Chapter 16. None

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Ewen Callaway An equine oddity with the head of a zebra and the rump of a donkey, the last quagga (Equus quagga quagga) died in 1883. A century later, researchers published1 around 200 nucleotides sequenced from a 140-year-old piece of quagga muscle. Those scraps of DNA — the first genetic secrets pulled from a long-dead organism — revealed that the quagga was distinct from the mountain zebra (Equus zebra). More significantly, the research showed that from then on, examining fossils would no longer be the only way to probe extinct life. “If the long-term survival of DNA proves to be a general phenomenon,” geneticists Russell Higuchi and Allan Wilson of the University of California, Berkeley, and their colleagues noted in their quagga paper1, “several fields including palaeontology, evolutionary biology, archaeology and forensic science may benefit.” At first, progress was fitful. Concerns over the authenticity of ancient-DNA research fuelled schisms in the field and deep scepticism outside it. But this has faded, thanks to laboratory rigour that borders on paranoia and sequencing techniques that help researchers to identify and exclude contaminating modern DNA. These advances have fostered an ancient-genomics boom. In the past year, researchers have unveiled the two oldest genomes on record: those of a horse that had been buried in Canadian permafrost for around 700,000 years2, and of a roughly 400,000-year-old human relative from a Spanish cavern3. A Neanderthal sequence every bit as complete and accurate as a contemporary human genome has been released4, as has the genome of a Siberian child connecting Native Americans to Europeans5. © 2014 Nature Publishing Group

Keyword: Evolution; Aggression
Link ID: 19417 - Posted: 03.27.2014

By Greg Miller Nobody knows what causes autism, a condition that varies so widely in severity that some people on the spectrum achieve enviable fame and success while others require lifelong assistance due to severe problems with communication, cognition, and behavior. Scientists have found countless clues, but so far they don’t quite add up. The genetics is complicated. The neuroscience is conflicted. Now, a new study adds an intriguing, unexpected, and sure-to-be controversial finding to the mix: It suggests the brains of children with autism contain small patches where the normally ordered arrangement of neurons in the cerebral cortex is disrupted. “We’ve found locations where there appears to be a failure of normal development,” said Eric Courchesne, a neuroscientist at the University of California, San Diego and an author of the study, which appears today in the New England Journal of Medicine. “It’s been really difficult to identify a lesion or anything in the brain that’s specific and diagnostic of autism,” said Thomas Insel, director of the National Institute of Mental Health, one of several agencies that funded the project. The new study is notable because it applies sophisticated molecular labeling methods to postmortem tissue from people with autism who died as children, which is incredibly hard to come by, Insel says. “If it’s real, if it’s replicated and it’s a consistent finding, it’s more evidence that autism starts prenatally and only manifests itself when kids start to have trouble with language or social behavior around age two or three,” Insel said. “These kinds of changes in cellular architecture would happen during brain development, probably around the first part of the second trimester.” © 2014 Condé Nast

Keyword: Autism; Aggression
Link ID: 19416 - Posted: 03.27.2014

by Erika Engelhaupt What gets us hot can be so revealing. For me, the slightest anxiety or excitement can trigger a warm spread across my face. I can feel the blood rushing up my neck and into the thousands of tiny capillaries across my cheeks. I’ve worn scarves or turtlenecks to job interviews, weather be damned, to keep my burning red neck from betraying my nerves. And the opposite can be true. Have you ever seen someone truly blanch? Given a real fright, the blood can literally drain from a person’s face, leaving a white mask. This all happens thanks to the autonomic nervous system, the fight-or-flight control system. Faced with danger, it tells blood vessels to pinch off the flow to the face and extremities, sending more blood to the muscles and body core so you’ll be pumped up for either the flight or the fight. Heat-sensing cameras can pick all this up, and in way more detail than my scarf could hide. Our nervous systems are constantly chugging away, largely out of our conscious control, tweaking our blood flow for every emotion. Just think of all the tiny wafts of heat flowing across your face as you negotiate with your boss, or talk to your lover. Feeling a bit anxious? Guilty? Stressed? Sexually aroused, perhaps? There’s a researcher out there with a thermal camera that can detect each of those. Even post-traumatic stress disorder may show up in your face’s heat map. In a pilot study of bank tellers who have been robbed, a team of researchers in Italy reports in the April 25 Neuroscience that tellers with mild PTSD have amped-up fear responses that show up in their facial heat signature. © Society for Science & the Public 2000 - 2013.

