Chapter 8. General Principles of Sensory Processing, Touch, and Pain
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By MICHAEL BEHAR One morning in May 1998, Kevin Tracey converted a room in his lab at the Feinstein Institute for Medical Research in Manhasset, N.Y., into a makeshift operating theater and then prepped his patient — a rat — for surgery. A neurosurgeon, and also Feinstein Institute’s president, Tracey had spent more than a decade searching for a link between nerves and the immune system. His work led him to hypothesize that stimulating the vagus nerve with electricity would alleviate harmful inflammation. “The vagus nerve is behind the artery where you feel your pulse,” he told me recently, pressing his right index finger to his neck. The vagus nerve and its branches conduct nerve impulses — called action potentials — to every major organ. But communication between nerves and the immune system was considered impossible, according to the scientific consensus in 1998. Textbooks from the era taught, he said, “that the immune system was just cells floating around. Nerves don’t float anywhere. Nerves are fixed in tissues.” It would have been “inconceivable,” he added, to propose that nerves were directly interacting with immune cells. Nonetheless, Tracey was certain that an interface existed, and that his rat would prove it. After anesthetizing the animal, Tracey cut an incision in its neck, using a surgical microscope to find his way around his patient’s anatomy. With a hand-held nerve stimulator, he delivered several one-second electrical pulses to the rat’s exposed vagus nerve. He stitched the cut closed and gave the rat a bacterial toxin known to promote the production of tumor necrosis factor, or T.N.F., a protein that triggers inflammation in animals, including humans. “We let it sleep for an hour, then took blood tests,” he said. The bacterial toxin should have triggered rampant inflammation, but instead the production of tumor necrosis factor was blocked by 75 percent. “For me, it was a life-changing moment,” Tracey said. What he had demonstrated was that the nervous system was like a computer terminal through which you could deliver commands to stop a problem, like acute inflammation, before it starts, or repair a body after it gets sick. “All the information is coming and going as electrical signals,” Tracey said. For months, he’d been arguing with his staff, whose members considered this rat project of his harebrained. “Half of them were in the hallway betting against me,” Tracey said. © 2014 The New York Times Company
Link ID: 19649 - Posted: 05.23.2014
Four common chronic pain conditions share a genetic element, suggesting they could - at least in part - be inherited diseases, say UK researchers. The four include irritable bowel syndrome, musculoskeletal pain, pelvic pain and dry eye disease. The study of more than 8,000 sets of twins found the ailments were common in identical pairs sharing the same DNA. The King's College London team say the discovery could ultimately help with managing these debilitating diseases. While environmental factors probably still play a role in the four conditions, genes could account for as much as two-thirds of someone's chances of developing the disease, they believe. They told the journal Pain that more research is needed to pinpoint the precise genes involved. Chronic pain - pain which persists or recurs for months on end - is common and has many different causes, which can make it difficult to diagnose and treat. While the pain can be related to other medical conditions, it is thought to be caused by problems with the nervous system, sending pain signals to the brain despite no obvious tissue damage. Experts are keen to understand more about chronic pain to improve the quality of life of the millions of people who have to endure it. Some have suspected that some people may have a genetic predisposition to chronic pain since many sufferers share similar symptoms and often have more than one of the different types of chronic pain conditions. The team at King's College London decided to study identical and non-identical twins because these two groups provide an ideal comparison for investigating inherited genes - identical twins share the same DNA while non-identical twins do not. BBC © 2014
