by Linda Geddes It's what women have been telling men for decades: stimulating the vagina is not the same as stimulating the clitoris. Now brain scan data has added weight to their argument. The precise locations that correspond to the vagina, cervix and female nipples on the brain's sensory cortex have been mapped for the first time, proving that vaginal stimulation activates different brain regions to stimulation of the clitoris. The study also found a direct link between the nipples and the genitals, which may explain why some women can orgasm through nipple stimulation alone. The discoveries could ultimately help women who have suffered nerve damage in childbirth or disease. The sensory cortex is a strip of brain tissue positioned roughly under where the band between a pair of headphones sits. Across it, neurons linked to different body parts exchange information about the sensory information feeding into them. This is often depicted as the "sensory homunculus", a distorted image of a man stretched across the brain, with his genitals lying next to his feet (click here). The size of the body's parts show how much of the brain is dedicated to processing the sensory information from each body part. The diagram was first published in 1951 after experiments conducted during brain surgery performed while the patients were conscious: the surgeon electrically stimulated different regions of the patients' brains and the patients reported the parts of their bodies in which they felt sensation as a result. But all the subjects were men. Until recently, the position of female genitalia on the homunculus had only been guessed at. © Copyright Reed Business Information Ltd.

Keyword: Sexual Behavior; Brain imaging
Link ID: 15652 - Posted: 08.08.2011

By Laura Sanders Nerve cell communication gets better with use. A neuron’s electrical activity triggers other cells to come and slather on a protective coating that makes messages travel faster, a study published online August 4 in Science shows. Like rubber insulation around electrical wires, myelin wraps around message-sending axons, protecting and speeding electrical impulses. Specialized brain cells called oligodendrocytes wrap up to 150 layers of this insulation around a single axon. In this image, a single oligodendrocyte (green) wraps several axons (purple). The process begins when neurons fire off an electrical signal and the chemical messenger glutamate is released. Mouse neurons treated so they were unable to release glutamate had lower levels of myelin, Hiroaki Wake of the National Institute of Child Health and Human Development in Bethesda, Md., and colleagues found. When the team activated normal axons, boosting their glutamate production, oligodendrocytes produced more of the fatty proteins that make up the myelin coating. The results suggest one way that the brain quickly adapts and improves when a person practices new tasks such as playing the violin or juggling. © Society for Science & the Public 2000 - 2011

Keyword: Glia; Development of the Brain
Link ID: 15651 - Posted: 08.08.2011

By Steve Mirsky Parents often wonder what their little ones are absorbing from them. For example, my mother had a wonderful vocabulary. So it may be more than a family fable that when I was asked as a two-year-old whether I was wet, I allegedly responded, “No, I’m saturated.” Then again, my father has always tended to interpret things quite literally, which may explain why, a year or two later, my supposed response to the question of how my favorite record went was “’round and around and around.” (This all happened shortly after the invention of movable type, when music was literally pressed onto large vinyl disks that “turned” on what was fittingly called a turntable. For more on turntables, see this space in the June issue.) I was reminded of preposterously precocious utterances by tiny tykes during a brief talk that string theorist Brian Greene gave at the opening of the 2011 World Science Festival in New York City on June 1. Greene said he sometimes wondered about how much information small children pick up from standard dinner-table conversation in a given home. He revealed that he got some data to mull over when he hugged his three-year-old daughter and told her he loved her more than anything in the universe, to which she replied, “The universe or the multiverse?” Closer to home (well, my home at least), my seven-year-old grandnephew has often exhibited an interest in various science and math topics. He, like many preschoolers at the time, was deeply disappointed by the 2006 demotion of Pluto from the family of planets. So great was his grief then that when I asked him about Pluto’s fall, he only said, “I don’t want to talk about it.” More recently, he was a passenger when his grandfather exited a highway onto a cloverleaf that took them off their northern route toward the east, then south and then west onto the next road. With that maneuver complete, the kid said, “That was a 270-degree turn.” Which he either learned from his smart parents or from watching the X Games. © 2011 Scientific American,

