Chapter 8. General Principles of Sensory Processing, Touch, and Pain

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By PERRI KLASS, M.D. My patient was missing a lot of middle school because of headaches. Her physical exam was completely normal, and the symptoms sounded like migraine — she had a throbbing sensation on both sides of her head, was more comfortable when the room was dark, and felt much better if she took ibuprofen. I asked her to keep a “headache diary,” noting when the headaches came, how long they lasted, what made them better or worse. Instead, that evening she and her mother went to the emergency room, where a head CT scan was done. The scan was normal, the diagnosis migraine, and mother and daughter felt better. They had been worried the girl might have had a brain tumor. Headaches are common in children, interfering with school, with activities, with life in general. Many children get migraines, even some too young to describe their symptoms: Sometimes they hit themselves in the head in reaction to the pain. Other children get “tension-type” headaches, sometimes related to muscle tightness or to stress. Children’s headaches can be related to ailments, from allergies to ear infections to sinus problems, and most of the time they don’t indicate a dangerous illness. But for many parents, the shadow of a terrible diagnosis lurks in the corner of the darkened room where a headachy child is lying with a cool cloth on her brow. Sometimes, children with headaches need neuroimaging — brain CTs or M.R.I.’s. But recently several large studies have raised concerns about CT scans done on children because the radiation from these scans can increase the risk of eventually developing cancer, though that overall risk is still very small. Copyright 2013 The New York Times Company

Keyword: Pain & Touch
Link ID: 18360 - Posted: 07.09.2013

Oxytocin, the naturally occuring human hormone linked to bonding with a newborn and romantic partner, could also help improve mood after rejection, a laboratory study suggests. When scientists in Montreal gave 100 students either oxytocin or a placebo through a nose spray and then tried to snub them in a conversation, feelings of trust were higher in the hormone group. But the hormone had no effect among those who weren't emotionally charged up by the social rejection of having researchers posing as students disagree, interrupt or ignore them. "Instead of the traditional 'fight or flight' response to social conflict where people get revved up to respond to a challenge or run away from it, oxytocin may promote the 'tend and befriend' response where people reach out to others for support after a stressful event. That can, in turn, strengthen social bonds and may be a healthier way to cope," study author Mark Ellenbogen said in a release. For a decade, researchers have speculated that oxytocin, known as the love hormone, motivates people to seek out social support to respond to challenges and blunt the negative hit of stress. Ellenbogen's team said its study offers the first experimental support of the idea that oxytocin motivates us to strengthen social bonds during times of distress. © CBC 2013

Keyword: Hormones & Behavior; Aggression
Link ID: 18351 - Posted: 07.06.2013

By SABRINA TAVERNISE PORTSMOUTH, Ohio — Prescription pain pill addiction was originally seen as a man’s problem, a national epidemic that began among workers doing backbreaking labor in the coal mines and factories of Appalachia. But a new analysis of federal data has found that deaths in recent years have been rising far faster among women, quintupling since 1999. More women now die of overdoses from pain pills like OxyContin than from cervical cancer or homicide. And though more men are dying, women are catching up, according to the analysis by the Centers for Disease Control and Prevention. And the problem is hitting white women harder than black women, and older women harder than younger ones. In this Ohio River town on the edge of Appalachia, women blamed the changing nature of American society. The rise of the single-parent household has thrust immense responsibility on women, who are not only mothers, but also, in many cases, primary breadwinners. Some who described feeling overwhelmed by their responsibilities said they craved the numbness that drugs bring. Others said highs made them feel pretty, strong and productive, a welcome respite from the chaos of their lives. “I thought I was supermom,” said Crystal D. Steele, 42, a recovering addict who said she began to take medicine for back pain she developed working at Kentucky Fried Chicken. “I took one kid to football, the other to baseball. I went to work. I washed the car. I cleaned the house. I didn’t even know I had a problem.” © 2013 The New York Times Company