By KATIE THOMAS Almost overnight, a powerful new painkiller has become a $100 million business and a hot Wall Street story. But nearly as quickly, questions are emerging about how the drug is being sold, and to whom. The drug, Subsys, is a form of fentanyl, a narcotic that is often used when painkillers like morphine fail to provide relief. The product was approved in 2012 for a relatively small number of people — cancer patients — but has since become an outsize moneymaker for the obscure company that makes it, Insys Therapeutics. In the last year, the company’s sales have soared and its share price has jumped nearly 270 percent. Behind that business success is an unusual marketing machine that may have pushed Subsys far beyond the use envisioned by the Food and Drug Administration. The F.D.A. approved Subsys only for cancer patients who are already using round-the-clock painkillers, and warned that it should be prescribed only by oncologists and pain specialists. But just 1 percent of prescriptions are written by oncologists, according to data provided by Symphony Health, which analyzes drug trends. About half of the prescriptions were written by pain specialists, and a wide range of doctors prescribed the rest, including general practice physicians, neurologists and even dentists and podiatrists. Interviews with several former Insys sales representatives suggest the company, based in Chandler, Ariz., has aggressively marketed the painkiller, including to physicians who did not treat many cancer patients and by paying its sales force higher commissions for selling higher doses of the drug. Under F.D.A. rules, manufacturers may market prescription drugs only for approved uses. But doctors may prescribe drugs as they see fit. Over the last decade, pharmaceutical companies have paid billions of dollars to settle claims that they encouraged doctors to use drugs for nonapproved treatments, or so-called off-label uses, to increase sales and profits. © 2014 The New York Times Compan
By BARRY MEIER Four years and a lifetime ago, a new war began for Sgt. Shane Savage. On Sept. 3, 2010, the armored truck he was commanding near Kandahar, Afghanistan, was blown apart by a roadside bomb. His head hit the ceiling so hard that his helmet cracked. His left foot was pinned against the dashboard, crushing 24 bones. Sergeant Savage came home eight days later, at age 27, with the signature injuries of the conflicts in Iraq and Afghanistan: severe concussion, post-traumatic stress and chronic pain. Doctors at Fort Hood in Killeen, Tex., did what doctors across the nation do for millions of ordinary Americans: They prescribed powerful narcotic painkillers. What followed was a familiar arc of abuse and dependence and despair. At one point, Sergeant Savage was so desperate that he went into the bathroom and began swallowing narcotic tablets. He would have died had his wife, Hilary, not burst through the door. Today Sergeant Savage has survived, even prevailed, through grit, his family and a radical experiment in managing pain without narcotics. When off-duty, he pulls on cowboy boots and plays with his children, does charity work and, as part of a therapy program, rides horses. The only medication he takes for pain is Celebrex, a non-narcotic drug. “You have to find alternative ways to get out and do stuff to stay active, to get your brain off the thought process of ‘I’m in pain,’ ” said Sergeant Savage, whose ears push out from under a Texas A&M baseball cap. The story of Sergeant Savage illuminates an effort by experts inside and outside the military to change how chronic, or long-term, pain is treated. By some estimates, tens of millions of Americans suffer from chronic pain, and the use of opioids — drugs like hydrocodone, methadone and oxycodone (the active ingredient in painkillers like OxyContin) — to treat such conditions has soared over the last decade. © 2014 The New York Times Company
Jessica Morrison Interference from electronics and AM radio signals can disrupt the internal magnetic compasses of migratory birds, researchers report today in Nature1. The work raises the possibility that cities have significant effects on bird migration patterns. Decades of experiments have shown that migratory birds can orient themselves on migration paths using internal compasses guided by Earth's magnetic field. But until now, there has been little evidence that electromagnetic radiation created by humans affects the process. Like most biologists studying magnetoreception, report co-author Henrik Mouritsen used to work at rural field sites far from cities teeming with electromagnetic noise. But in 2002, he moved to the University of Oldenburg, in a German city of around 160,000 people. As part of work to identify the part of the brain in which compass information is processed, he kept migratory European robins (Erithacus rubecula) inside wooden huts — a standard procedure that allows researchers to investigate magnetic navigation while being sure that the birds are not getting cues from the Sun or stars. But he found that on the city campus, the birds could not orient themselves in their proper migratory direction. “I tried all kinds of stuff to make it work, and I couldn’t make it work,” Mouritsen says, “until one day we screened the wooden hut with aluminium.” Mouritsen and his colleagues covered the huts with aluminium plates and electrically grounded them to cut out electromagnetic noise in frequencies ranging from 50 kilohertz to 5 megahertz — which includes the range used for AM radio transmissions. The shielding reduced the intensity of the noise by about two orders of magnitude. Under those conditions, the birds were able to orient themselves. © 2014 Nature Publishing Group,