Keyword: Development of the Brain; Intelligence
Link ID: 15650 - Posted: 08.08.2011

by Helen Fields Humans buy unripe bananas, then leave them on the kitchen counter. The tayra, a relative of the weasel native to Central and South America, appears to do much the same thing, picking unripe plantains and hiding them until they ripen, according to a new study. The authors speculate that tayras are showing a human-like capacity to plan for the future, which has previously been shown only in primates and birds. Biologist Fernando Soley was an undergraduate at the University of Costa Rica in 2004 when he first started thinking about tayras. He was studying poison dart frogs at La Selva Biological Station in northern Costa Rica, when he noticed a tayra—essentially a giant weasel with a bushy tail—approach a tree. "It climbed 4 meters high, went directly to a bromeliad [a plant growing in the tree], and came back down with a ripe plantain and ate it," Soley says. The trees in the forestry plantation where he was working are planted in neat rows, and it's easy for humans to get lost. Because the animal went straight to the plantain, he thought it couldn't have found it by chance. "I thought, wow, for sure this animal was the one that brought it there." A few years later, Soley came back for a closer look at the tayras, teaming up with Isaías Alvarado-Díaz, a self-taught biologist who lives near La Selva. Animals don't spend much time in the forestry plantation, so Soley thought tayras might hide their fruit there to keep it safe from prying snouts. The duo set up an Easter egg hunt for fruit thieves to find out if the tayras were doing a good job. "We hid pieces of banana, which pretty much tastes and smells very similar to plantains, in the forest and in the plantation, and after 2 days we went to count them," he says. Animals found fewer bananas in trees than on the ground, and fewer in the plantation than in the forest. That means hiding plantains in the plantation and up in tree is a smart move by tayras that don't want other animals to find their treasures. © 2010 American Association for the Advancement of Science

Keyword: Learning & Memory; Intelligence
Link ID: 15649 - Posted: 08.08.2011

David Cyranoski Mu-ming Poo leads a double life. For three weeks every month, he works in a cramped, cluttered office at the University of California, Berkeley. Looking drab in his dark-green pullover, olive trousers and black Adidas sports shoes, the 62-year-old neuroscientist slumps slightly in his chair. In the adjoining laboratory, half a dozen postdoctoral researchers, expected to work independently, go quietly about their business. Cut to Shanghai, China, where Poo spends the remaining quarter of his time. In the director's office at the Institute of Neurosciences (ION), he sports a pressed, light-blue shirt neatly tucked into belted trousers (same trainers). With few books and papers about, the room seems more spacious than its Californian counterpart; mangoes and other fruit in a bowl provide a tasteful flourish. Here, Poo supervises only one postdoctoral researcher, but a dozen chattering graduate students are stuffed into an office, waiting for the hour that he sets aside for each one during his whirlwind visits. Poo sits straighter, talks faster and seems more alert, alive — younger, even. As stimulating as he finds his research in the United States, where he is a member of the National Academy of Sciences, Poo finds a sense of mission in China. "It's more exciting, exhilarating here," he says. "They need me. I feel it's the best use of my life." China is alive with possibilities in science, but realizing them is a complicated affair. The country's fondness for speed — for short-term achievements and, increasingly, short-term profits — has worked relatively well in the chemical and physical sciences and in large-scale genomics, where researchers can systematically tick off the chemical compounds or genetic sequences that they have produced (see 'Eastern promise'). © 2011 Nature Publishing Group,

Keyword: Miscellaneous
Link ID: 15648 - Posted: 08.04.2011

By Victoria Gill Science reporter, BBC Nature The flamboyant "booming" display of the threatened Houbara bustard is linked to the rate at which the birds age A large, flamboyant bird has given biologists an insight into the relationship between sex and ageing. The male Houbara bustard has striking ornamental feathers that it displays while running around and "booming" to attract a mate. As scientists report in Ecology Letters, birds that indulge in more of these sexual displays age faster. The more "showy" males experienced earlier age-related declines in the quality of their sperm. The team used 10-years-worth of data on the sexual behaviour and fertility of more than 1,700 North African Houbara bustards that were bred by conservationists in Missour, Morocco. "The birds are a threatened species, and the data was collected as part of an ongoing conservation programme aimed at increasing their numbers in the wild," explained lead researcher Brian Preston, a scientist based at the University of Burgundy, France. The scientists measured how much time each male spent carrying out its elaborate display, and compared this to changes in its fertility that are associated with ageing. BBC © 2011

