Chapter 8. General Principles of Sensory Processing, Touch, and Pain
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The CDC recommends non-opioid therapy, including exercise and over-the-counter pain medications, as the preferred treatment for chronic pain. It says opioids should only be prescribed — at the lowest effective dosage possible — when the benefits from pain reduction and bodily function outweigh the risks. In 2014, American doctors wrote nearly 200 million prescriptions for opioid painkillers, while deaths linked to the drugs climbed to roughly 19,000 — the highest number on record. The number of Canadians who die every year from opioids is not readily known — the Canadian Centre on Substance Abuse does not track the statistics — but Toronto physician Nav Persaud told CBC News in 2014 that more than 1,000 Canadians die from painkillers every year. A 2012 study says one in eight deaths among young adults age 25 to 34 in Ontario and one out of every 170 deaths in the province as a whole are opioid overdoses. One in four people who entered a withdrawal management program at St. Joseph's Healthcare in Hamilton, Ont., were opioid patients in 2012, up from one in ten in 2002. Other studies have cast doubt on the effectiveness of opioids on chronic pain, raising questions on whether its limited long-term effects are worth the harmful risks. "The science is clear," CDC director Tom Frieden said Tuesday. "For the vast majority of patients, the known and often fatal risks [of opioids] far outweigh the proven and transient benefits." ©2016 CBC/Radio-Canada.
By Sandra G. Boodman Kim Pace was afraid he was dying. In six months he had lost more than 30 pounds because a terrible stabbing sensation on the left side of his face made eating or drinking too painful. Brushing his teeth was out of the question and even the slightest touch triggered waves of agony and a shocklike pain he imagined was comparable to electrocution. Painkillers, even morphine, brought little relief. Unable to work and on medical leave from his job as a financial consultant for a bank, Pace, then 59, had spent the first half of 2012 bouncing among specialists in his home state of Pennsylvania, searching for help from doctors who disagreed about the nature of his illness. Some thought his searing pain might be the side effect of a drug he was taking. Others suspected migraines, a dental problem, mental illness, or an attempt to obtain painkillers. Even after a junior doctor made what turned out to be the correct diagnosis, there was disagreement among specialists about its accuracy or how to treat Pace. His wife, Carol, a nurse, said she suspects that the couple’s persistence and propensity to ask questions led her husband to be branded “a difficult case” — the kind of patient whom some doctors avoid. And on top of that, a serious but entirely unrelated disorder further muddied the diagnostic picture. So on July 17, 2012, when Pace told his wife he thought he was dying, she fired off an emotional plea for help to the office of a prominent specialist in Baltimore. “I looked at Kim and it hit me: He was going to die,” she said. “He was losing weight and his color was ashen” and doctors were “blowing him off. I thought, ‘Okay, that’s it,’ and the nurse in me took over.”
Cathleen O'Grady When we speak, listen, read, or write, almost all of the language processing that happens in our brains goes on below the level of conscious awareness. We might be aware of grasping for a particular forgotten word, but we don’t actively think about linguistic concepts like morphemes (the building blocks of words, like the past tense morpheme “-ed”). Psycholinguists try to delve under the surface to figure out what’s actually going on in the brain, and how well this matches up with our theoretical ideas of how languages fit together. For instance, linguists talk about morphemes like “-ed”, but do our brains actually work with morphemes when we’re producing or interpreting language? That is, do theoretical linguistic concepts have any psychological reality? An upcoming paper in the journal Cognition suggests an unusual way to investigate this: by testing synaesthetes. Synaesthesia comes in many forms. Some synaesthetes associate musical tones or notes with particular colours; others attach personalities to letters or numbers. A huge number of synaesthetes have associations that are in some way linguistic, and one of the most common forms of all is grapheme-colour (GC) synaesthesia, which is the association of colours with particular letters or numbers. For instance, a GC synaesthete might have a consistent perception of the letter “A” being red. This association often extends to a whole word, so “ant” might be red, too. © 2016 Guardian News and Media Limited
Link ID: 21937 - Posted: 02.27.2016
