Chapter 5. The Sensorimotor System

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by Helen Thomson A brain implant that can decode what someone wants to do has allowed a man paralysed from the neck down to control a robotic arm with unprecedented fluidity – and enjoy a beer at his own pace. Erik Sorto was left unable to move any of his limbs after an accident severed his spinal cord 12 years ago. People with similar injuries have previously controlled prosthetic limbs using implants placed in their motor cortex – an area of the brain responsible for the mechanics of movement. This is far from ideal because it results in delayed, jerky motions as the person thinks about all the individual aspects of the movement. When reaching for a drink, for example, they would have to think about moving their arm forward, then left, then opening their hand, then closing their hand around the cup and so on. Richard Andersen at the California Institute of Technology in Pasadena and his colleagues hoped they could achieve a more fluid movement by placing an implant in the posterior parietal cortex – a part of the brain involved in planning motor movements. "We thought this would allow us to decode brain activity associated with the overall goal of a movement – for example, 'I want to pick up that cup', rather than the individual components," said Anderson at the NeuroGaming Conference in San Francisco, California, where he presented the work this month. © Copyright Reed Business Information Ltd.

Keyword: Robotics
Link ID: 20972 - Posted: 05.23.2015

Scientists at Mayo Clinic, Jacksonville, Florida created a novel mouse that exhibits the symptoms and neurodegeneration associated with the most common genetic forms of frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS, Lou Gehrig’s disease), both of which are caused by a mutation in the a gene called C9ORF72. The study was partially funded by the National Institutes of Health and published in the journal Science. More than 30,000 Americans live with ALS, which destroys nerves that control essential movements, including speaking, walking, breathing and swallowing. After Alzheimer’s disease, FTD is the most common form of early onset dementia. It is characterized by changes in personality, behavior and language due to loss of neurons in the brain’s frontal and temporal lobes. Patients with mutations in the chromosome 9 open reading frame 72 (C9ORF72) gene have all or some symptoms associated with both disorders. “Our mouse model exhibits the pathologies and symptoms of ALS and FTD seen in patients with theC9ORF72 mutation,” said the study’s lead author, Leonard Petrucelli, Ph.D., chair and Ralph and Ruth Abrams Professor of the Department of Neuroscience at Mayo Clinic, and a senior author of the study. “These mice could greatly improve our understanding of ALS and FTD and hasten the development of effective treatments.” To create the model, Ms. Jeannie Chew, a Mayo Graduate School student and member of Dr. Petrucelli’s team, injected the brains of newborn mice with a disease-causing version of the C9ORF72 gene. As the mice aged, they became hyperactive, anxious, and antisocial, in addition to having problems with movement that mirrored patient symptoms.

Keyword: ALS-Lou Gehrig's Disease ; Alzheimers
Link ID: 20964 - Posted: 05.21.2015

by Jessica Hamzelou Painful needle heading your way? A sharp intake of breath might be all that is needed to make that injection a little more bearable. When you are stressed, your blood pressure rises to fuel your brain or limbs should you need to fight or flee. But your body has a natural response for calming back down. Pressure sensors on blood vessels in your lungs can tell your brain to bring the pressure back down, and the signals from these sensors also make the brain dampen the nervous system, leaving you less sensitive to pain. This dampening mechanism might be why people with higher blood pressures appear to have higher pain thresholds. Gustavo Reyes del Paso at the University of Jaén in Spain wondered whether holding your breath – a stress-free way of raising blood pressure and triggering the pressure sensors – might also raise a person's pain threshold. To find out, he squashed the fingernails of 38 people for 5 seconds while they held their breath. Then he repeated the test while the volunteers breathed slowly. Both techniques were distracting, but the volunteers reported less pain when breath-holding than when slow breathing. Reyes del Paso thinks holding your breath might be a natural response to the expectation of pain. "Several of our volunteers told us they already do this when they are in pain," he says. But he doesn't think the trick will work for a stubbed toe or unexpected injury. You have to start before the pain kicks in, he says, for example, in anticipation of an injection. © Copyright Reed Business Information Ltd

