Chapter 8. General Principles of Sensory Processing, Touch, and Pain
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By Erica Westly Millions of patients benefit from opioids such as morphine and codeine, but the pain relief they provide often comes with intense itching. In some cases, the irritation is so bad that patients will opt to cut back on painkillers. Now a study in the October 14 issue of Cell has found a possible explanation—the first step to creating drugs that will not make patients choose between experiencing itchiness and pain. Until recently, many experts had assumed that itching from opioids was unavoidable because it is a common side effect of drugs that interact with the nervous system. The brain has four main types of receptors that respond to opioids, and every type has many structural variants, called isoforms. Most opioids are nonspecific, which means they bind to all the isoforms. This leads to powerful pain relief, although scientists do not know exactly why. In the new research, a team led by itch researcher Zhou-Feng Chen of Washington University in St. Louis showed that only one opioid receptor isoform is responsible for itching—and it is not involved in pain. Mice bred to have fewer of these particular receptors did not scratch themselves when given an opioid, but they did exhibit the telltale mouse signs of pain relief, such as less flinching when researchers flicked their tails. Now that scientists know that pain relief and itching can be decoupled, they will try to make itch-free opioid drugs a reality. © 2012 Scientific American
Keyword: Pain & Touch
Link ID: 16608 - Posted: 04.04.2012
Roger Dobson , Sanjeela Pahl It's bad enough that they suffer second-degree burns at the drop of a sunhat and hurt feelings from a barrage of barbs aimed at their fiery heads. Now it seems nature might have added injury to the insults heaped on redheads, by making them extra sensitive to physical pain. Researchers at Southampton University Hospital are carrying out trials this year to discover whether pale-skinned patients who share their hair colour with Elizabeth I may require more anaesthetic than the rest of the population. The results should either confirm or disprove previous research in the United States suggesting that redheads are indeed more susceptible to pain. Red hair results from variants of a gene that plays a key role in human hair and skin colour. The same gene is involved in the production of endorphins, the body's natural painkillers. The Southampton study aims to find out whether this could explain redheads' apparently heightened sensitivity. In the trials, due to end in September, volunteers aged over 30 with red hair are anaesthetised and subjected to electrical charges through their thigh. Their reactions will be compared with those of a group of men and women with brown or black hair. If it turns out that red-haired people do feel more pain, it will help to explain previous research showing they are more fearful than other groups about visiting the dentist. An American study found that redheads were more anxious about dental treatment and more than twice as likely to avoid it. A second study by the same researchers found that women with red hair needed 19 per cent more painkiller to stop them flinching from unpleasant stimulation than women with dark hair. "Redheads experience more pain from a given stimulus and therefore require more anaesthesia to alleviate that pain," said Dr Edwin Liem, who led the study at Louisville University. © independent.co.uk
By Sandra G. Boodman, Driving south on the Baltimore-Washington Parkway bound for his Adams Morgan home in June 2009, Michael Herndon struggled to cope with the implications of what the doctor had just told him. For months Herndon had tried to find out why the headache he developed on Nov. 15, 2008 — he remembered the exact date — had not gone away. The 41-year-old had consulted neurologists and ear, nose and throat specialists as well as an allergist and ophthalmologist, but none of them had figured out what was causing his pain. “I was starting to hit a mental and physical wall,” recalled Herndon, a consumer outreach specialist at the Commodity Futures Trading Commission. “I’d been chasing this for more than six months. No one could tell me what it was. I just remember thinking, ‘How am I going to be able to function if it never goes away?’ ” He had taken multiple courses of antibiotics and corticosteroids as well as over-the-counter pain relievers, and he had even undergone sinus surgery, all to no avail. Doctors had ruled out a brain tumor and other ailments but had no idea why his head, and increasingly his nose, still hurt. A month later, Herndon learned the name of his disorder. It would be another year before he found effective help to cope with his chronic, and still largely inexplicable, head pain. © 1996-2012 The Washington Post
