Chapter 8. General Principles of Sensory Processing, Touch, and Pain
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Content provided by Jeanna Bryner, LiveScience Sometimes mind-blowing sex is not cause for celebration, as some individuals experience intense headaches that explode in pain at the moment of orgasm. Until now, only two cases of these sex headaches had been reported in teenagers. Two new cases, 16-year-old boy and an 18-year-old girl, bring the odd, though not life-threatening, phenomenon to light. And doctors are hoping the sex-headache cases will make both other doctors and teens aware of the temporary disorder. "What I wonder about is whether there are many other adolescents out there who are having this problem and aren't telling anyone," said Dr. Amy Gelfand, a neurologist at the University of California, San Francisco School of Medicine. "This is why pediatricians should be aware of this, so an adolescent doesn't have to raise this issue." About 1 percent of Americans have experienced a headache as the result of sex, called a primary sex headache, in their lifetimes; about 50 percent of individuals who have primary sex headaches also get migraine headaches. Even so, their cause remains a mystery. Primary sex headaches come in two varieties — one that gradually builds up in intensity during sex and the other develops explosively at orgasm. © 2012 Discovery Communications, LLC.
by Sarah C. P. Williams The vast majority of adults have had a sore back at some point in their lives. If they're lucky, the pain subsides after a few days or weeks. But for some, whose initial injuries appear no different than the fortunate ones, back pain lasts for years. Now, researchers have discovered a difference in brain scans between the two groups of patients that appears early in the course of the pain. The finding could lead to not only ways of identifying patients who are the most at risk for long-term pain but to new treatments or preventions for chronic pain. "This is the very first time we can say that if we have two subjects who have the same type of injury for the same amount of time, we can predict who will become a chronic pain patient versus who will not," says neuroscientist Vania Apkarian of Northwestern University, Chicago, who led the new work. Over the past 2 decades, Apkarian's lab has run many studies comparing the brains of patients with chronic back pain with those of healthy people, finding differences in brain anatomy or the function of certain regions. But the study designs made it hard to sort out which brain changes were consequences of the chronic pain—or the patients' painkillers or altered lifestyles—versus those that drove the pain's chronic nature. Apkarian and colleagues have now tracked the brains of back pain patients over time rather than comparing single neural snapshots. His team began with 39 people who had experienced moderate back pain—a five or six on a self-described scale of 10—for 1 to 4 months. Over the next year, the team scanned the patients' brains four times and followed their pain. By year's end, 20 of the patients had recovered, while 19 continued to hurt, meeting the criteria for chronic pain. © 2010 American Association for the Advancement of Science
by Michael Marshall Step from a sunlit hillside into the darkness of a cave, and you immediately have a problem: you can't see. It's best to stand still for a few minutes until your eyes adjust to the dimness, otherwise you might blunder into a hibernating bear that doesn't appreciate your presence. The same thing will happen when you leave again: the brightness of the sun will dazzle you at first. That's because your eyes have two types of receptor: one set works in bright light and the other in dim light. Barring a few minutes around sunset, only one set of receptors is ever working at any given time. Peters' elephantnose fish has no such limitations. Its peculiar eyes allow it to use the two types of receptor at the same time. That could help it to spot predators as they approach through the murky water it calls home. It's electric Peters' elephantnose fish belongs to a large family called the elephantfish, all of which live in Africa. They get their name from the trunk-like protrusions on the front of their heads. But whereas the trunks of elephants are extensions of their noses, the trunks of elephantfish are extensions of their mouths. To find a Peters' elephantnose fish, you must lurk in muddy, slow-moving water. Look closely, because the fish is brown and so is the background. © Copyright Reed Business Information Ltd.