Keyword: Emotions; Aggression
Link ID: 19415 - Posted: 03.27.2014

Matt Wall Given the media coverage brain imaging studies get, you might think that they are constantly revealing important secrets about this mysterious organ. Catherine Loveday thinks otherwise. She makes the point that using brain-scanning technology to understand what a diseased brain is doing is only of academic interest. It is the study of the mind through behaviour and other cognitive functions, she argues, that leads to useful insights about disorders and treatments. There is some truth here, but as a scientist who uses brain scans every day, I would argue that they contribute a lot more than Loveday gives them credit for. The main problem is that, when it comes to the brain, all analogies are hopelessly crude. The distinction between hardware and software – or the brain and the mind – only has limited practical usefulness. Since all mental processes arise as a result of brain processes, it follows that all mental problems are also a result of dysfunctions in the physical brain. This will be seen by many as an extreme and reductionist position, but a specific example should help to show that it has some value. Parkinson’s disease is a degenerative disorder that causes a variety of symptoms including motor problems, sleep disturbance, various cognitive issues, and often depression. This variety of symptoms might suggest that the underlying problem in Parkinson’s is quite broad and complex, affecting several brain systems. However, it turns out the cause of all these symptoms is quite specific: a loss of neurons in a region of the brain called the substantia nigra. © 2014 Guardian News and Media Limited

Keyword: Brain imaging
Link ID: 19414 - Posted: 03.27.2014

by Aviva Rutkin Eureka! Like Archimedes in his bath, crows know how to displace water, showing that Aesop's fable The Crow and the Pitcher isn't purely fictional. To see if New Caledonian crows could handle some of the basic principles of volume displacement, Sarah Jelbert at the University of Auckland in New Zealand and her colleagues placed scraps of meat just out of a crow's reach, floating in a series of tubes that were part-filled with water. Objects potentially useful for bringing up the water level, like stones or heavy rubber erasers, were left nearby. The crows successfully figured out that heavy and solid objects would help them get a treat faster. They also preferred to drop objects in tubes where they could access a reward more easily, picking out tubes with higher water levels and choosing tubes of water over sand-filled ones. However, the crows failed at more challenging tasks that required an understanding of the effect of tube width or the ability to infer a hidden connection between two linked tubes. The crows displayed reasoning skills equivalent to an average 5 to 7 year old human child, the researchers claim. Previously, Eurasian jays have shown some understanding of water displacement, as have chimpanzees and orang-utans, but using similar experiments could assess and compare their skill levels. "Any animal capable of picking up stones could potentially participate," write the researchers. © Copyright Reed Business Information Ltd.

Keyword: Intelligence; Aggression
Link ID: 19413 - Posted: 03.27.2014

by Colin Barras What a nerve! Skin cells taken from people with bipolar disorder have been turned into brain cells. These in turn are offering up clues about the changes in the brain that drive the disorder, and may also provide a way to test new treatments. About three in every 100 people develop bipolar disorder – a mental illness characterised by episodes of depression and euphoria. But the condition remains poorly understood. That's because it would be too invasive to obtain and study viable nerve cells from the brains of people with the condition. There are also no good animal models, because bipolar disorder – although highly heritable – has, for the most part, not been linked to any specific genes that can be studied using animals. "People say the condition is probably the result of a lot of small contributions by multiple genes," says Sue O'Shea at the University of Michigan in Ann Arbor. Now O'Shea and her colleagues may have found an ethical way to make a genetic model of the condition. First, they took skin samples from 22 people with bipolar disorder and 10 healthy volunteers. They induced these adult skin cells to return to a stem-cell-like state, creating what are called induced pluripotent stem cells (iPSCs) and then encouraged these cells to mature into neurons. O'Shea was surprised to find that neurons derived from people with bipolar disorder grew differently from those from people without the condition. "I was expecting it would take decades of careful science before we would find any real differences," she says. © Copyright Reed Business Information Ltd.