Keyword: Pain & Touch
Link ID: 20930 - Posted: 05.14.2015

Patricia Neighmond Terri Bradford has suffered debilitating headache pain all her life. Some days the pain is so bad, she says, "By 11 o'clock in the morning, I'm on the couch in a darkened room with my head packed in ice." Over the years, Bradford, who is 50 years old and lives in Bedford, Mass., has searched desperately for pain relief. She's been to the doctor countless times for countless tests. "Everything I've had, I've had twice," she says. "I've had two spinal taps; I've had so many nerve blocks I've lost count." Bradford is not alone. It's estimated that every year 12 million Americans go to the doctor seeking help for headaches. Nearly one quarter of the population suffers from recurrent severe tension headaches or migraines. People who go to the doctor for headache pain are more likely to be sent for advanced testing and treatment, a study finds. That testing is expensive, it may not be necessary and could even be harmful, says lead researcher Dr. John Mafi of Beth Israel Deaconess Medical Center in Boston. Mafi looked at the rates of advanced imaging like CT scans and MRIs in people with headaches, as well as referrals to other doctors, presumably specialists. He found that from 1999 to 2010, the number of diagnostic tests rose from 6.7 percent of all doctor visits to 13.9 percent. At the same time, referrals to other doctors increased from 6.9 percent to 13.2 percent. So almost double what it was a decade ago. Mafi says this isn't because more people are suffering headaches. The headache rate has remained virtually the same over the past decade. But what has changed is supply and demand. Today there are a lot more advanced diagnostic machines than there were a decade ago, and more patients are asking to be tested. © 2015 NPR

Keyword: Parkinsons; Stress
Link ID: 20906 - Posted: 05.11.2015

By Lisa Sanders, M.D On Thursday we challenged Well readers to solve the difficult case of twin sisters who, in the prime of youth, developed a weakness that forced them to use their arms to rise from a chair. Nearly 300 of you wrote in with thoughts on this difficult case. Many of you recognized that this was likely to be a genetic disorder, though I greatly admired the “House”-ian thinking that led to a host of possible reasons why two sisters, living in different states, might develop the same symptoms independent of their shared DNA. It took this patient, Katie Buryk, four years to get her answer, which was: Late onset Tay-Sachs disease Although several of you made this difficult diagnosis, the first to do so was George Bonadurer, a second year medical student at Mayo Medical School in Rochester, Minn. He says he recently read about this disease in a book of unusual cases that had come to the Mayo clinic for help. This is actually Mr. Bonadurer’s second win of this contest. Strong work! Tay-Sachs disease was first identified by two physicians, independently, in the 1880s. Dr. Warren Tay was an ophthalmologist in London. Dr. Bernard Sachs was a neurologist in New York City. Each described a disease in infants that caused profound weakness, blindness and, usually by age 4, death. Careful consideration of cases over the following decades showed that the disease was inherited and often seen in children of Ashkenazi descent. Studying the patterns of inheritance, it became clear that both parents had to have the abnormal gene and that each of their children would have a one in four chance of being born with the disease. The terrible manifestations of the disease derive from an inherited inability to make an essential protein in the brain. This protein acts to break down discarded components of the cells. Without this protein, these discarded cell parts accumulate, interrupting normal nerve and brain cell functioning. This mechanism and the missing protein was identified in 1969, allowing for the development of a test for carriers. Since the development of this test, the incidence of Tay-Sachs in the United States has dropped by 90 percent. © 2015 The New York Times Company

Keyword: Movement Disorders; Genes & Behavior
Link ID: 20902 - Posted: 05.09.2015

Andrew Griffin Companies are taking out a huge amount of patents related to reading brainwaves, according to analysis, with a range of different applications. Fewer than 400 neuro-technology related patents were filed between 2000-2009. But in 2010 alone that reached 800, and last year 1,600 were filed, according to research company SharpBrains. The patents are for a range of uses, not just for the healthcare technology that might be expected. The company with the most patents is market research firm Nielsen, which has 100. Microsoft also has 89 related patents. Other uses of the technology that have been patented include devices that can change the thoughts of feelings of those that they are used on. But there are still medical uses — some of those patents awarded include technology to measure brain lesions and improve vision. The volume and diversity of the patents shows that we are at the beginning of “the pervasive neurotechnology age”, the company’s CEO Alvaro Fernandez said. "Neurotech has gone well beyond medicine, with non-medical corporations, often under the radar, developing neurotechnologies to enhance work and life," said Fernandez.