By KATIE THOMAS A research director for Pfizer was positively buoyant after reading that an important medical conference had just featured a study claiming that the new arthritis drug Celebrex was safer on the stomach than more established drugs. “They swallowed our story, hook, line and sinker,” he wrote in an e-mail to a colleague. The truth was that Celebrex was no better at protecting the stomach from serious complications than other drugs. It appeared that way only because Pfizer and its partner, Pharmacia, presented the results from the first six months of a yearlong study rather than the whole thing. The companies had a lot riding on the outcome of the study, given that Celebrex’s effect on the stomach was its principal selling point. Earlier studies had shown it was no better at relieving pain than common drugs — like ibuprofen — already on the market. The research chief’s e-mail, sent in 2000, is among thousands of pages of internal documents and depositions unsealed recently by a federal judge in a long-running securities fraud case against Pfizer. While the companies’ handling of the research was revealed a dozen years ago, the documents provide a vivid picture of the calculation made by Pfizer at the time and its efforts ever since to overcome doubts about the drug. The documents suggest that officials made a strategic decision during the early trial to be less than forthcoming about the drug’s safety. They show that executives considered attacking the trial’s design before they even knew the results and disregarded the advice of an employee and an outside consultant who had argued the companies should disclose the fact that they were using incomplete data. © 2012 The New York Times Company
By Deborah Kotz, Globe Staff I get occasional migraines, and the only good thing about the throbbing pain, nausea, and depressed mood is the sense of euphoria that comes when the pain finally lifts. For some headache sufferers, however, the pain never goes away -- for months, years, or even decades. I received a call recently from a relative whose teenage son developed a headache one day that’s lasted two months and counting, causing him to miss his final months of high school. His diagnosis: new daily persistent headache, a wastebasket term given when everything else has been ruled out. Dr. Elizabeth Loder, chief of the division of headache and pain at Brigham and Women’s/Faulkner Hospital, estimated that about 5 percent of the patients she sees at her clinic have new daily persistent headache. More commonly, patients come in with chronic migraines that result from medication overuse or because a particular drug isn’t working for them or has been prescribed at too low a dose. With new daily persistent headache, or NDPH, however, none of the array of migraine medications seems to work, even when prescribed at optimal doses. There’s no known cause such as a head injury, tumor, or seizure condition. And, unlike the typical headache sufferer, those with NDPH can name the exact day when their headache began -- even what they were doing when it started -- because they’ve never before had a problem with headaches and suddenly they’re in pain all the time with no relief in sight. © 2012 NY Times Co.
Keyword: Pain & Touch
Link ID: 16953 - Posted: 06.23.2012
By Laura Sanders In what seems like a blow for humanity, a very smart chimpanzee in Japan crushes any human challenger at a number memory game. After the numbers 1 through 9 make a split-second appearance on a computer screen, the chimp, Ayumu, gets to work. His bulky index finger flies gracefully across the screen, tapping white squares where the numbers had appeared, in order. So far, no human has topped him. Ayumu’s talent caused a stir when researchers first reported it in 2007 (SN: 12/8/2007, p. 355). Since then, the chimp’s feat has grown legendary, even earning him a starring role in a recent BBC documentary. But psychologist Nicholas Humphrey says the hype may be overblown. In an upcoming Trends in Cognitive Sciences essay, Humphrey floats a different explanation for Ayumu’s superlative performance, one that leaves humans’ memory skills unimpugned: Ayumu might have a curious brain condition that allows him to see numbers in colors. If Humphrey’s wild idea is right, the chimpanzee’s feat has nothing to do with memory. “When you get extraordinary results, you need to look for extraordinary ideas to explain them,” says Humphrey, of Darwin College at Cambridge University in England. The idea came to him after listening to two presentations at a consciousness conference in 2011. Tetsuro Matsuzawa of the Primate Research Institute at Kyoto University in Japan described his research on the memory skills of Ayumu, his mother Ai, and two other mom-offspring pairs. And neuroscientist David Eagleman of Baylor College of Medicine in Houston talked about the brain condition known as synesthesia, which causes people to attach sensory experiences to letters or numbers. A synesthete might always see the number four as blue, for instance. © Society for Science & the Public 2000 - 2012
by Helen Thomson EVER wanted to know what an invisible hand looks like? Well, it is slightly wider than a real hand, and it has shorter fingers too. For the first time, the perceived shape of a phantom limb has been measured. This should make it possible to learn more about how the brain represents what we look like. The illusion of a phantom limb can kick in after an amputation or in people missing limbs from congenital disease. The result is the sensation that the limb is, in fact, present. One theory suggests people with phantom limbs take cues from those around them to work out what their missing body part looks like. Another theory is that the sensation of an invisible limb reflects brain activity in regions that map our body in space. To clarify the sensory origins of phantom limbs, Matthew Longo at Birkbeck, University of London, and colleagues enlisted the help of CL - a 38-year-old woman born without a left arm, who periodically feels she has a phantom hand. They asked her to place her right hand beneath a board and indicate where she believed her fingertips and knuckles were. She then repeated the exercise imagining that her phantom left hand was beneath the board instead. Previous studies have shown that we tend to underestimate our finger length increasingly from thumb to little finger. This mirrors differences in the sensitivity and size of areas in the brain's somatosensory cortex that are thought to represent each digit, probably by making use of visual, mechanical and tactile feedback. The thumb is represented by a larger area of the cortex than the little finger. © Copyright Reed Business Information Ltd.
