By Nathan Seppa Just in time to combat the obesity epidemic sweeping the United States, a surgery called gastric bypass is riding a host of molecular and clinical findings to emerge as the preferred operation for severely overweight people. There is no shortage of patients; fully one-third of U.S. adults are now obese. Gastric bypass has gained popularity in part because it takes the pounds off. The operation leaves the stomach smaller, meaning a patient gets full faster, eats less and loses weight at a steady pace. Other common obesity surgeries have those effects too, but gastric bypass also reverses type 2 diabetes in most people, an outcome that bordered on alchemy when first noticed years ago. New research clarifies the molecular players that make this medical sleight of hand possible, as well as revealing other potential payoffs of the digestive changes — less heart disease, fewer breathing problems and lower blood pressure. Electing to have major surgery is a tough call; gastric bypass doesn’t always succeed. Patients can backslide, regaining lost weight. And about 10 percent of the surgeries have complications that can result in infections, blood clots or the need for repeat surgery. But many who witness the effects of gastric bypass firsthand suggest that the hard evidence has now tipped the scales in favor of the operation. © Society for Science & the Public 2000 - 2011

Keyword: Obesity
Link ID: 15726 - Posted: 08.27.2011

By Jeremy Laurance, Health Edtior Dieting is harder than you think. If you cut out a chocolate bar each day you will lose only one-third of the weight that experts had thought. For decades, doctors have based their advice to those who want to lose weight on the assumption that cutting 500 calories a day will see the weight fall off at the rate of 1lb a week. "This is wrong," Kevin Hill, of the National Institutes of Health in the United States, said. "It does not happen." The error has arisen because the calculation did not take account of changes in metabolism as weight falls. The body adjusts to reductions in energy intake (calories eaten) by slowing its energy output (calories expended). The result is that forgoing that daily chocolate bar containing 250 calories will lead to about 25lb of weight loss if it is sustained for three years, much less than the 78lb predicted by the old dieting assumption. A more sophisticated measure of weight loss, which takes account of metabolic changes and of differences between fat and thin people, has been developed by Dr Hill and colleagues of the National Institute of Diabetes and Digestive and Kidney Diseases. It shows that heavier people tend to lose weight faster than lighter people on the same diet, though they will take longer to reach the target weight than those who weigh less to begin with. Most people on a diet achieve their maximum weight loss after six to eight months and it has been assumed this is a natural "plateauing" effect, resulting from slowed metabolism. But evidence shows that people find it hard to stick to a diet for longer than six months and that is why they stop losing weight. Body-weight plateauing occurs much later, after two to three years. ©independent.co.uk

Keyword: Obesity
Link ID: 15725 - Posted: 08.27.2011

National Institutes of Health researchers have found that Parkin, an important protein linked with some cases of early-onset Parkinson’s disease, regulates how cells in our bodies take up and process dietary fats. Parkinson’s disease is a complex, progressive, and currently incurable neurological disorder characterized by shaking, stiffness, slowed movement, and impaired balance. Parkinson’s primarily affects people over 50, but in about 5 to10 percent of cases it occurs in people as young as their 20s. This form of the disease, which affects actor, author, and Parkinson’s activist Michael J. Fox, is known as early-onset Parkinson’s. Parkin mutations are present in as many as 37 percent of early-onset Parkinson’s cases. However, laboratory mice with defective Parkin do not display obvious signs of the disease. This preliminary study, which will appear online in the Journal of Clinical Investigation on Aug. 25, suggests defective Parkin may indirectly contribute to the development of some early-onset Parkinson's by changing the amount and types of fat in people’s bodies. The research team, composed of scientists from the NHLBI and the NIH’s National Institute of Neurological Disorders and Stroke, observed that mice with defective Parkin did not gain weight in response to a high-fat laboratory diet, as regular mice typically do. When the researchers examined several organs of the Parkin-defective mice, they noticed that the cells contained low levels of certain proteins that transport fat in the body. In contrast, normal mice that were fed the same high-fat diet had high levels of these fat-carrying proteins, as well as high levels of Parkin, suggesting that Parkin is involved in fat transportation.