Jo Marchant The brain cells of people with Parkinson’s disease can be trained to reliably respond to placebo drugs, Italian neuroscientists report. The training wears off after 24 hours but the effect shows it may be possible to reduce the medication needed to treat Parkinson’s by interspersing real drugs with inert injections or pills, says placebo researcher Fabrizio Benedetti at the University of Turin, Italy, who led the work. A few people with Parkinson’s disease do respond dramatically to placebos, but most do not1. People with the condition suffer characteristic tremors and stiff muscles because their dopamine-producing brain cells are gradually dying off. They alleviate their symptoms by taking drugs such as apomorphine, which activate receptors for dopamine. For some conditions — such as pain and immune disorders — trials have shown2 that it is possible to train people to respond to placebos, although this practice hasn’t made its way into clinical care. Benedetti and his colleagues wondered whether the same effect might be possible for neurological disorders. They studied 42 people with advanced Parkinson’s disease who were having electrodes implanted into their brains for a therapy called deep brain stimulation, which eases symptoms by stimulating affected brain areas directly. That surgery gave Benedetti’s team a rare opportunity to measure the activity of individual neurons in the thalamus, a brain region known to be inhibited by lack of dopamine in people with Parkinson's. © 2016 Nature Publishing Grou
Link ID: 21884 - Posted: 02.10.2016
Rare ‘allergy’ to vibrations tied to faulty gene By Kelly Servick If you have the rare condition known as vibratory urticaria, you may be wary of handling lawnmowers and electric mixers. Rubbing or vibration against your skin—even from drying off with a towel—can cause you to break out in hives, make your face flush, give you headaches, or produce the sensation of a metallic taste. The condition, which runs in families, is so rare that the researchers who work on it have only tracked down a few cases over years of searching. But a genetic study on three such unique families has revealed a potential mechanism for the strange symptoms. Research published online today in the New England Journal of Medicine describes a mutation in a gene called ADGRE2, found in 22 people with vibratory urticaria, but not in 14 of their unaffected relatives. The gene codes for a receptor protein that was found on the surface of mast cells—immune cells in the skin that dump out inflammatory molecules such as histamines that increase blood flow to an area and can cause hives. The researchers observed that shaking mast cells in a dish breaks apart two subunits of this receptor protein, which prompts histamine release. In people with the newly discovered mutation, the receptor is more prone to breakage, which causes this protective immune response at the site of physical trauma to run amok. © 2016 American Association for the Advancement of Science.
A map for other people’s faces has been discovered in the brain. It could help explain why some of us are better at recognising faces than others. Every part of your body that you can move or feel is represented in the outer layer of your brain. These “maps”, found in the motor and sensory cortices (see diagram, below), tend to preserve the basic spatial layout of the body – neurons that represent our fingers are closer to neurons that represent our arms than our feet, for example. The same goes for other people’s faces, says Linda Henriksson at Aalto University in Helsinki, Finland. Her team scanned 12 people’s brains while they looked at hundreds of images of noses, eyes, mouths and other facial features and recorded which bits of the brain became active. This revealed a region in the occipital face area in which features that are next to each other on a real face are organised together in the brain’s representation of that face. The team have called this map the “faciotopy”. The occipital face area is a region of the brain known to be involved in general facial processing. “Facial recognition is so fundamental to human behaviour that it makes sense that there would be a specialised area of the brain that maps features of the face,” she says. © Copyright Reed Business Information Ltd.
Laura Sanders Pain can sear memories into the brain, a new study finds. A full year after viewing a picture of a random, neutral object, people could remember it better if they had been feeling painful heat when they first saw it. “The results are fun, they are interesting and they are provocative,” says neuroscientist A. Vania Apkarian of Northwestern University in Chicago. The findings “speak to the idea that pain really engages memory.” Neuroscientists G. Elliott Wimmer and Christian Büchel of University Medical Center Hamburg-Eppendorf in Germany reported the results in a paper online at BioRxiv.org first posted December 24 and revised January 6. The findings are under review at a journal, and Wimmer declined to comment on the study until it is accepted for publication. Wimmer and Büchel recruited 31 brave souls who agreed to feel pain delivered by a heat-delivering thermode on their left forearms. Each person’s pain sensitivity was used to calibrate the amount of heat they received in the experiment, which was either not painful (a 2 on an 8-point scale) or the highest a person could endure multiple times (a full 8). While undergoing a functional MRI scan, participants looked at a series of pictures of unremarkable household objects, such as a camera, sometimes feeling pain and sometimes not. Right after seeing the images, the people took a pop quiz in which they answered whether an object was familiar. Pain didn’t influence memory right away. Right after their ordeal, participants remembered about three-quarters of the previously seen objects, regardless of whether pain was present, the researchers found. © Society for Science & the Public 2000 - 2015.
