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By Michele Solis Like truth and beauty, pain is subjective and hard to pin down. What hurts one moment might not register the next, and our moods and thoughts color the experience of pain. According to a report in April in the New England Journal of Medicine, however, researchers may one day be able to measure the experience of pain by scanning the brain—a much needed improvement over the subjective ratings of between one and 10 that patients are currently asked to give. Led by neuroscientist Tor Wager of the University of Colorado at Boulder, researchers used functional MRI on healthy participants who were given heated touches to their arm, some pleasantly warm, others painfully hot. During the painful touches, a scattered group of brain regions consistently turned on. Although these regions have been previously associated with pain, the new study detected a striking and consistent jump in their activity when people reported pain, with much greater accuracy than previous studies had attained. This neural signature appeared in 93 percent of subjects reporting to feel painful heat, ramping up as pain intensity increased and receding after participants took a painkiller. The researchers determined that the brain activity specifically marked physical pain rather than a generally unpleasant experience, because it did not emerge in people shown a picture of a lover who had recently dumped them. Although physical pain and emotional pain involve some of the same regions, the study showed that fine-grained differences in activation separate the two conditions. © 2013 Scientific American

Related chapters from BP7e: Chapter 8: General Principles of Sensory Processing, Touch, and Pain; Chapter 2: Functional Neuroanatomy: The Nervous System and Behavior
Related chapters from MM:Chapter 5: The Sensorimotor System; Chapter 2: Cells and Structures: The Anatomy of the Nervous System
Link ID: 18632 - Posted: 09.11.2013

by Nancy Shute It was hard to ignore those headlines saying that people with migraine have brain damage, even if you're not among the 12 percent or so who do suffer from these painful, recurring headaches. Don't panic, says the neurologist whose work sparked those alarming headlines. "It's still not something to stay up nights worrying about," says Dr. Richard Lipton, director of the Montefiore Headache Center in New York. But knowing about the brain anomalies that Lipton and his colleagues found might help people reduce their stroke risk. Some people who get do have a slightly . And some of the brain changes identified in the study look like mini-strokes. "On the MRI they look like very tiny strokes," Lipton tells Shots. But the people aren't having any stroke symptoms. Still, Lipton is convinced that the process is the same. "We now know it's a risk factor for these very small silent strokes," he says. The scientists evaluated data from 19 studies in which people with migraine headaches got MRI scans of their brains. Just about everybody is going to have some abnormalities show up in a scan. But the people who had migraines were more likely to have two common abnormalities: white matter abnormalities and infarct-like lesions. The were published in the journal Neurology. ©2013 NPR

Related chapters from BP7e: Chapter 8: General Principles of Sensory Processing, Touch, and Pain; Chapter 19: Language and Hemispheric Asymmetry
Related chapters from MM:Chapter 5: The Sensorimotor System; Chapter 15: Language and Our Divided Brain
Link ID: 18593 - Posted: 09.02.2013

By Katherine Harmon The past couple posts have described some pretty severe experiments on octopuses, including: showing how octopus arms can grow back after inflicted damage and how even severed octopus arms can react to stimuli. (For the record, animals in the studies were anesthetized and euthanized, respectively.) Without getting too far into the woods (or reefs) of animal treatment ethics, the question remains: How much pain and distress can these relatively short-lived invertebrates experience? Luckily for us, a new paper deals with that very question. Researchers from Europe, the UK and Japan teamed up to explore what we know about pain, perception and cognition in octopuses. The findings are described in the special “Cephalopod Research” issue of September’s Journal of Experimental Marine Biology and Ecology. And the issue is not just philo-scientific cloud (or wave) gazing. Starting this year the European Union asks researchers to make similarly humane accommodations for cephalopods as they do for vertebrates (Directive 2010/63/EU, pdf). But, do octopuses experience would-be painful experiences the same way mice do? As the researchers note in their paper, we know very little about whether cephalopods recognize pain or experience suffering and distress in a similar way that we humans—or even we vertebrates—do. Previous (as well as much current) research has looked largely to behavioral clues as an indication to an octopus’s internal state. For example, researchers have observed an octopus’s color changing and activity patterns and looked for any self-inflicted harm (swimming into the side of a tank or eating its own arms) to judge whether the animal is “stressed.” And to tell whether an animal has “gone under” anesthesia, they often look for movements, lack of response, posture change or, at the most, measure heart rate and breathing. © 2013 Scientific American

Related chapters from BP7e: Chapter 8: General Principles of Sensory Processing, Touch, and Pain; Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 5: The Sensorimotor System
Link ID: 18585 - Posted: 08.31.2013

