Posts tagged prosthetic limbs
Articles and news from the latest research reports.
Modelling how neurons work together
A newly-developed, highly accurate representation of the way in which neurons behave when performing movements such as reaching could not only enhance understanding of the complex dynamics at work in the brain, but aid in the development of robotic limbs which are capable of more complex and natural movements.
Researchers from the University of Cambridge, working in collaboration with the University of Oxford and the Ecole Polytechnique Fédérale de Lausanne (EPFL), have developed a new model of a neural network, offering a novel theory of how neurons work together when performing complex movements. The results are published in the 18 June edition of the journal Neuron.
While an action such as reaching for a cup of coffee may seem straightforward, the millions of neurons in the brain’s motor cortex must work together to prepare and execute the movement before the coffee ever reaches our lips. When we reach for the much-needed cup of coffee, the neurons spring into action, sending a series of signals from the brain to the hand. These signals are transmitted across synapses – the junctions between neurons.
Determining exactly how the neurons work together to execute these movements is difficult, however. The new theory was inspired by recent experiments carried out at Stanford University, which had uncovered some key aspects of the signals that neurons emit before, during and after the movement. “There is a remarkable synergy in the activity recorded simultaneously in hundreds of neurons,” said Dr Guillaume Hennequin of the University’s Department of Engineering, who led the research. “In contrast, previous models of cortical circuit dynamics predict a lot of redundancy, and therefore poorly explain what happens in the motor cortex during movements.”
Better models of how neurons behave will not only aid in our understanding of the brain, but could also be used to design prosthetic limbs controlled via electrodes implanted in the brain. “Our theory could provide a more accurate guess of how neurons would want to signal both movement intention and execution to the robotic limb,” said Dr Hennequin.
The behaviour of neurons in the motor cortex can be likened to a mousetrap or a spring-loaded box, in which the springs are waiting to be released and are let go once the lid is opened or the mouse takes the bait. As we plan a movement, the ‘neural springs’ are progressively flexed and compressed. When released, they orchestrate a series of neural activity bursts, all of which takes place in the blink of an eye.
The signals transmitted by the synapses in the motor cortex during complex movements can be either excitatory or inhibitory, which are in essence mirror reflections of each other. The signals cancel each other out for the most part, leaving occasional bursts of activity.
Using control theory, a branch of mathematics well-suited to the study of complex interacting systems such as the brain, the researchers devised a model of neural behaviour which achieves a balance between the excitatory and inhibitory synaptic signals. The model can accurately reproduce a range of multidimensional movement patterns.
The researchers found that neurons in the motor cortex might not be wired together with nearly as much randomness as had been previously thought. “Our model shows that the inhibitory synapses might be tuned to stabilise the dynamics of these brain networks,” said Dr Hennequin. “We think that accurate models like these can really aid in the understanding of the incredibly complex dynamics at work in the human brain.”
Future directions for the research include building a more realistic, ‘closed-loop’ model of movement generation in which feedback from the limbs is actively used by the brain to correct for small errors in movement execution. This will expose the new theory to the more thorough scrutiny of physiological and behavioural validation, potentially leading to a more complete mechanistic understanding of complex movements.
The U.S. Food and Drug Administration (FDA) today allowed marketing of the DEKA Arm System, the first prosthetic arm that can perform multiple, simultaneous powered movements controlled by electrical signals from electromyogram (EMG) electrodes.
EMG electrodes detect electrical activity caused by the contraction of muscles close to where the prosthesis is attached. The electrodes send the electrical signals to a computer processor in the prosthesis that translates them to a specific movement or movements.
The EMG electrodes in the DEKA Arm System convert electrical signals into up to 10 powered movements, and it is the same shape and weight as an adult arm. In addition to the EMG electrodes, the DEKA Arm System contains a combination of mechanisms including switches, movement sensors, and force sensors that cause the prosthesis to move.
“This innovative prosthesis provides a new option for people with certain kinds of arm amputations,” said Christy Foreman, director of the Office of Device Evaluation at the FDA’s Center for Devices and Radiological Health. “The DEKA Arm System may allow some people to perform more complex tasks than they can with current prostheses in a way that more closely resembles the natural motion of the arm.”
The FDA reviewed clinical information relating to the device, including a 4-site Department of Veterans Affairs study in which 36 DEKA Arm System study participants provided data on how the arm performed in common household and self-care tasks. The study found that approximately 90 percent of study participants were able to perform activities with the DEKA Arm System that they were not able to perform with their current prosthesis, such as using keys and locks, preparing food, feeding oneself, using zippers, and brushing and combing hair.
The DEKA Arm System can be configured for people with limb loss occurring at the shoulder joint, mid-upper arm, or mid-lower arm. It cannot be configured for limb loss at the elbow or wrist joint.