Keyword: Sexual Behavior; Evolution
Link ID: 15647 - Posted: 08.04.2011

by Frank Swain We need to talk about how the digital world might be changing our brains, says the neuroscientist and former director of the UK's Royal Institution You think that digital technology is having an impact on our brains. How do you respond to those who say there's no evidence for this? When people say there is no evidence, you can turn that back and say, what kind of evidence would you imagine there would be? Are we going to have to wait for 20 years and see that people are different from previous generations? Sometimes you can't just go into a lab and get the evidence overnight. I think there are enough pointers that we should be talking about this rather than stressing about not being able to replicate things in a lab instantly. So what evidence is there? There is lots of evidence, for example, the recent paper "Microstructure abnormalities in adolescents with internet addiction disorder" in the journal PLoS One. We know the human brain can change and the environment can change it. There is an increase in people with autistic spectrum disorders. There are issues with happy-slapping, the rise in the appeal of Twitter - I think these show that people's attitude to each other and themselves is changing. Anything else? There's a recent review by the cognitive scientist Daphne Bavelier in the high-impact journal Neuron, in which she says that this is a given, that the brain will change. She also reviews evidence showing there's a change in violence, distraction and addiction in children, linked to the pervasion of technology. © Copyright Reed Business Information Ltd.

Keyword: Attention
Link ID: 15646 - Posted: 08.04.2011

by Daniel Strain Agatha Christie, meet your tiniest villain yet: the African crested rat (Lophiomys imhausi). Dogs that try to grab a bite of this spiky-haired East African rodent, more closely related to lemmings or voles than true street rats, often wind up violently ill or even dead. Now, scientists have discovered the secret to the crested rat's fatal kiss: A poison once used by African hunters to kill elephants. When cornered, crested rats don't run or hide like a normal rodent. Instead, they twist to the side and arch their backs, parting their long, gray outer coats, to reveal black-and-white bands that run like racing stripes down their flanks. Like a hornet's yellow-and-black rear or a rattlesnake's rattle, these stripes seem to tell predators one thing: Back off. The rats' defensive postures are fearsome, but they don't explain the trails of sick dogs left in their wakes. Researchers suspected that the rodents were harboring poison, but they didn't know how. In the new study, Fritz Vollrath, an evolutionary biologist at the University of Oxford in the United Kingdom, and colleagues have turned Miss Marple and solved the mystery. Crested rats, it turns out, don't make their own poison; they gather it. The team's first clue was observing a captive crested rat diligently gnaw on pieces of bark from the African tree Acokanthera schimperi, also called the arrow poison tree. The animal would then "slather" its short hairs in fibrous spit. That bark carries large amounts of ouabain, a chemical that overstimulates heart muscle, similar to the poison curare, commonly obtained from South American plants. East African hunters once boiled down the bark to coat poisoned arrows for taking down elephants and other big game. © 2010 American Association for the Advancement of Science.