By Cristy Gelling Bacteria can directly trigger the nerves that sense pain, suggesting that the body’s own immune reaction is not always to blame for the extra tenderness of an infected wound. In fact, mice with staph-infected paws showed signs of pain even before immune cells had time to arrive at the site, researchers report online August 21 in Nature. “Most people think that when they get pain during infection it’s due to the immune system,” says coauthor Isaac Chiu of Boston Children’s Hospital and Harvard Medical School. Indeed, immune cells do release pain-causing molecules while fighting off invading microbes. But in recent years scientists have started uncovering evidence that bacteria can also cause pain. Chiu and his colleagues stumbled on this idea when they grew immune cells and pain-sensing cells together in a dish. The researchers were trying to activate the immune cells by adding bacteria to the mix but were surprised to see an immediate response in the nerve cells instead. This made them suspect that nerve cells were sensing the bacteria directly. To take a closer look at a real infection, the team injected the back paws of mice with Staphylococcus aureus, a bacterium that causes painful sores in humans. The researchers measured how tender the infected area was by poking it with flexible filaments of plastic. If the mouse didn’t like being prodded, it would lift its paw, giving a sensitive measure of each infection’s ouch factor. © Society for Science & the Public 2000 - 2013

Related chapters from BP7e: Chapter 8: General Principles of Sensory Processing, Touch, and Pain; Chapter 15: Emotions, Aggression, and Stress
Related chapters from MM:Chapter 5: The Sensorimotor System; Chapter 11: Emotions, Aggression, and Stress
Link ID: 18547 - Posted: 08.22.2013

By Susana Martinez-Conde Want to know an effective way to reduce pain from burns? Cover the affected red area, so you are unable to look at it. Ideally, use a blue bandage. Painfully hot stimuli applied to red skin feel more painful than applied to blue skin, a new research article published in Frontiers in Human Neuroscience shows. The scientists, Matteo Martini, Daniel Perez-Marcos and Maria Victoria Sanchez-Vives from the University of Barcelona, used immersive virtual reality in combination with the application of real heat stimuli to the wrists of experimental subjects. Participants saw their virtual arms get increasingly red, blue, or green as the heat rose, and indicated, by pressing a button, when the sensation became painful. In an additional experimental condition, a gray dot close to the virtual arm became red as the temperature increased, but the color of the arm itself remained unaltered. The results showed that subjects experienced pain earlier (that is, at lower physical temperatures) when the arm was red than when it was blue. Also, the experience of increased pain was not associated to seeing red per se, but it mattered whether the color was on the body or not. A patch of red near –but not on– the virtual arm resulted in significantly less pain than that recorded with the arm itself becoming red. © 2013 Scientific American

Related chapters from BP7e: Chapter 8: General Principles of Sensory Processing, Touch, and Pain; Chapter 15: Emotions, Aggression, and Stress
Related chapters from MM:Chapter 5: The Sensorimotor System; Chapter 11: Emotions, Aggression, and Stress
Link ID: 18520 - Posted: 08.17.2013

by Linda Geddes "IT WAS like red-hot pokers needling one side of my face," says Catherine, recalling the cluster headaches she experienced for six years. "I just wanted it to stop." But it wouldn't – none of the drugs she tried had any effect. Thinking she had nothing to lose, last year she enrolled in a pilot study to test a handheld device that applies a bolt of electricity to the neck, stimulating the vagus nerve – the superhighway that connects the brain to many of the body's organs, including the heart. The results of the trial were presented last month at the International Headache Congress in Boston, and while the trial is small, the findings are positive. Of the 21 volunteers, 18 reported a reduction in the severity and frequency of their headaches, rating them, on average, 50 per cent less painful after using the device daily and whenever they felt a headache coming on. This isn't the first time vagal nerve stimulation has been used as a treatment – but it is one of the first that hasn't required surgery. Some people with epilepsy have had a small generator that sends regular electrical signals to the vagus nerve implanted into their chest. Implanted devices have also been approved to treat depression. What's more, there is increasing evidence that such stimulation could treat many more disorders from headaches to stroke and possibly Alzheimer's disease (see "The many uses of the wonder nerve"). © Copyright Reed Business Information Ltd.

Related chapters from BP7e: Chapter 8: General Principles of Sensory Processing, Touch, and Pain
Related chapters from MM:Chapter 5: The Sensorimotor System
Link ID: 18519 - Posted: 08.17.2013

By NICHOLAS BAKALAR Well-established guidelines for the treatment of back pain require very conservative management — in most cases, no more than aspirin or acetaminophen (Tylenol) and physical therapy. Advanced imaging procedures, narcotics and referrals to other physicians are recommended only for the most refractory cases or those with serious other symptoms. But a study published in JAMA Internal Medicine suggests that doctors are not following the guidelines. Researchers studied 23,918 outpatient visits for back pain, a representative sample of an estimated 440 million visits made over 12 years in the United States. After controlling for age, sex, the nature of the pain and other factors, they found that during this time, Nsaid and Tylenol use fell more than 50 percent. But prescriptions for opiates increased by 51 percent, and CT or M.R.I. scans by 57 percent. Referrals to other physicians increased by 106 percent, which the authors said is a likely contributor to recent increases in expensive and often ineffective spine surgeries. The senior author, Dr. Bruce E. Landon, a professor of health care policy at Harvard, said that in most cases back pain improves by itself. But he added: “It’s a long conversation for physicians to educate patients. Often it’s easier just to order a test or give a narcotic rather than having a conversation. It’s not always easy to do the right thing.” Copyright 2013 The New York Times Company

