Mind-controlled prosthetic arms that work in daily life are now a reality

For the first time, robotic prostheses controlled via implanted neuromuscular interfaces have become a clinical reality. A novel osseointegrated (bone-anchored) implant system gives patients new opportunities in their daily life and professional activities.

In January 2013 a Swedish arm amputee was the first person in the world to receive a prosthesis with a direct connection to bone, nerves and muscles. An article about this achievement and its long-term stability will now be published in the Science Translational Medicine journal.

"Going beyond the lab to allow the patient to face real-world challenges is the main contribution of this work," says Max Ortiz Catalan, research scientist at Chalmers University of Technology and leading author of the publication.

"We have used osseointegration to create a long-term stable fusion between man and machine, where we have integrated them at different levels. The artificial arm is directly attached to the skeleton, thus providing mechanical stability. Then the human's biological control system, that is nerves and muscles, is also interfaced to the machine's control system via neuromuscular electrodes. This creates an intimate union between the body and the machine; between biology and mechatronics."

The direct skeletal attachment is created by what is known as osseointegration, a technology in limb prostheses pioneered by associate professor Rickard Brånemark and his colleagues at Sahlgrenska University Hospital. Rickard Brånemark led the surgical implantation and collaborated closely with Max Ortiz Catalan and Professor Bo Håkansson at Chalmers University of Technology on this project.

The patient's arm was amputated over ten years ago. Before the surgery, his prosthesis was controlled via electrodes placed over the skin. Robotic prostheses can be very advanced, but such a control system makes them unreliable and limits their functionality, and patients commonly reject them as a result.

Now, the patient has been given a control system that is directly connected to his own. He has a physically challenging job as a truck driver in northern Sweden, and since the surgery he has experienced that he can cope with all the situations he faces; everything from clamping his trailer load and operating machinery, to unpacking eggs and tying his children's skates, regardless of the environmental conditions (read more about the benefits of the new technology below).

The patient is also one of the first in the world to take part in an effort to achieve long-term sensation via the prosthesis. Because the implant is a bidirectional interface, it can also be used to send signals in the opposite direction -- from the prosthetic arm to the brain. This is the researchers' next step, to clinically implement their findings on sensory feedback.

"Reliable communication between the prosthesis and the body has been the missing link for the clinical implementation of neural control and sensory feedback, and this is now in place," says Max Ortiz Catalan. "So far we have shown that the patient has a long-term stable ability to perceive touch in different locations in the missing hand. Intuitive sensory feedback and control are crucial for interacting with the environment, for example to reliably hold an object despite disturbances or uncertainty. Today, no patient walks around with a prosthesis that provides such information, but we are working towards changing that in the very short term."

The researchers plan to treat more patients with the novel technology later this year.

"We see this technology as an important step towards more natural control of artificial limbs," says Max Ortiz Catalan. "It is the missing link for allowing sophisticated neural interfaces to control sophisticated prostheses. So far, this has only been possible in short experiments within controlled environments."

More about: How the technology works

The new technology is based on the OPRA treatment (osseointegrated prosthesis for the rehabilitation of amputees), where a titanium implant is surgically inserted into the bone and becomes fixated to it by a process known as osseointegration (Osseo = bone). A percutaneous component (abutment) is then attached to the titanium implant to serve as a metallic bone extension, where the prosthesis is then fixated. Electrodes are implanted in nerves and muscles as the interfaces to the biological control system. These electrodes record signals which are transmitted via the osseointegrated implant to the prostheses, where the signals are finally decoded and translated into motions.

More about: Benefits of the new technology, compared to socket prostheses

Direct skeletal attachment by osseointegration means:

• Increased range of motion since there are no physical limitations by the socket -- the patient can move the remaining joints freely
• Elimination of sores and pain caused by the constant pressure from the socket
• Stable and easy attachment/detachment
• Increased sensory feedback due to the direct transmission of forces and vibrations to the bone (osseoperception)
• The prosthesis can be worn all day, every day
• No socket adjustments required (there is no socket)

Implanting electrodes in nerves and muscles means that:

• Due to the intimate connection, the patients can control the prosthesis with less effort and more precisely, and can thus handle smaller and more delicate items.
• The close proximity between source and electrode also prevents activity from other muscles from interfering (cross-talk), so that the patient can move the arm to any position and still maintain control of the prosthesis.
• More motor signals can be obtained from muscles and nerves, so that more movements can be intuitively controlled in the prosthesis.
• After the first fitting of the controller, little or no recalibration is required because there is no need to reposition the electrodes on every occasion the prosthesis is worn (as opposed to superficial electrodes).
• Since the electrodes are implanted rather than placed over the skin, control is not affected by environmental conditions (cold and heat) that change the skin state, or by limb motions that displace the skin over the muscles. The control is also resilient to electromagnetic interference (noise from other electric devices or power lines) as the electrodes are shielded by the body itself.
• Electrodes in the nerves can be used to send signals to the brain as sensations coming from the prostheses.