Keyword: Brain imaging; Robotics
Link ID: 20897 - Posted: 05.08.2015

Roger Dobson Tapping your fingers on the table is usually a sign of boredom or irritation. But not all tappers are equal, it seems. Men drum their digits slightly faster than women and people in their twenties tap substantially faster than people twice their age. The results of the first study into finger-tapping speeds also found that smokers tap a little faster than non-smokers and fit people tap faster than those who avoid exercise. The research, carried out by scientists at two universities in Istanbul – Bogazici University and Fatih University – examined the tapping rates and “finger load capacities” of 148 people aged between 18 and 85. Each participant was asked to perform a one-minute tapping exercise on a keyboard at “maximum volitional tempo”. Researchers found that the index finger on the right hand of both men and women was the fastest digit, achieving a tapping rate of up to five beats a second among those in their twenties. The middle finger was almost as nifty as the index finger, but the little finger – the slowest digit in the bunch – was capable only of a sluggish 3.8 taps a second among people in the same age group. At first glance, the study might appear to be rather frivolous. But a deeper understanding of finger tapping could aid the design of computer keyboards and musical instruments. It may also aid researchers who use finger-tapping tests for medical assessment of neurological conditions such as Parkinson’s disease, schizophrenia and Alzheimer’s.

Keyword: Parkinsons; Alzheimers
Link ID: 20887 - Posted: 05.05.2015

by Helen Thomson Giving people the illusion of teleporting around a room has revealed how the brain constructs our sense of self. The findings may aid treatments for schizophrenia and asomatognosia – a rare condition characterised by a lack of awareness of a part of one's body. As we go about our daily lives, we experience our body as a physical entity with a specific location. For instance, when you sit at a desk you are aware of your body and its rough position with respect to objects around you. These experiences are thought to form a fundamental aspect of self-consciousness. Arvid Guterstam, a neuroscientist at the Karolinska Institute in Stockholm, Sweden, and his colleagues wondered how the brain produces these experiences. To find out, Guterstam's team had 15 people lie in an fMRI brain scanner while wearing a head-mounted display. This was connected to a camera on a dummy body lying elsewhere in the room, enabling the participants to see the room – and themselves inside the scanner - from the dummy's perspective. A member of the team then stroked the participant's body and the dummy's body at the same time. This induced the out-of-body experience of owning the dummy body and being at its location. The experiment was repeated with the dummy body positioned in different parts of the room, allowing the person to be perceptually teleported between the different locations, says Guterstam. All that was needed to break the illusion was to touch the participant's and the dummy's bodies at different times. © Copyright Reed Business Information Ltd.

Keyword: Pain & Touch; Attention
Link ID: 20874 - Posted: 05.02.2015

by Jacob Aron Now that's an in-flight meal. To snatch a mealworm in mid-air, the bat in this video performs impressive aerial acrobatics aided by a unique cluster of touch sensors on its wings. Bats are known to use echolocation to identify their dinner, steering towards prey by listening for reflected sounds. It turns out that their sense of touch plays a key role as well. Ellen Lumpkin of Columbia University, New York, and her colleagues have discovered that bats have a special arrangement of hairs and touch-sensitive receptors across their wings that detect changes in airflow to help stabilise flight. The team also found that sensory neurons arranged in a pattern on bat wings (pictured) send signals to the lower spinal cord, which is unusual for a mammal. This part of the spinal cord usually receives messages from an animal's torso. The bizarre circuitry reflects the embryonic origins of bat wings, which form when their front limbs, torso and hind limbs fuse together. Journal reference: Cell Reports, DOI: 10.1016/j.celrep.2015.04.001 © Copyright Reed Business Information Ltd