Related chapters from BP7e: Chapter 8: General Principles of Sensory Processing, Touch, and Pain
Related chapters from MM:Chapter 5: The Sensorimotor System
Link ID: 18449 - Posted: 08.03.2013

by Carl Zimmer Inside each of us is a miniature version of ourselves. The Canadian neurologist Wilder Penfield discovered this little person in the 1930s, when he opened up the skulls of his patients to perform brain surgery. He would sometimes apply a little electric jolt to different spots on the surface of the brain and ask his patients–still conscious–to tell him if they felt anything. Sometimes their tongues tingled. Other times their hand twitched. Penfield drew a map of these responses. He ended up with a surreal portrait of the human body stretched out across the surface of the brain. In a 1950 book, he offered a map of this so-called homunculus. For brain surgeons, Penfield’s map was a practical boon, helping them plan out their surgeries. But for scientists interested in more basic questions about the brain, it was downright fascinating. It revealed that the brain organized the sensory information coming from the skin into a body-like form. There were differences between the homunculus and the human body, of course. It was as if the face had been removed from the head and moved just out of reach. The area that each body part took up in the brain wasn’t proportional to its actual size. The lips and index finger were gigantic, for instance, while the forearm barely took up less space than the tongue. That difference in our brains is reflected in our nerve endings. Our fingertips are far more sensitive than our backs. We simply don’t need to make fine discriminations with our backs. But we use our hands for all sorts of things–like picking up objects or using tools–that demand that sort of sensory power.

Related chapters from BP7e: Chapter 8: General Principles of Sensory Processing, Touch, and Pain; Chapter 3: Neurophysiology: The Generation, Transmission, and Integration of Neural Signals
Related chapters from MM:Chapter 5: The Sensorimotor System; Chapter 3: Neurophysiology: The Generation, Transmission, and Integration of Neural Signals
Link ID: 18407 - Posted: 07.25.2013

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

Related chapters from BP7e: Chapter 8: General Principles of Sensory Processing, Touch, and Pain
Related chapters from MM:Chapter 5: The Sensorimotor System
Link ID: 18360 - Posted: 07.09.2013

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

Related chapters from BP7e: Chapter 8: General Principles of Sensory Processing, Touch, and Pain
Related chapters from MM:Chapter 5: The Sensorimotor System
Link ID: 18335 - Posted: 07.02.2013

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

Related chapters from BP7e: Chapter 16: Psychopathology: Biological Basis of Behavior Disorders; Chapter 8: General Principles of Sensory Processing, Touch, and Pain
Related chapters from MM:Chapter 12: Psychopathology: Biological Basis of Behavioral Disorders; Chapter 5: The Sensorimotor System
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

Related chapters from BP7e: Chapter 8: General Principles of Sensory Processing, Touch, and Pain; Chapter 11: Motor Control and Plasticity
Related chapters from MM:Chapter 5: The Sensorimotor System; Chapter 5: The Sensorimotor System
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

Related chapters from BP7e: Chapter 10: Vision: From Eye to Brain; Chapter 8: General Principles of Sensory Processing, Touch, and Pain
Related chapters from MM:Chapter 7: Vision: From Eye to Brain; Chapter 5: The Sensorimotor System
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

Related chapters from BP7e: Chapter 8: General Principles of Sensory Processing, Touch, and Pain
Related chapters from MM:Chapter 5: The Sensorimotor System
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

Related chapters from BP7e: Chapter 8: General Principles of Sensory Processing, Touch, and Pain
Related chapters from MM:Chapter 5: The Sensorimotor System
Link ID: 18194 - Posted: 05.25.2013

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

Related chapters from BP7e: Chapter 8: General Principles of Sensory Processing, Touch, and Pain; Chapter 4: The Chemistry of Behavior: Neurotransmitters and Neuropharmacology
Related chapters from MM:Chapter 5: The Sensorimotor System; Chapter 4: The Chemistry of Behavior: Neurotransmitters and Neuropharmacology
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,

Related chapters from BP7e: Chapter 8: General Principles of Sensory Processing, Touch, and Pain; Chapter 11: Motor Control and Plasticity
Related chapters from MM:Chapter 5: The Sensorimotor System; Chapter 5: The Sensorimotor System
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

Related chapters from BP7e: Chapter 8: General Principles of Sensory Processing, Touch, and Pain
Related chapters from MM:Chapter 5: The Sensorimotor System
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,

Related chapters from BP7e: Chapter 8: General Principles of Sensory Processing, Touch, and Pain
Related chapters from MM:Chapter 5: The Sensorimotor System
Link ID: 18066 - Posted: 04.24.2013

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

Related chapters from BP7e: Chapter 8: General Principles of Sensory Processing, Touch, and Pain
Related chapters from MM:Chapter 5: The Sensorimotor System
Link ID: 18036 - Posted: 04.15.2013