Keyword: Parkinsons; Obesity
Link ID: 15724 - Posted: 08.27.2011

by Sara Reardon Contrary to popular belief, ostriches don't sleep with their heads in the sand. In fact, to all appearances, they never sleep at all: their eyes stay open, although they appear to doze off from time to time. To learn more about the sleep patterns of this unusual bird, researchers captured six ostriches in South Africa and measured their brain wave patterns with data loggers while they slept They expected the brain waves to look like those of other birds and mammals, which cycle between two patterns: deep sleep and rapid eye movement (REM). When the loggers showed that the ostriches were in deep sleep, the birds looked entirely alert. But when they entered another sleep cycle, their heads started to droop. This second brainwave pattern wasn't classic REM, but a unique hybrid of REM and deep sleep patterns, the researchers report this week in PLoS ONE. The only other animal to show this pattern is the platypus, a member of an ancient group of egg-laying mammals known as monotremes. As ostriches are an ancient type of bird, this similarity suggests that the separation between REM and deep sleep may have evolved recently in birds and mammals. One can only speculate on whether ostriches and platypuses have similar dreams, too. © 2010 American Association for the Advancement of Science.

Keyword: Sleep; Evolution
Link ID: 15723 - Posted: 08.27.2011

Researchers at the University of Calgary have documented serious health complications in multiple sclerosis patients who travelled outside of Canada to undergo a controversial treatment for their disease. Many MS patients have travelled overseas to find clinics willing to provide the treatment invented by Italian physician Paolo Zamboni, which uses balloon angioplasty to open up blocked veins in the necks of those who suffer from the disease. The new study followed five patients who had the vein opening therapy and were treated in Calgary hospitals in October and November last year after complications from their surgeries. The lead author of the paper, Dr. Jodie Burton, admits that it is difficult to draw conclusions since there were only five patients involved and it's not known how many Canadians went to locations like the United States, Mexico, India, and Poland to have the procedure done. But she says the seriousness of the complications should serve as a — quote — "cautionary tale" to anyone considering having the procedure done. Burton says patients shouldn't be afraid to let their doctors know they had the treatment and physicians need to know what to watch for as a result. In June, the federal government announced it will hold early-stage clinical trials into the treatment. © The Canadian Press, 2011 © CBC 2011

Keyword: Multiple Sclerosis
Link ID: 15722 - Posted: 08.25.2011

by Caroline Williams Ever wondered how a dog, with a sense of smell that may be thousands of times more sensitive than ours, can bear to bury its face in the trash can? Alexandra Horowitz, a dog-cognition researcher at Columbia University in New York City and author of Inside of a Dog: What dogs see, smell, and know, says it's because the dog isn't simply smelling a stronger version of the revolting mono-stench that we smell. "It is not that smells are 'louder'," she says. "The smells have different layers, which probably give dogs a much bigger range of types of information." She compares it to the way we might enjoy a painting from across the room, but appreciate it in a different way when we can get up close and see the brush strokes. This makes a dog's experience fundamentally different to our own. When we go out for a walk, for example, we get almost all of our information from vision. But the dog's eyes are just a back-up. This was shown when police tracker dogs were given a scent trail that seemed to run in the opposite direction to a set of footprints on the ground; they invariably followed their noses and ignored the contradictory visual cues (Applied Animal Behaviour Science, vol 84, p 297). This reliance on smell explains why a dog that isn't expecting to see its owner will often stop a metre or so away for a quick sniff before jumping all over them. To imagine the scent-based world of a dog, says Horowitz, look around and imagine that everything you see has its own individual scent. And not just each object - different parts of the same object may hold different types of information. Horowitz gives the example of a rose: each petal might have a different scent, telling the dog it has been visited by different insects that left telltale traces of pollen from other flowers. Besides picking up on the individual scent of humans that had touched the flower, it could even guess when they may have passed by. © Copyright Reed Business Information Ltd.