Keyword: Animal Migration
Link ID: 19590 - Posted: 05.08.2014
by Susan Milius Sometimes called the unicorn of the sea, the male narwhal’s tusk is actually a tooth, and it grows directly through the whale’s upper lip instead of pushing the lip aside. It’s an exuberantly large version of a canine tooth that grows in a spiral; the only tooth known to do so. Otherwise narwhals are practically toothless, with only vestigial stubs that stop growing during development and rarely emerge into the mouth. This extreme anatomy has captivated dentist Martin Nweeia, who practices in Connecticut and teaches at Harvard University. For more than a decade, he has pioneered ways to study these difficult-to-reach Arctic whales, and he and his colleagues now describe in the April Anatomical Record that narwhals can detect changes in water salinity using only their tusks. The animals “don’t have a good sense of humor,” though, about being temporarily restrained for the testing, Nweeia says. © Society for Science & the Public 2000 - 2013
Keyword: Pain & Touch
Link ID: 19571 - Posted: 05.05.2014
By JAN HOFFMAN How well can computers interact with humans? Certainly computers play a mean game of chess, which requires strategy and logic, and “Jeopardy!,” in which they must process language to understand the clues read by Alex Trebek (and buzz in with the correct question). But in recent years, scientists have striven for an even more complex goal: programming computers to read human facial expressions. We all know what it’s like to experience pain that makes our faces twist into a grimace. But can you tell if someone else’s face of pain is real or feigned? The practical applications could be profound. Computers could supplement or even replace lie detectors. They could be installed at border crossings and airport security checks. They could serve as diagnostic aids for doctors. Researchers at the University of California, San Diego, have written software that not only detected whether a person’s face revealed genuine or faked pain, but did so far more accurately than human observers. While other scientists have already refined a computer’s ability to identify nuances of smiles and grimaces, this may be the first time a computer has triumphed over humans at reading their own species. “A particular success like this has been elusive,” said Matthew A. Turk, a professor of computer science at the University of California, Santa Barbara. “It’s one of several recent examples of how the field is now producing useful technologies rather than research that only stays in the lab. We’re affecting the real world.” People generally excel at using nonverbal cues, including facial expressions, to deceive others (hence the poker face). They are good at mimicking pain, instinctively knowing how to contort their features to convey physical discomfort. © 2014 The New York Times Company
It takes a lot to deter a male from wanting sex. A new study has found that male mice keep trying to copulate even when they are in pain, whereas females engage in less sex. But when given drugs that target pleasure centers in the human brain, the females again became interested. The findings could shed light on the nature of libido across various animal species. To assess how pain influences sexual desire, researchers first identified pairs of mice that wanted to have sex. “What we found early on was not all mice will mate with each other,” says clinical psychologist Melissa Farmer, who led the study while earning her Ph.D. at McGill University in Montreal, Canada. The team set up the rodents on a series of “dates,” during which a male and female were paired together for 30 minutes. Couples that copulated for most of the session were deemed compatible and moved into a cage with separate rooms. A small doorway allowed a female mouse to freely cross over from her chamber, but the male—which is larger—could not. The scientists then induced pain in males or females by applying a small dose of inflammatory compounds to the cheek, tail, foot, or genitals. The sensation would primarily be soreness, like a bad sunburn, says Farmer, who now works at Northwestern University’s Feinberg School of Medicine in Chicago, Illinois. Female mice that were in pain, whether genital or nongenital, spent 50% less time with their male partners, implying a decrease in sexual motivation. Even when they did visit their paramours, females wouldn’t allow males to mount them with the same frequency, the team reports online today in The Journal of Neuroscience. © 2014 American Association for the Advancement of Science.