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Amputees discern familiar sensations across prosthetic hand

Even before he lost his right hand to an industrial accident 4 years ago, Igor Spetic had family open his medicine bottles. Cotton balls give him goose bumps.

Now, blindfolded during an experiment, he feels his arm hairs rise when a researcher brushes the back of his prosthetic hand with a cotton ball.

Spetic, of course, can't feel the ball. But patterns of electric signals are sent by a computer into nerves in his arm and to his brain, which tells him different. "I knew immediately it was cotton," he said.

That's one of several types of sensation Spetic, of Madison, Ohio, can feel with the prosthetic system being developed by Case Western Reserve University and the Louis Stokes Cleveland Veterans Affairs Medical Center.

Spetic was excited just to "feel" again, and quickly received an unexpected benefit. The phantom pain he'd suffered, which he's described as a vice crushing his closed fist, subsided almost completely. A second patient, who had less phantom pain after losing his right hand and much of his forearm in an accident, said his, too, is nearly gone.

Despite having phantom pain, both men said that the first time they were connected to the system and received the electrical stimulation, was the first time they'd felt their hands since their accidents. In the ensuing months, they began feeling sensations that were familiar and were able to control their prosthetic hands with more -- well -- dexterity.

To watch a video of the research, click here: http://youtu.be/l7jht5vvzR4.

"The sense of touch is one of the ways we interact with objects around us," said Dustin Tyler, an associate professor of biomedical engineering at Case Western Reserve and director of the research. "Our goal is not just to restore function, but to build a reconnection to the world. This is long-lasting, chronic restoration of sensation over multiple points across the hand."

"The work reactivates areas of the brain that produce the sense of touch, said Tyler, who is also associate director of the Advanced Platform Technology Center at the Cleveland VA. "When the hand is lost, the inputs that switched on these areas were lost."

How the system works and the results will be published online in the journal Science Translational Medicine Oct. 8.

"The sense of touch actually gets better," said Keith Vonderhuevel, of Sidney, Ohio, who lost his hand in 2005 and had the system implanted in January 2013. "They change things on the computer to change the sensation.

"One time," he said, "it felt like water running across the back of my hand."

The system, which is limited to the lab at this point, uses electrical stimulation to give the sense of feeling. But there are key differences from other reported efforts.

First, the nerves that used to relay the sense of touch to the brain are stimulated by contact points on cuffs that encircle major nerve bundles in the arm, not by electrodes inserted through the protective nerve membranes.

Surgeons Michael W Keith, MD and J. Robert Anderson, MD, from Case Western Reserve School of Medicine and Cleveland VA, implanted three electrode cuffs in Spetic's forearm, enabling him to feel 19 distinct points; and two cuffs in Vonderhuevel's upper arm, enabling him to feel 16 distinct locations.

Second, when they began the study, the sensation Spetic felt when a sensor was touched was a tingle. To provide more natural sensations, the research team has developed algorithms that convert the input from sensors taped to a patient's hand into varying patterns and intensities of electrical signals. The sensors themselves aren't sophisticated enough to discern textures, they detect only pressure.

The different signal patterns, passed through the cuffs, are read as different stimuli by the brain. The scientists continue to fine-tune the patterns, and Spetic and Vonderhuevel appear to be becoming more attuned to them.

Third, the system has worked for 2 ½ years in Spetic and 1½ in Vonderhueval. Other research has reported sensation lasting one month and, in some cases, the ability to feel began to fade over weeks.

A blindfolded Vonderhuevel has held grapes or cherries in his prosthetic hand -- the signals enabling him to gauge how tightly he's squeezing -- and pulled out the stems.

"When the sensation's on, it's not too hard," he said. "When it's off, you make a lot of grape juice."