Data reviewed by the FDA also included testing of software and electrical and battery systems, mitigations to prevent or stop unintended movements of the arm and hand mechanisms, durability testing (such as ability to withstand exposure to common environmental factors such as dust and light rain), and impact testing.
The FDA reviewed the DEKA Arm System through its de novo classification process, a regulatory pathway for some novel low- to moderate-risk medical devices that are first-of-a-kind.
The DEKA Arm System is manufactured by DEKA Integrated Solutions in Manchester, N.H.
Students ‘print’ pink prosthetic arm for teen girl
Thirteen-year-old Sydney Kendall had one request for the Washington University in St. Louis students building her a robotic prosthetic arm: Make it pink.
Kendall Gretsch, Henry Lather and Kranti Peddada, seniors studying biomedical engineering in the School of Engineering & Applied Science, accomplished that and more. Using a 3-D printer, they created a robotic prosthetic arm out of bright-pink plastic. Total cost: $200, a fraction of the price of standard prosthetics, which start at $6,000.
“Currently, prosthetics are very expensive, and because kids keep growing, it is too costly for them to have the latest technology,” said Sydney’s mother, Beth Kendall. “With the 3-D printer, a prosthetic can be made much less expensive. The possibilities of what can be done to improve prosthetics using this technology is very exciting.”
Sydney lost her right arm in a boating accident when she was six years old. She learned to write with her left hand, but found most tasks difficult to accomplish with her prosthetic arm. Sydney said her new arm is easy to manipulate. By moving her shoulder, she can direct the arm to throw a ball, move a computer mouse and perform other tasks.
Peddada said it was thrilling to observe Sydney use her arm.
“It really showed us the great things you can accomplish when you bridge medicine and technology,” Peddada said.
The students developed the robotic hand as part of their engineering design course with Joseph Klaesner, PhD, associate professor of physical therapy at the School of Medicine. Several local medical practitioners, including orthopedic hand surgeons Charles A. Goldfarb, MD, and Lindley Wall, MD, both associate professors of orthopaedic surgery at the School of Medicine, served as mentors.
“They brought their engineering expertise, and we shared our practical experience with prosthetics and the needs of children,” Goldfarb wrote in a recent blog post about the project. “It was a valuable experience as Kendall, Henry and Kranti had no prosthetic experience and were able to think about the issues in a very different way.”
As Goldfarb explained, the WUSTL student design offers two key design differences that set it apart from similar “Robohand” devices that have been invented recently — the motor and the working thumb.
This prosthetic is battery-powered and controlled with an accelerometer (like in the iPhone). The thumb moves with a slightly different trigger (compared with finger motion).
Prosthetic limbs are tricky for patients of any age, and especially for children, noted Goldfarb, because they’re still growing and need to move to larger-sized devices on a regular basis. Since prosthetics have no sensation, some kids are more comfortable making do with their existing natural limbs, he added.
While 3-D printers can cost about $2,500, they are capable of producing artificial limbs at a relatively low individual cost.
“These prosthetic hands are really exciting because they are inexpensive, can be remade when the child grows, and they do offer functional abilities,” he said.
Human brains ‘hard-wired’ to link what we see with what we do
Your brain’s ability to instantly link what you see with what you do is down to a dedicated information ‘highway’, suggests new UCL-led research.
For the first time, researchers from UCL and Cambridge University have found evidence of a specialised mechanism for spatial self-awareness that combines visual cues with body motion.
Standard visual processing is prone to distractions, as it requires us to pay attention to objects of interest and filter out others. The new study has shown that our brains have separate ‘hard-wired’ systems to visually track our own bodies, even if we are not paying attention to them. In fact, the newly-discovered network triggers reactions even before the conscious brain has time to process them.
The researchers discovered the new mechanism by testing 52 healthy adults in a series of three experiments. In all experiments, participants used robotic arms to control cursors on two-dimensional displays, where cursor motion was directly linked to hand movement. Their eyes were kept fixed on a mark at the centre of the screen, confirmed with eye tracking.
In the first experiment, participants controlled two separate cursors with their left and right hands, both equally close to the centre. The goal was to guide each cursor to a corresponding target at the top of the screen. Occasionally the cursor or target on one side would jump left or right, requiring participants to take corrective action. Each jump was ‘cued’ with a flash on one side, but this was random so did not always correspond to the side about to change.
Unsurprisingly, people reacted faster to target jumps when their attention was drawn to the ‘correct’ side by the cue. However, reactions to cursor jumps were fast regardless of cuing, suggesting that a separate mechanism independent of attention is responsible for tracking our own movements.