Keyword: Drug Abuse; Aggression
Link ID: 18342 - Posted: 07.03.2013

By C. CLAIBORNE RAY Q. What effect does the barometric pressure have on humans? Can it cause headaches and other discomforts? A. Differences in air pressure because of the weather or changes in altitude can have noticeable effects on the human body, though some people are more sensitive than others. Low barometric pressure can cause headaches by creating a pressure difference between the surrounding atmosphere and the sinuses, which are filled with air, said Dr. Matthew Fink, neurologist in chief at NewYork-Presbyterian Hospital/Weill Cornell Medical Center. That leads to distended sinuses, especially if there is any congestion or blockage. “The same thing can happen with joints in people who have arthritis,” Dr. Fink said, with the low pressure associated with a coming storm aggravating joint pains in some. “High barometric pressure does not usually cause a problem, unless it is extreme,” he said. For example, water pressure can cause serious problems for a scuba diver because nitrogen dissolves in the blood when it is under pressure for some time. When the pressure is released as a diver ascends too quickly, the gas expands into bubbles; the resulting organic distress, often called the bends, can be fatal. One of the most noticeable effects of shifting air pressure occurs when a plane changes altitude rapidly. As expanding or contracting air in the inner ear equalizes its pressure with the surrounding atmosphere, ear popping and pain are common. © 2013 The New York Times Company

Keyword: Pain & Touch
Link ID: 18335 - Posted: 07.02.2013

by Katia Moskvitch In the days before GPS, we needed both a compass and a map to navigate. Migrating birds are no different. Studies have suggested that the animals rely on an internal map and compass to traverse large distances, though just where these senses reside is unclear. Now, scientists say they have the strongest evidence yet that map sense is associated with the beak. Researchers have long suspected that migrating birds navigate by sensing Earth's magnetic field. The idea was that their beaks, which contain a lot of iron, worked like real magnets, with the metal aligning itself relative to the field. Supposedly, the so-called trigeminal nerve transmitted this information to the brain. But in 2009, a team led by Henrik Mouritsen of the University of Oldenburg in Germany cut the trigeminal nerve in several European robins and found that the animals still oriented perfectly. In lab-based experiments, the birds were able to locate the natural and artificial magnetic north. It seemed that the beak played no role in the compass sense. The finding gave support to another hypothesis, one that suggested that the inner compass was instead a magnetism-sensing chemical reaction in the birds' eyes. But Mouritsen's team was still convinced that the beak had to be involved in the magnetosense in some way, and it decided to do another test. In 2010 and 2011, the scientists captured 57 Eurasian reed warblers near Kaliningrad, Russia. Every spring, these birds migrate northeast to their breeding grounds in southern Scandinavia, up to 1000 kilometers away. Once again, the scientists snapped the trigeminal nerve, in half of the birds. But then they also moved all 57 birds 1000 kilometers to the east, where the magnetic field differs from their home site, and released them. © 2010 American Association for the Advancement of Science

Keyword: Animal Migration
Link ID: 18327 - Posted: 06.29.2013

By Judith Graham, A year ago, Bernard Belisle was in a bad way. Pain throbbed in his legs all day, every day, and he was angry and irritable much of the time. Then, he enrolled in a novel study on preventing depression in older adults at the University of Pittsburgh Medical Center. Belisle says the move has changed his life. While this 73-year-old still has pain, he’s less oppressed by it after four months of therapy that taught him new ways to adapt to his osteoarthritis. “My pain is still there, but I can manage it better and I have a much more positive attitude,” says Belisle, whose emotional response to his chronic pain had put him at risk of becoming depressed. “If I feel I’m becoming upset these days, I stop and go on to something else,” he said. “I take more breaks, and I don’t take on more than I can handle.” The Pittsburgh investigation is the largest effort to explore whether helping older adults cope with their illnesses can forestall major depression, an underrecognized and undertreated mental health problem that often has a dramatic impact on seniors’ overall health. “It’s a vicious cycle: Pain can make people feel hopeless and helpless, which leads to depression, which can lead to [fitness] deconditioning, fatigue, worse sleep at night, which then amplifies pain and just perpetuates the cycle,” said Jordan Karp, who is heading up part of the study. © 1996-2013 The Washington Post