Keyword: Chemical Senses (Smell & Taste)
Link ID: 15721 - Posted: 08.25.2011

by Linda Geddes KENZO LOW could always look people in the eyes, but it hurt. "I felt a piercing intrusive sensation, like they were threatening me," he says. All that changed when he had a non-invasive form of brain stimulation. The idea was to see if it would alter any of his Asperger's symptoms. Several months afterwards, he noticed a positive change in the way he interacted with his aunt: "I could look at her the entire time she spoke to me without flinching or cringing inside." Low is one of a handful of people participating in the first clinical trials to test whether transcranial magnetic stimulation (TMS) might boost social skills in people with autism spectrum disorders. As well as gaining insight into how an autistic person's brain functions, it is beginning to look as if certain facets of ASD might be treatable - assuming of course that a person wants such intervention. Early results suggest that empathy and social functioning improve when a small area at the front of the brain is stimulated, while ability to communicate and concentration appear to be boosted when TMS is used to suppress activity in a different region of the brain. "We're not proposing that this is likely to be a cure," says Paul Fitzgerald of the Monash Alfred Psychiatry Research Centre in Melbourne, Australia, who is leading the research that Low has been participating in. "But even if we only get short-term benefits, or they only occur in a small percentage of patients, it is really one of the first demonstrations that we can do something at a biological level that might be therapeutic." © Copyright Reed Business Information Ltd.

Keyword: Autism; Emotions
Link ID: 15720 - Posted: 08.25.2011

MacGregor Campbell, consultant Want to get rid of destructive lampreys? In this video, you can see how the smell of death can be a particularly effective repellant. Michael Wagner of Michigan State University exposed a group of lampreys to a mixture of chemicals from putrefying carcasses and ethanol. Another group was subjected to a similar amount of plain ethanol as a control. The animals exposed to the death-scented chemicals jumped out of the tank with a panic-like response. Sea lampreys are an invasive species in the US Great Lakes. They live as parasites on the bodies of lake trout and other commercially-important fish and have contributed to collapsing fish stocks in the region. Currently, wildlife officials use pheromones to lure lampreys into large cages where they can be destroyed or sterilised. These are the same chemicals the lampreys rely on to attract mates or to find good spawning grounds. But using natural cues to attract lampreys can be inefficient since a variety of scents in natural waterways compete for their attention. According to Wagner, repellants could be a better alternative to divert them since even tiny quantities can provoke a response. The smell of death could be used to form a chemical dam to steer lampreys away from environmentally-sensitive waterways. The chemicals could also be used to corral the animals into groups, making them easier to eliminate. © Copyright Reed Business Information Ltd.

Keyword: Chemical Senses (Smell & Taste)
Link ID: 15719 - Posted: 08.25.2011

By LYNN ZINSER Pat Summitt, the longtime women’s basketball coach at Tennessee who has won more games than any other major college coach, said she forgot things at crucial points in games at times last season and struggled to keep track of when meetings were scheduled. She grew so confused that on a few days she simply stayed home from work. It was not until after the season ended that she sought a medical diagnosis and learned she has symptoms of early onset Alzheimer’s disease. Ms. Summitt, 59, revealed the diagnosis on Tuesday, and said she planned to continue to coach. She said her doctor at the Mayo Clinic in Rochester, Minn., encouraged her to continue as long as she felt up to it. “I plan to continue to be your coach,” Ms. Summitt said in a videotaped statement posted on the university’s Web site. “Obviously, I realize I may have some limitations with this condition since there will be some good days and some bad days.” Ms. Summitt built a powerhouse program in Knoxville that often outshone the university’s men’s team, amassing 1,079 victories that make her the most successful Division I coach of either gender. She will enter her 38th season at Tennessee in pursuit of her ninth national title. Long known for a steely, intense coaching style, Ms. Summitt will now also be the public face of a debilitating disease. © 2011 The New York Times Company