Keyword: Pain & Touch
Link ID: 16572 - Posted: 03.26.2012
Scientists are now one step closer to developing anti-addiction medications, thanks to new research that provides a better understanding of the properties of the only member of the opioid receptor family whose activation counteracts the rewarding effects of addictive drugs. The study was supported by the National Institute on Drug Abuse (NIDA), the National Institute of General Medical Sciences and the National Institute of Mental Health, all components of the National Institutes of Health. Unlike the other opioid receptor subtypes, the kappa opioid receptor (KOR) is not associated with the development of physical dependence or the abuse potential of opiate drugs (e.g., heroin, morphine). Therefore, medications that act at the KOR could have broad therapeutic potential for addressing addiction, pain, as well as other mental disorders. The leading compound in this context is JDTic because its specific binding to the KOR has been shown to reduce relapse to cocaine seeking in animal models. JDTic is currently in clinical trials to assess its safety and tolerability in humans. In this new study, scientists produced a high resolution three-dimensional image of JDTic bound to the human KOR. By mapping all the points of contact between JDTic and the human KOR, researchers were able to see how the two fit together. The emerging picture reveals critical new information that helps explain why JDTic binds so tightly and specifically to this particular opioid receptor. This advance opens the door to the development of compounds targeting the KOR with improved therapeutic profiles, including that of non-addictive pain medications. The study by Wu et al., can be found at: www.nature.com. For information on prescription drug abuse, go to: www.drugabuse.gov/drugs-abuse/prescription-medications.
By Devin Powell Proteins turned on by opium and similar substances in the body have now been caught in action. Two new snapshots show how cellular proteins lasso molecules in the opium family, revealing the 3-D structure of such pairings for the first time. The work represents a major step toward designing more specific analgesics and other drugs that lack opioids’ nasty side effects, two teams of researchers report online March 21 in Nature. “Both are landmark studies,” says Gavril Pasternak, a neuroscientist who designs opioids at the Sloan-Kettering Institute in New York City, and who wasn’t involved in either study. “These structures will quickly be utilized with goal of developing nonaddicting painkillers and new ways to combat drug abuse.” Proteins that respond to opium and opiumlike molecules protrude from the surfaces of cells throughout the brain, spinal cord and gut. The body’s own hormones and brain chemicals such as endorphins can bind to these proteins to turn the molecular switches on and off to control pain, regulate breathing and change mood. Many of today’s most powerful painkillers work by switching on one of these proteins, called the mu opioid receptor. But the relief this provides comes at a price. Derivatives of opium, such as morphine and codeine, are addictive and can cause breathing problems and constipation. © Society for Science & the Public 2000 - 2012
By Maia Szalavitz One of the hardest challenges for families facing autism is the problem of touch. Often, autistic children resist hugging and other types of physical contact, causing distress all around. Now, a new study offers insight into why some people shrug off physical touches and how families affected by autism may learn to share hugs without overwhelming an autistic child’s senses. Yale neuroscientists recruited 19 young adults and imaged their brain activity as a researcher lightly brushed them on the forearm with a soft watercolor paintbrush. In some cases, the brushing was quick, and in others slow: prior studies have shown that most people like slow brushing and perceive it as affectionate contact, while the faster version is felt as less pleasant and more tickle-like. None of the participants in the current study had autism, but the researchers evaluated them for autistic traits — things like a preference for sameness, order and systems, rather than social interaction. They found that participants with the highest levels of autistic traits had a lower response in key social brain regions — the superior temporal sulcus (STS) and orbitofrontal cortex (OFC) — to the slow brushing. According to Martha Kaiser, senior author of the study and associate director of the Child Neuroscience Laboratory at the Yale Child Study Center, the STS is a critical hub of the social brain. “This region is important for perceiving the people around us, for visual social stimuli and for perceiving social versus nonsocial sounds,” she says. © 2012 Time Inc.