Keyword: Neurotoxins; Aggression
Link ID: 15645 - Posted: 08.04.2011

by Greg Miller Vampire bats must consume 70% to 80% of their body weight in blood almost every night. To satisfy this never-ending thirst, they bite their prey—typically sleeping livestock, but also the occasional human toe poking out from under the covers—in areas where warm blood courses close to the surface. Now scientists have discovered a molecular heat sensor that helps the bats home in on their dinner. Researchers led by neuroscientist David Julius of the University of California, San Francisco, searched for genes related to known molecular heat sensors in several bat species collected by colleagues in Venezuela. In the vampire bat Desmodus rotundus, the researchers found evidence of a change in how cells use the gene for an ion channel called TRPV1. This molecular pore resides on the surface of sensory neurons, and in other animals it stimulates the neurons in response to painful heat or capsaicin, the compound that gives chili peppers their sting. In Desmodus, neurons in the nerve connected to the small heat-sensing pits near the bat's nose splice together different parts of the Trpv1 gene to produce a version of the ion channel that's shorter at one end than the version made by other animals, including bats that feed on fruit, nectar, or insects, the team reports in tomorrow's Nature. To investigate the workings of the shorter TRPV1 channel, Julius and colleagues inserted the genetic instructions into frog egg cells, causing the cells to make the channels and stick them on their surface. Probing the egg cells with electrodes, the researchers discovered that the short version of TRPV1 opens at about 31˚C, which in a neuron would increase firing. That's well below the 40˚C or higher threshold for the long version of TRPV1. © 2010 American Association for the Advancement of Science.

Keyword: Pain & Touch; Animal Migration
Link ID: 15644 - Posted: 08.04.2011

By Jason Castro If you’ve never watched bees carefully, you’re missing out. Looking up close as they gently curl and uncoil their tapered mouths toward food, you sense that they’re not just eating, but enjoying. Watch a bit more, and the hesitant flicks and sags of their antennae seem to convey some kind of emotion. Maybe annoyance? Or something like agitation? Whether bees really experience any of these things is an open scientific question. It’s also an important one with implications for how we should treat not just bees, but the great majority of animals. Recently, studies by Geraldine Wright and her colleagues at Newcastle University in the UK have rekindled debate over these issues by showing that honeybees may experience something akin to moods. Using simple behavioral tests, Wright’s research team showed that like other lab-tested brooders -- which so far include us, monkeys, dogs, and starlings -- stressed bees tend to see the glass as half empty. While this doesn’t (and can’t) prove that bees experience human-like emotions, it does give pause. We should take seriously the possibility that it feels like something to be an insect. As invertebrates -- animals without backbones -- bees are representatives of a diverse group accounting for over 95 percent of animal species. But despite their prevalence, not to mention their varied and often nuanced behaviors, invertebrates are sometimes regarded as life’s second string, as a mindless and unfeeling band of alien critters. If that seems a bit melodramatic, just consider our willingness to boil some of them alive. © 2011 Scientific American,

Keyword: Emotions; Evolution
Link ID: 15643 - Posted: 08.04.2011

THE extraordinary success of Homo sapiens is a result of four things: intelligence, language, an ability to manipulate objects dexterously in order to make tools, and co-operation. Over the decades the anthropological spotlight has shifted from one to another of these as the prime mover of the package, and thus the fundament of the human condition. At the moment co-operation is the most fashionable subject of investigation. In particular, why are humans so willing to collaborate with unrelated strangers, even to the point of risking being cheated by people whose characters they cannot possibly know? Evidence from economic games played in the laboratory for real money suggests humans are both trusting of those they have no reason to expect they will ever see again, and surprisingly unwilling to cheat them—and that these phenomena are deeply ingrained in the species’s psychology. Existing theories of the evolution of trust depend either on the participants being relatives (and thus sharing genes) or on their relationship being long-term, with each keeping count to make sure the overall benefits of collaboration exceed the costs. Neither applies in the case of passing strangers, and that has led to speculation that something extraordinary, such as a need for extreme collaboration prompted by the emergence of warfare that uses weapons, has happened in recent human evolution to promote the emergence of an instinct for unconditional generosity. Leda Cosmides and John Tooby, two doyens of the field, who work at the University of California, Santa Barbara, do not agree. They see no need for extraordinary mechanisms and the latest study to come from their group (the actual work was done by Andrew Delton and Max Krasnow, who have just published the results in the Proceedings of the National Academy of Sciences) suggests they are right. It also shows the value of applying common sense to psychological analyses—but then of backing that common sense with some solid mathematical modelling. © The Economist Newspaper Limited 2011.

