Science Translational Medicine. 2014;6(222):222ra19. DOI: 10.1126/scitranslmed.3006820.
  5. Tan, D. W. et al. A neural interface provides long-term stable natural touch perception. Science Translational Medicine. 2014;6(257):257ra138. DOI: 10.1126/scitranslmed.3008669.
  6. Ortiz-Catalan, M., Håkansson, B., and Brånemark, R. An osseointegrated human-machine gateway for long-term sensory feedback and motor control of artificial limbs. Science Translational Medicine. 2014;6(257):257re6. DOI: 10.1126/scitranslmed.3008933.
  7. Abraira, V. and Ginty, D. The sensory neurons of touch. Neuron. 2013;79(4):618-39. DOI: 10.1016/j.neuron.2013.07.051.
  8. Wendelken, S. et al. Restoration of motor control and proprioceptive and cutaneous sensation in humans with prior upper-limb amputation via multiple utah slanted electrode arrays (USEAs) implanted in residual peripheral arm nerves. Journal of Neuroengineering and Rehabilitation. 2017;14(1):121. DOI: 10.1186/s12984-017-0320-4.
  9. Oddo, C. M. et al. Intraneural stimulation elicits discrimination of textural features by artificial fingertip in intact and amputee humans. eLife. 2016;5:e09148. DOI: 10.7554/eLife.09148.
  10. Marasco, P. D. et al. Illusory movement perception improves motor control for prosthetic hands. Science Translational Medicine. 2018;10(432):eaao6990. DOI: 10.1126/scitranslmed.aao6990.
  11. Osborn, L. E. et al. Prosthesis with neuromorphic multilayered e-dermis perceives touch and pain. Science Robotics. 2018;3(19):eaat3818. DOI: 10.1126/scirobotics.aat3818.
  12. Kim, J. et al. Stretchable silicon nanoribbon electronics for skin prosthesis. Nature Communications. 2014;5:5747. DOI: 10.1038/ncomms6747.
  13. Yokota, T. et al. Ultraflexible organic photonic skin. Science Advances. 2016;2(4):e1501856. DOI: 10.1126/sciadv.1501856.
  14. Tee, B. C. K. et al. A skin-inspired organic digital mechanoreceptor. Science. 2015;350(6258):313-6. DOI: 10.1126/science.aaa9306.
  15. Kim, Y. et al. A bioinspired flexible organic artificial afferent nerve. Science. 2018;360(6392):998-1003. DOI: 10.1126/science.aao0098.

Biography

Luke Osborn
Luke Osborn, MSE, is a PhD student in biomedical engineering at Johns Hopkins University. His research in the Neuroengineering and Biomedical Instrumentation Lab focuses on developing tactile sensing technologies, neuromorphic modeling of sensory information, and sensory feedback for upper limb prostheses. He is a student member of the IEEE.

Nitish Thakor
Nitish Thakor, PhD, is a professor of biomedical engineering, electrical and computer engineering, and neurology at Johns Hopkins and directs the Laboratory for Neuroengineering. He is also the director the Singapore Institute for Neurotechnology (SINAPSE) at the National University of Singapore. His research focus is in the field of neuroengineering, including neural diagnostic instrumentation, neural microsystems, neural signal processing, optical imaging of the nervous system, neural control of prostheses, and brain-machine interfaces. He is a recipient of a Research Career Development Award from the National Institutes of Health and a Presidential Young Investigator Award from the US National Science Foundation. He is a founding fellow of the Biomedical Engineering Society and fellow of the IEEE.

About BrainInsight

BrainInsight, the IEEE Brain Initiative eNewsletter, is a quarterly online publication, featuring practical and timely information and forward-looking commentary on neurotechnologies. BrainInsight describes recent breakthroughs in research, primers on methods of interests, or report recent events such as conferences or workshops.