Keyword: Pain & Touch
Link ID: 16917 - Posted: 06.16.2012
By Rachel Ehrenberg Among a small number of related families from northern Pakistan, some individuals never feel pain in any part of their bodies. Scientists studying six such children found that by the age of 4, they all had injuries to the lips or tongue from repeatedly biting themselves. Bruises, cuts and broken bones were common, though fractures were diagnosed only long after the fact, when weird, painless limping or the inability to use a limb called attention to the injury. Tests showed that the pain-free children perceived sensations of warm and cold, tickling and pressure. They could feel the prick of a needle, but it didn’t hurt. Two had been scalded — painlessly — by hot liquids. And one boy who performed street theater by putting knives through his arms and walking on hot coals died after jumping off a roof on his 14th birthday. Besides their inability to feel pain, the Pakistani individuals studied by the scientists had something else in common: mutations in a gene called SCN9A. That gene encodes the instructions for a protein that forms a passageway for letting sodium ions into nerve cells. Known as Nav1.7, this particular ion channel sits on pain-sensing nerves; when a nerve is stimulated enough to warrant sending a signal to the brain, a flood of sodium ions rush into the cell. Among the pain-free Pakistanis, various mutations in SCN9A altered the blueprints for Nav1.7 in different ways, but with the same result: The channel didn’t work. Muted nerve cells could no longer alert the brain when the body encountered something painful. © Society for Science & the Public 2000 - 2012
Keyword: Pain & Touch
Link ID: 16916 - Posted: 06.16.2012
By Keith Seinfeld If you came face to face with a great whale, you might find a few surprises in its chin: Like whiskers, if you look closely at the surface. And, hidden inside the chin, lies a mysterious sensory organ, unknown to centuries of whalers and biologists. You just need the right tools to find it: a high-tech, oversized x-ray machine, and the right saws to slice it into thin pieces that fit in a microscope. A group of scientists based at the University of British Columbia, in Vancouver, BC, have done all that looking—and they discovered an organ that serves a crucial purpose and answers a longstanding mystery. Here is a graphic from the science study, published in Nature (expand the graphic to full screen to for best browsing of the information and images): How do great whales, such as humpbacks and blues, drive their jaws so wide open and then snap them shut, while swimming at full speed? “These heads are five meters long and weigh close to ten tons,” says Nick Pyenson, first author of the new study, published in the journal Nature. He’s now the curator of fossil marine mammals at the Smithsonian Institution. “What we found in the course of our investigation into the jaw and skull anatomy was this surprising structure in the chin. We had no idea what it was.” KPLU is a service of Pacific Lutheran University | ©2012
By Stephani Sutherland Amputees who experience phantom limb pain can sometimes get relief from an optical illusion. This trick involves looking in a mirror at the reflection of a healthy limb from a certain angle, which causes it to appear where the missing limb should be. Seeing the limb move freely fools the brain into relieving the pain. Now a study suggests this technique might also work for arthritis pain. Cognitive scientist Laura Case, working in the lab of Vilayanur S. Ramachandran (a member of Scientific American Mind’s board of advisers) at the University of California, San Diego, used a modified version of the mirror technique to superimpose a researcher’s healthy hand over a subject’s arthritic hand, which was painfully constricted or contorted. Subjects mimicked the slow, purposeful movements of the researcher’s hand with their own unseen hand. After experiencing the illusion of their hand moving smoothly, subjects rated their arthritis pain slightly lower than before and had an increased range of motion. The result suggests that the toxic soup of inflammatory molecules bathing an arthritic joint is not the only source of painful sensations. “The brain has learned to associate movement with pain,” says Case, who presented her results at the Society for Neuroscience meeting last November in Washington, D.C. The illusion provides the brain with a way to disconnect the sight from the sensation. Next, the group will investigate whether this type of mirror therapy might provide long-term benefits for arthritis, a condition that affects about 50 million Americans. © 2012 Scientific American,