Pete Etchells Autonomous Sensory Meridian Response, or ASMR, is a curious phenomenon. Those who experience it often characterise it as a tingling sensation in the back of the head or neck, or another part of the body, in response to some sort of sensory stimulus. That stimulus could be anything, but over the past few years, a subculture has developed around YouTube videos, and their growing popularity was the focus of a video posted on the Guardian this last week. It’s well worth a watch, but I couldn’t help but feel it would have been a bit more interesting if there had been some scientific background in it. The trouble is, there isn’t actually much research on ASMR out there. To date, only one research paper has been published on the phenomenon. In March last year, Emma Barratt, a graduate student at Swansea University, and Dr Nick Davis, then a lecturer at the same institution, published the results of a survey of some 500 ASMR enthusiasts. “ASMR is interesting to me as a psychologist because it’s a bit ‘weird’” says Davis, now at Manchester Metropolitan University. “The sensations people describe are quite hard to describe, and that’s odd because people are usually quite good at describing bodily sensation. So we wanted to know if everybody’s ASMR experience is the same, and of people tend to be triggered by the same sorts of things.” The study asked a range of questions about where, when and why people watch ASMR videos, whether there was any consistency in ASMR-triggering content, as well as whether individuals felt it had any effect on their mood. There was a remarkable consistency across participants in terms of triggering content – whispering worked for the majority of people, followed by videos involving some sort of personal attention, crisp sounds, and slow movements. For the most part, participants reported that they watched ASMR videos for relaxation purposes, or to help them sleep or deal with stress. © 2016 Guardian News and Media Limited
Keyword: Pain & Touch
Link ID: 21767 - Posted: 01.09.2016
By Emily Underwood As long as she can remember, 53-year-old Rosa Sundquist has tallied the number of days per month when her head explodes with pain. The migraines started in childhood and have gotten worse as she’s grown older. Since 2008, they have incapacitated her at least 15 days per month, year-round. Head-splitting pain isn’t the worst of Sundquist’s symptoms. Nausea, vomiting, and an intense sensitivity to light, sound, and smell make it impossible for her to work—she used to be an office manager—or often even to leave her light-proofed home in Dumfries, Virginia. On the rare occasions when she does go out to dinner or a movie with her husband and two college-aged children, she wears sunglasses and noise-canceling headphones. A short trip to the grocery store can turn into a full-blown attack “on a dime,” she says. Every 10 weeks, Sundquist gets 32 bee sting–like injections of the nerve-numbing botulism toxin into her face and neck. She also visits a neurologist in Philadelphia, Pennsylvania, who gives her a continuous intravenous infusion of the anesthetic lidocaine over 7 days. The lidocaine makes Sundquist hallucinate, but it can reduce her attacks, she says—she recently counted 20 migraine days per month instead of 30. Sundquist can also sometimes ward off an attack with triptans, the only drugs specifically designed to interrupt migraines after they start. Millions of others similarly dread the onset of a migraine, although many are not afflicted as severely as Sundquist. Worldwide, migraines strike roughly 12% of people at least once per year, with women roughly three times as likely as men to have an attack. © 2016 American Association for the Advancement of Science.