IEEE
Source of the article: Brain.ieee.org

DOCTORS WIRED A PROSTHETIC HAND DIRECTLY INTO A WOMAN’S NERVES

JON CHRISTIAN__FILED UNDER: ENHANCED HUMANS
VICTOR TANGERMANN

Sans Hand

In a world first, doctors in Sweden say they’ve wired a prosthetic hand directly into a woman’s nervesallowing her to move its fingers with her mind and even feel tactile sensations.

The hand is an enormous step up from existing prostheses, which often rely on electrodes placed on the outside of the skin — and it could herald a future in which robotic devices interface seamlessly with our bodies.

Nerve Case

Researchers at Chalmers University of Technology and biotech firm Integrum AB created the prosthetic hand as part of DeTOP, an ambitious European research program on prosthetic limbs.

Surgeons anchored the hand to the woman’s forearm bones using titanium implants. They connected an array of 16 electrodes directly to her nerves and muscles, allowing her to control the hand with her mind — and, according to photos, use it to tie shoelaces and type on a laptop computer.

“The breakthrough of our technology consists on enabling patients to use implanted neuromuscular interfaces to control their prosthesis while perceiving sensations where it matters for them, in their daily life,” Chalmers researcher Ortiz Catalan said in a press release.

Virtual Light

Electronics wired straight into a human nervous system allow for mind-bending new ways to interact with technology. A video released by the Swedish researchers even shows the woman using the implant to flex a virtual hand on a computer screen — before the actual physical hand was installed.

For decades, cyborg limbs like those depicted in “Star Wars” or “Neuromancer” seemed relegated to the realm of science fiction. New research shows that they’re already here — just not yet widely available.

Source of the Article: https://futurism.com/the-byte/prosthetic-hand-womans-nerves

Surgical technique improves sensation, control of prosthetic limb

Surgical technique improves sensation, control of prosthetic limb
A schematic demonstrating the control mechanism of the neural interface. The subject’s leg movement is sent to the prosthesis as an EMG signal (blue arrows), and the movement of the prosthesis is communicated back to the subject’s nervous system (green arrow). Credit: T.R. Clites et al., Science Translational Medicine (2018)

Humans can accurately sense the position, speed, and torque of their limbs, even with their eyes shut. This sense, known as proprioception, allows humans to precisely control their body movements.

Despite significant improvements to prosthetic devices in recent years, researchers have been unable to provide this essential sensation to people with artificial limbs, limiting their ability to accurately control their movements.

Researchers at the Center for Extreme Bionics at the MIT Media Lab have invented a new neural interface and communication paradigm that is able to send movement commands from the central nervous system to a robotic prosthesis, and relay proprioceptive feedback describing movement of the joint back to the central nervous system in return.

This new paradigm, known as the agonist-antagonist myoneural interface (AMI), involves a novel surgical approach to  amputation in which dynamic muscle relationships are preserved within the amputated limb. The AMI was validated in extensive preclinical experimentation at MIT prior to its first surgical implementation in a human patient at Brigham and Women’s Faulkner Hospital.

In a paper published today in Science Translational Medicine, the researchers describe the first human implementation of the agonist-antagonist myoneural interface (AMI), in a person with below-knee amputation.

The paper represents the first time information on joint position, speed, and torque has been fed from a prosthetic limb into the nervous system, according to senior author and project director Hugh Herr, a professor of media arts and sciences at the MIT Media Lab.

“Our goal is to close the loop between the peripheral nervous system’s muscles and nerves, and the bionic appendage,” says Herr.

To do this, the researchers used the same biological sensors that create the body’s natural proprioceptive sensations.

The AMI consists of two opposing muscle-tendons, known as an agonist and an antagonist, which are surgically connected in series so that when one muscle contracts and shortens—upon either volitional or electrical activation—the other stretches, and vice versa.

This coupled movement enables natural biological sensors within the muscle-tendon to transmit electrical signals to the central nervous system, communicating muscle length, speed, and force information, which is interpreted by the brain as natural joint proprioception.