By Fergus Walsh Medical correspondent Many patients with advanced cancer and other debilitating conditions are being "under-treated" for their pain, new guidance from the health watchdog says. NICE wants doctors in England and Wales to make more use of morphine and other strong opioids - the only adequate pain relief source for many patients. The guidelines recommend doctors discuss patients' concerns. These may include addiction, tolerance, side-effects and fears that treatment implies the final stage of life. The guidance deals with five opioids: morphine, diamorphine (heroin), buprenorphine, fentanyl and oxycodone. They come either from the opium poppy or are synthetically produced versions. NICE - the National Institute for Clinical Excellence - says "misinterpretations and misunderstanding" have surrounded the use of strong opioids for decades, which has resulted in errors "causing under-dosing and avoidable pain, or overdosing and distressing adverse effects". There is also the legacy of Dr Harold Shipman who used diamorphine to murder his victims. It has made many doctors wary of prescribing strong opioids. NICE says the aim is to improve both pain management and patient safety. BBC © 2012
Keyword: Pain & Touch
Link ID: 16834 - Posted: 05.23.2012
By Daisy Yuhas Thinking of something else is a time-honored method for coping with pain. Indeed, psychologists have demonstrated repeatedly that what you think about can modulate the pain you experience. But what's less clear is how exactly that effect plays out in the body. In a study published today in Current Biology, neuroscientists have found that distraction does more than merely divert your mind; it actually sends signals that bar pain from reaching the central nervous system. "This study connects two important fields of pain research," says lead author Christian Sprenger, a physician and neuroscientist at the University Medical Center Hamburg–Eppendorf in Germany. "There are many studies describing the sensitization processes of the spinal cord. On the other hand, it is well known that certain psychological factors are good predictors of the development of pain." Sprenger and his colleagues told 20 male volunteers they would be participating in an experiment that would study concentration and memory. Each subject, while undergoing functional magnetic resonance imaging (fMRI) to map their neural activity, used a computer screen to take a memory test called an "n-back test." In such a test, subjects recall a specific letter either one or two letters back from the end of a series. As initial sessions confirmed, remembering a letter two-back is more challenging than a letter one-back. Researchers gave volunteers either the one- or two-back test so that they could study the nervous system under two levels of cognitive load. © 2012 Scientific American,
DULL fingers? Blame your genes. It has just been discovered that sensitivity to touch is heritable, and apparently linked to hearing as well. Gary Lewin and colleagues at the Max Delbrück Center for Molecular Medicine in Berlin, Germany, measured touch in 100 healthy pairs of fraternal and identical twins. They tested finger sensitivity in two ways: by response to a high-frequency vibration and the ability to identify the orientation of very fine grating. Lewin's team found that up to 50 per cent of the variation in sensitivity to touch was genetically determined. Audio tests also showed that those with good hearing were more likely to have sensitive touch. The link between the two is logical, as both touch and hearing rely on sensory cells that detect mechanical forces. Next the researchers studied touch sensitivity in students with congenital deafness. They found that 1 in 5 also had impaired touch, indicating that some genes causing deafness may also dull the sense of touch. When they looked at a subset of individuals who were deaf and blind due to Usher syndrome, they found that mutations in a single gene, USH2A, caused both the disease and reduced sensitivity to touch (PLoS Biology, DOI: 10.1371/journal.pbio.1001318). The next step is to try to identify more genes that affect our sense of touch. "There are many more genes than just the one we found," says Lewin, adding that finding them "will hopefully show us more about the biology of touch". © Copyright Reed Business Information Ltd.