By Jason G. Goldman The more scientists discover about desert ants, the more impressive they seem. Decades of research have established that ants use path integration – an innate form of mental trigonometry – in order to navigate the visually featureless environments that are the salt pans of Tunisia. They do this by calibrating a mental clock based on the motion of the sun, which they combine with a “mental chronometer,” a step counter. Together, this allows a desert ant to estimate both the distance and direction they must travel to make it back home. It also turns out that they represent their location in three dimensions; they account for hills and valleys in their mental calculations. But desert ants are able to use other cues as well to help them get home. Variations in soil composition, breaks in the salt, and dead plants, all contribute to the creation of an odor gradient across the landscape. Ants who have had one or both of their antennae removed were less successful in some navigation tasks, suggesting that they are able to use smell in guiding their navigation as well. And since they needed both antennae to perform optimally, it seems as if ants smell in stereo. New research just published in the journal PLoS ONE has added ground vibrations and magnetic fields to the list of cues desert ants can possibly use as aids to navigation. For this experiment, rather than using Cataglyphis fortis, the ants of Tunisia, they used a related species, Cataglyphis noda, of Cirali, Turkey. © 2012 Scientific American
Powerful but misleading marketing that for years pushed the highly addictive painkiller OxyContin has left potentially tens of thousands of Canadians with the burden of addiction, critics claim. OxyContin helped transform the medical landscape after it was introduced in the late 1990s, touted by doctors and pitched as a less addictive alternative to other opioids. Cancer patients and others suffering from chronic pain considered the pill — twice as strong as morphine — to be a godsend. But the CBC's The Fifth Estate found that as soon as several provinces dropped OxyContin this year as a publicly funded medication and it vanished from shelves, the drug once praised as a blessing became a curse for some addicts. Watch The Fifth Estate Unknown to some doctors and pharmacists when OxyContin debuted were its extremely addictive properties, a fact that may have contributed to its becoming an international best-selling painkiller. OxyContin was taken off the Canadian market this month. To replace the drug, Purdue Pharma, the company that makes OxyContin, began manufacturing a new formulation called OxyNeo. The replacement pill can't be crushed or liquefied and has thus been promoted as less prone to abuse. There are otherwise no clinical differences between the two brand names. © CBC 2012
By Richard Black Environment correspondent, BBC News The spectacular snouts of sawfish are revealed as complete hunting weapons, sensing prey and killing them. The saws, which can grow more than a metre long in some species, have previously been identified as able to sense prey by their electric fields. Now, researchers have filmed the fish impaling prey on the teeth of the saws. They suggest in Current Biology that sawfish are more active hunters than previously thought, which could help in their much-needed conservation. All seven species are listed as Critically Endangered on the internationally-recognised Red List. The researchers, mainly based in Australia, suggest sawfish may be unique among their peers in possessing a snout, or rostrum, that works both as a sensory organ and a hunting weapon. "I like to call it an antenna and a weapon, because that's what it is - it helps them to find the prey, but then also to kill it," said Barbara Wueringer from the University of Queensland, who led the research team. The research was done using captive sawfish. BBC © 2012
By Lena Groeger Our five senses–sight, hearing, touch, taste and smell–seem to operate independently, as five distinct modes of perceiving the world. In reality, however, they collaborate closely to enable the mind to better understand its surroundings. We can become aware of this collaboration under special circumstances. In some cases, a sense may covertly influence the one we think is dominant. When visual information clashes with that from sound, sensory crosstalk can cause what we see to alter what we hear. When one sense drops out, another can pick up the slack. For instance, people who are blind can train their hearing to play double duty. Those who are both blind and deaf can make touch step in—to say, help them interpret speech. For a few individuals with a condition called synesthesia, the senses collide dramatically to form a kaleidoscope world in which chicken tastes like triangles, a symphony smells of baked bread or words bask in a halo of red, green or purple. (For more on how the senses can cross each other and into unusual territory, see “Edges of Perception,” by Ariel Bleicher, Scientific American Mind, March/April 2012.) Our senses must also regularly meet and greet in the brain to provide accurate impressions of the world. Our ability to perceive the emotions of others relies on combinations of cues from sounds, sights and even smells (see “I Know How You Feel,” by Janina Seubert and Christina Regenbogen, Scientific American Mind, March/April 2012). Perceptual systems, particularly smell, connect with memory and emotion centers to enable sensory cues to trigger feelings and recollections, and to be incorporated within them. © 2012 Scientific American
