Chapter 5. The Sensorimotor System

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Joe Palca The sea snail Conus magus looks harmless enough, but it packs a venomous punch that lets it paralyze and eat fish. A peptide modeled on the venom is a powerful painkiller, though sneaking it past the blood-brain barrier has proved hard. The sea snail Conus magus looks harmless enough, but it packs a venomous punch that lets it paralyze and eat fish. A peptide modeled on the venom is a powerful painkiller, though sneaking it past the blood-brain barrier has proved hard. Courtesy of Jeanette Johnson and Scott Johnson Researchers are increasingly turning to nature for inspiration for new drugs. One example is Prialt. It's an incredibly powerful painkiller that people sometimes use when morphine no longer works. Prialt is based on a component in the venom of a marine snail. Prialt hasn't become a widely used drug because it's hard to administer. Mandë Holford is hoping to change that. She and colleagues explain how in their study published online Monday in the journal Scientific Reports. Holford is an associate professor of chemical biology at Hunter College in New York and on the scientific staff of the American Museum of Natural History. As is so often the case in science, her path to working on Prialt wasn't exactly a direct one. She's a chemist, and her first passion was peptides — short strings of amino acids that do things inside cells. "I started out with this love for peptides," Holford says, then laughs. "Love! Sounds weird to say you love peptides out loud." © 2015 NPR

Keyword: Pain & Touch
Link ID: 21255 - Posted: 08.04.2015

RACHEL MARTIN, HOST: Every day, according to the Centers for Disease Control, 44 Americans die because they have overdosed on prescription painkillers. The CDC calls it an epidemic, and drug companies are responding by trying to develop versions of the most addictive painkillers, opioids, that will diminish a user's physical craving for the medicine. Now, to do this, to create these less addictive drugs, pharmaceutical companies are recruiting thousands of self-identified drug users to test their products. David Crow is a reporter for the Financial Times. He's just published a big report on this, and he joins me now to talk more about it. Thanks so much for being with us. Opioids, as we mentioned, are the worst in terms of their addictive quality. These companies are trying to come up with drugs that will achieve the same painkilling effect without the addictiveness. So this is actually possible? CROW: What they're trying to do is develop a new generation of opioid painkillers that have features that make them harder to abuse. Some of the strategies that have been pursued include hard shells that make it harder to crush up the pill so that you can snort it or gumming agents that make it harder to put into a syringe so that you can inject it. And some companies are experimenting with putting different chemicals in the center of the pill that will remain dormant. But if it's tampered with, that chemical would be released, and it would counteract the effect of the opioid. They're testing these drugs on recreational drug users. And the participants go through a screening process where they have to wash out, where they don't have any opioid in their system, and also where they're given a drug called naloxone, which cuts off the effects of opioids. And at that point, if you were addicted or physically dependent, your body would show signs of withdrawal. And that is the screening process. © 2015 NPR

Keyword: Drug Abuse; Pain & Touch
Link ID: 21253 - Posted: 08.02.2015

By David Noonan Leaping through the air with ease and spinning in place like tops, ballet dancers are visions of the human body in action at its most spectacular and controlled. Their brains, too, appear to be special, able to evade the dizziness that normally would result from rapid pirouettes. When compared with ordinary people's brains, researchers found in a study published early this year, parts of dancers' brains involved in the perception of spinning seem less sensitive, which may help them resist vertigo. For millions of other people, it is their whole world, not themselves, that suddenly starts to whirl. Even the simplest task, like walking across the room, may become impossible when vertigo strikes, and the condition can last for months or years. Thirty-five percent of adults older than 39 in the U.S.—69 million people—experience vertigo at one time or another, often because of damage to parts of the inner ear that sense the body's position or to the nerve that transmits that information to the brain. Whereas drugs and physical therapy can help many, tens of thousands of people do not benefit from existing treatments. “Our patients with severe loss of balance have been told over and over again that there's nothing we can do for you,” says Charles Della Santina, an otolaryngologist who studies inner ear disorders and directs the Johns Hopkins Vestibular NeuroEngineering Laboratory. Steve Bach's nightmare started in November 2013. The construction manager was at home in Parsippany, N.J. “All of a sudden the room was whipping around like a 78 record,” says Bach, now age 57. He was curled up on the living room floor in a fetal position when his daughter found him and called 911. He spent the next five days in the hospital. © 2015 Scientific American