By Deborah Kotz, Globe Staff Most people who suffer regularly from debilitating migraine headaches don’t get the appropriate treatment to prevent them, according to new guidelines issued earlier this week from the American Academy of Neurology. And a disappointing study published Tuesday in the Journal of the American Medical Association found that injections of Botulinum toxin A, or Botox, had smaller-than-expected benefits for those with chronic, near-daily headaches, working only modestly better than a placebo. “There are several reasons why patients aren’t being properly treated,” said Dr. Stephen Silberstein, a neurologist at Thomas Jefferson University in Philadelphia who led the guideline committee. “They may be misdiagnosed with tension or sinus headaches or may be using a medication that doesn’t work or is prescribed at too low a dose.” (Five of the six guideline authors, including Silberstein, disclosed that they had previously served on advisory boards or accepted honoraria or consulting fees from manufacturers of drugs used to treat migraines.) Migraines -- which are frequently accompanied by nausea, vomiting, visual disturbances or aura, and sensitivity to light -- affect about 1 in 10 Americans and can be triggered by certain foods, lack of sleep, stress, jet lag, fasting, and hormonal changes during a woman’s menstrual cycle. Nearly 40 percent of migraine sufferers have at least four or five headaches a month, and a smaller percentage have “chronic migraines” defined as having pain at least 15 days a month. Women are also more likely to get them than men. © 2012 NY Times Co.
Keyword: Pain & Touch
Link ID: 16726 - Posted: 04.30.2012
By Linda Carroll It sounds like the stuff of nightmares: A man wakes up in the middle of a surgery and can’t speak, or even twitch a muscle. But that’s exactly what a young man from Sweden says happened to him. The 22-year-old Swede was in the middle of surgery for a collapsed lung when he woke up to hear doctors moving around and operating on him, the Swedish newspaper The Local reported. “It was terrible, my worst nightmare,” he told the Sweden’s English-language paper. The operation was in March and the patient, Simon Rosenqvist, recently filed a complaint with Sweden’s National Board of Health and Welfare, according to a report in the New York Daily News. “My brain kept telling me over and over ‘say your name, say something, do something, wiggle your toes,’ but I was completely incapable of saying something or moving my body at all,’” Rosenqvist wrote in his report. Rosenqvist told The Local that he was awake for some 30 to 35 minutes of the 50 minute procedure and that he was in serious pain and was very angry at the end of the procedure. Experts say that although it’s rare, patients do sometimes wake up during surgeries even when they’ve been given general anesthesia. Overall, this happens in 1 to 2 out of 1,000 procedures, says Dr. Lee A. Fleisher, a professor and chair of anesthesiology and critical care at the Perelman School of Medicine at the University of Pennsylvania. © 2012 msnbc.com
By Jason Palmer Science and technology reporter, BBC News Researchers have spotted a group of 53 cells within pigeons' brains that respond to the direction and strength of the Earth's magnetic field. The question of how birds navigate using - among other signals - magnetic fields is the subject of much debate. These new "GPS neurons" seem to show how magnetic information is represented in birds' brains. However, the study reported by Science leaves open the question of how they actually sense the magnetic field. David Dickman of the Baylor College of Medicine in the US set up an experiment in which pigeons were held in place, while the magnetic field around them was varied in its strength and direction. Prof Dickman and his colleague Le-Qing Wu believed that the 53 neurons were candidates for sensors, so they measured the electrical signals from each one as the field was changed. Every neuron had its own characteristic response to the magnetic field, with each giving a sort of 3-D compass reading along the familiar north-south directions as well as pointing directly upward or downward. BBC © 2012
Keyword: Animal Migration
Link ID: 16720 - Posted: 04.28.2012
By NICHOLAS BAKALAR A randomized trial of steroid injections for back pain has shown that they are no more effective than a placebo. Because the long-term benefits of surgery remain unproven and pain medicines often have serious side effects, doctors have increasingly turned to steroid injections to treat lumbosacral radiculopathy, a common cause of back pain. The condition stems from damage to the discs between the vertebrae that often leads to sciatica, numbness or pain in the legs. Researchers tested 84 adults with back pain of less than six months’ duration, dividing them into three groups. They received either steroids, etanercept (an arthritis medicine) or an inactive saline solution in two injections given two weeks apart. At the end of one month, they were assessed for pain. Leg and back pain decreased in all three groups, but there were no statistically significant differences among them. The researchers conclude that steroids may provide some short-term analgesic effect, but that the improvement in all of the patients was mainly due to normal healing. The lead author, Dr. Steven P. Cohen, an associate professor of anesthesiology at Johns Hopkins, was disappointed with the results but said that he still hopes drugs like etanercept might someday be proven effective. But for now, he said, “the strongest evidence for back pain relief is with exercise.” Copyright 2012 The New York Times Company