“The first experiment showed us that we react very quickly to changes relating to objects directly under our own control, even when we are not paying attention to them,” explains Dr Alexandra Reichenbach of the UCL Institute of Cognitive Neuroscience, lead author of the study. “This provides strong evidence for a dedicated neural pathway linking motor control to visual information, independently of the standard visual systems that are dependent on attention.”
The second experiment was similar to the first, but also introduced changes in brightness to demonstrate the attention effect on the visual perception system. In the third experiment, participants had to guide one cursor to its target in the presence of up to four dummy targets and cursors, ‘distractors’, alongside the real ones. In this experiment, responses to cursor jumps were less affected by distractors than responses to target jumps. Reactions to cursor jumps remained vigorous with one or two distractors, but were significantly decreased when there were four.
“These results provide further evidence of a dedicated ‘visuomotor binding’ mechanism that is less prone to distractions than standard visual processing,’ says Dr Reichenbach. “It looks like the specialised system has a higher tolerance for distractions, but in the end it is still affected. Exactly why we evolved a separate mechanism remains to be seen, but the need to react rapidly to different visual cues about ourselves and the environment may have been enough to necessitate a specialised pathway.”
The newly-discovered system could explain why some schizophrenia patients feel like their actions are controlled by someone else.
“Schizophrenia often manifests as delusion of control, and a dysfunction in the visuomotor mechanism identified in this study might be a cause for this symptom,” explains Dr Reichenbach. “If someone does not automatically link corresponding visual cues with body motion, then they might have the feeling that they are not controlling their movements. We would need further research to confirm this, and it would be fascinating to see how schizophrenia patients perform in these experiments.”
These findings could also explain why people with even the most advanced prosthetic limbs can have trouble coordinating movements.
“People often describe their prosthetic limbs as feeling ‘other’, not a true extension of their body,’ says Dr Reichenbach. “Even on the best prosthetic hands, if the observed movement of the fingers is not exactly what you would expect, then it will not feel like you are in direct control. These small details might have a big effect on how people perceive prostheses.”
(Source: ucl.ac.uk)
Bionic leg is controlled by brain power
A team of specialists has designed a bionic prosthetic leg that can reproduce a full range of ambulatory movements by communicating with the brain of the person wearing it.
The act of walking may not seem like a feat of agility, balance, strength and brainpower. But lose a leg, as Zac Vawter did after a motorcycle accident in 2009, and you will appreciate the myriad calculations that go into putting one foot in front of the other.
Taking on the challenge, a team of software and biomedical engineers, neuroscientists, surgeons and prosthetists has designed a prosthetic limb that can reproduce a full repertoire of ambulatory tricks by communicating seamlessly with Vawter’s brain.
A report published Wednesday in the New England Journal of Medicine describes how the team fit Vawter with a prosthetic leg that has learned — with the help of a computer and some electrodes — to read his intentions from a bundle of nerves that end above his missing knee.
For the roughly 1 million Americans who have lost a leg or part of one due to injury or disease, Vawter and his robotic leg offer the hope that future prosthetics might return the feel of a natural gait, kicking a soccer ball or climbing into a car without hoisting an inert artificial limb into the vehicle.
Vawter’s prosthetic is a marvel of 21st century engineering. But it is Vawter’s ability to control the prosthetic with his thoughts that makes the latest case remarkable. If he wants his artificial toes to curl toward him, or his artificial ankle to shift so he can walk down a ramp, all he has to do is imagine such movements.
The work was done at the Rehabilitation Institute of Chicago under an $8-million grant from the Army. The armed forces hope to apply findings from such studies to the care of about 1,200 service personnel who have lost a lower limb in Iraq and Afghanistan.
"We want to restore full capabilities" to people who’ve lost a lower limb, said Levi J. Hargrove, lead author of the new report. "While we’re focused and committed to developing this system for our wounded warriors, we’re very much thinking of this other, much larger population that could benefit as well."
The report describes advances across a wide range of disciplines: in orthopedic and peripheral nerve surgery, neuroscience, and the application of pattern-recognition software to the field of prosthetics.
Weighing just over 10 pounds, the leg has two independent engines powering movement in the ankle and knee. And it bristles with sensors, including an accelerometer and gyroscope, each capable of detecting and measuring movement in three dimensions.
Most prosthetics in use today require the physical turn of a key to transition from one movement to another. But with the robotic leg, those transitions are effortless, Vawter said.
"With this leg, it just flows," said the 32-year-old software engineer, who spends most of his days using a typical prosthetic but travels to Chicago several times a year from his home in Yelm, Wash. "The control system is very intuitive. There isn’t anything special I have to do to make it work right."
Before Vawter could strap on the bionic lower limb, engineers in Chicago had to “teach” the prosthetic how to read his motor intentions from tiny muscle contractions in his right thigh.