Keyword: Pain & Touch; Aggression
Link ID: 18307 - Posted: 06.25.2013

By Amy Mathews Amos, My symptoms started in January 2008, with deep pain in my bladder and the sense that I had to urinate constantly. I was given a diagnosis of interstitial cystitis, a chronic bladder condition with no known cure. But in the following months, pain spread to my thighs, knees, hips, buttocks, abdomen and back. By the time my condition was properly diagnosed three years later, I had seen two urogynecologists, three orthopedists, six physical therapists, two manual therapists, a rheumatologist, a neurologist, a chiropractor and a homeopath. What was wrong? Something completely unexpected, given my symptoms: myofascial pain syndrome, a condition caused by muscle fibers that contract but don’t release. That constant contraction creates knots of taut muscle, or trigger points, that send pain throughout the body, even to parts that are perfectly healthy. Most doctors have never heard of myofascial pain syndrome and few know how to treat it. In my case, trigger points in my pelvic floor — the bowl of muscle on the bottom of the pelvis — referred pain to my bladder. Points along my thighs pulled on my knee joints, creating sharp pain when I walked. Points in my hips, buttocks and abdomen threw my pelvis and lower spine out of alignment, pushing even more pain up my back. The pain was so severe at times that I could sit for only brief periods. “Why didn’t anybody know this?” I asked my doctor, Timothy Taylor, soon after he correctly diagnosed the reason for my pain. “Because doctors don’t specialize in muscles,” he said. “It’s the forgotten organ.” © 1996-2013 The Washington Post

Keyword: Pain & Touch; Aggression
Link ID: 18292 - Posted: 06.20.2013

By Sandra G. Boodman, Through repeated painful experience, Shannon Bream had learned to keep her eyedrops close at hand wherever she went — even in the shower. Although they did little to quell the near-constant thrum of pain, the lubricating drops were better than nothing. She clutched the bottle while working out at the gym and kept extras in her purse, car and desk. At night, she set her alarm clock to ring every few hours so she could use them; failing to do so, she had discovered, meant waking up in pain that felt “like someone was stabbing me in the eye,” she said. “Daytime was okay, I could function, but nights had become an absolute nightmare,” said Bream, who covers the Supreme Court for Fox News. But a doctor’s suggestion that she was exaggerating her worsening misery, coupled with the bleak future presented on the Internet message boards she trolled night after night searching for help, plunged her into despair. “I didn’t think I could live like this for another 40 years,” she recalled thinking during her 18-month ordeal. Ironically, it was those same message boards that helped steer Bream to the doctor who provided a correct diagnosis and a satisfactory resolution. In the middle of one night in February 2010, Bream, then 39, awoke suddenly with pain in her left eye “so searing it sat me straight up in bed.” She stumbled to the bathroom, where she frantically rummaged through the medicine cabinet and grabbed various eyedrops, hoping to dull the pain. Her eye was tearing profusely; after about three hours, both the pain and tearing subsided. © 1996-2013 The Washington Post

Keyword: Pain & Touch; Aggression
Link ID: 18256 - Posted: 06.11.2013

By Susana Martinez-Conde This week’s illusion was discovered by Dartmouth College neuroscientist Peter Tse, author of “The Neural Basis of Free Will: Criterial Causation“, and presented as a Top 10 finalist at the recent Best Illusion of the Year Contest. The Knobby Sphere Illusion tricks your sense of touch. To experience it, you will need a regular pencil (for instance, with a hexagonal cross-section, and a small hard sphere (such a marble or ball bearing). Squeeze the pencil lengthwise very hard between your thumb and first finger for a full minute, until you can see deep indentations in your skin. Now feel the sphere by rolling it around against the parts of your fingers where the indentations are. The sphere no longer feels round, but bumpy. Your brain assumes that the touch receptors in your skin lie on a flat sheet, and misattributes the skin deformations to the sphere. © 2013 Scientific American