By Maia Szalavitz Sticks and stones may break your bones, but names can hurt just as much. Indeed, according to converging evidence reported in a new review in Current Directions in Psychological Science, physical and social pain are processed in some of the same regions of the brain. Naomi Eisenberger, co-director of the Social Cognitive Neuroscience Lab at UCLA, published the first brain-imaging paper revealing the overlap in 2003. She had been studying participants’ reactions to being rejected by other players (actually just a computer opponent) in a video game. “The first time we noticed the similarity, I was analyzing data next to a colleague of mine who was analyzing data on physical pain in irritable bowel syndrome,” she says. “We noticed similarities in the way that the neural data looked.” Physical pain has two components, Eisenberger explains: sensory and emotional. The sensory part of physical pain is mapped in the brain depending on which part of the body is hurt, but the emotional component — how distressing your brain determines the pain to be — is registered in the dorsal anterior cingulate cortex (dACC). That’s also where the sting of social pain is processed. “The affective component, which tells you more how much the pain is bothering [you], how much suffering it is causing — that experience seems to be more localized to the dACC and the anterior insula,” Eisenberger says. © 2012 Time Inc.
Erin Allday For a few months after she was born, Ashley Chase cried inconsolably every day, for hours at a time. Her mother didn't call it colic at the time, but now she wonders. There was never any obvious cause for Ashley's distress, and she was an otherwise happy and healthy baby. The fussiness eventually went away without cause, as is often the case with colicky babies. And perhaps most intriguing - Ashley, now 14, suffers migraines. Just like her mom. Colic, it turns out, may be closely connected to migraines, say researchers at UCSF. A study released this week found that moms who suffer migraines are 2 1/2 times more likely to have colicky infants than those who don't. "It kind of makes sense," said Ashley, a patient at the UCSF Headache Center who lives in Pleasanton with her parents. "Everything's 'more' when you have a migraine. Everything's too loud, everything's too much. I imagine it would feel the same for a baby." The UCSF research, which will be formally presented at an American Academy of Neurology meeting in New Orleans next month, could shed light on two poorly understood and difficult-to-treat conditions: migraines and colic. Earlier research has hinted at a connection between the two conditions, but the UCSF study is the most convincing so far, neurologists and headache experts said. The study looked at 154 mothers of infants and found that more than 28 percent of women who suffered migraines had colicky babies, compared with 11 percent of women without migraines. © 2012 Hearst Communications Inc.
By Linda Thrasybule Women who have had migraine headaches are more likely than other women to develop depression, according to a new finding based on 14 years of health data. The findings are to be presented today (Feb. 22) in New Orleans at the annual meeting of the American Academy of Neurology. "This study confirms it: Having migraines increases your risk of depression, which we've suspected for many years," said Dr. Timothy A. Collins, a Duke University Medical Center neurologist who was not involved with the research. Collins specializes in headache treatment. Researchers looked at more than 36,000 women enrolled in the Women's Health Study, and found that after 14 years, depression had developed among those who suffered from migraines at a higher rate than among those who didn't get the throbbing headaches. Study researcher Dr. Tobias Kurth, an epidemiologist at Brigham and Women's Hospital in Boston, said women who have migraines shouldn't assume they'll develop depression, but should be aware of the link to the increased risk. Migraines can last four to 72 hours and are often accompanied by pulsating pain, nausea, vomiting and sensitivity to light and sound. One in 10 Americans has migraines, according to the National Institute of Neurological Disorders and Stroke, but they affect women three times more often than men. © 2012 msnbc.com