Keyword: Schizophrenia; Aggression
Link ID: 19412 - Posted: 03.26.2014

By RICHARD A. FRIEDMAN FEELING down? Smile. Cheer up. Put on a happy face. No doubt you’ve dismissed these bromides from friends and loved ones because everyone knows that you can’t feel better just by aping a happy look. Or perhaps you can. New research suggests that it is possible to treat depression by paralyzing key facial muscles with Botox, which prevents patients from frowning and having unhappy-looking faces. In a study forthcoming in the Journal of Psychiatric Research, Eric Finzi, a cosmetic dermatologist, and Norman Rosenthal, a professor of psychiatry at Georgetown Medical School, randomly assigned a group of 74 patients with major depression to receive either Botox or saline injections in the forehead muscles whose contraction makes it possible to frown. Six weeks after the injection, 52 percent of the subjects who got Botox showed relief from depression, compared with only 15 percent of those who received the saline placebo. (You might think that patients would easily be able to tell whether they got the placebo or Botox. Actually, it wasn’t so obvious: Only about half of the subjects getting Botox guessed correctly. More important, knowing which treatment was received had no significant effect on treatment response.) Other studies over the past several years have found similar effects of Botox on mood. Michael Lewis at Cardiff University reported that nondepressed patients at a cosmetic dermatology clinic receiving Botox injection above the eyes frowned less and felt better than those who did not receive this injection. And M. Axel Wollmer at the University of Basel found that Botox injection was superior to a placebo in a group of depressed patients. © 2014 The New York Times Company

Keyword: Emotions
Link ID: 19410 - Posted: 03.26.2014

By Jennifer Richler A few days ago, an old friend sent me a panicked email. She had just finished reading Ron Suskind’s beautiful essay in the New York Times Magazine about raising a son with autism: “Reaching My Autistic Son Through Disney.” Suskind describes how, at almost 3 years of age, his son Owen “disappeared.” The child was once “engaged, chatty, full of typical speech,” but then he stopped talking, lost eye contact, even struggled to use a sippy cup. Owen was eventually diagnosed with a regressive form of autism, which Suskind says affects about a third of children with the disorder. “Unlike the kids born with it,” he continues, “this group seems typical until somewhere between 18 and 36 months—then they vanish.” That was the line that alarmed my friend, whose son is nearing his third birthday. “What is this ‘regressive autism?’ ” she asked me, the resident autism expert in her peer group. (I conducted research on autism and regression in autism before becoming a freelance writer.) “I thought we were out of the woods!” I’m sure many parents of young children who read the piece had the same reaction, and it’s completely understandable. It’s also unwarranted. The claim that many kids with autism develop typically for almost three years and then experience a near-complete loss of language, social skills, and motor ability—a claim I’ve read many times before—simply isn’t true. It’s time to set the record straight. © 2014 The Slate Group LLC.

Keyword: Autism
Link ID: 19409 - Posted: 03.26.2014

Andreas von Bubnoff People who are unable to recognize faces can still learn to distinguish between other types of very similar objects, researchers report. The finding provides fresh support for the idea that the brain mechanisms that process face images are specialized for that task. It also offers evidence against an 'expertise' hypothesis, in which the same mechanisms are responsible for recognition of faces and other highly similar objects we have learned to tell apart — the way bird watchers can recognize birds after years of training. Constantin Rezlescu, a psychologist at Harvard University in Cambridge, Massachusetts, and his colleagues worked with two volunteers nicknamed Florence and Herschel, who had acquired prosopagnosia, or face blindness, following brain damage. The condition renders people unable to recognize and distinguish between faces — in some cases, even those of their own family members. The team trained Florence and Herschel to recognize greebles, computer-generated objects that differ from one another in similar ways to faces. The two volunteers spent eight training sessions of up to one hour learning to recognize 20 different greebles. The objects belonged to five different ‘families’ that were easier to distinguish between than were the individual greebles, and initially the participants took longer to discriminate individual greebles within the same family than they did the different families. But by the end of the training, they could tell individual greebles apart just as quickly — a sign that they had become experts in recognizing them, just as dog trainers can recognize individual dogs as easily as different breeds of dog. The study appears in Proceedings of the National Academy of Sciences1. © 2014 Nature Publishing Group