Keyword: Pain & Touch
Link ID: 18243 - Posted: 06.08.2013

Chris Palmer Once thought to be a low-level form of pain, itch is instead a distinct sensation with a dedicated neural circuit linking cells in the periphery of the body to the brain, a study in mice suggests. Neuroscientists Mark Hoon and Santosh Mishra of the National Institute of Dental and Craniofacial Research in Bethesda, Maryland, searched for the molecule that encodes the sensation of itch by screening genes in sensory neurons that are activated by touch, heat, pain and itch. They found that one particular protein, called natriuretic polypeptide b, or Nppb, was expressed in only a subset of these neurons. Mutant mice lacking Nppb did not respond to itch-inducing compounds, but did respond normally to heat and pain. The researchers also found that when they injected Nppb in the mice's necks, it put them into a self-scratching frenzy. This occurred both in the mutants and in control mice. “Our research reveals the primary transmitter used by itch sensory neurons and confirms that itch is detected by specialized sensory neurons,” says Hoon. Hoon and Mishra went on to find neurons bearing receptors for Nppb in the spinal cord. Injection of a toxin made from soapwort seeds that targeted these spinal-cord neurons blocked itch responses, but not other sensory responses, suggesting that information about the itch sensation is transmitted along a distinct pathway. The researchers' results are published today in Science1. The result “explains problems in the literature and provides a very testable hypothesis for how itch works”, says Glenn Giesler, a neuroscientist at the University of Minnesota in Minneapolis. © 2013 Nature Publishing Group

Keyword: Pain & Touch
Link ID: 18194 - Posted: 05.25.2013

By ALLISON HERSH LONDON I’M in line at the supermarket holding three items close to my chest. But I might as well be juggling my Kleenex box, toothpaste tube and an orange. Because — as you’d surely notice if you were behind me in line — I‘m bent forward at a sharp angle, which makes holding things difficult. I know you don’t want to stare, but you do. Maybe you think you’re being considerate when you say, apropos of nothing, “You look like you’re in pain.” Well, thanks, I am — but I’ll resist replying the way I want (“You look like you’re having a bad hair day”). I’m sorry. I know you mean well. Anyway it’s my turn at the register which means I’m closer to being at home where I can lie down and wait for the spasms to subside. Besides, if I told you what my issue was, you would probably shrug and reply that you’d never heard of it. There aren’t any public service announcements about it or telethons. No Angelina Jolies to bravely inform the world. Just people like me, in supermarket checkout lines. And this, I realize, is at the core of a problem that extends beyond me and my condition and that affects the way all of us respond to illnesses, some of which are the subject of public attention — and resources — and some of which are not. I have dystonia, a neurological disorder. Some years ago, for reasons no one knows, the muscles in my back and neck began to spasm involuntarily; the spasms multiply quickly, fatigue the muscles and force the body into repetitive movements and awkward postures like mine. There is no cure, only treatment options like deep brain stimulation, which requires a surgery I underwent last year as a last resort. © 2013 The New York Times Company