By Gary Stix One of brain researchers’ closest brushes with science fiction in the last 10 years came with the discovery of a chemical that could completely wipe out memory, a molecule that evoked a real-life version of the scenario depicted in the film Eternal Sunshine of the Spotless Mind, in which a couple undertakes a procedure to erase their memory of each other when the relationship falls apart. Fortunately, the artificial amnesia occurred only in laboratory rats. But the experiment raised an obvious question: What would anyone do with a drug that essentially reformats your mental hard drive? Who would be interested besides a neurotic Woody Allen trying to reboot his life, or a sadistic Josef Mengele type attempting to conduct the kind of scientific experiment that would be judged a war crime at The Hague? A group of researchers have now come up with a more pragmatic answer to this question than incorporating the memory-erasing agent as a plot device in a cyberpunk novel Neuroscientists at McGill University and collaborators have just reported in Molecular Pain that the chemical with the evocative acronym ZIP can selectively wipe out the nervous system’s “memory” of the chronic aches and pains that plague about one in four North Americans, apparently leaving other memories intact. © 2012 Scientific American,
An Ontario First Nations leader says a catastrophe is looming with the decision to stop manufacturing the drug OxyContin. Nishnawbe Aski Nation Chief Stan Beardy says thousands of residents of Ontario reserves are addicted to the drug, which is up to twice as strong as morphine. The organization, which represents 49 First Nation communities in northern Ontario, estimates close to half its members are addicted to OxyContin. Health Canada says when the pill is chewed or crushed, then injected or inhaled, it produces a "heroin-like euphoria." The company that produces OxyContin will stop manufacturing the drug in Canada at the end of the month. Purdue Pharma Canada will replace OxyContin with a new formulation called OxyNEO, which is formulated to make abuse more difficult. Beardy says addicts will go into withdrawal, and that scares him. Benedikt Fischer of the Centre for Applied Mental Health and Addictions at B.C.'s Simon Fraser University says there will be a lot of sick people. He says without treatment to help deal with the addiction, a public-health catastrophe is imminent. Copyright © CBC 2012
By Rachel Ehrenberg When it comes to feeling good vibrations, the eyes have it. Experiments in mice and humans show that a protein important for eye development also plays a role in sensing vibrations. An international team has found that mice lacking a protein called c-Maf have deformed Pacinian corpuscles (shown here in a mouse’s leg), the vibration-detectors that surround mouse bones. People have Pacinian corpuscles in their palms and fingertips. When the researchers tested four people with eye cataracts due to malfunctioning c-Maf, those individuals had a hard time detecting high-frequency vibrations, the scientists report online February 16 in Science. © Society for Science & the Public 2000 - 2012
by Gisela Telis The right turn of phrase can activate the brain's sensory centers, a new study suggests. Researchers have found that textural metaphors—phrases such as "soft-hearted"—turn on a part of the brain that's important to the sense of touch. The result may help resolve a long-standing controversy over how the brain understands metaphors and may offer scientists a new way to study how different brain regions communicate. Scientists have disagreed for decades about how the brain processes metaphors, those figures of speech that liken one thing to another without using "like" or "as." One camp claims that when we hear a metaphor—a friend tells us she's had a rough day—we understand the expression only because we've heard it so many times. The brain learns that "rough" means both "abrasive" and "bad," this camp says, and it toggles from one definition to the other. The other camp claims the brain calls on sensory experiences, such as what roughness feels like, to comprehend the metaphor. Researchers from both camps have scanned the brain for signs of sensory activity triggered by metaphors, but these past studies, which tested a variety of metaphors without targeting specific senses or regions of the brain, have come up dry. Neurologist Krish Sathian of Emory University in Atlanta wondered whether using metaphors specific to only one of the senses might be a better strategy. He and his colleagues settled on touch and asked seven college students to distinguish between different textures while their brains were scanned using functional magnetic resonance imaging. This enabled them to map the brain regions each subject used to feel and classify textures. Then they scanned the subjects' brains again as they listened to a torrent of textural metaphors and their literal counterparts: "he is wet behind the ears" versus "he is naïve," for example, or "it was a hairy situation" versus "it was a precarious situation." © 2010 American Association for the Advancement of Science