Keyword: Evolution
Link ID: 15642 - Posted: 08.04.2011

By RICHARD A. FRIEDMAN, M.D. Shortly after the singer Amy Winehouse, 27, was found dead in her London home, the airwaves were ringing with her popular hit “Rehab,” a song about her refusal to be treated for drug addiction. The official cause of Ms. Winehouse’s death won’t be announced until October pending toxicology reports, but her highly publicized battle with alcohol and drug addiction seems to have played a significant role. Indeed, her mother echoed a sentiment heard everywhere when she told The Sunday Mirror that her daughter’s death was “only a matter of time.” But was it? Why is it that some people survive drug and alcohol abuse, even manage their lives with it, while others succumb to addiction? It’s a question scientists have been wrestling with for decades, but only recently have they begun to find answers. Illicit drug use in the United States, as in Britain, is very common and usually begins in adolescence. According to the 2008 National Survey of Drug Use and Health, 46 percent of Americans have tried an illicit drug at some point in their lives. But only 8 percent have used an illicit drug in the past month. By comparison, 51 percent have used alcohol in the past year. Most people who experiment with drugs, then, do not become addicted. So who is at risk? © 2011 The New York Times Company

Keyword: Drug Abuse
Link ID: 15641 - Posted: 08.02.2011

By PAM BELLUCK Many people consider dyslexia simply a reading problem in which children mix up letters and misconstrue written words. But increasingly scientists have come to believe that the reading difficulties of dyslexia are part of a larger puzzle: a problem with how the brain processes speech and puts together words from smaller units of sound. Now, a study published last week in the journal Science suggests that how dyslexics hear language may be more important than previously realized. Researchers at the Massachusetts Institute of Technology have found that people with dyslexia have more trouble recognizing voices than those without dyslexia. John Gabrieli, a professor of cognitive neuroscience, and Tyler Perrachione, a graduate student, asked people with and without dyslexia to listen to recorded voices paired with cartoon avatars on computer screens. The subjects tried matching the voices to the correct avatars speaking English and then an unfamiliar language, Mandarin. Nondyslexics matched voices to avatars correctly almost 70 percent of the time when the language was English and half the time when the language was Mandarin. But people with dyslexia were able to do so only half the time, whether the language was English or Mandarin. Experts not involved in the study said that was a striking disparity. © 2011 The New York Times Company

Keyword: Dyslexia; Hearing
Link ID: 15640 - Posted: 08.02.2011

Zoë Corbyn The placenta has long been thought of as a passive organ that simply enables a fetus to take up nutrients from its mother. But new research in mice shows that when calories are restricted, the placenta steps up to the plate – actively sacrificing itself to protect the fetal brain from damage. Researchers at Cambridge University, UK, examined what happened to 10 fetuses from 8 mice when their pregnant mothers were deprived of food for 24 hours – as might happen in the wild — about mid-way through gestation. This point in pregnancy is critical in the development of the hypothalamus, the part of the brain that controls primal urges, including maternal instincts. Behavioural neuroscientists Kevin Broad and Barry Keverne found that the placenta responded by breaking down its own tissues, recycling proteins inside its cells to provide a steady supply of nutrients to the developing hypothalamus despite the mother's interrupted food intake. Their study is published today in the Proceedings of the National Academy of Sciences1. "We didn't know before that this protection of the fetus goes on," says Keverne. "I expected the lack of food to affect the fetal brain and the placenta equally, but instead we see the placenta acting as an interface to make sure the fetuses' particular stage of brain development is protected." © 2011 Nature Publishing Group