Keyword: Pain & Touch
Link ID: 20872 - Posted: 05.02.2015

Scientists have raised hopes that they may be able to create a vaccine to block the progress of Parkinson’s disease. They believe new research provides evidence that an abnormal protein may trigger the condition. If the theory is correct, researchers say it might be possible to prime a person’s immune system – using a special vaccine – so it is ready to attack the rogue protein as it passes through the body. In this way, the protein would be prevented from destroying a person’s dopamine-manufacturing cells, where the disease inflicts its greatest damage. This new vision of Parkinson’s has been arousing excitement among researchers. “It has transformed the way we see Parkinson’s,” said Roger Barker, professor of clinical neurosciences at Cambridge University. Parkinson’s does not usually affect people until they are over 50. However, researchers have uncovered recent evidence that suggests it may be caused by an event occurring 10 to 20 years before its main symptoms – tremors, rigidity and slowness of movement – manifest themselves. “If you ask Parkinson’s patients if, in the past, they have experienced loss of sense of smell or suffer from disturbed sleep or have problems with their bowels, very often they reply they have,” said Barker, whose work is backed by the charity Parkinson’s UK, whose Parkinson Awareness week ends on Sunday. “Frequently these patients manifest symptoms several years before it becomes apparent they have the disease. We now believe there is a link.” © 2015 Guardian News and Media Limited

Keyword: Parkinsons
Link ID: 20855 - Posted: 04.28.2015

By Emily Dwass In the frightening world of brain tumors, “benign” is a good word to hear. But even a nonmalignant tumor can be dangerous — especially if, as in my case, it goes undetected, becoming a stealth invader. “Anecdotally, we often hear about women who were originally misdiagnosed — sometimes for years,” said Tom Halkin, a spokesman for the patient advocacy nonprofit National Brain Tumor Society. When I developed tingling in my limbs 12 years ago, two Los Angeles neurologists diagnosed Guillain-Barré syndrome, a disorder in which the immune system attacks the nervous system. The symptoms of numbness and weakness ebbed and flowed for three years. Then one day, I couldn’t slide my right foot into a flip-flop. This got me a ride in a magnetic resonance imaging machine, which revealed a brain mass the size of a tennis ball. It was a benign meningioma, a tumor that grows in the membranes surrounding the brain and spinal cord. After the diagnosis, I consulted with Los Angeles surgeons. “We’re going to cut your head open like a pumpkin,” one told me. I chose someone else, who had a stellar reputation, who was compassionate, and who did not compare my skull to a squash. “You’re cured,” he said as I awoke in the operating room. Recovery took about six weeks and went smoothly, except for my right foot, which remains partly numb. I relearned to walk and to drive with my left foot, using adaptive equipment. Had my tumor been diagnosed earlier, I might have avoided a large craniotomy and permanent foot issues. “It’s critical to find these tumors when they are small, when radiosurgery is an option, rather than when they are very big or produce a lot of symptoms, at which point it’s not optimal to treat them without doing open surgery,” said Dr. Susan Pannullo, the director of neuro-oncology and neurosurgical radiosurgery at NewYork-Presbyterian Hospital and Weill Cornell Medical College. © 2015 The New York Times Company