by Sarah C. P. Williams What do you get when you combine a monkey's brain with the whiskers of a rat? A robotic rodent that can sense its environment almost as well as the real thing. The new rat-bot could lead to the development of robots that can feel their way through earthquake rubble and could provide clues to how live rats analyze sensory information from their whiskers. Although recent research has helped scientists understand what information whiskers send to the brains of rodents, deciphering how rats and mice interpret that sensory information has been trickier. Previous models assumed that rodents looked at whisker movement patterns and vibrations over a set duration of time and that their brain made a decision, based on the whole of the data, about the most likely surface the whiskers were touching. If the overall data best matched the known patterns for a hard vinyl floor, for example, the rats would conclude that's the surface that they're on. But different robots created using this model of reasoning were only 50% to 80% accurate at guessing the floor underneath them after 0.4 seconds of exposure, multiple studies have found. Computational neuroscientist Nathan Lepora of the University of Sheffield in the United Kingdom and his team thought that a model of information processing recently discovered in monkeys might help the robots make better judgments on floor type. The primates don't use a single piece of evidence to make a decision about what they're seeing. Rather, their brains rely on an accumulation of data. When the monkeys watch screens of randomly moving dots, for example, different neurons sense each direction of movement: up, down, left, and right. As dots on the screen flit about, more neurons of each type begin to fire, accumulating a total activity level for the group of neurons. Once, say, the "up" neurons reach a specific threshold, they pass on the message that the dots are moving in that direction. © 2010 American Association for the Advancement of Science.
Erin Allday, Chronicle Staff Writer A Stanford study sheds new light on the old cliche about women having a higher tolerance for pain than men - according to tens of thousands of electronic patient records, women tend to report much more severe pain than men, no matter the source of the pain. The study being released today found that when asked to rate their pain on a scale of 0 to 10 - with 0 being no pain at all, and 10 being the worst pain imaginable - women on average scored their pain 20 percent more intense than men. The results held up across a wide variety of diseases and injuries, including back and neck pain, digestive disorders, sinus infections, and even ankle strains and sprains. In almost every category researchers looked at, women reported more pain than men. "We may have to adjust our thinking about how men and women report their pain. The killer question is: Do women actually feel more pain than men?" said Dr. Atul Butte, lead author of the study, which was published in the Journal of Pain. "That may be more philosophy than anything - how can we tell that for sure?" Of course, the fact that women report more pain overall doesn't necessarily mean they have more or less tolerance to pain than men, Butte said, adding that his results have been the source of some lighthearted debate with his wife. The study doesn't explain the reason for the difference, and researchers say it could include social, psychological or biological factors. Men may be more reluctant to confess intense pain to a female nurse, for example. Women are more likely than men to suffer from depression and anxiety, two psychological conditions that can increase susceptibility to pain. © 2012 Hearst Communications Inc.
Katharine Sanderson An uncharted trawl through thousands of small molecules involved in the body's metabolism may have uncovered a potential route to treating pain caused by nerve damage. Neuropathic pain is a widespread and distressing condition, and is notoriously difficult to treat. So Gary Siuzdak, a chemist and molecular biologist at the Scripps Research Institute in La Jolla, California, and his team decided to take an unusual route to finding a therapy. Their results are published today in Nature Chemical Biology1. They took rats with surgically damaged paws, who were consequently suffering from neuropathic pain, and instead of analysing changes in gene expression and proteins in the animals, focused on metabolites – the biochemical intermediates and end-products of bodily processes such as respiration and the synthesis and breakdown of molecules. The science that looks at the body's metabolite composition is known as metabolomics. Using mass spectrometry, which can detect many different chemicals simultaneously, the researchers were able to identify the metabolites present in these animals 21 days after surgery. The team analysed samples of the injured rats’ blood plasma, of tissue near the injured paw, and of tissue from different areas of the spinal column, and compared the metabolites present with that of the same site in healthy rats. One particular area differed markedly between the two cases: the dorsal horn in the spinal column. © 2012 Nature Publishing Group,
Keyword: Pain & Touch
Link ID: 16286 - Posted: 01.23.2012