“Because the muscles have a natural nerve supply, when this agonist-antagonist muscle movement occurs information is sent through the nerve to the brain, enabling the person to feel those muscles moving, both their position, speed, and load,” he says.

By connecting the AMI with electrodes, the researchers can detect electrical pulses from the muscle, or apply electricity to the muscle to cause it to contract.

“When a person is thinking about moving their phantom ankle, the AMI that maps to that bionic ankle is moving back and forth, sending signals through the nerves to the brain, enabling the person with an amputation to actually feel their bionic ankle moving throughout the whole angular range,” Herr says.

Decoding the electrical language of proprioception within nerves is extremely difficult, according to Tyler Clites, first author of the paper and graduate student lead on the project.

“Using this approach, rather than needing to speak that electrical language ourselves, we use these  to speak the language for us,” Clites says. “These sensors translate mechanical stretch into electrical signals that can be interpreted by the brain as sensations of position, speed, and force.”The AMI was first implemented surgically in a human patient at Brigham and Women’s Faulkner Hospital, Boston, by Matthew Carty, one of the paper’s authors, a surgeon in the Division of Plastic and Reconstructive Surgery, and an MIT research scientist.

In this operation, two AMIs were constructed in the residual limb at the time of primary below-knee amputation, with one AMI to control the prosthetic ankle joint, and the other to control the prosthetic subtalar joint.

“We knew that in order for us to validate the success of this new approach to amputation, we would need to couple the procedure with a novel prosthesis that could take advantage of the additional capabilities of this new type of residual limb,” Carty says. “Collaboration was critical, as the design of the procedure informed the design of the robotic limb, and vice versa.”

Toward this end, an advanced prosthetic limb was built at MIT and electrically linked to the patient’s peripheral nervous system using electrodes placed over each AMI muscle following the amputation surgery.

Surgical technique improves sensation, control of prosthetic limb
Credit: Massachusetts Institute of Technology

The researchers then compared the movement of the AMI patient with that of four people who had undergone a traditional below-knee amputation procedure, using the same advanced prosthetic limb.

They found that the AMI patient had more stable control over movement of the prosthetic device and was able to move more efficiently than those with the conventional amputation. They also found that the AMI patient quickly displayed natural, reflexive behaviors such as extending the toes toward the next step when walking down a set of stairs.

These behaviors are essential to natural human movement and were absent in all of the people who had undergone a traditional amputation.

What’s more, while the patients with conventional  reported feeling disconnected to the prosthesis, the AMI patient quickly described feeling that the bionic ankle and foot had become a part of their own body.

“This is pretty significant evidence that the brain and the spinal cord in this patient adopted the prosthetic leg as if it were their biological limb, enabling those biological pathways to become active once again,” Clites says. “We believe proprioception is fundamental to that adoption.”

Surgical technique improves sensation, control of prosthetic limb
Credit: Massachusetts Institute of Technology

The researchers have since carried out the AMI procedure on nine other below-knee amputees and are planning to adapt the technique for those needing above-knee, below-elbow, and above-elbow amputations.

“Previously humans have used technology in a tool-like fashion,” Herr says. “We are now starting to see a new era of human-device interaction, of full neurological embodiment, in which what we design becomes truly part of us, part of our identity.”

Source of the Article: https://medicalxpress.com/news/2018-05-surgical-technique-sensation-prosthetic-limb.html

Source of the Article: https://medicalxpress.com/news/2018-05-surgical-technique-sensation-prosthetic-limb.html

Researchers demonstrate key to success of nerve transfer technique in bionic reconstruction

Modern prostheses offer patients who have had a hand amputated much greater capability in everyday life than was possible with previous prosthetic reconstructive techniques. Redundant nerves from the amputated extremity can be surgically transferred to provide a much better connection between the patient’s body and the prosthesis. This technique has proven to be successful, although the specific reasons for its success were not fully understood. A team of researchers led by Konstantin Bergmeister and Oskar Aszmann from the Division of Plastic and Reconstructive Surgery and the Christian Doppler Laboratory for Recovery of Limb Function at MedUni Vienna, demonstrated, in an animal model, that the key to success lies in the muscle undergoing a change of identity triggered by the donor nerve.