By Stephani Sutherland A technique called optogenetics has transformed neuroscience during the past 10 years by allowing researchers to turn specific neurons on and off in experimental animals. By flipping these neural switches, it has provided clues about which brain pathways are involved in diseases like depression and obsessive-compulsive disorder. “Optogenetics is not just a flash in the pan,” says neuroscientist Robert Gereau of Washington University in Saint Louis. “It allows us to do experiments that were not doable before. This is a true game changer like few other techniques in science.” Since the first papers were published on optogenetics in the mid-aughts some researchers have mused about one day using optogenetics in patients, imagining the possibility of an off-switch for depression, for instance. The technique, however, would require that a patient submit to a set of highly invasive medical procedures: genetic engineering of neurons to insert molecular switches to activate or switch off cells, along with threading of an optical fiber into the brain to flip those switches. Spurred on by a set of technical advances, optogenetics pioneer Karl Deisseroth, together with other Stanford University researchers, has formed a company to pursue optogenetics trials in patients within the next several years—one of several start-ups that are now contemplating clinical trials of the technique. Circuit Therapeutics, founded in 2010, is moving forward with specific plans to treat neurological diseases. (It also partners with pharmaceutical companies to help them use optogenetics in animal research to develop novel drug targets for human diseases.) © 2016 Scientific America
Keyword: Pain & Touch
Link ID: 21758 - Posted: 01.07.2016
A woman born incapable of feeling pain has been hurt for the first time – thanks to a drug normally prescribed for opioid overdoses. She was burned with a laser, and quite liked the experience. The breakthrough may lead to powerful new ways to treat painful conditions such as arthritis. Only a handful people around the world are born unable to feel pain. These individuals can often suffer a range of injuries when they are young. Babies with the condition tend to chew their fingers, toes and lips until they bleed, and toddlers can suffer an increased range of knocks, tumbles and encounters with sharp or hot objects. The disorder is caused by a rare genetic mutation that results in a lack of ion channels that transport sodium across sensory nerves. Without these channels, known as Nav1.7 channels, nerve cells are unable to communicate pain. Researchers quickly sought to make compounds that blocked Nav1.7 channels, thinking they might be able to block pain in people without the disorder. “It looked like a fantastic drug target,” says John Wood at University College London. “Pharma companies went bananas and made lots of drugs.” But while a few compounds saw some success, none brought about the total pain loss seen in people who lack the channel naturally. © Copyright Reed Business Information Ltd.
By David Noonan The 63-year-old chief executive couldn't do his job. He had been crippled by migraine headaches throughout his adult life and was in the middle of a new string of attacks. “I have but a little moment in the morning in which I can either read, write or think,” he wrote to a friend. After that, he had to shut himself up in a dark room until night. So President Thomas Jefferson, in the early spring of 1807, during his second term in office, was incapacitated every afternoon by the most common neurological disability in the world. The co-author of the Declaration of Independence never vanquished what he called his “periodical head-ach,” although his attacks appear to have lessened after 1808. Two centuries later 36 million American migraine sufferers grapple with the pain the president felt. Like Jefferson, who often treated himself with a concoction brewed from tree bark that contained quinine, they try different therapies, ranging from heart drugs to yoga to herbal remedies. Their quest goes on because modern medicine, repeatedly baffled in attempts to find the cause of migraine, has struggled to provide reliable relief. Now a new chapter in the long and often curious history of migraine is being written. Neurologists believe they have identified a hypersensitive nerve system that triggers the pain and are in the final stages of testing medicines that soothe its overly active cells. These are the first ever drugs specifically designed to prevent the crippling headaches before they start, and they could be approved by the U.S. Food and Drug Administration next year. If they deliver on the promise they have shown in studies conducted so far, which have involved around 1,300 patients, millions of headaches may never happen. © 2015 Scientific American
Keyword: Pain & Touch
Link ID: 21662 - Posted: 11.28.2015
By Nala Rogers If you travel with a group of friends, you might delegate navigation to the person with the best sense of direction. But among homing pigeons, the leader is whoever flies the fastest—even if that pigeon has to pick up navigation skills on the job, according to a new study. To find out how the skills of individual pigeons influence flock direction, researchers tested four flocks on journeys from three different locations, each about 5 kilometers from their home loft near Oxford, U.K. At each site, the researchers tracked the pigeons during solo flights before releasing them together for several group journeys. The fastest birds surged to the front during group flights and determined when the flock turned, despite the fact that these leaders were often poor navigators during their initial solo expeditions. But on a final set of solo flights—made after the group journeys—these same leaders chose straighter routes than followers, the researchers report today in Current Biology. Apparently, being responsible for group decisions helped pigeons learn the route, say scientists, raising questions about the two-way interplay between skills and leadership. © 2015 American Association for the Advancement of Science