At the institute’s Center for Bionic Medicine, Vawter spent countless hours with his thigh wired up with electrodes, imagining making certain movements on command with his missing knee, ankle and foot.
Using pattern-recognition software, engineers discerned, distilled and digitized those recorded electrical signals to catalog an entire repertoire of movements. The prosthetic could thus be programmed to recognize the subtlest contraction of a muscle in Vawter’s thigh as a specific motor command.
Given surgical practices still in wide use, the prospects for such a connection between a patient’s prosthetic and his or her peripheral nerves are generally dim. In most amputations, the nerves in the thigh are left to languish or die.
Dr. Todd Kuiken, a neurosurgeon at the rehabilitation institute, pioneered a practice called “reinervation” of nerves severed by amputation, and Vawter’s orthopedic surgeon at the University of Washington Medical Center was trained to conduct the delicate operation. Dr. Douglas Smith rewired the severed nerves to control some of the muscles in Vawter’s thigh that would be used less frequently in the absence of his lower leg.
Within a few months of the amputation, those nerves had recovered from the shock of the injury and begun to regenerate and carry electrical impulses. When Vawter thought about flexing his right foot in a particular way, the rerouted nerve endings would consistently cause a distinctive contraction in his hamstring. When he pondered how he would position his foot on a stair step and ready it for the weight of his body, the muscle contraction would be elsewhere — but equally consistent.
Compared with prosthetics that were not able to “read” the intent of their wearers, the robotic leg programmed to follow Vawter’s commands reduced the kinds of errors that cause unnatural movements, discomfort and falls by as much as 44%, according to the New England Journal of Medicine report.
Vawter said he had “fallen down a whole bunch of times” while wearing his everyday prosthetic, but not once while moving around on his bionic leg.
He said he could move a lot faster too — which would be helpful for keeping up with his 5-year-old son and 3-year-old daughter. But first, Vawter added, he needs to persuade Hargrove’s team to let him wear it home.
Movement without muscles study in insects could inspire robot and prosthetic limb developments
Neurobiologists from the University of Leicester have shown that insect limbs can move without muscles – a finding that may provide engineers with new ways to improve the control of robotic and prosthetic limbs.
Their work helps to explain how insects control their movements using a close interplay of neuronal control and ‘clever biomechanical tricks,’ says lead researcher Dr Tom Matheson, a Reader in Neurobiology at the University of Leicester.
In a study published today in the journal Current Biology, the researchers show that the structure of some insect leg joints causes the legs to move even in the absence of muscles. So-called ‘passive joint forces’ serve to return the limb back towards a preferred resting position.
The passive movements differ in limbs that have different behavioural roles and different musculature, suggesting that the joint structures are specifically adapted to complement muscle forces. The researchers propose a motor control scheme for insect limb joints in which not all movements are driven by muscles.
The study was funded by the Biotechnology and Biological Sciences Research Council (BBSRC), The Royal Society, and the Heinrich Hertz-Foundation of the German State of North Rhine-Westphalia.
Dr Matheson, of the Department of Biology, said:
“It is well known that some animals store energy in elastic muscle tendons and other structures. Such energy storage permits forces to be applied explosively to generate movements that are much more rapid than those which may be generated by muscle contractions alone. This is, for example, crucial when grasshoppers or fleas jump.
“This University of Leicester study provides a new insight into the ways that energy storage mechanisms can operate in a much wider range of movements.
“Our work set out to identify how the biomechanical properties of the limbs of a range of insects influence relatively slow movements such as those that occur during walking, scratching or climbing. The surprising result was that although some movements are influenced by properties of the muscles and tendons, other movements are generated by forces that arise from within the joints themselves.
“Even when we removed all of the muscles and associated tissues from a particular joint at the ‘knee’ of a locust, the lower part of the limb (the tibia) still moved back towards a midpoint from extended angles.”
Dr Matheson said that it was known from previous studies that some movements can be generated by spring-like properties of limbs, but the team was surprised to find passive forces that contribute to almost all movements made by the limbs that were studied - not just the highly specialised rapid movements needed to propel powerful jumps and kicks.
“We expected the forces to be generated within the muscles of the leg, but found that some continued to occur even when we detached both muscles – the extensor and the flexor tibiae – from the tibia.
“In the locust hind leg, which is specialised for jumping and kicking, the extensor muscle is much larger and stronger than the antagonist flexor muscle. This enables the animal to generate powerful kicks and jumps propelled by extensions of the tibia that are driven by contractions of the extensor muscle. When locusts prepare to jump, large amounts of energy generated by the extensor muscle are stored in the muscle’s tendon and in the hard exoskeleton of the leg.
“Surprisingly, we noticed that when the muscles were removed, the tibia naturally flexed back towards a midpoint, and we hypothesised that these passive return movements might be counterbalancing the strong extensor muscle.”