Keyword: Movement Disorders; Aggression
Link ID: 18171 - Posted: 05.20.2013

By ABIGAIL ZUGER, M.D. I hadn’t seen Larry in a dozen years when he reappeared in my office a few months ago, grinning. We were both grinning. I always liked Larry, even though he was a bit of a hustler, a little erratic in his appointments, a persistent dabbler in a variety of illegal substances. But he was always careful to avoid the hard stuff; he said he had a bad problem as a teenager and was going to stay out of trouble. It was to stay out of trouble that he left town all those years ago, and now he was back, grayer and thinner but still smiling. Then he pulled out a list of the medications he needed, and we both stopped smiling. According to Larry’s list, he was now taking giant quantities of one of the most addictive painkillers around, an immensely popular black-market drug most doctors automatically avoid prescribing except under the most exceptional circumstances. “I got a bad back now, Doc,” Larry said. Doctors hate pain. Let me count the ways. We hate it because we are (mostly) kindhearted and hate to see people suffer. We hate it because it is invisible, cannot be measured or monitored, and varies wildly and unpredictably from person to person. We hate it because it can drag us closer to the perilous zones of illegal practice than any other complaint. And we hate it most of all because unless we specifically seek out training in how to manage pain, we get virtually none at all, and wind up flying over all kinds of scary territory absolutely solo, without a map or a net. Copyright 2013 The New York Times Company

Keyword: Pain & Touch; Aggression
Link ID: 18153 - Posted: 05.14.2013

Roberta Kwok Sitting motionless in her wheelchair, paralysed from the neck down by a stroke, Cathy Hutchinson seems to take no notice of the cable rising from the top of her head through her curly dark hair. Instead, she stares intently at a bottle sitting on the table in front of her, a straw protruding from the top. Her gaze never wavers as she mentally guides a robot arm beside her to reach across the table, close its grippers around the bottle, then slowly lift the vessel towards her mouth. Only when she finally manages to take a sip does her face relax into a luminous smile. This video of 58-year-old Hutchinson illustrates the strides being taken in brain-controlled prosthetics1. Over the past 15 years, researchers have shown that a rat can make a robotic arm push a lever2, a monkey can play a video game3 and a person with quadriplegia — Hutchinson — can sip from a bottle of coffee1, all by simply thinking about the action. Improvements in prosthetic limbs have been equally dramatic, with devices now able to move individual fingers and bend at more than two dozen joints. But Hutchinson's focused stare in that video also illustrates the one crucial feature still missing from prosthetics. Her eyes could tell her where the arm was, but she could not feel what it was doing. Nor could she sense when the grippers touched the bottle, or whether it was slipping out of their grasp. Without this type of sensory feedback, even the simplest actions can be slow and clumsy, as Igor Spetic of Madison, Ohio, knows well. Fitted with a prosthetic after his right hand was crushed in an industrial accident in 2010, Spetic describes breaking dishes, grabbing fruit too hard and bruising it and dropping a can when trying to pick it up at the local shop. Having a sense of touch would be “tremendous”, he says. “It'd be one step closer to having the hand back.” © 2013 Nature Publishing Group,

Keyword: Pain & Touch; Aggression
Link ID: 18138 - Posted: 05.09.2013

By Stephani Sutherland Itching is not the only sensation to arise from unique neurons. A team at the California Institute of Technology has identified neurons that transmit the pleasurable sensations of massage, at least in mice. The cells responded to gentle rubbing but not to pinching or poking. Activation of the cells requires “a pressure component,” says lead investigator David Anderson, a neuroscientist at Caltech, “much like you would apply if you were stroking your cat.” The team first identified the mysterious cells several years ago by an unusual protein on their surface called MrgprB4—closely related to the receptor expressed by the newly identified itch cells. The rare sensory cells make up only about 2 percent of the body's peripheral neurons that respond to external stimuli, but they seem to cover about half the skin's surface with large, branching nerve endings. Whereas sensory neurons that transmit pain have been intensely studied, this is the first demonstration in live animals of a sensory cell that gives pleasure. After the scientists activated those neurons with a designer drug, the mice came to favor the place where they received the drug, according to the paper published January 31 in Nature. © 2013 Scientific American