Keyword: Movement Disorders
Link ID: 21248 - Posted: 08.01.2015

Mo Costandi When we say that we are “in pain”, we usually mean that an injured body part is hurting us. But the phenomenon we call pain consists of more than just physical sensations, and often has mental and emotional aspects, too. Pain signals entering the black box of the brain can be subjected further processing, and these hidden thought processes can alter the way we perceive them. We still know very little about these non-physical aspects of pain, or about the brain processes responsible for them. We do know, however, that learning and mental imagery can both diminish and enhance the experience of felt pain. Two new studies now extend these findings – one shows that subliminal learning can also alter pain responses, and the other explains how mental imagery can do so. It’s well known that simple associative learning procedures can alter responses to pain. For example, newborn babies who have diabetic mothers and are repeatedly exposed to heel pricks in the first few days of life exhibit larger pain responses during subsequent blood tests than healthy infants. Learning also appears to explain the placebo effect, and why it is often so variable. Several years ago, Karin Jensen, who is now at Harvard Medical School, and her colleagues showed that subliminal cues can reactivate consciously-learned associations to either enhance or diminish pain responses. In their latest study, the researchers set out to determine the extent to which this type of learning can occur non-consciously. © 2015 Guardian News and Media Limited

Keyword: Pain & Touch; Emotions
Link ID: 21247 - Posted: 08.01.2015

Five men with complete motor paralysis were able to voluntarily generate step-like movements thanks to a new strategy that non-invasively delivers electrical stimulation to their spinal cords, according to a new study funded in part by the National Institutes of Health. The strategy, called transcutaneous stimulation, delivers electrical current to the spinal cord by way of electrodes strategically placed on the skin of the lower back. This expands to nine the number of completely paralyzed individuals who have achieved voluntary movement while receiving spinal stimulation, though this is the first time the stimulation was delivered non-invasively. Previously it was delivered via an electrical stimulation device surgically implanted on the spinal cord. In the study, the men’s movements occurred while their legs were suspended in braces that hung from the ceiling, allowing them to move freely without resistance from gravity. Movement in this environment is not comparable to walking; nevertheless, the results signal significant progress towards the eventual goal of developing a therapy for a wide range of individuals with spinal cord injury. “These encouraging results provide continued evidence that spinal cord injury may no longer mean a life-long sentence of paralysis and support the need for more research,” said Roderic Pettigrew, Ph.D., M.D., director of the National Institute of Biomedical Imaging and Bioengineering at NIH. “The potential to offer a life-changing therapy to patients without requiring surgery would be a major advance; it could greatly expand the number of individuals who might benefit from spinal stimulation. It’s a wonderful example of the power that comes from combining advances in basic biological research with technological innovation.”