Jan M. Ache, a Masters student from the Department of Animal Physiology at the University of Cologne who worked in Matheson’s lab and is the first author on the paper, continues: “To test this idea we looked at the literature and examined other legs where the extensor and flexor muscles are more closely balanced in size or strength, or where the flexor is stronger than the extensor.
“We found that the passive joint forces really do counterbalance the stronger of the flexor or extensor muscle in the animals and legs we looked at. In the horsehead grasshopper, for example, passive joint forces even differ between the middle legs (which are primarily used for walking) and the hind legs (which are adapted for jumping), even in the same individual animal. In both pairs of legs, the passive joint forces support the weaker muscle.
“This could be very important for the generation of movements in insects because the passive forces enable a transfer of energy from the stronger to the weaker muscle.”
This work helps to explain how insects control their movements using a close interplay of neuronal control and clever biomechanical tricks. Using balanced passive forces may provide engineers with new ways to improve the control of robotic and prosthetic limbs, say the researchers.
Dr Matheson concluded: “We hope that our work on locusts and grasshoppers will spur a new understanding of how limbs work and can be controlled, by not just insects, but by other animals, people, and even by robots.”
Sense of Touch Reproduced Through Prosthetic Hand
In a study recently published in IEEE Transactions on Neural Systems and Rehabilitation Engineering, neurobiologists at the University of Chicago show how an organism can sense a tactile stimulus, in real time, through an artificial sensor in a prosthetic hand.
Scientists have made tremendous advances toward building lifelike prosthetic limbs that move and function like the real thing. These are amazing accomplishments, but an important element to creating a realistic replacement for a hand is the sense of touch. Without somatosensory feedback from the fingertips about how hard you’re squeezing something or where it’s positioned relative to the hand, grasping an object is about as accurate as using one of those skill cranes to grab a stuffed animal at an arcade. Sure, you can do it, but you have to concentrate intently while watching every movement. You’re relying on your sense of vision to compensate for the lack of touch.
Sliman Bensmaia, assistant professor of organismal biology and anatomy at the University of Chicago, studies the neural basis of the sense of touch. Now, he and his colleagues are working with a robotic hand equipped with sensors that send electrical signals to electrodes implanted in the brain to recreate the same response to touch as a real hand.
Bensmaia spoke about how important the sense of touch is to creating a lifelike experience with a prosthetic limb.
“If you lose your somatosensory system it almost looks like your motor system is impaired,” he said. “If you really want to create an arm that can actually be used dexterously without the enormous amount of concentration it takes without sensory feedback, you need to restore the somatosensory feedback.”
The researchers performed a series of experiments with rhesus macaques that were trained to respond to stimulation of the hand. In one setting, they were gently poked on the hand with a physical probe at varying levels of pressure. In a second setting, some of the animals had electrodes implanted into the area of the brain that responds to touch. These animals were given electrical pulses to simulate the sensation of touch, and their hands were hidden so they wouldn’t see that they weren’t actually being touched.
Using data from the animals’ responses to each type of stimulus, the researchers were able to create a function, or equation, that described the requisite electrical pulse to go with each physical poke of the hand. Then, they repeated the experiments with a prosthetic hand that was wired to the brain implants. They touched the prosthetic hand with the physical probe, which in turn sent electrical signals to the brain.
Bensmaia said that the animals performed identically whether poked on their own hand or on the prosthetic one.
“This is the first time as far as I know where an animal or organism actually perceives a tactile stimulus through an artificial transducer,” Bensmaia said. “It’s an engineering milestone. But from a neuroengineering standpoint, this validates this function. You can use this function to have an animal perform this very precise task, precisely identically.”
The FDA is in the process of approving similar devices for human trials, and Bensmaia said he hopes such a system is implemented within the next year. Producing a lifelike sense of touch would go a long way toward improving the dexterity and performance of prosthetic hands, but he said it would also help bridge a mental divide for amputees or people who have lost the use of a limb. Until now, prosthetics and robotic arms feel more like tools than real replacements because they don’t produce the expected sensations.
“If every time you see your robotic arm touching something, you get a sensation that is projected to it, I think it’s very possible that in fact, you will consider this new thing as being part of your body,” he said.
(Source: newswise.com)
Paralyzed Patient Moves Prosthetic Arm With Her Mind
It sounds like science fiction, but researchers are gaining ground in developing mind-controlled robotic arms that could give people with paralysis or amputated limbs more independence.
The technology, known as brain-computer (or brain-machine) interface, is in its infancy as far as human use — though scientists have been studying the concept for years. But experts say that people with paralysis or amputations could be using the technology at home within the next decade.