Keyword: Alzheimers
Link ID: 15718 - Posted: 08.25.2011

A new atlas of gene expression in the mouse brain provides insight into how genes work in the outer part of the brain called the cerebral cortex. In humans, the cerebral cortex is the largest part of the brain, and the region responsible for memory, sensory perception and language. Mice and people share 90 percent of their genes so the atlas, which is based on the study of normal mice, lays a foundation for future studies of mouse models for human diseases and, eventually, the development of treatments. Researchers from the National Human Genome Research Institute (NHGRI), part of the National Institutes of Health, and from Oxford University in the United Kingdom, published a description of the new atlas in the Aug. 25, 2011, journal Neuron. The study describes the activity of more than 11,000 genes in the six layers of brain cells that make up the cerebral cortex. To map gene activity in all six layers of the mouse cerebral cortex, the research team first micro-dissected the brains of eight adult mice, separating the layers of the cortex. They then purified processed RNAs, including messenger RNA, from each cortical layer. The international collaborators have made the new atlas freely available at http://genserv.anat.ox.ac.uk/layers.

Keyword: Genes & Behavior; Development of the Brain
Link ID: 15717 - Posted: 08.25.2011

by Dan Hurley 10:19 p.m. on a Monday evening in October, I sat in a booth at Chevys Fresh Mex in Clifton, New Jersey, reviewing the latest research into the neurobiology of hunger and obesity. While I read I ate a shrimp and crab enchilada, consuming two-thirds of it, maybe less. With all this information in front of me, I thought, I had an edge over my brain’s wily efforts to thwart my months-long campaign to get under 190 pounds. But even as I was taking in a study about the powerful lure of guacamole and other salty, fatty foods, I experienced something extraordinary. That bowl of chips and salsa at the edge of the table? It was whispering to me: Just one more. You know you want us. Aren’t we delicious? In 10 minutes, all that was left of the chips, and my willpower, were crumbs. I am not alone. An overabundance of chips, Baconator Double burgers, and Venti White Chocolate Mochas have aided a widespread epidemic of obesity in this country. Our waists are laying waste to our health and to our health-care economy: According to a study published by the Centers for Disease Control and Prevention in 2010, nine states had an obesity rate of at least 30 percent—compared with zero states some 10 years earlier—and the cost of treatment for obesity-related conditions had reached nearly 10 percent of total U.S. medical expenditure. So-called normal weight is no longer normal, with two-thirds of adults and one third of children and adolescents now classified as overweight or obese. Dubbed the “Age of Obesity and Inactivity” by the Journal of the American Medical Association, this runaway weight gain threatens to decrease average U.S. life span, reversing gains made over the past century by lowering risk factors from smoking, hypertension, and cholesterol. We all know what we should do—eat less, exercise more—but to no avail. An estimated 25 percent of American men and 43 percent of women attempt to lose weight each year; of those who succeed in their diets, between 5 and 20 percent (and it is closer to 5 percent) manage to keep it off for the long haul. © 2011, Kalmbach Publishing Co.

Keyword: Obesity
Link ID: 15716 - Posted: 08.25.2011

by Elizabeth Norton Time is what keeps everything from happening at once, the American theoretical physicist John Wheeler once said. In the mind, as in the outside world, the flow of events contains individual experiences strung together in sequence yet separated by gaps in time. New research shows that during these gaps, neurons in a part of the brain called the hippocampus encode each "empty" moment as precisely as the surrounding events, allowing the brain to make detailed representations of time. The hippocampus has long been known as a center for navigation and memory. Research into this sea horse-shaped structure shows the importance of "place cells," groups of which fire when a person or animal is at a certain location. The firing pattern provides the neural basis of the mental maps used to find one's way around. But the hippocampus also encodes "episodic" memories of events as they occur in time. Thus, many researchers wondered whether the hippocampus also contains "time cells." To test the idea, Howard Eichenbaum and colleagues at Boston University trained rats to perform a two-part task with a delay in the middle while fitted with surgically implanted electrodes that recorded neural activity in the hippocampus. The rats were taught to associate an object with an odor: a ball with oregano, for example, and a cube with cinnamon. Then they were presented with one of the objects, after which they entered a chamber for 10 seconds. After this delay, a partition opened, leading to a flowerpot full of scented sand. If the scent paired with the object seen earlier, the rats knew to dig for a food reward. If the odor and object didn't match, the rats refrained from digging. (This correct response was rewarded with a treat in another part of the run.) © 2010 American Association for the Advancement of Science