Ian Sample Science editor Tiny biological compasses made from clumps of protein may help scores of animals, and potentially even humans, to find their way around, researchers say. Scientists discovered the minuscule magnetic field sensors in fruit flies, but found that the same protein structures appeared in retinal cells in pigeons’ eyes. They can also form in butterfly, rat, whale and human cells. The rod-like compasses align themselves with Earth’s geomagnetic field lines, leading researchers to propose that when they move, they act on neighbouring cell structures that feed information into the nervous system to create a broader direction-sensing system. Professor Can Xie, who led the work at Peking University, said the compass might serve as a “universal mechanism for animal magnetoreception,” referring to the ability of a range of animals from butterflies and lobsters to bats and birds, to navigate with help from Earth’s magnetic field. Whether the compasses have any bearing on human navigation is unknown, but the Peking team is investigating the possibility. “Human sense of direction is complicated,” said Xie. “However, I believe that magnetic sense plays a key role in explaining why some people have a good sense of direction.” The idea that animals could sense Earth’s magnetic field was once widely dismissed, but the ability is now well established, at least among some species. The greatest mystery that remains is how the sensing is done. © 2015 Guardian News and Media Limited
Keyword: Animal Migration
Link ID: 21638 - Posted: 11.17.2015
By Virginia Morell Plunge a live crab into a pot of boiling water, and it’s likely to try to scramble out. Is the crab’s behavior simply a reflex, or is it a sign of pain? Many scientists doubt that any invertebrate (or fish) feels pain because they lack the areas in the brain associated with human pain. Others argue this is an unfair comparison, noting that despite the major differences between vertebrate and invertebrate brains, their functions (such as seeing) are much the same. To get around this problem, researchers in 2014 argued that an animal could be classified as experiencing pain if, among other things, it changes its behavior in a way that indicates it’s trying to prevent further injury, such as through increased wariness, and if it shows a physiological change, such as elevated stress hormones. To find out whether crabs meet these criteria, scientists collected 40 European shore crabs (Carcinus maenas), shown in the photo above, in Northern Ireland. They placed the animals into individual tanks, and gave half 200-millisecond electrical shocks every 10 seconds for 2 minutes in their right and left legs. The other 20 crabs served as controls. Sixteen of the shocked crabs began walking in their tanks, and four tried to climb out. None of the control crabs attempted to clamber up the walls, but 14 walked, whereas six didn’t move at all. There was, however, one big physiological difference between the 16 shocked, walking crabs and the 14 control walkers, the scientists report in today’s issue of Biology Letters: Those that received electrical jolts had almost three times the amount of lactic acid in their haemolymph, a fluid that’s analogous to the blood of vertebrates—a clear sign of stress. Thus, crabs pass the bar scientists set for showing that an animal feels pain. © 2015 American Association for the Advancement of Science.
By Arlene Karidis Several years ago, Peggy Chenoweth began having excruciating cramping in her ankle. It felt severely sprained and as if her toe were twisting to the point where it was being ripped off her foot. “The pain is right here,” she told an orthopedic surgeon, “in my ankle and foot.” But the 41-year-old Gainesville, Va., resident no longer had that ankle and foot. Her leg had been amputated below the knee after a large piece of computer equipment fell off a cart, crushed her foot and caused nerve damage. Further, she insisted that since the amputation, she could feel her missing toes move. Chenoweth’s surgeon knew exactly what was going on: phantom pain. Lynn Webster, an anesthesiologist and past president of the American Academy of Pain Medicine, explains the phenomenon: “With ‘phantom pain,’ nerves that transmitted information from the brain to the now-missing body part continue to send impulses, which relay the message of pain.” It feels as if the removed part is still there and hurting, but pain is actually in the brain. The sensation ranges from annoying itching to red-hot burning. Physicians wrote about phantom pain as early as the 1860s, but U.S. research on this condition has increased recently, spurred by the surge of amputees returning from warfare in Iraq and Afghanistan and by increasing rates of diabetes. (Since 2003, nearly 1,650 service members have lost limbs, according to the Congressional Research Service. In 2010, about 73,000 amputations were performed on diabetics in the United States, according to the Centers for Disease Control and Prevention.)