Bionic prostheses are mentally controlled, in that they register the activation of residual muscles in the limb stump. Theoretically it should be possible for the latest generation prostheses to execute the same number of movements as a healthy human hand. However, the link between man and prosthesis is not yet capable of controlling all mechanically possible functions, because the interface between man and prostheses is limited in terms of signal transmission. “If we could solve this problem, the latest prostheses could actually become an intuitively operated replacement that functions just like a human hand,” underscore the researchers.

To enable the prosthesis to move at all, nerves have to be surgically transferred during the amputation procedure to increase the total number of muscle control signals. This involves connecting amputated peripheral nerves to residual muscles in the amputation stump. This method is very successful, because these muscles regenerate after a few months to provide better control of the prosthesis. However, until now, it was not clear what specific changes this nerve transfer technique produces in muscles and nerves.

Previously unknown neurophysiological effects discovered

As part of an experimental study conducted over several years, a research team led by Konstantin Bergmeister and Oskar Aszmann from MedUni Vienna’s Division of Plastic and Reconstructive Surgery (Head: Christine Radtke) and Christian Doppler Laboratory for Recovery of Limb Function have now shown that this nerve transfer technique has previously unidentified neurophysiological effects. These result in more accurate muscle contractility and much more finely controlled muscle signals than previously thought.

It was also found that muscles take on the identity of the donor nerves, that is to say the function of the muscle from which the nerve was originally harvested. This means that muscles can be modified very specifically to achieve the desired control of the lost extremity. This information will now be used in follow-up studies to refine the surgical technique of nerve transfer and adapt it more accurately to fine control systems. The vision of an intuitively controlled prosthesis that can perform all the natural manual functions could become a reality within the next few years.

Source:

https://www.meduniwien.ac.at/web/en/about-us/news/detailsite/2019/news-im-jaenner-2019/bionic-reconstruction-after-amputation-of-a-hand-muscles-can-be-repurposed-using-nerve-transfers/

Source of Article: https://www.news-medical.net/news/20190107/Researchers-demonstrate-key-to-success-of-nerve-transfer-technique-in-bionic-reconstruction.aspx

BIOMEDICAL ENGINEERING BRINGING A HUMAN TOUCH TO MODERN PROSTHETICS

‘Electronic skin’ allows user to experience a sense of touch and pain; ‘After many years, I felt my hand, as if a hollow shell got filled with life again,’ amputee volunteer says

Amputees often experience the sensation of a “phantom limb”—a feeling that a missing body part is still there.

That sensory illusion is closer to becoming a reality thanks to a team of engineers at Johns Hopkins University that has created an electronic skin. When layered on top of prosthetic hands, this e-dermis brings back a real sense of touch through the fingertips.

“After many years, I felt my hand, as if a hollow shell got filled with life again,” says the amputee who served as the team’s principal volunteer. (The research protocol used in the study does not allow identification of the amputee volunteers.)

Made of fabric and rubber laced with sensors to mimic nerve endings, e-dermis recreates a sense of touch as well as pain by sensing stimuli and relaying the impulses back to the peripheral nerves.

“We’ve made a sensor that goes over the fingertips of a prosthetic hand and acts like your own skin would,” says Luke Osborn, a graduate student in biomedical engineering. “It’s inspired by what is happening in human biology, with receptors for both touch and pain.

Luke Osborn interacts with prosthetic hand

Image caption:Luke Osborn interacts with a prosthetic hand sporting the e-dermis

IMAGE CREDIT: LARRY CANNER / HOMEWOOD PHOTOGRAPHY

“This is interesting and new,” Osborn adds, “because now we can have a prosthetic hand that is already on the market and fit it with an e-dermis that can tell the wearer whether he or she is picking up something that is round or whether it has sharp points.”