Keyword: Attention
Link ID: 15715 - Posted: 08.25.2011

By Francie Diep To the list of cocaine’s many dangers, health officials have added at least one more: purpura, a rash caused by internal bleeding from small blood vessels. Two recent papers in major medical journals have documented cases of cocaine users showing up in emergency rooms with patches of blackened, dying skin on the ears, face, trunk or extremities. The condition causes scarring and sometimes requires reconstructive surgery. Noah Craft, a dermatologist at the Harbor-UCLA Medical Center who co-authored a paper on the condition published online by the Journal of the American Academy of Dermatology in June, says he now sees about one case per month: “It’s become almost routine.” The cause of the outbreak is a veterinary deworming medication that has become the most common ingredient used to dilute, or cut, cocaine coming into the U.S. from South America. The drug, called levamisole, was once approved for cancer treatment but was later pulled because of its side effects. Three quarters of the cocaine bricks seized by the U.S. Drug Enforcement Administration now contain levamisole. Equally worrying is another of its side effects: a sometimes fatal lowered count of white blood cells that are called neutrophils. Doctors suspect that both conditions are allergic reactions to the drug. In one disease, the body’s immune system attacks the skin; in the other, it attacks the bone marrow. Traffickers may add levamisole to cocaine because it is cheaper than pure cocaine and may contribute to the cocaine high. Papers between the 1970s and 1990s, when levamisole was being suggested and then approved for medical use in the U.S., found it improved mood and caused insomnia and hyperalertness, effects that are similar to cocaine’s. © 2011 Scientific American,

Keyword: Drug Abuse
Link ID: 15714 - Posted: 08.25.2011

Adam Kolber Several studies suggest that memories can be pharmaceutically dampened. A few months ago, for instance, researchers showed that a drug called ZIP causes cocaine-addicted rats to forget the locations where they had regularly been receiving cocaine1. Other drugs, already tested in humans, may ease the emotional pain associated with memories of traumatic events. Indeed, the use of memory-altering drugs to treat addicts or victims of assaults, car accidents, natural disasters and terrorist attacks looks increasingly promising. Many are alarmed by the prospect. As far back as 2003, the US President's Council on Bioethics issued a report that largely decried the use of such drugs2. Since then, journal articles and news stories have reiterated concerns that memory manipulators could interfere with the ability to lead true and honourable lives or could undermine a person's sense of identity. The fears about pharmaceutical memory manipulation are overblown. Thoughtful regulation may some day be appropriate, but excessive hand-wringing now over the ethics of tampering with memory could stall research into preventing post-traumatic stress in millions of people. Delay could also hinder people who are already debilitated by harrowing memories from being offered the best hope yet of reclaiming their lives. Various drugs are being investigated3, 4. Propranolol, for instance — which is already approved by the US Food and Drug Administration to treat hypertension — may dull the emotional pain associated with the recall of an upsetting experience by interfering with the release of stress hormones that otherwise strengthen memories. Preliminary studies suggest that propranolol can inhibit the formation of traumatic memories even when taken a few hours after a distressing event5, 6. © 2011 Nature Publishing Group,