Keyword: Robotics
Link ID: 21242 - Posted: 08.01.2015

Victoria E Brings & Mark J Zylka A study finds that pain hypersensitivity in male and female mice is differentially dependent on microglia and T cells, and describes a sex-specific response to microglia-targeted pain treatments. This sex difference will be important to consider when developing treatments for pain and other neurological disorders involving microglia and immune cells. Animal studies1, 2 have spawned great interest in using microglial inhibitors such as minocycline to treat pain in humans. However, these studies were conducted largely on male rodents. Now, Sorge et al.3 have evaluated several microglial inhibitors in nerve-injured mice of both sexes. The study—led by Jeffrey Mogil, who has championed the testing of males and females in pain studies4—found that microglial inhibitors did reduce allodynia, a form of pain hypersensitivity to touch, in males. Surprisingly, however, these inhibitors were ineffective in female mice, despite a robust activation of spinal microglia (Fig. 1). The authors instead found that cells of the adaptive immune system promote pain hypersensitivity in females. Although focused on pain, these findings could have implications for other neurological disorders that disproportionately affect one sex, such as autism and neurodegeneration, and in which microglia and immune cells are implicated5, 6. Figure 1: Pain mechanisms differ in male and female mice. Pain mechanisms differ in male and female mice. Nerve injury activates microglial cells in the spinal cord of male and female mice, but microglial inhibitors only block allodynia in males. P2RX4 is upregulated in males only. Female mice have about twice as many T cells as males. Testosterone increases PPARα and decreases PPARγ gene expression in T cells. Compounds that activate PPARα inhibit mechanical pain hypersensitivity (allodynia) in males, whereas those that activate PPARγ inhibit allodynia in females. © 2015 Macmillan Publishers Limited

Keyword: Pain & Touch; Glia
Link ID: 21229 - Posted: 07.29.2015

By Annick Laurent Can you tell a pygmy blue whale from an Antarctic blue whale? If not, you aren’t alone. Marine biologists have had trouble distinguishing these enormous mammals with mottled skin patterns ever since they began studying them—and that has complicated efforts to figure out where they breed and how to best protect them. Now, researchers have caught a break thanks to a pygmy whale named Isabela. Researchers first photographed the whale and collected her DNA in 1998 in the waters off the Galapagos Islands. Then, in 2006, another team photographed and collected samples from a similar looking whale off Chile (both photos above). Now, in a study published online before print in Marine Mammal Science, scientists compared those samples and photographs, and discovered that they both belonged to the same whale. That means Isabela (named after the lead author’s daughter to represent hope for future preservation efforts) migrated a minimum of 5200 km, the longest recorded latitudinal migration made by any Southern Hemisphere blue whale on record. The findings suggest Chile's and the Galapagos’ blue whale aggregations are connected, meaning those feeding in the Gulf of Corcovado off Chile may be breeding in the Tropical Eastern Pacific. Knowing where this species migrates—including its feeding and breeding grounds—can help conservationists and governments better establish marine protected areas, the team says. © 2015 American Association for the Advancement of Science

Keyword: Animal Migration
Link ID: 21213 - Posted: 07.25.2015

By Smitha Mundasad Health reporter A type of diabetes drug may offer a glimmer of hope in the fight against Parkinson's disease, research in the journal Plos Medicine suggests. Scientists found people taking glitazone pills were less likely to develop Parkinson's than patients on other diabetes drugs. But they caution the drugs can have serious side-effects and should not be given to healthy people. Instead, they suggest the findings should prompt further research. 'Unintended benefits' There are an estimated 127,000 people in the UK with Parkinson's disease, which can lead to tremor, slow movement and stiff muscles. And charities say with no drugs yet proven to treat the condition, much more work is needed in this area. The latest study focuses solely on people with diabetes who did not have Parkinson's disease at the beginning of the project. Researchers scoured UK electronic health records to compare 44,597 people prescribed glitazone pills with 120,373 people using other anti-diabetic treatment. They matched participants to ensure their age and stage of diabetes treatment were similar. Scientists found fewer people developed Parkinson's in the glitazone group - but the drug did not have a long-lasting benefit. Any potential protection disappeared once patients switched to another type of pill. Dr Ian Douglas, lead researcher at the London School of Hygiene and Tropical Medicine, said: "We often hear about negative side-effects associated with medications, but sometimes there can also be unintended beneficial effects. "Our findings provide unique evidence that we hope will drive further investigation into potential drug treatments for Parkinson's disease." © 2015 BBC