Keyword: Development of the Brain
Link ID: 15639 - Posted: 08.02.2011

David Cyranoski The largest-ever study of the genetics of depression is set to go ahead in China, after a major survey found that the condition largely has the same triggers and symptoms there as in the West — albeit with a few startling exceptions. Previous studies on twins in Sweden have shown that genetics explains about 40% of a woman's risk of depression, and about 30% of a man's1. Finding the genes responsible may help to make treatments more targeted and thus more effective, but identifying those genes has proved exceedingly difficult. The sheer diversity of symptoms involved in depression can make it difficult to be sure that patients actually have the same underlying disorder, and any genetic contribution is likely to come from many genes, each having a small effect. "It was clear that we needed a very large sample, [one that was] ethically homogenous, and to do it cheaply," says molecular geneticist Jonathan Flint at the University of Oxford, UK. Flint is one of the leaders on the CONVERGE consortium, a collaboration between Oxford, the Virginia Commonwealth University in Richmond and 53 provincial mental-health centres in China. "The only place that fitted was China. Where else could we access that many people and have sufficient control over quality?" asks Flint. The consortium, which began in 2008 with a £1.5-million (US$2.5-million) grant from UK charitable funder the Wellcome Trust, chose to study only women, who are known to have a two-fold higher risk of depression across the globe than men. They also selected only patients whose four grandparents were all Han Chinese; and only those with recurrent depression, an indicator of a likely genetic component. © 2011 Nature Publishing Group,

Keyword: Depression
Link ID: 15638 - Posted: 08.02.2011

By DAN HURLEY Early in the evening of June 25, 1995, hours after the birth of his first and only child, the course of Dr. Alberto Costa’s life and work took an abrupt turn. Still recovering from a traumatic delivery that required an emergency Caesarean section, Costa’s wife, Daisy, lay in bed, groggy from sedation. Into their dimly lighted room at Methodist Hospital in Houston walked the clinical geneticist. He took Costa aside to deliver some unfortunate news. The baby girl, he said, appeared to have Down syndrome, the most common genetic cause of cognitive disabilities, or what used to be called “mental retardation.” Costa, himself a physician and neuroscientist, had only a basic knowledge of Down syndrome. Yet there in the hospital room, he debated the diagnosis with the geneticist. The baby’s heart did not have any of the defects often associated with Down syndrome, he argued, and her head circumference was normal. She just didn’t look like a typical Down syndrome baby. And after all, it would take a couple weeks before a definitive examination would show whether she had been born with three copies of all or most of the genes on the 21st chromosome, instead of the usual two. Costa had dreamed that a child of his might grow up to become a mathematician. He had even prevailed upon Daisy to name their daughter Tyche, after the Greek goddess of fortune or chance, and in honor of the Renaissance astronomer Tycho Brahe. Now he asked the geneticist what the chances were that Tyche (pronounced Tishy) really had Down syndrome. “In my experience,” he said, “close to a hundred percent.” © 2011 The New York Times Company

Keyword: Development of the Brain; Neurogenesis
Link ID: 15637 - Posted: 08.02.2011

By Laura Sanders In a fast-moving car, the brain can hit the brakes faster than the foot. By relying on brain waves that signal the intent to jam on the brakes, a new technology could shave critical milliseconds off the reaction time, researchers report online July 28 in the Journal of Neural Engineering. The work adds to a growing trend in car technology that assists drivers. Though it may eventually lead to improvements in emergency braking, the new brain signal technology isn’t ready for the road. “As a basic science study, I was quite impressed with it,” says cognitive neuroscientist Raja Parasuraman of George Mason University in Fairfax, Va. “I just think a lot more needs to be done.” In the study, computer scientist Stefan Haufe of the Berlin Institute of Technology in Germany and his colleagues measured brain wave changes while participants drove in a car simulator. The participants drove around 60 miles per hour, following a lead car on a curvy road with heavy oncoming traffic. Every so often the lead car would slam on its brakes, so that the participant would have to either do the same or crash. For most drivers, the lag between the lead car stopping and themselves slamming the brakes was around 700 milliseconds. Particular neural signatures were evident during this lag time, and they could be early indicators that the drivers wanted to brake. “Our approach was to obtain the intention of the driver faster than he could actually act,” Haufe says. “That’s what the neural signature is good for.” © Society for Science & the Public 2000 - 2011