Keyword: Attention
Link ID: 19408 - Posted: 03.25.2014

By CATHERINE SAINT LOUIS ALEXANDRIA, N.H. — For most of his life, Kevin Ramsey has lived with epileptic seizures that drugs cannot control. At least once a month, he would collapse, unconscious and shaking violently, sometimes injuring himself. Nighttime seizures left him exhausted at dawn, his tongue a bloody mess. After episodes at work, he struggled to stay employed. Driving became too risky. At 28, he sold his truck and moved into his mother’s spare bedroom. Cases of intractable epilepsy rarely have happy endings, but today Mr. Ramsey is seizure-free. A novel battery-powered device implanted in his skull, its wires threaded into his brain, tracks its electrical activity and quells impending seizures. At night, he holds a sort of wand to his head and downloads brain data from the device to a laptop for his doctors to review. “I’m still having seizures on the inside, but my stimulator is stopping all of them,” said Mr. Ramsey, 36, whose hands shake because of one of the three anti-seizure drugs he still must take. “I can do things on my own I couldn’t do before. I can go to the store on my own, and get my groceries. Before, I wouldn’t have been able to drive.” Just approved by the Food and Drug Administration, the long-awaited device, called the RNS System, aims to reduce seizures and to improve the lives of an estimated 400,000 Americans whose epilepsy cannot be treated with drugs or brain surgery. “This is the first in what I believe is a new generation of therapy for epilepsy,” said Dr. Dileep R. Nair, head of adult epilepsy at the Cleveland Clinic and an investigator in the pivotal trial for NeuroPace’s RNS. “It’s delivering local therapy. It’s not taking tissue out; the brain is left intact. And it’s unlike a drug, which is a shotgun approach.” © 2014 The New York Times Company

Keyword: Epilepsy
Link ID: 19407 - Posted: 03.25.2014

Dragonflies are full of surprises. They have six legs, but most can’t walk. Their giant, 30,000-lens eyes can detect ultraviolet light. And though they lack the brain architecture normally required for a sense of smell, a new study finds that dragonflies may use odors to hunt prey. Smelling, as we humans understand it, requires certain hardware. Our noses are packed with olfactory receptors, each of which is tuned to a precise scent molecule. (Indeed, a recent study suggests we can detect a trillion smells.) When one wafts into our nostrils, these receptors send nerve signals to sensory way stations called glomeruli, which pass them along to the brain for interpretation—“Oh, a rose!” Glomeruli are shared by most terrestrial mammals and insects, and until now, scientists believed they represented the only possible route to a sense of smell. Because dragonflies and their close cousins, damselflies, don’t possess glomeruli or any higher order smell centers in their brains, most scientists believed these insects were unable to smell anything at all. Invertebrate biologist Manuela Rebora at the University of Perugia in Italy was not one of them. When her team took a closer look at dragonfly and damselfly antennae with an electron microscope, they spotted tiny bulbs in pits that resembled olfactory sensilla. Like the insect equivalent of a nose, these sensilla house olfactory neurons. When Rebora’s team exposed the suspected sensilla to scents, they emitted nerve pulses, supporting the idea that damselflies and dragonflies perceive odors. © 2014 American Association for the Advancement of Science.

