Chapter 8. General Principles of Sensory Processing, Touch, and Pain
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By William Skaggs At the level of personal experience, there is nothing that seems easier to understand than pain. When I jam my finger in a doorway, I have no difficulty at all recognizing the sensation that results. But this superficial simplicity covers up a world of complexity at the level of brain mechanisms, and the complexities are even greater when we try to identify pain in other people or other species of animals. Some of the complexities are purely scientific, but others are caused by moral or philosophical issues getting mixed up with scientific issues. My provocation for writing this post was a blog post called Do Octopuses Feel Pain?, by Katherine Harmon, who writes the blog Octopus Chronicles, It’s basically a nice article—there’s nothing objectionable about it—but it pressed one of my buttons. She made a number of important points, and altogether what she wrote is well worth reading, but nevertheless the result left me with a feeling of dissatisfaction, as do most scientific discussions about pain in animals. I’d like to try to explain where that discomfort comes from. In her blog post, Harmon listed three elements that are involved in feeling pain: (1) nociception, that is, having mechanisms in the body that are capable of detecting damage and transmuting it into neural signals; (2) the experience of pain; (3) the ability to communicate pain information from sensation to perception. I’m not sure I understand the third aspect, but I take it to mean the ability to transform nociception into experience. In any case, the essence of pain as most people understand it is aspect 2. Most people think of pain as a particular type of experience—as something that happens inside our minds and can only be observed by ourselves. © 2013 Scientific American
Keyword: Pain & Touch
Link ID: 18679 - Posted: 09.21.2013
The structure of the brain may predict whether a person will suffer chronic low back pain, according to researchers who used brain scans. The results, published in the journal Pain, support the growing idea that the brain plays a critical role in chronic pain, a concept that may lead to changes in the way doctors treat patients. The research was supported by the National Institute of Neurological Disorders and Stroke (NINDS), part of the National Institutes of Health. “We may have found an anatomical marker for chronic pain in the brain,” said Vania Apkarian, Ph.D., a senior author of the study and professor of physiology at Northwestern University Feinberg School of Medicine in Chicago. Chronic pain affects nearly 100 million Americans and costs the United States up to $635 billion per year to treat. According to the Institute of Medicine, an independent research organization, chronic pain affects a growing number of people. “Pain is becoming an enormous burden on the public. The U.S. government recently outlined steps to reduce the future burden of pain through broad-ranging efforts, including enhanced research,” said Linda Porter, Ph.D, the pain policy advisor at NINDS and a leader of NIH’s Pain Consortium. “This study is a good example of the kind of innovative research we hope will reduce chronic pain which affects a huge portion of the population.” Low back pain represents about 28 percent of all causes of pain in the United States; about 23 percent of these patients suffer chronic, or long-term, low back pain.
Keyword: Pain & Touch
Link ID: 18663 - Posted: 09.18.2013
By PAM BELLUCK It is a new frontier of the anti-abortion movement: laws banning abortion at 20 weeks after conception, contending that fetuses can feel pain then. Since 2010, a dozen states have enacted them, most recently Texas. Nationally, a bill passed the Republican-dominated House of Representatives in June. The science of fetal pain is highly complex. Most scientists who have expressed views on the issue have said they believe that if fetuses can feel pain, the neurological wiring is not in place until later, after the time when nearly all abortions occur. Several scientists have done research that abortion opponents say shows that fetuses can feel pain at 20 weeks after conception. One of those scientists said he believed fetuses could likely feel pain then, but he added that he believed the few abortions performed then could be done in ways to avoid pain. He and two other scientists said they did not think their work or current evidence provided scientific support for fetal-pain laws. Some scientists’ views have evolved as more research has been done. Dr. Nicholas Fisk, a senior maternal-fetal medicine specialist at Royal Brisbane and Women’s Hospital in Australia, said he once considered early fetal pain “a major possibility” after finding that fetuses receiving blood transfusions produced increased stress hormones and blood flow to the brain, and that painkillers lowered those levels. But Dr. Fisk, a former president of the International Fetal Medicine and Surgery Society, said neurological research has convinced him that pain “is not possible at all” before 24 weeks. © 2013 The New York Times Company
by Andy Coghlan A girl who does not feel physical pain has helped researchers identify a gene mutation that disrupts pain perception. The discovery may spur the development of new painkillers that will block pain signals in the same way. People with congenital analgesia cannot feel physical pain and often injure themselves as a result – they might badly scald their skin, for example, through being unaware that they are touching something hot. By comparing the gene sequence of a girl with the disorder against those of her parents, who do not, Ingo Kurth at Jena University Hospital in Germany and his colleagues identified a mutation in a gene called SCN11A. This gene controls the development of channels on pain-sensing neurons. Sodium ions travel through these channels, creating electrical nerve impulses that are sent to the brain, which registers pain. Overactivity in the mutated version of SCN11A prevents the build-up of the charge that the neurons need to transmit an electrical impulse, numbing the body to pain. "The outcome is blocked transmission of pain signals," says Kurth. To confirm their findings, the team inserted a mutated version of SCN11A into mice and tested their ability to perceive pain. They found that 11 per cent of the mice with the modified gene developed injuries similar to those seen in people with congenital analgesia, such as bone fractures and skin wounds. They also tested a control group of mice with the normal SCN11A gene, none of which developed such injuries. © Copyright Reed Business Information Ltd.