Chelsea Wald The sailfish’s sword-like bill looks as if it was made to slash at prey. But a study published today in Proceedings of the Royal Society B1 reveals that the bill is actually a multifunctional killing tool, enabling the fish to perform delicate, as well as swashbuckling, manoeuvres. By following throngs of predatory birds off the coast of Cancún, Mexico, the study’s authors were able to track Atlantic sailfish (Istiophorus albicans) hunting sardines, says co-author Alexander Wilson, a behavioural ecologist now at Carleton University in Ottawa, Canada. He and his colleagues made high-speed, high-resolution films in the open ocean over six days in 2012. Sailfish hunt in groups, taking turns to approach the ball of schooling fish. Their bodies darken and sometimes flash stripes and spots, perhaps to confuse the prey, or to signal to each other. “It’s a very orderly process,” Wilson says. “They don’t want to risk breaking their bills.” Although sailfish are among the fastest creatures in the ocean — they have been documented to swim at more than 110 kilometres per hour, or 60 knots — the new research shows that their strategy is to approach their prey slowly from behind and gently insert their bills into the school, without eliciting an evasive manoeuvre from the sardines. Then, by whipping their heads in powerful, sudden jerks, they can slash their bills left and right, with their upright fins providing stability. In fact, their bill tips slash with about the same acceleration as the tip of a swinging baseball bat, even in the water, says co-author Paolo Domenici, an environmental physiologist at the Institute for the Marine and Coastal Environment of Italy's National Research Council in Torregrande, on the island of Sardinia. The result is a scene of fishy carnage, as the surrounding water fills with iridescent fragments of sardine skin. © 2014 Nature Publishing Group,
Keyword: Pain & Touch
Link ID: 19523 - Posted: 04.23.2014
By SABRINA TAVERNISE Federal health regulators approved a drug overdose treatment device on Thursday that experts say will provide a powerful lifesaving tool in the midst of a surging epidemic of prescription drug abuse. Similar to an EpiPen used to stop allergic reactions to bee stings, the easy-to-use injector — small enough to tuck into a pocket or a medicine cabinet — can be used by the relatives or friends of people who have overdosed. The hand-held device, called Evzio, delivers a single dose of naloxone, a medication that reverses the effects of an overdose, and will be used on those who have stopped breathing or lost consciousness from an opioid drug overdose. Naloxone is the standard treatment in such circumstances, but until now, has been available mostly in hospitals and other medical settings, when it is often used too late to save the patient. The decision to quickly approve the new treatment, which is expected to be available this summer, comes as deaths from opioids continue to mount, including an increase in those from heroin, which contributed to the death of the actor Philip Seymour Hoffman in February. Federal health officials, facing criticism for failing to slow the rising death toll, are under pressure to act, experts say. “This is a big deal, and I hope gets wide attention,” said Dr. Carl R. Sullivan III, director of the addictions program at West Virginia University. “It’s pretty simple: Having these things in the hands of people around drug addicts just makes sense because you’re going to prevent unnecessary mortality.” The scourge of drug abuse has battered states across the country, with deaths from overdoses now outstripping those from traffic crashes. Prescription drugs alone now account for more than half of all drug overdose deaths, and one major category of them, opioids, or painkillers, take the lives of more Americans than heroin and cocaine combined. Deaths from opioids have quadrupled in 10 years to more than 16,500 in 2010, according to federal data. © 2014 The New York Times Company
by Andy Coghlan Burmese pythons can find their way home even if they are taken dozens of kilometres away. It is the first demonstration that big snakes can navigate at all, and far exceeds the distances known to have been travelled by any other snake. At over 3 metres long, Burmese pythons (Python molurus bivitattus) are among the world's largest snakes. For the last two decades they have been eating their way through native species of Florida's Everglades National Park, having been abandoned to the wild by former owners. "Adult Burmese pythons were able to navigate back to their capture locations after having been displaced by between 21 and 36 kilometres," says Shannon Pittman of Davidson College in North Carolina. Pittman and her colleagues caught 12 pythons and fitted them with radiofrequency tags (see video). She released half of them where they were caught, as controls, and transported the other six to distant locations before releasing them. Five pythons made it back to within 5 kilometres of their capture location, and the sixth at least moved in the right direction. The displaced snakes made progress towards their destination most days and seldom strayed more than 22 degrees from the correct path. They kept this up for 94 to 296 days. By contrast, the control snakes moved randomly. On average, displaced snakes travelled 300 metres each day, while control snakes averaged just 100 metres per day. © Copyright Reed Business Information Ltd.