Keyword: Pain & Touch
Link ID: 21620 - Posted: 11.10.2015
By Jason G. Goldman When a monkey has the sniffles or a headache, it doesn't have the luxury of popping a few painkillers from the medicine cabinet. So how does it deal with the common colds and coughs of the wildlife world? University of Georgia ecologist Ria R. Ghai and her colleagues observed a troop of more than 100 red colobus monkeys in Uganda's Kibale National Park for four years to figure out whether the rain forest provides a Tylenol equivalent. Monkeys infected with a whipworm parasite were found to spend more time resting and less time moving, grooming and having sex. The infected monkeys also ate twice as much tree bark as their healthy counterparts even though they kept the same feeding schedules. The findings were published in September in the journal Proceedings of the Royal Society B. The fibrous snack could help literally sweep the intestinal intruder out of the simians' gastrointestinal tracts, but Ghai suspects a more convincing reason. Seven of the nine species of trees and shrubs preferred by sick monkeys have known pharmacological properties, such as antisepsis and analgesia. Thus, the monkeys could have been self-medicating, although she cannot rule out other possibilities. The sick individuals were, however, using the very same plants that local people use to treat illnesses, including infection by whipworm parasites. And that “just doesn't seem like a coincidence,” Ghai says. © 2015 Scientific American,
by Laura Sanders Babies’ minds are mysterious. Thoughts might be totally different in a brain that lacks words, and sensations might feel alien in a body so new. Are babies’ perceptions like ours, or are they completely different? Even if babies could talk, words would surely fail to convey what it’s like to experience, oh, every single thing for the first time. A recent paper offers a sliver of insight into young babies’ inner lives. The study, published October 19 in Current Biology, finds an example in which 4-month-old babies are happily oblivious to the external world. The research focuses on a perceptual trick that suckers adults and 6-month-old babies alike. When the hands are crossed, people often mistake which hand feels a touch. Let’s say your left hand (now crossed over to the right side of your body) gets a tickle. Your eyes would see a hand on the right side of your body get touched — a place usually claimed by your right hand, but now occupied by your left. Those mismatches between sight, touch and expectation can thwart you from quickly and correctly saying which hand was touched. Here’s the twist: 4-month-old babies don’t fall for this trick, Andrew Bremner of Goldsmiths, University of London and his colleagues found. In the experiment, a researcher would hold infants’ legs in either a crossed position or straight, while one of two remote-controlled buzzers taped to their feet tickled one foot. The researchers then watched which foot or leg wiggled as a result. If the buzzed foot moved, that meant that the baby got it right. © Society for Science & the Public 2000 - 2015.
David Cyranoski A Chinese neuroscientist has been sacked after reporting he had used magnetic fields to control neurons and muscle cells in nematode worms (pictured), using a protein that senses magnetism. Tsinghua University in Beijing has sacked a neuroscientist embroiled in a dispute over work on a long-sought protein that can sense magnetic fields. The university has not given a specific reason for its dismissal, however, and the scientist involved, Zhang Sheng-jia, says that he will contest their action. In September, Zhang reported in the journal Science Bulletin1 that he could manipulate neurons in worms by applying a magnetic field — a process that uses a magnetic-sensing protein. But a biophysicist at neighbouring Peking University, Xie Can, who claims to have discovered the protein’s magnetic-sensing capacity and to have a paper detailing his research under review, complained that Zhang should not have published his paper before Xie’s own work appeared. Xie said that by publishing, Zhang violated an agreement that the pair had reached — although the two scientists tell different versions about the terms of their agreement, and have different explanations of how Zhang came to be working with the protein. © 2015 Nature Publishing Group
Keyword: Animal Migration
Link ID: 21608 - Posted: 11.06.2015
By SINDYA N. BHANOO Some kinds of itching can be caused by the lightest of touches, a barely felt graze that rustles tiny hairs on the skin’s surface. This type of itch is created via a dedicated neural pathway, a new study suggests. The finding, which appears in the journal Science, could help researchers better understand chronic itchiness in conditions like eczema, diabetic neuropathy, multiple sclerosis and some cancers. The study also may help researchers determine why certain patients do not respond well to antihistamine drugs. “In the future, we may have some way to manipulate neuron activity to inhibit itching,” said Quifu Ma, a neurobiologist at Harvard University and one of the study’s authors. In the study, Dr. Ma and his colleagues inhibited neurons that express a neuropeptide known as Y or NPY in mice. When these neurons were suppressed and the mice were poked with a tiny filament, they fell into scratching fits. Normally, mice would not even respond to this sort of stimuli. “We start to see skin lesions — they don’t stop scratching,” Dr. Ma said. “It’s pretty traumatic.” The neurons only seem related to itches prompted by light touching, known as mechanically induced itches. Chemical itches, like those caused by a mosquito bite or an allergic reaction, are not transmitted by the same neurons. © 2015 The New York Times Company
Keyword: Pain & Touch
Link ID: 21593 - Posted: 11.03.2015