It basically boils down to people using their thoughts to control a robot arm that then performs a desired task, like grasping and moving a cup. That’s done via tiny electrode “grids” implanted in the brain that read the movement signals firing from individual nerve cells, then translate them to the robot arm.
"We have the ability to capture information from the brain and use it to control the robotic arm," said Dr. Elizabeth Tyler-Kabara, who presented her team’s latest findings on the technology Tuesday, at the annual meeting of the American Association of Neurological Surgeons, in New Orleans.
However, she stressed, “we still have a ton to learn.”
Right now, the robot arm is confined to the lab. After getting their electrodes implanted, study patients come to the lab to work with the robotic limb under the researchers’ supervision. So far, Tyler-Kabara and her colleagues at the University of Pittsburgh School of Medicine have tested the approach in one patient. Researchers at Brown University in Providence, R.I., have done it in a handful of others.
One of the big questions, Tyler-Kabara said, is “how much control is enough?” That is, how well does the mind-controlled arm need to work to bring real everyday benefits to people?
At the meeting on Tuesday, Tyler-Kabara presented an update on how her team’s patient is faring. The 53-year-old woman had long-standing quadriplegia due to a disease called spinocerebellar degeneration — where, for unknown reasons, the connections between the brain and muscles slowly deteriorate.
Tyler-Kabara performed the surgery, where two tiny electrode grids were placed in the area of the brain that would normally control the movement of the right hand and arm. The electrode points penetrate the brain’s surface by about one-sixteenth of an inch.
"The idea is pretty scary," Tyler-Kabara acknowledged. But her team’s patient had no complications from the surgery and left the hospital the next day. There’ve been no longer-term problems either, she said — though, in theory, there would be concerns about infection or bleeding over the long haul.
The surgery left the patient with two terminals that protrude through her skull. The researchers used those to connect the implanted electrodes to a computer, where they could see brain cells firing when the patient thought about moving her hand.
She was quickly able to master simple movements with the robotic arm, like high-fiving the researchers. And after six months, she was performing “10-degrees-of-freedom” movements, Tyler-Kabara reported at the meeting.
That includes not only moving the arm, but also flexing and rotating the wrist, grasping objects and affecting several different hand “postures.” She has accomplished feats like feeding herself chocolate.
The researchers initially used a computer in training sessions with the patient, but after that the robot arm is directly linked to the electrodes — so there is no need for “computer assistance,” according to Tyler-Kabara.
Still, before the technology can ultimately be used at home, she said, researchers have to devise a “fully implanted” wireless system for controlling the robot arm.
Another expert talked about the new technology.
"This is one more encouraging step toward developing something practical that people can use in their daily lives," said Dr. Robert Grossman, a neurosurgeon at Methodist Neurological Institute in Houston, who was not involved in the research.
It’s hard to put a time line on it all, Grossman said, since technological advances could changes things. He also noted that several research groups are looking at different approaches to brain-computer interfaces.
One, Grossman said, is to do it noninvasively, through electrodes placed on the scalp.
Study author Tyler-Kabara said that noninvasive approach has met with success in helping people perform simple tasks, like moving a cursor on a computer screen. “But I don’t think it will ever be good enough for performing complicated tasks,” she said, noting that it can’t work as precisely as the implanted electrodes.
A next step, Tyler-Kabara said, is to develop a “two-way” electrode system that stimulates the brain to generate sensation — with the aim of helping people adjust the robot’s grip strength.
She said there is also much to learn about which people will ultimately be good candidates for the technology. There may, for example, be some brain injuries that prevent people from benefiting.
Because this study was presented at a medical meeting, the data and conclusions should be viewed as preliminary until published in a peer-reviewed journal.
(Source: health.usnews.com)
![Rats’ brains are more like ours than scientists previously thought
Neuroscientists face a multitude of challenges in their efforts to better understand the human brain. If not for model organisms such as the rat, they might never know what really goes on inside our heads.
The brain is a phenomenal processor that in a year’s time can generate roughly 300,000 petabytes of data — 30,000 times the amount generated by the Large Hadron Collider. Trying to decipher its signals is a daunting prospect.
But particularly for individuals who have lost a limb or been partially or fully paralyzed, such research has potentially life-changing results because it can enable such biotechnological advances as the development of a brain-computer interface for controlling prosthetic limbs.
Such devices require a detailed understanding of the motor cortex, a part of the brain that is crucial in issuing the neural commands that execute behavioral movements. A recent paper published in the journal Frontiers in Neural Circuits by Jared Smith and Kevin Alloway, researchers at the Penn State Center for Neural Engineering and affiliates of the Huck Institutes of the Life Sciences, details their discovery of a parallel between the motor cortices of rats and humans that signifies a greater relevance of the rat model to studies of the human brain than scientists had previously known.