Keyword: Animal Migration
Link ID: 19380 - Posted: 03.19.2014
By Ella Davies Reporter, BBC Nature The whales are known for their tusks which can reach 2.6m (9ft) in length, earning them comparisons with mythological unicorns. The tusk is an exaggerated front tooth and scientists have discovered that it helps the animals sense changes in their environment. Dr Martin Nweeia from the Harvard School of Dental Medicine, US, undertook the study alongside an international team of colleagues. Through the years, many theories have tried to explain the function of the narwhal's impressive tusk. "People have said it's everything from an ice pick to an acoustic probe, but this is the first time that someone has discovered sensory function and has the science to show it," said Dr Nweeia. More recently, experts have agreed that the tusk is a sexual characteristic because it is more often exhibited by males and they appear to use them during fights to assert their social hierarchy. But because the animals are rarely seen, the exact function of the tusk has remained a mystery. Previous studies have revealed that the animals have no enamel on their tusk - the external layer of the tooth that provides a barrier in most mammal teeth. Dr Nweeia and the team's analysis revealed that the outer cementum layer of the tusk is porous and the inner dentin layer has microscopic tubes that channel in towards the centre. In the middle of the tusk lies the pulp, where nerve endings which connect to the narwhal's brain are found. BBC © 2014
Daniel Cressey Researchers have called for a common method of killing zebrafish used in laboratories to be abandoned amid growing evidence that it causes unnecessary suffering. The anaesthetic MS-222, which can be added to tanks to cause overdose, seems to distress the fish, two separate studies have shown. The studies’ authors propose that alternative anaesthetics or methods should be used instead. “These two studies — carried out independently — use different methodologies to reach the same conclusion: zebrafish detect and avoid MS-222 in the water,” says Stewart Owen, a senior environmental scientist at AstraZeneca’s Brixham Environmental Laboratory in Brixham, UK, and a co-author of one of the studies. “As this is a clear aversive response, as a humane choice, one would no longer use this agent for routine zebrafish anaesthesia.” The use of zebrafish (Danio rerio) in research has skyrocketed in recent years as scientists have sought alternatives to more controversial animal models, such as mammals. The fish are cheap and easy to keep, and although no firm data on numbers have been collected, millions are known to be housed in laboratories around the world. Nearly all will eventually be killed. MS-222 (ethyl 3-aminobenzoate methanesulphate, also known as TMS) is one of the agents most frequently used to kill the creatures. It is listed as an acceptable method of euthanasia by many institutions, and also by societies such as the American Veterinary Medical Association. But the study by Owen and his co-authors, published last year (G. D. Readman et al. PLoS ONE 8, e73773; 2013), and the second study, published earlier this month by Daniel Weary and his colleagues at the University of British Columbia in Vancouver, Canada (D. Wong et al. PLoS ONE 9, e88030; 2014), show that zebrafish seem to find the chemical distressing. The research should fundamentally change the practice, say the authors of both papers. © 2014 Nature Publishing Group
Keyword: Pain & Touch
Link ID: 19294 - Posted: 02.26.2014
By Michelle Roberts Health editor, BBC News online Doctors have devised a new way to treat amputees with phantom limb pain. Using computer-generated augmented reality, the patient can see and move a virtual arm controlled by their stump. Electric signals from the muscles in the amputated limb "talk" to the computer, allowing real-time movement. Amputee Ture Johanson says his pain has reduced dramatically thanks to the new computer program, which he now uses regularly in his home. He now has periods when he is free of pain and he is no longer woken at night by intense periods of pain. Mr Johanson, who is 73 and lives in Sweden, lost half of his right arm in a car accident 48 years ago. After a below-elbow amputation he faced daily pain and discomfort emanating from his now missing arm and hand. Over the decades he has tried numerous therapies, including hypnosis, to no avail. Within weeks of starting on the augmented reality treatment in Max Ortiz Catalan's clinic at Chalmers University of Technology, his pain has now eased. "The pain is much less now. I still have it often but it is shorter, for only a few seconds where before it was for minutes. BBC © 2014