Keyword: Parkinsons
Link ID: 21199 - Posted: 07.22.2015

Results from tests of the drug, announced this week, show that it breaks up plaques in mice affected with Alzheimer’s disease or Parkinson’s disease, and improves the memories and cognitive abilities of the animals. Other promising results in rats and monkeys mean that the drug developers, NeuroPhage Pharmaceuticals, are poised to apply for permission to start testing it in people, with trials starting perhaps as early as next year. The drug is the first that seems to target and destroy the multiple types of plaque implicated in human brain disease. Plaques are clumps of misfolded proteins that gradually accumulate into sticky, brain-clogging gunk that kills neurons and robs people of their memories and other mental faculties. Different kinds of misfolded proteins are implicated in different brain diseases, and some can be seen within the same condition (see “Proteins gone rogue”, below). One thing they share, however, is a structural kink known as a canonical amyloid fold, and it is this on which the new drug acts (Journal of Molecular Biology, DOI: 10.1016/j.jmb.2014.04.015). Animal tests show that the drug reduces levels of amyloid beta plaques and tau protein deposits implicated in Alzheimer’s disease, and the alpha-synuclein protein deposits thought to play a role in Parkinson’s disease. Tests on lab-made samples show that the drug also targets misfolded transthyretin, clumps of which can clog up the heart and kidney, and prion aggregates, the cause of CJD, another neurodegenerative condition. Because correctly folded proteins do not have the distinct “kink”, the drug has no effect on them. © Copyright Reed Business Information Ltd.

Keyword: Alzheimers; Prions
Link ID: 21190 - Posted: 07.20.2015

By Sarah Schwartz Scientists think they have a new understanding of a potential long-lasting, targeted treatment for chronic pain. When injected into the spinal cord of a mouse with nerve damage, cells extracted from mouse bone marrow flock to injured cells and produce a pain-relieving protein, researchers report July 13 in the Journal of Clinical Investigation. The results may lead to better chronic pain treatments in humans. The specialized cells honed in on their ultimate destination by following chemical signals released by the injured nerve cells. There, the injected cells produced an anti-inflammatory protein, called transforming growth factor beta 1 (TGFB1), which provided long-term pain relief. Researchers had known that the marrow cells relieved pain, but didn’t know how, says study coauthor Ru-Rong Ji, a neurobiologist at Duke University Medical Center. “These cells make drugs at sites of injury,” says biologist Arnold Caplan of Case Western Reserve University in Cleveland. “They’re drugstores.” Ji and colleagues found that they could relieve chronic nerve pain in mice by injecting 250,000 cells or fewer into the narrow space under the spinal cord membrane. This site is protected by the blood-brain barrier, preventing immune attacks on the injected cells and allowing these cells to live longer, Ji says. Some clinical trials inject cells like these into the bloodstream, Caplan says, requiring the use of many more cells, many of which get stuck in the lungs and liver. © Society for Science & the Public 2000 - 2015

Keyword: Pain & Touch
Link ID: 21167 - Posted: 07.14.2015

Carl Zimmer A single neuron can’t do much on its own, but link billions of them together into a network and you’ve got a brain. But why stop there? In recent years, scientists have wondered what brains could do if they were linked together into even bigger networks. Miguel A. Nicolelis, director of the Center for Neuroengineering at Duke University, and his colleagues have now made the idea a bit more tangible by linking together animal brains with electrodes. In a pair of studies published on Thursday in the journal Scientific Reports, the researchers report that rats and monkeys can coordinate their brains to carry out such tasks as moving a simulated arm or recognizing simple patterns. In many of the trials, the networked animals performed better than individuals. “At least some times, more brains are better than one,” said Karen S. Rommelfanger, director of the Neuroethics Program at the Center for Ethics at Emory University, who was not involved in the study. Brain-networking research might someday allow people to join together in useful ways, Dr. Rommelfanger noted. Police officers might be able to make collective decisions on search-and-rescue missions. Surgeons might collectively operate on a single patient. But she also warned that brain networks could create a host of exotic ethical quandaries involving privacy and legal responsibility. If a brain network were to commit a crime, for example, who exactly would be guilty? © 2015 The New York Times Company