Keyword: Movement Disorders
Link ID: 20854 - Posted: 04.28.2015

By Jerry Adler Smithsonian Magazine | In London, Benjamin Franklin once opened a bottle of fortified wine from Virginia and poured out, along with the refreshment, three drowned flies, two of which revived after a few hours and flew away. Ever the visionary, he wondered about the possibility of incarcerating himself in a wine barrel for future resurrection, “to see and observe the state of America a hundred years hence.” Alas, he wrote to a friend in 1773, “we live in an age too early . . . to see such an art brought in our time to its perfection.” If Franklin were alive today he would find a kindred spirit in Ken Hayworth, a neuroscientist who also wants to be around in 100 years but recognizes that, at 43, he’s not likely to make it on his own. Nor does he expect to get there preserved in alcohol or a freezer; despite the claims made by advocates of cryonics, he says, the ability to revivify a frozen body “isn’t really on the horizon.” So Hayworth is hoping for what he considers the next best thing. He wishes to upload his mind—his memories, skills and personality—to a computer that can be programmed to emulate the processes of his brain, making him, or a simulacrum, effectively immortal (as long as someone keeps the power on). Hayworth’s dream, which he is pursuing as president of the Brain Preservation Foundation, is one version of the “technological singularity.” It envisions a future of “substrate-independent minds,” in which human and machine consciousness will merge, transcending biological limits of time, space and memory. “This new substrate won’t be dependent on an oxygen atmosphere,” says Randal Koene, who works on the same problem at his organization, Carboncopies.org. “It can go on a journey of 1,000 years, it can process more information at a higher speed, it can see in the X-ray spectrum if we build it that way.”

Keyword: Consciousness; Robotics
Link ID: 20841 - Posted: 04.25.2015

By Brady Dennis In recent months, Pasadena-based Genervon has galvanized many patients with ALS by repeatedly touting the results of 12-week, 12-person trial involving the company's drug, GM604. The company asserted its early results were “statistically significant,” “very robust” and “dramatic.” It also has said it "submitted an accelerated approval application" to the FDA which, if approved, "would allow immediate access" to patients with ALS, also known as Lou Gehrig's disease. But the Wall Street Journal reported Monday that Genervon said in an email that it is “at the point of communicating with FDA about whether [the agency] would accept our formal application” for accelerated approval. In other words, the company has not yet submitted a New Drug Application, a step needed to officially set the FDA approval process in motion. The company's acknowledgement that it has not filed an NDA appears to contradict earlier press releases and statements made by the firm's owners, Winston and Dorothy Ko -- or at least to have sown confusion about the actual status of GM604. In one February press release, for example, the company said that in a meeting with the FDA, "three times during the one-hour meeting we requested that the FDA grant GM604 accelerated approval." Asking, however, is not the same as filing the necessary paperwork and the accompanying data required for the FDA to accept it as sufficient. The difference might seem to be a matter of semantics. But the real-world consequence is that, if Genervon has no application pending at the FDA, there is no imminent decision for the FDA to make about approving GM604.

Keyword: ALS-Lou Gehrig's Disease
Link ID: 20833 - Posted: 04.22.2015

The brains of babies “light up” in a similar way to adults when exposed to the same painful stimulus, suggesting they feel pain much like adults do, researchers said on Tuesday. In the first of its kind study using magnetic resonance imaging (MRI), scientists from Britain’s Oxford University found that 18 of the 20 brain regions active in adults experiencing pain were also active in babies. Brain scans of the sleeping infants while they were subjected to mild pokes on the bottom of their feet with a special rod – creating a sensation “like being poked with a pencil” – also showed their brains had the same response to a slighter “poke” as adults did to a stimulus four times as strong, suggesting babies have a much lower pain threshold. “Obviously babies can’t tell us about their experience of pain and it is difficult to infer pain from visual observations,” said Rebeccah Slater, a doctor at Oxford’s paediatrics department who led the study. “In fact some people have argued that babies’ brains are not developed enough for them to really feel pain ... [yet] our study provides the first really strong evidence this is not the case.” Even as recently as the 1980s it was common practice for babies undergoing surgery to be given neuromuscular blocks but no pain relief medication. Last year, a review of neonatal pain management in intensive care found that although these babies experience an average of 11 painful procedures per day, 60% do not receive any kind of pain medication. © 2015 Guardian News and Media Limited

Keyword: Pain & Touch; Development of the Brain
Link ID: 20824 - Posted: 04.21.2015