Amanda Fiegl What's the difference between a spicy meal and being tickled? Not much, from your lips' perspective. A new study reports that Szechuan pepper activates the same nerves that respond to a light physical touch. Researchers at the University College London Institute of Cognitive Neuroscience found that people experienced the same sensation when either Szechuan pepper—a spice used in many types of Asian cuisine—or a machine vibrating at a particular frequency was placed on their lips. "The pepper is sending the same information to the brain as having a buzzer on your lips," the study's lead author, Nobuhiro Hagura, said in an email. The study, published today in Proceedings of the Royal Society B with the wry headline "Food Vibrations," delves into the little-known field of psychophysics, which "describes the relation between physical reality and what we actually perceive," Hagura said. "Our research shows just one interesting example of a case where we perceive something quite different than what is actually there," he said. "In many cases, the difference between perception and reality can be explained by understanding how the nervous system transmits information about the outside world to the brain." Previous studies have shown that other spicy ingredients, such as chili peppers and mustard oils, activate the nerve fibers associated with pain and physical heat. And studies in animals indicated that the spicy chemical in Szechuan pepper—sanshool—acts on the nervous system's "light touch" fibers. So Hagura and his colleagues wanted to find out whether sanshool produces a conscious sensation of touch in humans. © 1996-2013 National Geographic Society.
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
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
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
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
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
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.
Keyword: Pain & Touch
Link ID: 18519 - Posted: 08.17.2013
By Melinda Wenner Moyer Our world is determined by the limits of our five senses. We can't hear pitches that are too high or low, nor can we see ultraviolet or infrared light—even though these phenomena are not fundamentally different from the sounds and sights that our ears and eyes can detect. But what if it were possible to widen our sensory boundaries beyond the physical limitations of our anatomy? In a study published recently in Nature Communications, scientists used brain implants to teach rats to “see” infrared light, which they usually find invisible. The implications are tremendous: if the brain is so flexible it can learn to process novel sensory signals, people could one day feel touch through prosthetic limbs, see heat via infrared light or even develop a sixth sense for magnetic north. Miguel Nicolelis, a neurobiologist at Duke University, and his colleagues trained six rats to poke their nose inside a port when the LED light above it lit up. Then the researchers surgically attached infrared cameras to the rats' head and wired the cameras to electrodes they implanted into the rats' primary somatosensory cortex, a brain region responsible for sensory processing. When the camera detected infrared light, it stimulated the animals' whisker neurons. The stimulation became stronger the closer the rats got to the infrared light or the more they turned their head toward it, just as brain activation responds to light seen by the eyes. Then the scientists let the animals loose in their chambers, this time using infrared light instead of LEDs to signal the ports the rats should visit. At first, none of the rats used the infrared signals. But after about 26 days of practice, all six had learned how to use the once invisible light to find the right ports. © 2013 Scientific American
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
Keyword: Pain & Touch
Link ID: 18449 - Posted: 08.03.2013
A stroke patient has developed a rare neurological condition nine months into his recovery that leaves him disgusted by words printed in a certain shade of blue and lifted to ecstasy by the sound of music by brass instruments, a Toronto neuroscientist says. The case, described in today's issue of the medical journal Neurology, involves an anonymous 45-year-old patient in Toronto who was initially frightened by the conflicting senses he began to experience. It is only the second known case of a patient developing the neurological condition after a brain injury. High-pitched brass instruments like those played in the theme from James Bond movies elicited feelings of ecstasy and created light blue flashes in his peripheral vision. They also caused large parts of his brain to light up in tests, the report says. "I heard it one day some time after the stroke and I went for a ride that was, it was cosmic in its voyage and it was wonderful," the patient said in a hospital YouTube interview. In contrast, when the euphonium was played in the study, the man said the response was cut off. Synesthesia is a neurological condition in which one sense, such as hearing, is simultaneously perceived by one or more additional senses, such as sight. The word synesthesia comes from two Greek words, syn (together) and aisthesis (perception); literally, "joined perception." People who report such experiences are known as synesthetes. © CBC 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.
Keyword: Pain & Touch
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
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
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
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