Keyword: Robotics
Link ID: 21160 - Posted: 07.11.2015

By Esther Hsieh Strap on a headset, immerse yourself in an alternate reality and cure your pain—that's the idea of a recent study in Psychological Science. Most people think of pain as something that happens in the body—I twist my head too far, and my neck sends a “pain signal” to the brain to indicate that the twisting hurts. In reality, pain is simply the brain telling us we are in danger. Although certain nerve endings throughout the body can indeed detect bodily harm, their signals are only one factor that the brain uses to determine if we should experience pain. Many cases of chronic pain are thought to be the result of obsolete brain associations between movement and pain. To explore the mind's influence over pain, Daniel Harvie, a Ph.D. candidate at the University of South Australia, and his colleagues asked 24 participants who suffer from chronic neck pain to sit in a chair while wearing virtual-reality glasses and turn their head. The displays were manipulated to make the participants think that they were turning their head more or less than they actually were. Subjects could swivel their head 6 percent more than usual if the virtual reality made them think they were turning less, and they could rotate 7 percent less than usual when they thought they were turning more. The findings suggest that virtual-reality therapy has the potential to retrain the brain to understand that once painful movements are now safe, extinguishing the association with danger. © 2015 Scientific American

Keyword: Pain & Touch
Link ID: 21155 - Posted: 07.11.2015

By JAMES GORMAN Call it the case of the homing lizards. It’s a small mystery. No one of any species is murdered. But the central question is one that has prompted plenty of scientific research: How do animals find their way home? The lizards in this case are anoles — abundant, mostly small reptiles that thrive in the Caribbean. The species is Anolis gundlachi. The lead detective is Manuel Leal, a biologist at the University of Missouri. He has been studying the behavior of anoles for more than 20 years. For about three years, Dr. Leal has been trying to understand how the anole finds its way back to its own territory after being carried into the rain forest. And as he told an audience in June at the annual meeting of the Animal Behavior Society in Anchorage, the case is far from closed. First, a bit of background. Anoles are particularly abundant in the dense vegetation of the rain forests in Puerto Rico, where Dr. Leal studies them. Each species is tied to a very specific environment. For instance, many live on tree trunks, but only a particular part of the trunk. Trunk-ground anoles live only in the space from the ground up to six feet or so. Trunk-crown anoles live above them, up to the crown of the tree. Twig anoles live way up high. Several years ago, Dr. Leal was studying competition between two species. If he removed all of the trunk-ground anoles, he wondered, would the trunk-crown lizards extend their territory farther down the tree? He ran into a problem, however. He would take the trunk-ground lizards far from their home territory to make room for their upstairs neighbors, and then release them. But in a reptilian version of the children’s song, “The Cat Came Back,” the lizards wouldn’t stay away. “Lizards kept showing up in the territory that had just been scoured for lizards,” he said. Dr. Leal wondered whether new anoles were appearing in empty territory or the old ones were returning. But how could a lizard that had never left home find its way back through 25 yards or so of dense rain forest? © 2015 The New York Times Company

Keyword: Animal Migration
Link ID: 21141 - Posted: 07.07.2015

Moheb Costandi Different immune cells regulate pain sensitization in male and female mice, according to research published on 29 June in Nature Neuroscience1. The surprising biological divide may explain why some clinical trials of pain drugs have failed, and highlights shortcomings in the way that many researchers design their experiments. The immune system has important roles in chronic pain, with cells called microglia being key players. Microglia express a protein called brain-derived neurotrophic factor (BDNF) to signal to spinal-cord neurons. When injury or inflammation occurs, this signal sensitizes the body to pain, so that even light touch hurts. Robert Sorge, a psychologist at the University of Alabama in Birmingham, and his colleagues induced persistent pain and inflammation in healthy male and female mice by severing two of the three sciatic nerve branches in their hind paws. Seven days later, they injected the animals with one of three drugs that inhibit microglial function. They found that all three drugs reversed pain sensitization in the male animals, as had been previously reported. But the treatments had no effect on the females, even though the animals had displayed equivalent levels of pain. The researchers also genetically engineered mice in which the BDNF gene could be deleted in microglia at any time during the animals' lives. At first, these animals exhibited normal responses to a nerve injury. Killing the microglia one week later extinguished that hypersensitivity in the male animals, but not in the females. This confirmed that in males, hypersensitivity to pain depends on BDNF signals from microglia, but that in females it is mediated by some other mechanism. © 2015 Nature Publishing Group,