Keyword: Chemical Senses (Smell & Taste)
Link ID: 19406 - Posted: 03.25.2014

Daniel Cressey The controversy over electronic cigarettes has been reignited today with the publication of a study claiming that they do not help smokers to quit their habit. Whether or not ‘e-cigarettes’ are an effective aid in the cessation of smoking has become a major issue for the rapidly growing industry that produces the devices, and for the tobacco researchers struggling to assess their impact. There is widespread agreement that inhaling from an e-cigarette, where a heating element vapourizes a liquid containing nicotine, is not as harmful as smoking a conventional cigarette, and proponents say that the products could save millions of lives. But some researchers and tobacco-control activists fear that the devices could make tobacco use seem socially acceptable again and may not assist people in actually reducing their addiction. Pamela Ling, a tobacco researcher at the University of California, San Francisco, and her colleagues followed 949 people who detailed their smoking habits though an online survey, and found that 88 of those who had used e-cigarettes were no more likely to have quit or reduced their smoking after a year than other smokers. “We found that there was no difference in the rate of quitting between smokers who used an e-cigarette and those who did not”, even after controlling for factors such as the user's dependence on tobacco, Ling told Nature in an e-mail. She added: “Advertising suggesting that e-cigarettes are effective for smoking cessation should be prohibited until such claims are supported by scientific evidence.” Her team reports the results today in JAMA Internal Medicine1. © 2014 Nature Publishing Group

Keyword: Drug Abuse
Link ID: 19405 - Posted: 03.25.2014

Claudia Dreifus The biochemist Ricardo E. Dolmetsch has pioneered a major shift in autism research, largely putting aside behavioral questions to focus on cell biology and biochemistry. Dr. Dolmetsch, 45, has done most of his work at Stanford. Since our interviews — a condensed and edited version of which follows — he has taken a leave to join Novartis, where his mission is to organize an international team to develop autism therapies. “Pharmaceutical companies have financial and organizational resources permitting you to do things you might not be able to do as an academic,” he said. “I really want to find a drug.” Q. Did you start out your professional life studying the biochemistry of autism? A. No. In graduate school and as a postdoc, I’d done basic research on the ion channels on the membranes of cells. By my mid-20s, I had my name on some high-profile papers. Then, around 2006, my son who was then 4 was diagnosed with autism. We had suspected it. He didn’t talk much, was hyperactive, very moody. He assembled huge towers based on the color spectrum. He did all sorts of things that were very unusual. Given the signs, why did you wait that long to seek a diagnosis? I’m from Latin America [Cali, Colombia], and my Latin thing was, “This is the way boys are.” But he would just scream for hours and hours, uncontrollable. He didn’t sleep. We didn’t understand it. After a while, his teachers said, “You probably ought to have him seen.” So we went to a psychiatrist and neurologist and ultimately we got differing diagnoses. © 2014 The New York Times Company

Keyword: Autism
Link ID: 19404 - Posted: 03.25.2014

By Gisela Telis, Jodi Corbitt had been battling depression for decades and by 2010 had resigned herself to taking antidepressant medication for the rest of her life. Then she decided to start a dietary experiment. To lose weight, the 47-year-old Catonsville, Md., mother stopped eating gluten, a protein found in wheat and related grains. Within a month she had shed several pounds — and her lifelong depression. “It was like a veil lifted and I could see life more clearly,” she recalled. “It changed everything.” Corbitt had stumbled into an area that scientists have recently begun to investigate: whether food can have as powerful an impact on the mind as it does on the body. Research exploring the link between diet and mental health “is a very new field; the first papers only came out a few years ago,” said Michael Berk, a professor of psychiatry at the Deakin University School of Medicine in Australia. “But the results are unusually consistent, and they show a link between diet quality and mental health.” “Diet quality” refers to the kinds of foods that people eat, how often they eat them and how much of them they eat. In several studies, including a 2011 analysis of more than 5,000 Norwegians, Berk and his collaborators have found lower rates of depression, anxiety and bipolar disorder among those who consumed a traditional diet of meat and vegetables than among people who followed a modern Western diet heavy with processed and fast foods or even a health-food diet of tofu and salads. © 1996-2014 The Washington Post