The work, published online in the journal Science Robotics, shows it’s possible to restore a range of natural, touch-based feelings to amputees who use prosthetic limbs. The ability to detect pain could be useful, for instance, not only in prosthetic hands but also in lower limb prostheses, alerting the user to potential damage to the device.

Human skin is made up of a complex network of receptors that relay a variety of sensations to the brain. This network provided a biological template for the research team, which includes members from the Johns Hopkins departments of Biomedical EngineeringElectrical and Computer Engineering, and Neurology, and from the Singapore Institute of Neurotechnology.

VIDEO: AMERICAN ACADEMY FOR THE ADVANCEMENT OF SCIENCE

Bringing a more human touch to modern prosthetic designs is critical, especially when it comes to incorporating the ability to feel pain, Osborn says.

“Pain is, of course, unpleasant, but it’s also an essential, protective sense of touch that is lacking in the prostheses that are currently available to amputees,” he says. “Advances in prosthesis designs and control mechanisms can aid an amputee’s ability to regain lost function, but they often lack meaningful, tactile feedback or perception.”

That’s where the e-dermis comes in, conveying information to the amputee by stimulating peripheral nerves in the arm, making the so-called phantom limb come to life. Inspired by human biology, the e-dermis enables its user to sense a continuous spectrum of tactile perceptions, from light touch to noxious or painful stimulus.

The e-dermis does this by electrically stimulating the amputee’s nerves in a non-invasive way, through the skin, says the paper’s senior author, Nitish Thakor, a professor of biomedical engineering and director of the Biomedical Instrumentation and Neuroengineering Laboratory at Johns Hopkins.

“For the first time, a prosthesis can provide a range of perceptions from fine touch to noxious to an amputee, making it more like a human hand,” says Thakor, co-founder of Infinite Biomedical Technologies, the Baltimore-based company that provided the prosthetic hardware used in the study.

THE TEAM FOCUSED ON DEVELOPING A SYSTEM CAPABLE OF DETECTING OBJECT CURVATURE (FOR TOUCH AND SHAPE PERCEPTION) AND SHARPNESS (FOR PAIN PERCEPTION).

The team created a “neuromorphic model” mimicking the touch and pain receptors of the human nervous system, allowing the e-dermis to electronically encode sensations just as the receptors in the skin would. Tracking brain activity via electroencephalography, or EEG, the team determined that the test subject was able to perceive these sensations in his phantom hand.

The researchers then connected the e-dermis output to the volunteer by using a noninvasive method known as transcutaneous electrical nerve stimulation, or TENS. In a pain-detection task the team determined that the test subject and the prosthesis were able to experience a natural, reflexive reaction to both pain while touching a pointed object and non-pain when touching a round object.

The e-dermis is not sensitive to temperature—for this study, the team focused on detecting object curvature (for touch and shape perception) and sharpness (for pain perception). The e-dermis technology could be used to make robotic systems more human, and it could also be used to expand or extend to astronaut gloves and space suits, Osborn says.

The researchers plan to further develop the technology and work to better understand how to provide meaningful sensory information to amputees in the hopes of making the system ready for widespread patient use.

Johns Hopkins is a pioneer in the field of upper limb dexterous prosthesis. More than a decade ago, the university’s Applied Physics Laboratory led the development of the advanced Modular Prosthetic Limb, which an amputee patient controls with the muscles and nerves that once controlled his or her real arm or hand.

Posted in Science+Technology

Source of article: https://hub.jhu.edu/2018/06/20/e-dermis-prosthetic-sense-of-touch/

Vibrations Restore Sense of Movement in Prosthetics

Scientists recreate proprioception for people with artificial arms using a perceptual illusion.