By DENISE GRADY The experiment was not for the squirmish. Volunteers were made to itch like crazy on one arm, but not allowed to scratch. Then they were whisked into an M.R.I. scanner to see what parts of their brains lit up when they itched, when researchers scratched them and when they were finally allowed to scratch themselves. The scientific question was this: Why does it feel so good to scratch an itch? “It’s quite intriguing to see how many brain centers are activated,” said Dr. Gil Yosipovitch, chairman of dermatology at the Temple University School of Medicine and director of the Temple Center for Itch (he conducted the experiment while working at Wake Forest School of Medicine). “There is no one itch center. Everyone wants that target, but it doesn’t work in real life like that.” Instead, itching and scratching engage brain areas involved not only in sensation, but also in mental processes that help explain why we love to scratch: motivation and reward, pleasure, craving and even addiction. What an itch turns on, a scratch turns off — and scratching oneself does it better than being scratched by someone else. The study results were published in December in the journal PLOS One. Itching was long overshadowed by pain in both research and treatment, and was even considered just a mild form of pain. But millions of people suffer from itching, and times have changed. Research has found nerves, molecules and cellular receptors that are specific for itching and set it apart from pain, and the medical profession has begun to take it seriously as a debilitating problem that deserves to be studied and treated. Within the last decade, there has been a flurry of research into what causes itching and how to stop it. Along with brain imaging, studies have begun to look at gene activity and to map the signals that flow between cells in the skin, the immune system, the spinal cord and the brain. © 2014 The New York Times Company
Keyword: Pain & Touch
Link ID: 19264 - Posted: 02.18.2014
by Bethany Brookshire There are times when science is a painful experience. My most excruciating moment in science involved a heated electrode placed on my bare leg. This wasn’t some sort of graduate school hazing ritual. I was a volunteer in a study to determine how we process feelings of pain. As part of the experiment I was exposed to different levels of heat and asked how painful I thought they were. When the electrode was removed, I eagerly asked how my pain tolerance compared with that of others. I secretly hoped that I was some sort of superwoman, capable of feeling pain that would send other people into screaming fits and brushing it off with a stoic grimace. It turns out, however, that I was a bit of a wuss. Ouch. I figured I could just blame my genes. About half of our susceptibility to pain can be explained by genetic differences. The other half, however, remains up for grabs. And a new study published February 4 in Nature Communications suggests that part of our susceptibility to pain might lie in chemical markers on our genes. These “notes” on your DNA, known as epigenetic changes, can be affected by environment, behavior and even diet. So the findings reveal that our genetic susceptibility to pain might not be our destiny. Tim Spector and Jordana Bell, genetic epidemiologists at King’s College London, were interested in the role of the epigenome in pain sensitivity. Epigenetic changes such as the addition (or subtraction) of a methyl group on a gene make that gene more or less likely to be used in a cell by altering how much protein can be made from it. These differences in proteins can affect everything from obesity to memory to whether you end up like your mother. © Society for Science & the Public 2000 - 2013.
By Veronique Greenwood Young animals are capable of some pretty astounding feats of navigation. To a species like ours, whose native sense of direction isn’t much to speak of—have you ever seen a human baby crawl five thousand miles home?—the intercontinental odysseys some critters make seem incomprehensible. Arctic tern chicks take part in the longest migration on Earth—more than ten thousand miles (16,000 km)—almost as soon as they fledge. Soon after hatching, young sea turtles take to the waves and confidently paddle many thousands of miles to feeding grounds. Young Chinook salmon likewise make their way from freshwater hatching grounds to specific feeding areas in the open ocean. Biologists know that these species are able to sense things that humans can’t, from the Earth’s magnetic field to extremely faint scents, that could help with navigation. But they may also be inheriting some specific knowledge of the paths they have to follow. A paper in this week’s Current Biology reports that young salmon appear to possess an inborn map of the geomagnetic field that can help them get where they need to go. The researchers, who are primarily based at Oregon State University, performed a series of experiments with Chinook salmon less than a year old that were born and raised in a hatchery and had not yet taken part in a migration. They placed the salmon in pools surrounded by magnetic coils that they could tune to mimic the Earth’s magnetic field at various points in and around the salmons’ feeding grounds. (Kenneth Lohmann at University of North Carolina, Chapel Hill, who has done similar studies that established that baby sea turtles have inborn maps, is also an author of the paper.) © 2014 Time Inc.