Carl Zimmer In 1998, Dr. Philip A. Starr started putting electrodes in people’s brains. A neurosurgeon at the University of California, San Francisco, Dr. Starr was treating people with Parkinson’s disease, which slowly destroys essential bits of brain tissue, robbing people of control of their bodies. At first, drugs had given his patients some relief, but now they needed more help. After the surgery, Dr. Starr closed up his patients’ skulls and switched on the electrodes, releasing a steady buzz of electric pulses in their brains. For many patients, the effect was immediate. “We have people who, when they’re not taking their meds, can be frozen,” said Dr. Starr. “When we turn on the stimulator, they start walking.” First developed in the early 1990s, deep brain stimulation, or D.B.S., was approved by the Food and Drug Administration for treating Parkinson’s disease in 2002. Since its invention, about 100,000 people have received implants. While D.B.S. doesn’t halt Parkinson’s, it can turn back the clock a few years for many patients. Yet despite its clear effectiveness, scientists like Dr. Starr have struggled to understand what D.B.S. actually does to the brain. “We do D.B.S. because it works,” said Dr. Starr, “but we don’t really know how.” In a recent experiment, Dr. Starr and his colleagues believe they found a clue. D.B.S. may counter Parkinson’s disease by liberating the brain from a devastating electrical lock-step. The new research, published on Monday in Nature Neuroscience, may help scientists develop better treatments for Parkinson’s disease. It may also help researchers adapt D.B.S. for treatment of such brain disorders as depression and obsessive compulsive disorder. © 2015 The New York Times Company

Keyword: Parkinsons
Link ID: 20817 - Posted: 04.18.2015

Angus Chen A common pain medication might make you go from "so cute!" to "so what?" when you look at a photo of an adorable kitten. And it might make you less sensitive to horrifying things too. It's acetaminophen, the active ingredient in Tylenol. Researchers say the drug might be taking the edge off emotions – not just pain. "It seems to take off the highs of your daily highs and the lows off your daily lows," says Baldwin Way, a psychologist at Ohio State University and the principal investigator on the study, "It kind of flattens out the vicissitudes of your life." The idea that over-the-counter pain pills might affect emotions has been circulating since 2010, when two psychologists, Naomi Eisenberger and Nathan DeWall, led a study showing that acetaminophen seemed to be having both a psychological and a neurological effect on people. They asked volunteers to play a rigged game that simulated social rejection. Not only did the acetaminophen appear to be deflecting social anxieties, it also seemed to be dimming activity in the insula, a region of the brain involved in processing emotional pain. A brain that can let other thoughts bubble up despite being in pain might help its owner benefit from meditation or other cognitive therapies. "But [the insula] is a portion of the brain that seems to be involved in a lot of things," Way says. In older studies, scientists saw that people with damage in their insula didn't react as strongly to either negative or positive images. So Way and one of his students, Geoffrey Durso, figured that if acetaminophen is doing something to the insula, then it might be having a wider effect, too. © 2015 NPR

Keyword: Emotions; Pain & Touch
Link ID: 20807 - Posted: 04.16.2015

by Jessica Hamzelou An exoskeleton that enables movement and provides tactile feedback has helped eight paralysed people regain sensation and move previously paralysed muscles "I FELT the ball!" yelled Juliano Pinto as he kicked off the Football World Cup in Brazil last year. Pinto, aged 29 at the time, lost the use of his lower body after a car accident in 2006. "It was the most moving moment," says Miguel Nicolelis at Duke University in North Carolina, head of the Walk Again Project, which developed the thought-controlled exoskeleton that enabled Pinto to make his kick. Since November 2013, Nicolelis and his team have been training Pinto and seven other people with similar injuries to use the exoskeleton – a robotic device that encases the limbs and converts brain signals into movement. The device also feeds sensory information to its wearer, which seems to have partially reawakened their nervous system. When Nicolelis reassessed his volunteers after a year of training, he found that all eight people had regained sensations and the ability to move muscles in their once-paralysed limbs. "Nobody expected it at all," says Nicolelis, who presented the results at the Brain Forum in Lausanne, Switzerland, on 31 March. "When we first saw the level of recovery, there was not a single person in the room with a dry eye." When a person's spinal cord is injured, the connection between body and brain can be damaged, leaving them unable to feel or move parts of their body. If a few spinal nerves remain, people can sometimes regain control over their limbs, although this can involve years of rehabilitation. © Copyright Reed Business Information Ltd.