Keyword: Pain & Touch; Sexual Behavior
Link ID: 21113 - Posted: 06.30.2015

By Megan Cartwright Don’t pet the platypus. I know it’s tempting: Given the chance, I’d want to stroke their thick brown fur, tickle those big webbed feet, and pat that funny duck bill. And why not? What harm could come from this cute, egg-laying mammal from eastern Australia? Plenty. As someone who doesn’t enjoy “long lasting excruciating pain that cannot be relieved with conventional painkillers,” I’d really regret petting a platypus. Especially a male platypus, in late winter, when there’s only one thing on his mind and, even worse, something nasty on his feet. When British biologist Sir Everard Home got ahold of some platypus specimens in 1801, he told his fellow nerds at the Royal Society how the male specimen had a half-inch long “strong crooked spur” on the heel of each rear foot. The female, however, was spur-free. Home suggested that it “is probably by means of these spurs or hooks, that the female is kept from withdrawing herself in the act of copulation.” A very reasonable suggestion. But a wrong one. To be fair to Home, he could only study dead platypuses. If Home could have spent a year hanging out with living platypuses in their river homes, he would’ve seen that this “shy, semi-aquatic, mainly nocturnal” mammal is mostly interested in hunting on the river bottom for delicious insect larvae, crayfish, and shrimp. In other words, the platypus is usually an eater, not a lover. © 2014 The Slate Group

Keyword: Neurotoxins; Pain & Touch
Link ID: 21090 - Posted: 06.25.2015

Skinny jeans can seriously damage muscles and nerves, doctors have said. A 35-year-old woman had to be cut out of a pair after her calves ballooned in size, the medics said in the Journal of Neurology, Neurosurgery and Psychiatry. She had spent hours squatting to empty cupboards for a house move in Australia. By evening, her feet were numb and she found it hard to walk. Doctors believe the woman developed a condition called compartment syndrome, made worse by her skinny jeans. Compartment syndrome is a painful and potentially serious condition caused by bleeding or swelling within an enclosed bundle of muscles - in this case, the calves. The condition caused the woman to trip and fall and, unable to get up, she then spent several hours lying on the ground. On examination at the Royal Adelaide Hospital, her lower legs were severely swollen. Although her feet were warm and had enough blood supplying them, her muscles were weak and she had lost some feeling. As the pressure had built in her lower legs, her muscles and nerves became damaged. She was put on an intravenous drip and after four days was able to walk unaided. Other medics have reported a number of cases where patients have developed tingly, numb thighs from wearing the figure-hugging low-cut denim trousers - although the chance of it happening is still slim for most people. Priya Dasoju, professional adviser at the Chartered Society of Physiotherapy, said: "As with many of these warnings, the very unfortunate case highlighted is an extreme one. © 2015 BBC

Keyword: Movement Disorders
Link ID: 21084 - Posted: 06.23.2015

Patricia Neighmond We all know that listening to music can soothe emotional pain, but Taylor Swift, Jay-Z and Alicia Keys can also ease physical pain, according to a study of children and teenagers who had major surgery. The analgesic effects of music are well known, but most of the studies have been done with adults and most of the music has been classical. Now a recent study finds that children who choose their own music or audiobook to listen to after major surgery experience less pain. The catalyst for the research was a very personal experience. Sunitha Suresh was a college student when her grandmother had major surgery and was put in intensive care with three other patients. This meant her family couldn't always be with her. So they decided to put her favorite south Indian classical Carnatic music on an iPod, so she could listen around the clock. It was very calming, Sunitha says. "She knew that someone who loved her had left that music for her and she was in a familiar place." This may be the most efficient way to get in shape, but it may also be the least fun. Suresh could see the music relaxed her grandmother and made her feel less anxious, but she wondered if she also felt less pain. That would make sense, because anxiety can make people more vulnerable to pain. At the time Suresh was majoring in biomedical engineering with a minor in music cognition at Northwestern University where her father, Santhanam Suresh, is a professor of anesthesiology and pediatrics. © 2015 NPR