Different signal patterns interpreted as sandpaper, a smooth surface and a ridged surface enabled a blindfolded Spetic to discern each as they were applied to his hand. And when researchers touched two different locations with two different textures at the same time, he could discern the type and location of each.

Tyler believes that everyone creates a map of sensations from their life history that enables them to correlate an input to a given sensation.

"I don't presume the stimuli we're giving is hitting the spots on the map exactly, but they're familiar enough that the brain identifies what it is," he said.

Because of Vonderheuval's and Spetic's continuing progress, Tyler is hopeful the method can lead to a lifetime of use. He's optimistic his team can develop a system a patient could use at home, within five years.

In addition to hand prosthetics, Tyler believes the technology can be used to help those using prosthetic legs receive input from the ground and adjust to gravel or uneven surfaces. Beyond that, the neural interfacing and new stimulation techniques may be useful in controlling tremors, deep brain stimulation and more.

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Manipulating memory with light: Scientists erase specific memories in mice

Just look into the light: not quite, but researchers at the UC Davis Center for Neuroscience and Department of Psychology have used light to erase specific memories in mice, and proved a basic theory of how different parts of the brain work together to retrieve episodic memories.

Optogenetics, pioneered by Karl Diesseroth at Stanford University, is a new technique for manipulating and studying nerve cells using light. The techniques of optogenetics are rapidly becoming the standard method for investigating brain function.

Kazumasa Tanaka, Brian Wiltgen and colleagues at UC Davis applied the technique totest a long-standing idea about memory retrieval. For about 40 years, Wiltgen said, neuroscientists have theorized that retrieving episodic memories -- memories about specific places and events -- involves coordinated activity between the cerebral cortex and the hippocampus, a small structure deep in the brain.

"The theory is that learning involves processing in the cortex, and the hippocampus reproduces this pattern of activity during retrieval, allowing you to re-experience the event," Wiltgen said. If the hippocampus is damaged, patients can lose decades of memories.

But this model has been difficult to test directly, until the arrival of optogenetics.

Wiltgen and Tanaka used mice genetically modified so that when nerve cells are activated, they both fluoresce green and express a protein that allows the cells to be switched off by light. They were therefore able both to follow exactly which nerve cells in the cortex and hippocampus were activated in learning and memory retrieval, and switch them off with light directed through a fiber-optic cable.

They trained the mice by placing them in a cage where they got a mild electric shock. Normally, mice placed in a new environment will nose around and explore. But when placed in a cage where they have previously received a shock, they freeze in place in a "fear response."

Tanaka and Wiltgen first showed that they could label the cells involved in learning and demonstrate that they were reactivated during memory recall. Then they were able to switch off the specific nerve cells in the hippocampus, and show that the mice lost their memories of the unpleasant event. They were also able to show that turning off other cells in the hippocampus did not affect retrieval of that memory, and to follow fibers from the hippocampus to specific cells in the cortex.

"The cortex can't do it alone, it needs input from the hippocampus," Wiltgen said. "This has been a fundamental assumption in our field for a long time and Kazu’s data provides the first direct evidence that it is true."

They could also see how the specific cells in the cortex were connected to the amygdala, a structure in the brain that is involved in emotion and in generating the freezing response.

Co-authors are Aleksandr Pevzner, Anahita B. Hamidi, Yuki Nakazawa and Jalina Graham, all at the Center for Neuroscience. The work was funded by grants from the Whitehall Foundation, McKnight Foundation, Nakajima Foundation and the National Science Foundation.

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Temperature and water vapor on an exoplanet mapped

A team of scientists using NASA's Hubble Space Telescope has made the most detailed global map yet of the glow from a planet orbiting another star, revealing secrets of air temperatures and water.

eThe map provides information about temperatures at different layers of the world's atmosphere and traces the amount and distribution of water vapor on the planet. The findings have ramifications for the understanding of atmospheric dynamics and the formation of giant planets like Jupiter.

"These measurements have opened the door for a new kind of comparative planetology," said team leader Jacob Bean of the University of Chicago.

"Our observations are the first of their kind in terms of providing a two-dimensional map of the planet's thermal structure that can be used to constrain atmospheric circulation and dynamical models for hot exoplanets," said team member Kevin Stevenson of the University of Chicago.