"The motor cortex in primates is subdivided into multiple regions, each of which receives unique inputs that allow it to perform a specific motor function," said Alloway, professor of neural and behavioral sciences. "In the rat brain, the motor cortex is small and it appeared that all of it received the same type of input. We know now that sensory inputs to the rat motor cortex terminate in a small region of the motor cortex that is distinct from the larger region that issues the motor commands. Our work demonstrates that the rat motor cortex is parcellated into distinct subregions that perform specific functions, and this result appears to be similar to what is seen in the primate brain."
"You have to take into account the animal’s natural behaviors to best understand how its brain is structured for sensory and motor processing," said Jared Smith, graduate student in the Huck Institutes’ neuroscience program and the first author of the paper. "For primates like us, that means a strong reliance on visual information from the eyes, but for rats it’s more about the somatosensory inputs from their whiskers."
In fact, nearly a third of the rat’s sensorimotor cortex is devoted to processing whisker-related information, even though the whiskers’ occupy only one-third of one percent of the rat’s total body surface. In humans, nearly 40 percent of the entire cortex is devoted to processing visual information even though the eyes occupy a very tiny portion of our body’s surface.
To understand the structure and function of the rat motor cortex, Smith and Alloway conducted a series of experiments focused on the medial agranular region, which responds to whisker stimulation and elicits whisker movements when stimulated.
"Our research," said Smith, "was conducted in two stages to investigate the functional organization of the brain: first tracing the neuronal connectivity, and then measuring how the circuits behave in terms of their electrophysiology. Just like in any electrical circuit, the first thing you need to do is trace the wires to see how the different components are connected. Then you can use this information to make sense of the activity going on at any particular node. In the end, you can step back and see how all the circuits work together to achieve something more complex, such as motor control."
"We discovered different sensory input regions that were distinct from the region that issued the motor commands to move the whiskers," said Alloway. "In this respect, we were fortunate to have Patrick Drew [assistant professor of engineering science and mechanics and neurosurgery at Penn State] help us analyze the EMG signals produced by microstimulation because this showed that the sensory input region was significantly less effective in evoking whisker movements."
As a result of Smith and Alloway’s discovery, previously published data on the rat motor cortex can be revisited with a new degree of specificity, and more similarities between the brains and neural processes of rats and humans may eventually come to light, perhaps even informing studies of other model organisms. This discovery is also likely to advance the study of the human brain.
"This study opens up avenues for studying some very complex neural processes in rodents that are more like our own than we had previously thought," said Smith. "The tools now available for studying activity in the rodent brain are improving at a remarkable pace, and the findings are even more interesting as we discover just how similar these mammalian relatives are to us. This is a very exciting time in neuroscience."](http://40.media.tumblr.com/83be1aaf105cf910df73670e1609c4ca/tumblr_mkdegdpsys1rog5d1o1_500.jpg)
Rats’ brains are more like ours than scientists previously thought
Neuroscientists face a multitude of challenges in their efforts to better understand the human brain. If not for model organisms such as the rat, they might never know what really goes on inside our heads.
The brain is a phenomenal processor that in a year’s time can generate roughly 300,000 petabytes of data — 30,000 times the amount generated by the Large Hadron Collider. Trying to decipher its signals is a daunting prospect.
But particularly for individuals who have lost a limb or been partially or fully paralyzed, such research has potentially life-changing results because it can enable such biotechnological advances as the development of a brain-computer interface for controlling prosthetic limbs.
Such devices require a detailed understanding of the motor cortex, a part of the brain that is crucial in issuing the neural commands that execute behavioral movements. A recent paper published in the journal Frontiers in Neural Circuits by Jared Smith and Kevin Alloway, researchers at the Penn State Center for Neural Engineering and affiliates of the Huck Institutes of the Life Sciences, details their discovery of a parallel between the motor cortices of rats and humans that signifies a greater relevance of the rat model to studies of the human brain than scientists had previously known.
"The motor cortex in primates is subdivided into multiple regions, each of which receives unique inputs that allow it to perform a specific motor function," said Alloway, professor of neural and behavioral sciences. "In the rat brain, the motor cortex is small and it appeared that all of it received the same type of input. We know now that sensory inputs to the rat motor cortex terminate in a small region of the motor cortex that is distinct from the larger region that issues the motor commands. Our work demonstrates that the rat motor cortex is parcellated into distinct subregions that perform specific functions, and this result appears to be similar to what is seen in the primate brain."
"You have to take into account the animal’s natural behaviors to best understand how its brain is structured for sensory and motor processing," said Jared Smith, graduate student in the Huck Institutes’ neuroscience program and the first author of the paper. "For primates like us, that means a strong reliance on visual information from the eyes, but for rats it’s more about the somatosensory inputs from their whiskers."