Keyword: Pain & Touch
Link ID: 16719 - Posted: 04.28.2012
By Tina Hesman Saey A new treatment mimics acupuncture’s the pain-blocking mechanism of acupuncture but offers longer-lasting pain relief, at least in mice. Injections of an enzyme called PAP into an acupuncture point behind the knees of mice relieved pain caused by inflammation for up to six days, Julie Hurt and Mark Zylka of the University of North Carolina at Chapel Hill report online April 23 in Molecular Pain. That’s almost 100 times longer than pain relief from acupuncture, which typically lasts about 1½ hours. Long-lasting pain relief “is truly important, clinically,” says Maiken Nedergaard, a neuroscientist at the University of Rochester in New York. She and colleagues previously demonstrated that inserting and manipulating acupuncture needles causes the body to release a chemical called adenosine. Adenosine acts as a local anesthetic to slow down pain messages sent to the brain, she says. “The beauty of Mark’s study is that it takes advantage of the molecular mechanism of acupuncture and improves upon it,” Nedergaard says. Zylka had already been studying PAP, which stands for prostatic acid phosphatase, when Nedergaard’s research on the release of adenosine during acupuncture was published. The study gave him the idea that boosting adenosine at acupuncture points, which are located where nerves contact muscle, could be a localized way to treat pain. Adenosine lasts only minutes in the human body, so injections of the chemical itself were not an option. © Society for Science & the Public 2000 - 2012
Keyword: Pain & Touch
Link ID: 16718 - Posted: 04.28.2012
Jeannine Stamatakis We often feel rejected when faced with the popular clique at school or the office bully. Learning to protect yourself against such social assaults can prove quite difficult, but new research shows a common painkiller may reduce the impact of these upsetting interactions. A recent study published in the journal Psychological Science suggests that acetaminophen, the active ingredient in Tylenol, may buffer against social pain. The lead investigator, psychologist C. Nathan DeWall of the University of Kentucky, hypothesized that the neural overlap between physical and emotional pain might enable a drug designed to alleviate physical pain to cushion emotional pain. In one experiment, DeWall and his team examined 62 healthy volunteers who took 1,000 milligrams of either acetaminophen or a placebo daily for three weeks. In the evening the participants described to what extent they experienced social disappointment or felt upset during the day using a version of the Hurt Feelings Scale, a social pain measurement tool. Participants who took acetaminophen reported fewer hurt feelings and more resilience to social pain than the subjects receiving the placebo. In a second experiment, the investigators looked at 25 healthy volunteers who ingested 2,000 milligrams of either acetaminophen or a placebo every day over the course of three weeks. During the investigation, subjects played a computer game geared to evoke feelings of social rejection while lying in a functional MRI machine. The resulting brain scans revealed that the participants who received the drug exhibited reduced neural responses to social rejection in brain regions associated with interpreting emotional and physical pain. In contrast, the regions associated with physical pain became more active in the placebo subjects when they were rebuffed in the video game. Overall, these results indicate that acetaminophen may decrease self-reported social pain over time. © 2012 Scientific American
By Katherine Harmon Eager eaters know that gulping a Slurpee or inhaling a sundae can cause that brief seizing sensation known in the not-so-technical literature as “brain freeze” or “ice cream headache.” Just what causes this common cautionary condition has remained mysterious to sufferers and scientists alike (not that the two categories need remain mutually exclusive). A new study, presented April 22 at the Experimental Biology 2012 annual meeting in San Diego, proposes a probable answer. And it’s one that could also suggest new treatments for more serious conditions, such as migraines and traumatic brain injuries. The findings were not easy to obtain and required 17 courageous volunteers to submit themselves to brain freeze. These healthy, self-sacrificing adults took sips of extra-cold water through a straw, which they aimed at the roof of their mouths. While their lips were sipping away, subjects’ brains were monitored via transcranial Doppler, which can sense changes in arterial blood flow. As soon as volunteers achieved and then emerged from a freeze, they alerted the researchers. Researchers then were able to pinpoint changes in brain activity at those precise moments, comparing those signals with measurements taken under control conditions when subject sipped on room temperature water. © 2012 Scientific American
Keyword: Pain & Touch
Link ID: 16694 - Posted: 04.23.2012