Keyword: Depression
Link ID: 19403 - Posted: 03.25.2014

By Maggie Fox Medical marijuana pills or an oral spray made from cannabis may help ease some of the painful spasms caused by multiple sclerosis that make day-to-day life hard for patients, according to new guidelines from the American Academy of Neurology. But the synthetic formulations of marijuana don’t change the course of the disease and might cause unpleasant side-effects, the experts at the academy caution. There is not enough evidence to make any recommendation on smoking marijuana for MS patients, stresses Dr. Vijayshree Yadav of Oregon Health & Science University, who led the team writing the guidelines. Synthetic marijuana in pill form, including the Marinol brand, is legal for use in treating nausea and loss of appetite in cancer. An oral spray called Sativex is approved for treating MS symptoms in Britain but not in the U.S. MS patients often seek alternative and complementary therapies because they have so few options for the chronic and incurable condition, caused when the immune system mistakenly attacks the nerves. A review of those therapies found there's no evidence most of them work. The review found that the herb Ginkgo biloba might help fatigue, but not thinking and memory problems. There’s also some evidence that magnetic therapy may help fatigue.

Keyword: Multiple Sclerosis
Link ID: 19402 - Posted: 03.25.2014

By ANNE EISENBERG People who strain to hear conversations in noisy places sometimes shun hearing appliances as telltale signs of aging. But what if those devices looked like wireless phone receivers? Some companies are betting that the high-tech look of a new generation of sound amplifiers will tempt people to try them. The new in-ear amps come with wireless technology and typically cost $300 to $500. The devices include directional microphones and can be fine-tuned by smartphone apps. Whatever you do, don’t call these amplifiers hearing aids. They are not considered medical devices like the ones overseen by the Food and Drug Administration and dispensed by professionals to aid those with impaired hearing. Rather, they are over-the-counter systems cleared by the F.D.A. for occasional use in situations when speech and other sounds are hard to discern — say, in a noisy restaurant or while bird-watching. “The market is proliferating with lots of devices not necessarily made for impaired hearing, but for someone who wants a boost in certain challenging conditions like lectures,” said Neil J. DiSarno, chief staff officer for audiology at the American Speech-Language-Hearing Association. Dr. DiSarno is among the many audiologists who strongly urge people to see a physician first, in order to rule out medical causes of hearing loss, which could vary from earwax to a tumor, rather than self-diagnosing and self-treating a condition. Carole Rogin, president of the Hearing Industries Association, a trade group, said the biggest problem with personal amplification products was that people might use them instead of seeking appropriate medical oversight. “Untreated hearing loss is not a benign condition,” she said. “We want people to do something about it as soon as they notice a problem,” rather than using these devices to mask a potentially dangerous condition. © 2014 The New York Times Company

Keyword: Hearing
Link ID: 19401 - Posted: 03.24.2014

By MATT RICHTEL A dangerous new form of a powerful stimulant is hitting markets nationwide, for sale by the vial, the gallon and even the barrel. The drug is nicotine, in its potent, liquid form — extracted from tobacco and tinctured with a cocktail of flavorings, colorings and assorted chemicals to feed the fast-growing electronic cigarette industry. These “e-liquids,” the key ingredients in e-cigarettes, are powerful neurotoxins. Tiny amounts, whether ingested or absorbed through the skin, can cause vomiting and seizures and even be lethal. A teaspoon of even highly diluted e-liquid can kill a small child. But, like e-cigarettes, e-liquids are not regulated by federal authorities. They are mixed on factory floors and in the back rooms of shops, and sold legally in stores and online in small bottles that are kept casually around the house for regular refilling of e-cigarettes. Evidence of the potential dangers is already emerging. Toxicologists warn that e-liquids pose a significant risk to public health, particularly to children, who may be drawn to their bright colors and fragrant flavorings like cherry, chocolate and bubble gum. “It’s not a matter of if a child will be seriously poisoned or killed,” said Lee Cantrell, director of the San Diego division of the California Poison Control System and a professor of pharmacy at the University of California, San Francisco. “It’s a matter of when.” © 2014 The New York Times Company