In fact, nearly a third of the rat’s sensorimotor cortex is devoted to processing whisker-related information, even though the whiskers’ occupy only one-third of one percent of the rat’s total body surface. In humans, nearly 40 percent of the entire cortex is devoted to processing visual information even though the eyes occupy a very tiny portion of our body’s surface.
To understand the structure and function of the rat motor cortex, Smith and Alloway conducted a series of experiments focused on the medial agranular region, which responds to whisker stimulation and elicits whisker movements when stimulated.
"Our research," said Smith, "was conducted in two stages to investigate the functional organization of the brain: first tracing the neuronal connectivity, and then measuring how the circuits behave in terms of their electrophysiology. Just like in any electrical circuit, the first thing you need to do is trace the wires to see how the different components are connected. Then you can use this information to make sense of the activity going on at any particular node. In the end, you can step back and see how all the circuits work together to achieve something more complex, such as motor control."
"We discovered different sensory input regions that were distinct from the region that issued the motor commands to move the whiskers," said Alloway. "In this respect, we were fortunate to have Patrick Drew [assistant professor of engineering science and mechanics and neurosurgery at Penn State] help us analyze the EMG signals produced by microstimulation because this showed that the sensory input region was significantly less effective in evoking whisker movements."
As a result of Smith and Alloway’s discovery, previously published data on the rat motor cortex can be revisited with a new degree of specificity, and more similarities between the brains and neural processes of rats and humans may eventually come to light, perhaps even informing studies of other model organisms. This discovery is also likely to advance the study of the human brain.
"This study opens up avenues for studying some very complex neural processes in rodents that are more like our own than we had previously thought," said Smith. "The tools now available for studying activity in the rodent brain are improving at a remarkable pace, and the findings are even more interesting as we discover just how similar these mammalian relatives are to us. This is a very exciting time in neuroscience."
World premiere of muscle and nerve controlled arm prosthesis
For the first time an operation has been conducted, at Sahlgrenska University Hospital, where electrodes have been permanently implanted in nerves and muscles of an amputee to directly control an arm prosthesis. The result allows natural control of an advanced robotic prosthesis, similarly to the motions of a natural limb.
A surgical team led by Dr Rickard Brånemark, Sahlgrenska University Hospital, has carried out the first operation of its kind, where neuromuscular electrodes have been permanently implanted in an amputee. The operation was possible thanks to new advanced technology developed by Max Ortiz Catalan, supervised by Rickard Brånemark at Sahlgrenska University Hospital and Bo Håkansson at Chalmers University of Technology.
“The new technology is a major breakthrough that has many advantages over current technology, which provides very limited functionality to patients with missing limbs,” says Rickard Brånemark.
Big challenges
There have been two major issues on the advancement of robotic prostheses: 1) how to firmly attach an artificial limb to the human body; 2) how to intuitively and efficiently control the prosthesis in order to be truly useful and regain lost functionality.
“This technology solves both these problems by combining a bone anchored prosthesis with implanted electrodes,” said Rickard Brånemark, who along with his team has developed a pioneering implant system called Opra, Osseointegrated Prostheses for the Rehabilitation of Amputees.
A titanium screw, so-called osseointegrated implant, is used to anchor the prosthesis directly to the stump, which provides many advantages over a traditionally used socket prosthesis.
“It allows complete degree of motion for the patient, fewer skin related problems and a more natural feeling that the prosthesis is part of the body. Overall, it brings better quality of life to people who are amputees,” says Rickard Brånemark.
How it works
Presently, robotic prostheses rely on electrodes over the skin to pick up the muscles electrical activity to drive few actions by the prosthesis. The problem with this approach is that normally only two functions are regained out of the tens of different movements an able-body is capable of. By using implanted electrodes, more signals can be retrieved, and therefore control of more movements is possible. Furthermore, it is also possible to provide the patient with natural perception, or “feeling”, through neural stimulation.
“We believe that implanted electrodes, together with a long-term stable human-machine interface provided by the osseointegrated implant, is a breakthrough that will pave the way for a new era in limb replacement,” says Rickard Brånemark.
The patient
The first patient has recently been treated with this technology, and the first tests gave excellent results. The patient, a previous user of a robotic hand, reported major difficulties in operating that device in cold and hot environments and interference from shoulder muscles. These issues have now disappeared, thanks to the new system, and the patient has now reported that almost no effort is required to generate control signals. Moreover, tests have shown that more movements may be performed in a coordinated way, and that several movements can be performed simultaneously.
“The next step will be to test electrical stimulation of nerves to see if the patient can sense environmental stimuli, that is, get an artificial sensation. The ultimate goal is to make a more natural way to replace a lost limb, to improve the quality of life for people with amputations,” says Rickard Brånemark.