Keyword: Learning & Memory; Stress
Link ID: 15713 - Posted: 08.23.2011

Bob Holmes, contributor HUMANS are very good at language. Computers are just beginning to cope with the complexities of speech, but almost every child masters language easily. This remarkable talent has led some anthropologists and psychologists to conclude that we have an innate "language instinct" - that evolution shaped our brains into language-learning devices. In Harnessed, psychologist Mark Changizi turns this argument on its head: instead of our brains adapting to language, he claims, language has evolved to take advantage of sound-processing skills the brain already possessed. Music has done the same, adapting itself to fit our brain's pre-existing talents and borrowing - harnessing - them for a new purpose. Our prelinguistic ancestors used their ears to inform them about events in their surroundings, and we are still good at this. Close your eyes for a moment and listen: not only can you hear a person walking nearby, but you know how close they are, whether they are going up or down stairs, often who they are and what their mood is, and whether they just filled a coffee mug or a water glass. You do that by discriminating many small details of the sounds you hear - the particular "clink" of a coffee mug, the characteristic rhythm of someone's gait, and the like. Crucially, most of this discrimination takes place subliminally, before your conscious mind assembles and labels the perception. © Copyright Reed Business Information Ltd.

Keyword: Hearing; Evolution
Link ID: 15712 - Posted: 08.23.2011

by Sujata Gupta In spring last year, the number of narcolepsy cases in Beijing, China, multiplied threefold. Now, it looks like the swine flu pandemic of the previous winter was to blame. Previously, similar rises in cases of narcolepsy – a disorder that causes sleepiness at inappropriate times – have been linked to use of a swine flu vaccine. The cause was presumed to lie in the drug's adjuvants – additives that boost the immune response to the vaccine. The claim puzzled researchers who saw a concurrent rise in narcolepsy cases in China, where few people had opted to get vaccinated and those who did received a vaccine without adjuvants. Could the flu itself be to blame? To find out, Fang Han and his colleagues at Beijing University People's Hospital studied the medical profiles of 906 people who had come to the hospital with narcolepsy since 1998. The group found that, even in the years before the vaccine was introduced in October 2009, the number of narcolepsy cases followed a seasonal pattern – cases dropped significantly around November and spiked in April. The peak was higher than normal in the spring after the swine flu pandemic (Annals of Neurology, DOI: 10.1002/ana.22587). The idea that flu causes narcolepsy fits in with the theory that narcolepsy is triggered by the immune system's response to airway infections. © Copyright Reed Business Information Ltd.

Keyword: Narcolepsy
Link ID: 15711 - Posted: 08.23.2011

By SINDYA N. BHANOO Acorn woodpeckers are industrious, cooperative birds that live in family groups. Each family has several “helper” woodpeckers that do not breed. These birds devote their time to gathering acorns and other food for the young. Researchers were surprised to find that helpers are more beneficial in the spring after a good crop than in one after a poor harvest. “It makes a lot of intuitive sense that the helpers are a lot more useful when conditions are bad,” said Walter Koenig, an ornithologist at Cornell University. “But in fact it seems to be exactly the opposite.” In the spring after a good acorn crop, the average number of new offspring in a family group increased by about seven-tenths of an offspring per helper. In a bad year, helpers slightly reduced the overall reproductive success. That’s because when an acorn crop is bad, having a helper may not help much, Dr. Koenig said. In fact, helpers might be eating up food that could otherwise go to fledglings. But in a good year, helpers are able to help harvest extra food and contribute to the family’s food reserves. Helper woodpeckers are generally young adults that are actively looking for breeding opportunities, within the family group or outside of it. Until they make a match, they maintain their roles as assistants and help raise their younger siblings and other relatives. © 2011 The New York Times Company