Sep 1, 2018
By DIANA KWON

 

 

When Amanda Kitts’s car was hit head-on by a Ford F-350 truck in 2006, her arm was damaged beyond repair. “It looked like minced meat,” Kitts, now 50, recalls. She was immediately rushed to the hospital, where doctors amputated what remained of her mangled limb.

While still in the hospital, Kitts discovered that researchers at the Rehabilitation Institute of Chicago (now the Shirley Ryan AbilityLab) were investigating a new technique called targeted muscle reinnervation, which would enable people to control motorized prosthetics with their minds. The procedure, which involves surgically rewiring residual nerves from an amputated limb into a nearby muscle, allows movement-related electrical signals—sent from the brain to the innervated muscles—to move a prosthetic device.

Kitts immediately enrolled in the study and had the reinnervation surgery around a year after her accident. With her new prosthetic, Kitts regained a functional limb that she could use with her thoughts alone. But something important was missing. “I was able to move a prosthetic just by thinking about it, but I still couldn’t tell if I was holding or letting go of something,” Kitts says. “Sometimes my muscle might contract, and whatever I was holding would drop—so I found myself [often] looking at my arm when I was using it.”

What Kitts’s prosthetic limb failed to provide was a sense of kinesthesia—the awareness of where one’s body parts are and how they are moving. (Kinesthesia is a form of proprioception with a more specific focus on motion than on position.) Taken for granted by most people, kinesthesia is what allows us to unconsciously grab a coffee mug off a desk or to rapidly catch a falling object before it hits the ground. “It’s how we make such nice, elegant, coordinated movements, but you don’t necessarily think about it when it happens,” explains Paul Marasco, a neuroscientist at the Cleveland Clinic in Ohio. “There’s constant and rapid communication that goes on between the muscles and the brain.” The brain sends the intent to move the muscle, the muscle moves, and the awareness of that movement is fed back to the brain (see “Proprioception: The Sense Within,” The Scientist, September 2016).

GOOD VIBRATIONS: The prosthetic makes use of a kinesthetic phenomenon whereby vibrating a person’s muscle provides a false sense of movement.
PAUL MARASCO, LABORATORY FOR BIONIC INTEGRATION

Prosthetic technology has advanced significantly in recent years, but proprioception is one thing that many of these modern devices still cannot reproduce, Marasco says. And it’s clear that this is something that people find important, he adds, because many individuals with upper-limb amputations still prefer old-school body-powered hook prosthetics. Despite being low tech—the devices work using a bicycle brake–like cable system that’s powered by the body’s own movements—they provide an inherent sense of proprioception.

To restore this sense for amputees who use the more modern prosthetics, Marasco and his colleagues decided to create a device based on what’s known as the kinesthetic illusion: the strange phenomenon in which vibrating a person’s muscle gives her the false sense of movement. A buzz to the triceps will make you think your arm is flexing, while stimulating the biceps will make you feel that it’s extending (Exp Brain Res, 47:177–90, 1982). The best illustration of this effect is the so-called Pinocchio illusion: holding your nose while someone applies a vibrating device to your bicep will confuse your brain into thinking your nose is growing (Brain, 111:281–97, 1988). “Your brain doesn’t like conflict,” Marasco explains. So if it thinks “my arm’s moving and I’m holding onto my nose, that must mean my nose is extending.”

To test the device, the team applied vibrations to the reinnervated muscles on six amputee participants’ chests or upper arms and asked them to indicate how they felt their hands were moving. Each amputee reported feeling various hand, wrist, and elbow motions, or “percepts,” in their missing limbs. Kitts, who had met Marasco while taking part in the studies he was involved in at the institute in Chicago, was one of the subjects in the experiment. “The first time I felt the sense of movement was remarkable,” she says.

In total, the experimenters documented 22 different percepts from their participants. “It’s hard to get this sense reliably, so I was encouraged to see the capability of several different subjects to get a reasonable sense of hand position from this illusion,” says Dustin Tyler, a biomedical engineer at Case Western Reserve University who was not involved in the work. He adds that while this is a new, noninvasive approach to proprioception, he and others are also working on devices that restore this sense by stimulating nerves directly with implanted devices (Sci Rep, 8:9866, 2018).