Keyword: Pain & Touch
Link ID: 21080 - Posted: 06.22.2015

Bill Chappell In what researchers say is a first, they've discovered the neuron in worms that detects Earth's magnetic field. Animals have been known to sense the magnetic field; a new study identifies the microscopic, antenna-shaped sensor that helps worms orient themselves underground. The sensory neuron that the worm C. elegans uses to migrate up or down through the soil could be similar to what many other animals use, according to the team of scientists and engineers at The University of Texas at Austin. The team's work was published Wednesday by eLife. In contrast to previous breakthroughs — such as a 2012 study on how pigeons' brains use information about magnetic fields, and another from the same year on olfactory cells in trout — the new work identifies the sensory neuron that detects magnetic fields. "We also found the first hint at a novel sensory mechanism for detecting the magnetic field," says Jon Pierce-Shimomura, an assistant professor of neuroscience who worked on the study. "Now researchers can check to see if this is used in other animals too." The list of animals that could be studied for their use of magnetic fields is long — and it seems to grow each year. In early 2014, for instance, a study found that dogs who need to relieve themselves of waste prefer to align themselves on a north-south axis when the magnetic conditions are right. Pierce-Shimomura says his team was surprised to make a new breakthrough in magnetism by looking at worms, which aren't known for their sophisticated migrations. © 2015 NPR

Keyword: Pain & Touch
Link ID: 21072 - Posted: 06.18.2015

By Andrea Alfano There are many types of touch. A cold splash of water, the tug of a strong breeze or the heat and heft of your coffee mug will each play on your skin in a different way. Within your skin is an array of touch sensors, each associated with nerve fibers that connect to the central nervous system. These sensors comprise specialized nerve endings and skin cells. Along with the fibers, they translate our physical interactions with the world into electrical signals that our brain can process. They help to bridge the gap between the physical act of touching and the cognitive awareness of tactile sensation. Even a simple stroke across the forearm engages several distinct nerve fibers. Three types—A-beta, A-delta and C fibers—have subtypes that are specialized for sensing particular types of touch; other subtypes carry information related to pain. The integration of information from these fibers is what allows us to gain such rich sensory experiences through our skin, but it has also made it more challenging for researchers to understand the fibers’ individual roles. Although these fibers do not act in isolation, the examples that follow highlight the primary nerve fibers engaged by different types of touch. © 2015 Scientific American

Keyword: Pain & Touch
Link ID: 21066 - Posted: 06.18.2015

by Laura Sanders The motor homunculus is a funny-looking fellow with a hulking thumb, delicate toes and a tongue that wags below his head. His body parts and proportions stem from decades-old experiments that mapped brain areas to the body parts they control. Now, a new study suggests that the motor homunculus’ neck was in the wrong place. Hyder Jinnah of Emory University in Atlanta and colleagues used fMRI to scan the brains of volunteers as they activated their head-turning neck muscles. (Pads held participants’ heads still, so the muscles fired but heads didn’t move.) This head turn was accompanied by activity in part of the brain that controls movement. The exact spot seems to be between the brain areas that control the shoulder and the trunk — not between the areas responsible for moving the thumb and the top of the head as earlier motor homunculi had suggested, the team reports in the June 17 Journal of Neuroscience. © Society for Science & the Public 2000 - 2015.

Keyword: Pain & Touch
Link ID: 21060 - Posted: 06.17.2015