Keyword: Pain & Touch
Link ID: 18092 - Posted: 04.30.2013

By R. Douglas Fields Scientists have speculated that it is a mild manifestation of pain or perhaps a malfunction of overly sensitive nerve endings stuck in a feedback loop. They have even wondered whether itching is mostly psychological (just think about bed bugs for a minute). Now a study rules out these possibilities by succeeding where past attempts have failed: a group of neuroscientists have finally isolated a unique type of nerve cell that makes us itch and only itch. In previous research, neuroscientists Liang Han and Xinzhong Dong of Johns Hopkins University and their colleagues determined that some sensory neurons with nerve endings in the skin have a unique protein receptor on them called MrgprA3. They observed under a microscope that chemicals known to create itching caused these neurons to generate electrical signals but that painful stimuli such as hot water or capsaicin, the potent substance in hot peppers, did not. In the new study published in Nature Neuroscience, the researchers used genetic engineering to selectively kill the entire population of MrgprA3 neurons in mice while leaving all the other sensory neurons intact. These mice no longer scratched themselves when exposed to itchy substances or allergens, but they showed no changes at all in responding to touch or pain-producing stimulation. The mice's behavior confirms that MrgprA3-containing neurons are essential for itch, but it does not rule out the possibility that these cells might respond to other sensations as well. To find out, the neuroscientists engineered a receptor that responds to capsaicin injected into the MrgprA3 neurons, in a type of mouse that lacks the capsaicin receptor in all its other cells. Now the only neurons that would be stimulated by capsaicin were the MrgprA3 neurons. If these cells are indeed itch-specific, injecting capsaicin into a tiny spot on the mouse's skin should make the rodent scratch instead of wincing in pain—which is exactly what happened. © 2013 Scientific American,

Keyword: Pain & Touch
Link ID: 18066 - Posted: 04.24.2013

By Sandra G. Boodman, For someone who had been such a healthy child, Nancy Kennedy couldn’t figure out how she had become the kind of sickly adult whose life revolved around visits to a seemingly endless series of doctors. Beginning in 2005, shortly after a job transfer took her from Northern Virginia to St. Louis, Kennedy, then 47, developed a string of vexing medical problems. Her white blood cell count was inexplicably elevated. Her sinuses were chronically infected, although her respiratory tract seemed unusually dry. She often felt fatigued, and her joints hurt. “It felt as though an alien had invaded my body,” said Kennedy, formerly a manager at the National Geospatial-Intelligence Agency. “I felt like I was in doctors’ offices all the time.” Tests for possible ailments — including blood disorders, cancer, multiple sclerosis and rheumatoid arthritis — were negative. For seven years. Kennedy and her primary-care physician, who said she felt as though she sent Kennedy to “every specialist that walked,” had no clear idea what might be wrong. But during a physical in January 2012, her doctor, Melissa Johnson, struck by Kennedy’s trouble walking and her accelerating deterioration, decided to check for a condition not previously considered. © 1996-2013 The Washington Post

Keyword: Neuroimmunology; Aggression
Link ID: 18040 - Posted: 04.16.2013

By Gary Stix People who lose a limb often experience the sensation of still having the missing arm or leg. Phantom limbs, in fact, have spurred a whole line of independent research among neuroscientists. But it appears that all of us may be capable of these sensations, even if arms and legs remain intact. If we can conjure a phantom limb just like that, it raises all kinds of enticing questions for philosophers as well as scientists about what exactly constitutes our perception of the physical self. Karolinska Institute researchers report online in the Journal of Cognitive Neuroscience that they can induce a sensation of a phantom hand in just a short time. Watch this simple experiment here: © 2013 Scientific American