Marasco and his colleagues then melded the vibration with the movement-controlled prostheses, so that when participants decided to move their artificial limbs, a vibrating stimulus was applied to the muscles to provide them with proprioceptive feedback. When the subjects conducted various movement-related tasks with this new system, their performance significantly improved (Sci Transl Med, 10:eaao6990, 2018).

The first time I felt the sense of movement was remarkable.

“This was an extremely thorough set of experiments,” says Marcia O’Malley, a biomedical engineer at Rice University who did not take part in that study. “I think it is really promising.”

Although the mechanisms behind the illusion largely remain a mystery, Marasco says, the vibrations may be activating specific muscle receptors that provide the body with a sense of movement. Interestingly, he and his colleagues have found that the “sweet spot” vibration frequency for movement perception is nearly identical in humans and rats—about 90 Hz (PLOS ONE, 12:e0188559, 2017).

For Kitts, a system that provides proprioceptive feedback means being able to use her prosthetic without constantly watching it—and feeling it instead. “It’s whole new level of having a real part of your body,” she says.

Source of the article: www.the-scientist.com

New artificial nerves could transform prosthetics

Source of the Article: www.sciencemag.org

 

Prosthetics may soon take on a whole new feel. That’s because researchers have created a new type of artificial nerve that can sense touch, process information, and communicate with other nerves much like those in our own bodies do. Future versions could add sensors to track changes in texture, position, and different types of pressure, leading to potentially dramatic improvements in how people with artificial limbs—and someday robots—sense and interact with their environments.

“It’s a pretty nice advance,” says Robert Shepherd, an organic electronics expert at Cornell University. Not only are the soft, flexible, organic materials used to make the artificial nerve ideal for integrating with pliable human tissue, but they are also relatively cheap to manufacture in large arrays, Shepherd says.

Modern prosthetics are already impressive: Some allow amputees to control arm movement with just their thoughts; others have pressure sensors in the fingertips that help wearers control their grip without the need to constantly monitor progress with their eyes. But our natural sense of touch is far more complex, integrating thousands of sensors that track different types of pressure, such as soft and forceful touch, along with the ability to sense heat and changes in position. This vast amount of information is ferried by a network that passes signals through local clusters of nerves to the spinal cord and ultimately the brain. Only when the signals combine to become strong enough do they make it up the next link in the chain.

Now, researchers led by chemist Zhenan Bao at Stanford University in Palo Alto, California, have constructed an artificial sensory nerve that works in much the same way. Made of flexible organic components, the nerve consists of three parts. First, a series of dozens of sensors pick up on pressure cues. Pressing on one of these sensors causes an increase in voltage between two electrodes. This change is then picked up by a second device called a ring oscillator, which converts voltage changes into a string of electrical pulses. These pulses, and those from other pressure sensor/ring oscillator combos, are fed into a third device called a synaptic transistor, which sends out a series of electrical pulses in patterns that match those produced by biological neurons.

Bao and her colleagues used their setup to detect the motion of a small rod moving in different directions across their pressure sensors, as well as identify Braille characters. What’s more, they managed to connect their artificial neuron to a biological counterpart. The researchers detached a leg from a cockroach and inserted an electrode from the artificial neuron to a neuron in the roach leg; signals coming from the artificial neuron caused muscles in the leg to contract, they report today in Science.

Because organic electronics like this are inexpensive to make, the approach should allow scientists to integrate large numbers of artificial nerves that could pick up on multiple types of sensory information, Shepherd says. Such a system could provide far more sensory information to future prosthetics wearers, helping them better control their new appendages. It could also give future robots a greater ability to interact with their ever-changing environments—something vital for performing complex tasks, such as caring for the elderly.