by Jessica Hamzelou Being a teenager can be a drag. As if dealing with peer pressure and raging hormones weren't hard enough, your ability to learn new things is also reduced. Now the brain molecules behind this learning deficit have been identified in mice - and blocked. When children hit puberty, their ability to learn a second language drops, they find it harder to learn their way around a new location and they are worse at detecting errors in cognitive tests. Why is this? Sheryl Smith and her colleagues at the State University of New York now reckon that all of these behavioural changes could be due to a temporary increase in a chemical receptor that inhibits brain activity in an area responsible for learning. In 2007, Smith's team discovered that the number of these receptors soared in mice when they hit puberty, before falling back in adulthood. In their latest study, Smith's team set about finding out if these receptor changes in mice might lead to impaired learning abilities, rather like those seen in pubescent humans. Shocking memory The group examined the hippocampus – a region known to be involved in learning – in mouse brains. Sure enough, pubertal mice had seven times as many of the receptors as infant mice. In adulthood, the number of these receptors fell back to an intermediate level. © Copyright Reed Business Information Ltd.

Keyword: Learning & Memory; Development of the Brain
Link ID: 13893 - Posted: 06.24.2010

by Wendy Zukerman IN THE YouTube age it is easy to forget that artists rely on clever tricks to create a sense of motion in still images. Now brain scans show why one method of creating "implicit motion", used by an 18th-century Japanese artist, works so well. While admiring line drawings by Hokusai Katsushika, psychophysicist Naoyuki Osaka of Kyoto University, Japan, was struck by the vivid motion they convey. Instead of using blur to suggest movement, as much modern art has done since the advent of photography, Katsushika created motion by drawing bodies in highly unstable positions (see picture). This is thought to work because the brain "fills in" the effects of gravity pulling the bodies down. Previous research has shown that blurred photographs stimulate the same regions of the visual cortex as real-life motion, including the extrastriate visual cortex. To find out whether sketches of unstable bodies would also activate these regions, Osaka showed Japanese students Katsushika's drawings while scanning their brains with functional MRI. The scans revealed that drawings depicting motion did indeed prompt activity in the extrastriate visual cortex, unlike those of people or objects in static positions. Osaka concludes that there is a "common neural pathway" for interpreting implicit motion in art that is similar to the pathway used for perceiving real-life motion (NeuroReport, DOI: 10.1097/wnr.0b013e328335b371). © Copyright Reed Business Information Ltd.

Keyword: Vision
Link ID: 13892 - Posted: 06.24.2010

by Nic Fleming The "legal high" mephedrone – also known as M-Cat, plant food, and miaow miaow – is getting a lot of attention because a series of deaths have been linked to the drug. Most recently, two teenaged men in the UK died after taking it on Sunday night, although the results of medical tests to determine the causes of their deaths will not be known for several weeks. It has become the fourth most popular drug in the UK behind cannabis, ecstasy and cocaine over the past year. The British government's official drug advisers are expected to recommend that it be banned, but some drugs policy experts say criminalisation could do more harm than good. Now New Scientist cuts through the hype. The leaves of the khat plant, Catha edulis, are chewed for the stimulant, amphetamine-like properties of its active ingredients cathinone and cathine, mostly in east Africa and in migrant groups elsewhere. Mephedrone – more properly 4-methylmethcathinone – is the best known of a family of synthetic or substituted cathinones. It is commonly sold as a white powder or in capsules and is usually snorted or swallowed. The vast majority is produced by Chinese chemical companies, which sell it for around £4,000 a kilogram, mostly to European dealers who sell it online for £10 to £15 per gram or less for larger quantities. © Copyright Reed Business Information Ltd.