Keyword: Pain & Touch
Link ID: 18036 - Posted: 04.15.2013

by Patrick Russell Many people who have had a limb amputated report feeling sensations that appear to come from their missing arm or leg. Now researchers have found that anyone can experience having such a phantom limb. "Previous research shows that you can convince a person that a rubber hand is their own by putting it on a table in front of them and stroking it in synchrony with their real hand," explains Arvid Guterstam at the Karolinska Institute in Stockholm, Sweden, who led the study. The illusion does not work with a block of wood, he says. "But our study shows that if you take away this rubber hand, people will attribute sensations to an invisible entity." Guterstam and his colleagues made volunteers sit at a table with their right arm hidden from view behind a screenMovie Camera. An experimenter then applied brush strokes to the concealed hand and, simultaneously, to a portion of empty space in full view of each volunteer. "We discovered that most participants, within less than a minute, transfer the sensation of touch to the region of empty space where they see the paintbrush move, and experience an invisible hand in that position," says Guterstam. Mock stabbing Experimenters also mimicked stabbing the phantom hand with a kitchen knife, while monitoring volunteers' stress level. To minimise any effect related to seeing the knife for the first time, the volunteers were warned that it would be used at some point. The researchers found that during the mock stabbing, stress levels, measured using a type of sweat test, went up in about 75 per cent of the 234 participants. © Copyright Reed Business Information Ltd.

Keyword: Pain & Touch; Aggression
Link ID: 18029 - Posted: 04.13.2013

by Helen Shen A thermometer is great for measuring a fever, but when it comes to pain, doctors must rely on the age-old question, "How bad is it?" Scientists have long struggled to find physiological signs that can reliably tell "ouch" from "@#%!" and everything in between. Now, a brain scanning study suggests that painful heat excites a specific pattern of neural activity that could hold the key to better diagnosis and treatment of all kinds of pain in the future. Functional magnetic resonance imaging (fMRI) studies have shown that certain areas of the brain—including the anterior cingulate cortex, somatosensory cortex, and thalamus—activate when people experience pain. But those same regions also light up in response to other experiences, such as painful thoughts or social rejection. In recent years, scientists have looked for a particular pattern of activity across these areas that single out the experience of physical pain. "What we're evolving towards is trying to predict quantitatively from patterns of brain activity how much an individual is feeling," says Tor Wager, a neuroscientist at the University of Colorado, Boulder. In the new study, Wager's group performed fMRI brain scans on a total of 114 healthy participants while delivering different amounts of heat to the volunteers' arms with a computer-controlled hot plate. In an initial experiment, the scientists used data from 20 people to find a brain-wide pattern of excitation and inhibition—a neural "signature"—that changed reliably as people experienced varying degrees of heat, ranging from painless to scalding. In the remainder of the study, Wager and his colleagues were able use the signature derived from the first group to predict pain responses in a completely different set of subjects—a promising sign for one day using such a model on patients suffering from unknown conditions, he says. © 2010 American Association for the Advancement of Science.

Keyword: Pain & Touch; Aggression
Link ID: 18024 - Posted: 04.11.2013

Ed Yong Every autumn, millions of monarch butterflies (Danaus plexippus) converge on a small cluster of Mexican mountains to spend the winter. They have journeyed for up to 4,000 kilometres from breeding grounds across eastern North America. And according to a study, they accomplish this prodigious migration without ever knowing where they are relative to their destination. The monarchs can use the position of the Sun as a compass, but when Henrik Mouritsen, a biologist at the University of Oldenburg in Germany, displaced them by 2,500 kilometres, he found that they did not correct their heading. “People seemed to assume that they had some kind of a map that allowed them to narrow in on a site a few kilometres across after travelling several thousands of kilometres,” he says. Now, “it is clear that they don’t”. His results are published in the Proceedings of the National Academy of Sciences1. For more than five decades, scientists have teamed up with amateurs to tag and monitor free-flying monarchs, creating a database of their migrations. When Mouritsen analysed these records, he realized that the monarchs tend to spread out over the course of their migration. Their distribution was a good fit with the predictions of a mathematical model that assumed that the monarchs were flying with just a compass, rather than a compass and a map. Mouritsen also captured 76 southwesterly flying monarchs from fields near Guelph in Ontario, Canada, and transported them 2,500 kilometres to the west, to Calgary in the Canadian province of Alberta. He placed the butterflies in a “flight simulator” — a plastic cylinder that kept them from seeing any landmarks except the sky — and tethered them to a rod that let them point in any direction without actually flying away. © 2013 Nature Publishing Group

Keyword: Animal Migration
Link ID: 18013 - Posted: 04.10.2013