Keyword: Robotics
Link ID: 20805 - Posted: 04.16.2015

by Penny Sarchet You've got a splitting migraine. If you were offered a sugar pill, would you bother taking it? What if you were told your genetic make-up means it is very likely to make you feel better? This is one of the questions raised by the burgeoning effort to understand which genes influence the placebo effect, and how these genes – collectively known as the placebome – determine a person's susceptibility to the phenomenon. There are tremendous differences in the placebo effect between individuals, says Kathryn Hall of Harvard Medical School. "It can vary from no measurable response to someone getting significantly better." Having drawn together all the studies carried out so far, Hall says there is reasonable evidence for at least 11 genes that influence a person's susceptibility. This is enough to warrant discussing the use of genetic screening to assess how likely a person is to respond to a placebo treatment, such as a sugar pill or saline injection. The idea is that this could lead to more personalised treatments for conditions like pain syndromes, migraines, depression, irritable bowel syndrome and even Parkinson's disease, symptoms of which seem to be relieved by placebo in some individuals. It could also lead to the design of more balanced clinical trials. Your personality can help you guess whether you're among the estimated third of the population who are placebo responders. Being agreeable, extroverted and open to new experiences all appear to be associated with placebo susceptibility. Although brain imaging techniques can also indicate a person's likely susceptibility, a genetic read-out would offer a convenient, easily applicable and clearly codified measure. © Copyright Reed Business Information Ltd

Keyword: Pain & Touch
Link ID: 20794 - Posted: 04.14.2015

|By Andrea Alfano To scratch an itch is to scratch many itches: placing nails to skin brings sweet yet short-lived relief because it often instigates another bout of itchiness. The unexpected culprit behind this vicious cycle, new research reveals, is serotonin, the so-called happiness hormone. Scientists thought itch was merely a mild form of pain until 2009, when Zhou-Feng Chen and his colleagues at the Center for the Study of Itch at Washington University in St. Louis discovered itch-specific neurons in mice. Though not identical, itch and pain are closely related; they share the same pathways in certain brain areas. Because of the doubling up, activating one suppresses the other, which is why scratching blocks the itch sensation momentarily. The act, however, also triggers the release of the chemical serotonin, which helps to alleviate pain. It is that burst that makes scratching feel good, but recent work by Chen's group showed that it exacerbates the itch-scratch cycle, too. Itch-sensing neurons have a set of receptors that facilitates pain relief and another that induces itch. Serotonin can bind only to the pain-related receptor, but because the two sets sit close to each other and physically interact, the chemical's arrival indirectly enhances the itch pathway. When Chen and his colleagues activated both receptors simultaneously in mice, the rodents scratched much more than if the itch-inducing receptor was turned on alone. In another experiment, mice lacking the cells that produce serotonin scratched less than normal mice when exposed to a skin irritant. The findings were published in the journal Neuron. © 2015 Scientific American

Keyword: Pain & Touch
Link ID: 20793 - Posted: 04.14.2015

Jon Hamilton Researchers have discovered the exact structure of the receptor that makes our sensory nerves tingle when we eat sushi garnished with wasabi. And because the "wasabi receptor" is also involved in pain perception, knowing its shape should help pharmaceutical companies develop new drugs to fight pain. The receptor, which scientists call TRPA1, is "an important molecule in the pain pathway," says David Julius, a professor of physiology at the University of California, San Francisco and an author of a paper published in this week's Nature. "A dream of mine is that some of the work we do will translate into medicines people can take for chronic pain." Julius led a team that discovered the receptor about a decade ago. Since then, researchers have shown that TRPA1 receptors begin sending distress signals to the brain whenever they encounter pungent chemical irritants, including not only wasabi but tear gas and air pollution from cars or wood fires. The receptors also become activated in response to chemicals released by the body itself when tissue becomes inflamed from an injury or a disease like rheumatoid arthritis. © 2015 NPR

Keyword: Pain & Touch
Link ID: 20780 - Posted: 04.10.2015