Keyword: Robotics; Attention
Link ID: 15636 - Posted: 07.30.2011

By Laura Sanders Though the diagnostic code scrawled on a doctor’s chart might suggest otherwise, each person who lives with an autism spectrum disorder has a very private disease. An avalanche of new genetic data shows clearly that there is no single culprit in autism. Each case stems from a unique jumble of genetic and environmental triggers, which makes figuring out one clear cause for every person’s disorder impossible. This news may sound grim, but it contains a glimmer of hope. By uncovering huge numbers of genetic aberrations, scientists say, they have the opportunity to begin piecing together all of the disparate threads weaving through autism to find the commonalities. A suite of new studies have identified numerous genetic changes that may have a role in the disorder, some of which could help scientists understand why boys are more vulnerable than girls, for instance. And some of the genes affected by these changes appear to be players in common networks of molecular activity in the brain. New work shows that many genetic changes impair nerve cell communication. Understanding this process and finding other common cellular activities that go awry may lead to powerful ways to combat autism, regardless of what caused it. “Parents and families have been tremendously patient,” says child psychiatrist and geneticist Matthew State of the Yale University School of Medicine. “They’ve been promised a lot by geneticists for a long time, and it’s been tougher than any of us expected to deliver.” But the flood of studies in the last few months reflects tremendous progress, he says. “These are all, in their own way, making a chink in the armor.” © Society for Science & the Public 2000 - 2011

Keyword: Autism; Genes & Behavior
Link ID: 15635 - Posted: 07.30.2011

Sandrine Ceurstemont, video producer Can you trust a moving shadow? Not according to this dramatic illusion created by animator David Phillips (see video above). If you follow the shadow as it moves around, it will look like the ball is bouncing all over the place. But try looking at the animation again - this time while fixing your eyes on the ball's trajectory - and you'll see that it's always following the same route. So why is an artificial shadow able to trick our brain and override an object's actual motion? Back in 1997, Daniel Kersten and his team from University of Minnesota first studied the effect and found that it is consistent with how our visual system uses shadows to determine the layout of a scene. We assume a fixed viewpoint illuminated by a stationary light source, where an object is paired with its shadow. So when a fake shadow is introduced into an animation, our brain is primed to link it to the moving object above since in the real world this type of motion wouldn't arise from independent objects. "The robustness of this illusion may in fact be a consequence of perception's ability to use global constraints which are needed to cope with the complexity and ambiguity of natural viewing," write Kersten and colleagues. "Specifically, this may owe in part to the fact that dynamic displays contain an important piece of information not available in static scenes: the correlation between the motion of an object and its shadow." The team found that the effect persists even when the shadow has the wrong contrast polarity or brightness. © Copyright Reed Business Information Ltd.

Keyword: Vision
Link ID: 15634 - Posted: 07.30.2011

By SINDYA N. BHANOO The Marcgravia evenia plant has dish-shaped leaves that bounce back echoes that bats can identify through echolocation. The vine, Marcgravia evenia, has dish-shaped leaves that bounce back echoes that are easy for the bats to identify through echolocation. “They have a very special kind of echo,” said the lead author, Ralph Simon, a biologist at the University of Ulm in Germany. “This echo is very loud and has a constant signature from different angles.” Dr. Simon and his colleagues trained bats in the laboratory to look for a feeder. They then placed it in different locations — attached to a dish-shaped leaf, an ordinary leaf or no leaf. The bats located the feeder in half the time when it was attached to a dish-shaped leaf. And that was good for the bats and the vine. “For the plants, it increases the success of pollination,” Dr. Simon said. “For the bats, it’s good because it helps them find the flowers faster — they have to make several hundred visits to flowers every night.” The study, which appears in the current issue of the journal Science, is one of the first to focus on the evolution of echo-acoustic signals in plants. Several hundred species of plants in the Neotropics rely on about 40 nectar-feeding bat species for pollination, Dr. Simon said. © 2011 The New York Times Company

Keyword: Hearing; Evolution
Link ID: 15633 - Posted: 07.30.2011