Keyword: Animal Migration
Link ID: 19220 - Posted: 02.08.2014
by Douglas Heaven We have the world at our fingertips. A sense of touch can sometimes be as important as sight, helping us to avoid crushing delicate objects or ensuring that we hold on firmly when carrying hot cups of coffee. Now, for the first time, a person who lost his left hand has had a near-natural sense of touch restored thanks to a prosthesis. "I didn't realise it was possible," says Dennis Aabo Sørensen, who is so far the only person to have been fitted with the new prosthesis. "The feeling is very close to the sensation you get when you touch things with your normal hand." To restore Sørensen's sense of touch, Silvestro Micera at the Swiss Federal Institute of Technology in Lausanne and his colleagues implanted tiny electrodes inside the ulnar and median nerve bundles in Sørensen's upper arm. Between them, the ulnar nerve – which runs down to the little finger and ring finger – and the median nerve – which runs down to the index and middle fingers – carry sensations from most of the hand, including the palm. The team then connected the electrodes to pressure sensors on the fingertips and palm of a robotic prosthetic hand via cables running down the outside of Sørensen's arm. When he used the hand to grasp an object, electrical signals from the pressure pads were fired directly into the nerves, providing him with a sense of touch. Getting to grips The electrical signals were calibrated so that Sørensen could feel a range of sensation, from the slightest touch to firm pressure just below his pain threshold, depending on the strength of his grip. © Copyright Reed Business Information Ltd.
by Andy Coghlan If you flinch where others merely frown, you might want to take a look at your lifestyle. That's because environmental factors may have retuned your genes to make you more sensitive to pain. "We know that stressful life events such as diet, smoking, drinking and exposure to pollution all have effects on your genes, but we didn't know if they specifically affected pain genes," says Tim Spector of King's College London. Now, a study of identical twins suggests they do. It seems that epigenetic changes – environmentally triggered chemical alterations that affect how active your genes are – can dial your pain threshold up or down. This implies that genetic tweaks of this kind, such as the addition of one or more methyl groups to a gene, may account for some differences in how our senses operate. Spector and his colleagues assessed the ability of hundreds of pairs of twins to withstand the heat of a laser on their skin, a standard pain test. They selected 25 pairs who showed the greatest difference in the highest temperature they could bear. Since identical twins have the same genes, any variation in pain sensitivity can be attributed to epigenetic differences. Pain thermostat The researchers screened the twins' DNA for differences in methylation levels across 10 million gene regions. They found a significant difference in nine genes, most of which then turned out to have been previously implicated in pain-sensitivity in animal experiments. © Copyright Reed Business Information Ltd.
by Kat Arney Next time you struggle to resist an itchy rash or insect bite, you could find relief in the mirror. Perception of our own bodies can be easily manipulated using tricks such as the rubber hand illusion, which fools people into thinking a rubber hand is their own. Reflecting someone's limb in a mirror has also been used to treat phantom limb pain. Now Christoph Helmchen and his colleagues at the University of Lübeck in Germany have shown that a similar mirror illusion can fool people into feeling relief from an itch, even when they scratch the wrong place. The team injected the right forearms of 26 male volunteers with itch-inducing chemical histamine. Because the injection creates a red spot, they painted a corresponding dot on the opposite arm so both looked identical. One of the researchers then scratched each arm in turn. Unsurprisingly, scratching the itchy arm produced relief, while scratching the other one did not. Next, they placed a large vertical mirror in front of the itchy arm, blocking off the subject's view of their right arm and reflecting back the non-itchy one in its place . They asked the volunteers to look only at the reflected limb in the mirror, whilst a member of the team again scratched each arm. This time the participants felt relief when the unaffected, reflected arm was scratched. © Copyright Reed Business Information Ltd.