Keyword: Sexual Behavior; Evolution
Link ID: 15710 - Posted: 08.23.2011

By AMANDA SCHAFFER For years, scientists thought they understood the skeleton. It serves as structural support for the body. It stores calcium and phosphate. It contributes to blood cell development. And it serves, indispensably, as the creepy mascot of Halloween. But as it turns out, there may be still more to bone. A few years ago, researchers at Columbia University Medical Center discovered, to everyone’s surprise, that the skeleton seems to help regulate blood sugar. Now the team, led by Dr. Gerard Karsenty, geneticist and endocrinologist at Columbia University, has found that bone may play an unexpected role in reproduction. If the work pans out, it may help to explain some cases of low fertility in men. “It’s definitely an attention-grabber,” Dr. William Crowley of Harvard Medical School, who was not involved in the research, said of the new finding regarding fertility. “I think it will turn out to be a seminal observation.” (No pun intended, presumably.) It is well known that the hormones estrogen and testosterone, produced in the ovaries and testes, help to regulate bone growth. When women reach menopause, estrogen levels decrease along with bone mass, putting them at increased risk for osteoporosis. As men age, their testosterone and estrogen levels decline, as well. Men lose bone, but much more slowly than women do. “We thought that if the sex organs talk to the skeleton, then the skeleton should talk back to the sex organs,” Dr. Karsenty said. Apparently it does. © 2011 The New York Times Company

Keyword: Sexual Behavior; Hormones & Behavior
Link ID: 15709 - Posted: 08.23.2011

by Caroline Williams A bat would probably have no trouble imagining how it is to see like a human: some species have eyesight that is at least as good as ours, and some see better than us in dim light. For us to imagine their world, though, is somewhat trickier. Insect-eating bats and some fruit-eaters get much of the detail they need to find food through echolocation: clicks, squeals and screams that they belt out at up to 120 decibels. That's the volume of a passing ambulance siren. Thankfully they do it in ultrasound, above the range of human hearing. The echoes of these sounds give them a huge amount of information about their surroundings. The time it takes for an echo to return, for example, reveals the distance of an object, and the changes in the sound's frequency as it bounces off another creature can even reveal the speed and direction of the animal's movement. The sensitivity of echolocation is phenomenal. A study published last year found that some bats can detect differences in the distance between themselves and their prey with an accuracy of between 4 and 13 millimetres (Journal of the Acoustical Society of America, vol 128, p 1467). For an insect-eating bat, that's enough to scoop up the insect with its wings before passing it to its mouth. Subtle differences in the tone of these sounds, meanwhile, reveal a bat's identity to its peers, in much the same way that we recognise someone's speaking voice (PLoS Computer Biology, vol 6, p e1000400). © Copyright Reed Business Information Ltd.

Keyword: Hearing
Link ID: 15708 - Posted: 08.23.2011

by Caroline Williams The idea that animals can navigate using their own internal compass is so startling it was once dismissed as pure fantasy. Now there is good evidence that many species - including pigeons, sea turtles, chickens, naked mole rats and possibly cattle - can detect the Earth's geomagnetic field, sometimes with astonishing accuracy. Young loggerhead turtles, for example, read the Earth's magnetic field to adjust the direction in which they swim. They seem to hatch with a set of directions, which, with the help of their magnetic sense, ensures that they always stay in warm waters during their first migration around the rim of the North Atlantic. Over time they build a more detailed magnetic map by learning to recognise variations in the strength and direction of the field lines, which are angled more steeply towards the poles and flatter at the magnetic equator. What isn't known, however, is how they sense magnetism. Part of the problem is that magnetic fields can pass through biological tissues without being altered, so the sensors could, in theory, be located in any part of the body. What's more, the detection might not need specialised structures at all, but may instead be based on a series of chemical reactions. Even so, many researchers think that magnetic receptors probably exist in the head of turtles and perhaps other animals. These might be based on crystals of magnetite, which align with the Earth's magnetic field and could pull on some kind of stretch receptor or hair-like cell as it changes polarity. The mineral has already been found in some bacteria, and in the noses of fish like salmon and rainbow trout, which also seem to track the Earth's magnetic field as they migrate. © Copyright Reed Business Information Ltd.

Keyword: Animal Migration
Link ID: 15707 - Posted: 08.23.2011