The Hubble observations show that the planet, called WASP-43b, is no place to call home. It's a world of extremes, where seething winds howl at the speed of sound from a 3,000-degree-Fahrenheit day side that is hot enough to melt steel to a pitch-black night side that sees temperatures plunge below a relatively cool 1,000 degrees Fahrenheit.

As a hot ball of predominantly hydrogen gas, there are no surface features on the planet, such as oceans or continents that can be used to track its rotation. Only the severe temperature difference between the day and night sides can be used by a remote observer to mark the passage of a day on this world.

WASP-43b is located 260 light-years away and was first discovered in 2011. WASP-43b is too distant to be photographed, but because its orbit is observed edge-on to Earth, astronomers detected it by observing regular dips in the light of its parent star as the planet passes in front of it.

The planet is about the same size as Jupiter, but is nearly twice as massive. The planet is so close to its orange dwarf host star that it completes an orbit in just 19 hours. The planet is also gravitationally locked so that it keeps one hemisphere facing the star, just as our moon keeps one face toward Earth.

The scientists combined two previous methods of analyzing exoplanets and put them together in one for the first time to study the atmosphere of WASP-43b. Spectroscopy allowed them to determine the water abundance and temperature structure of the atmosphere. By observing the planet's rotation, the astronomers were also able to measure the water abundances and temperatures at different longitudes.

Because there's no planet with these tortured conditions in our 

solar

 system, characterizing the atmosphere of such a bizarre world provides a unique laboratory for better understanding planet formation and planetary physics. "The planet is so hot that all the water in its atmosphere is vaporized, rather than condensed into icy clouds like on Jupiter," said team member Laura Kreidberg of the University of Chicago.

"Water is thought to play an important role in the formation of giant planets, since comet-like bodies bombard young planets, delivering most of the water and other molecules that we can observe," said Jonathan Fortney, a member of the team from the University of California, Santa Cruz.

However, the water abundances in the giant planets of our solar system are poorly known because water is locked away as ice that has precipitated out of their upper atmospheres. But on "hot Jupiters" -- that is, large planets like Jupiter that have high surface temperatures because they orbit very close to their stars -- water is in a vapor that can be readily traced. Kreidberg also emphasized that the team didn't simply detect water in the atmosphere of WASP-43b, but also precisely measured how much of it there is and how it is distributed with longitude.

In order to understand how giant planets form, astronomers want to know how enriched they are in different elements. The team found that WASP-43b has about the same amount of water as we would expect for an object with the same chemical composition as the Sun. Kreidberg said that this tells something fundamental about how the planet formed.

For the first time astronomers were able to observe three complete rotations of a planet, which occurred during a span of four days. This was essential to making such a precise measurement according to Jean-Michel Désert of the University of Colorado, Boulder.

The team next aims to make water-abundance measurements for different planets to explore their chemical abundances. Hubble's planned successor, the James Webb Space Telescope, will be able to not only measure water abundances, but also the abundances of carbon monoxide, carbon dioxide, ammonia, and methane, depending on the planet's temperature.

The results are presented in two new papers, one published online in Science Expresson Oct. 9, and the other published in The Astrophysical Journal Letters on Sept. 12.

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Story Source:

The above story is based on materials provided by Space Telescope Science Institute (STScI). Note: Materials may be edited for content and length.

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Journal References:

1. Kevin B. Stevenson, Jean-Michel Désert, Michael R. Line, Jacob L. Bean, Jonathan J. Fortney, Adam P. Showman, Tiffany Kataria, Laura Kreidberg, Peter R. McCullough, Gregory W. Henry, David Charbonneau, Adam Burrows, Sara Seager, Nikku Madhusudhan, Michael H. Williamson, and Derek Homeier. Thermal structure of an exoplanet atmosphere from phase-resolved emission spectroscopy. Science, 9 October 2014 DOI: 10.1126/science.1256758
2. Laura Kreidberg, Jacob L. Bean, Jean-Michel Désert, Michael R. Line, Jonathan J. Fortney, Nikku Madhusudhan, Kevin B. Stevenson, Adam P. Showman, David Charbonneau, Peter R. McCullough, Sara Seager, Adam Burrows, Gregory W. Henry, Michael Williamson, Tiffany Kataria, Derek Homeier. A PRECISE WATER ABUNDANCE MEASUREMENT FOR THE HOT JUPITER WASP-43b. The Astrophysical Journal, 2014; 793 (2): L27 DOI: 10.1088/2041-8205/793/2/L27

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