Keyword: Drug Abuse; Aggression
Link ID: 19399 - Posted: 03.24.2014

Visual illusions, such as the rabbit-duck (shown above) and café wall (shown below) are fascinating because they remind us of the discrepancy between perception and reality. But our knowledge of such illusions has been largely limited to studying humans. That is now changing. There is mounting evidence that other animals can fall prey to the same illusions. Understanding whether these illusions arise in different brains could help us understand how evolution shapes visual perception. For neuroscientists and psychologists, illusions not only reveal how visual scenes are interpreted and mentally reconstructed, they also highlight constraints in our perception. They can take hundreds of different forms and can affect our perception of size, motion, colour, brightness, 3D form and much more. Artists, architects and designers have used illusions for centuries to distort our perception. Some of the most common types of illusory percepts are those that affect the impression of size, length or distance. For example, Ancient Greek architects designed columns for buildings so that they tapered and narrowed towards the top, creating the impression of a taller building when viewed from the ground. This type of illusion is called forced perspective, commonly used in ornamental gardens and stage design to make scenes appear larger or smaller. As visual processing needs to be both rapid and generally accurate, the brain constantly uses shortcuts and makes assumptions about the world that can, in some cases, be misleading. For example, the brain uses assumptions and the visual information surrounding an object (such as light level and presence of shadows) to adjust the perception of colour accordingly. © 2014 Guardian News and Media Limited

Keyword: Vision
Link ID: 19398 - Posted: 03.22.2014

Jessica Morrison The human nose has roughly 400 types of scent receptors that can detect at least 1 trillion different odours. The human nose can distinguish at least 1 trillion different odours, a resolution orders of magnitude beyond the previous estimate of just 10,000 scents, researchers report today in Science1. Scientists who study smell have suspected a higher number for some time, but few studies have attempted to explore the limits of the human nose’s sensory capacity. “It has just been sitting there for somebody to do,” says study co-author Andreas Keller, an olfactory researcher at the Rockefeller University in New York. To investigate the limits of humans' sense of smell, Keller and his colleagues prepared scent mixtures with 10, 20 or 30 components selected from a collection of 128 odorous molecules. Then they asked 26 study participants to identify the mixture that smelled differently in a sample set where two of three scents were the same. When the two scents contained components that overlapped by more than about 51%, most participants struggled to discriminate between them. The authors then calculated the number of possible mixtures that overlap by less than 51% to arrive at their estimate of how many smells a human nose can detect: at least 1 trillion. Donald Wilson, an olfactory researcher at the New York University School of Medicine, says the findings are “thrilling.” He hopes that the new estimate will help researchers begin to unravel an enduring mystery: how the nose and brain work together to process smells. © 2014 Nature Publishing Group,

Keyword: Chemical Senses (Smell & Taste)
Link ID: 19394 - Posted: 03.21.2014

by Simon Makin How much can environmental factors explain the apparent rise in autism spectrum disorders? Roughly 1 per cent of children in the US population are affected by autism spectrum disorder (ASD). Rates in many countries, including the US, have risen sharply in recent years but no one is sure why. It is still not clear whether this is prompted by something in the environment, increased awareness of the condition and changes in diagnoses, or a result of people having children later. The environmental case is hotly debated. There is some evidence that maternal infections during pregnancy can increase the risk. Other studies have pointed to a possible link with antidepressants while others have looked at elevated levels of mercury. But determining prenatal exposure to any substance is difficult because it is hard to know what substances people have been exposed to and when. To get around this, Andrey Rzhetsky and colleagues at the University of Chicago analysed US health insurance claims containing over 100 million patient records – a third of the population – dating from 2003 to 2010. They used rates of genital malformations in newborn boys as a proxy of parents' exposure to environmental risk factors. This is based on research linking a proportion of these malformations to toxins in the environment, including pesticides, lead and medicines. Toxic environment? The team compared the rates of these malformations to rates of ASD county by county. After adjusting for gender, income, ethnicity and socio-economic status, they found that a 1 per cent increase in birth defects – their measure for environmental effects - was associated with an average increase of 283 per cent in cases of ASD. © Copyright Reed Business Information Ltd.

Keyword: Autism
Link ID: 19393 - Posted: 03.21.2014