Keyword: Drug Abuse
Link ID: 13891 - Posted: 06.24.2010

By MARC BEKOFF and Jessica Pierce Every dog owner knows a pooch can learn the house rules—and when she breaks one, her subsequent groveling is usually ingratiating enough to ensure quick forgiveness. But few people have stopped to ask why dogs have such a keen sense of right and wrong. Chimpanzees and other nonhuman primates regularly make the news when researchers, logically looking to our closest relatives for traits similar to our own, uncover evidence of their instinct for fairness. But our work has suggested that wild canine societies may be even better analogues for early hominid groups—and when we study dogs, wolves and coyotes, we discover behaviors that hint at the roots of human morality. Morality, as we define it in our book Wild Justice, is a suite of interrelated other-regarding behaviors that cultivate and regulate social interactions. These behaviors, including altruism, tolerance, forgiveness, reciprocity and fairness, are readily evident in the egalitarian way wolves and coyotes play with one another. Canids (animals in the dog family) follow a strict code of conduct when they play, which teaches pups the rules of social engagement that allow their societies to succeed. Play also builds trusting relationships among pack members, which enables divisions of labor, dominance hierarchies and cooperation in hunting, raising young, and defending food and territory. Because this social organization closely resembles that of early humans (as anthropologists and other experts believe it existed), studying canid play may offer a glimpse of the moral code that allowed our ancestral societies to grow and flourish. © 2010 Scientific American

Keyword: Emotions; Evolution
Link ID: 13890 - Posted: 06.24.2010

By Wray Herbert When Pulitzer Prize–winning music critic Tim Page was in second grade, he and his classmates went on a field trip to Boston. He later wrote about the experience as a class assignment, and what follows is an excerpt: “Well, we went to Boston, Massachusetts, through the town of Warrenville, Connecticut, on Route 44A. It was very pretty, and there was a church that reminded me of pictures of Russia from our book that is published by Time-Life. We arrived in Boston at 9:17. At 11 we went on a big tour of Boston on Gray Line 43, made by the Superior Bus Company like School Bus Six, which goes down Hunting Lodge Road where Maria lives and then on to Separatist Road and then to South Eagleville before it comes to our school. We saw lots of good things like the Boston Massacre site. The tour ended at 1:05. Before I knew, it we were going home. We went through Warrenville again, but it was too dark to see much. A few days later it was Easter. We got a cuckoo clock.” Page received an unsatisfactory grade on his essay. What’s more, his irate teacher scrawled in red across the top of the essay: “See me!” As he recalls in his new memoir Parallel Play (Doubleday, 2009), such incidents were not uncommon in his childhood, and he knew why he was being scolded: “I had noticed the wrong things.” The subtitle of Page’s memoir is Growing Up with Undiagnosed Asperger’s, and indeed Page didn’t learn until age 45 that he suffers from what is called autism spectrum disorder, or ASD. ASD is usually defined by impairments in social interaction and communication, but many people with autism and Asperger’s syndrome (in which symptoms are milder) also tend to fixate on and remember seemingly irrelevant information in their world. Their attention seems to be awry, or to use Page’s words, they notice the wrong things. © 2010 Scientific American,

Keyword: Autism; Attention
Link ID: 13889 - Posted: 06.24.2010

Deep brain stimulation is a promising therapy for epilepsy, US researchers from Stanford University have said. In a clinical trial, 110 people had electrodes implanted in their brains and their seizures were monitored. Forty-one per cent of patients showed a reduction in seizures after 13 months while 56% experienced a reduction after two years. The patients all suffered from regular epileptic seizures and had failed to respond to drug treatment. Deep brain stimulation (DBS) is a surgical treatment involving the implantation of a medical device called a brain pacemaker, which sends electrical impulses to specific parts of the brain. In the group of patients who received brain stimulation, researchers noted a 41% reduction in seizures compared to a 14.5% decline in seizures in a control group. This group did not receive stimulation. Epilepsy is a common neurological disorder which is characterised by recurrent seizures. These seizures can cause temporary loss of consciousness, convulsions, confusion or disturbances in sensations. According to the World Health Organization, epilepsy affects 50 million people worldwide. Previous studies indicate that one third of those with epilepsy do not respond to anti-epileptic drugs. Dr Robert Fisher, director of the Epilepsy Centre at Stanford University and lead author of the study, said electrical deep brain stimulation does reduce seizure frequency in patients. But he cautioned: "DBS therapy is invasive and serious complications can occur. Additional clinical knowledge would help to determine the best candidates for DBS therapy." (C)BBC

Keyword: Epilepsy
Link ID: 13888 - Posted: 03.18.2010

By Doreen Walton In the battle for our money and loyalty, companies wanting to sell us products have turned their attention to something right under our noses. Or behind our noses. The brain is now being called the ultimate business frontier and technology is letting firms take a look inside our heads. In this neurological market research participants wear a cap fitted with brain sensors as they watch adverts. Emotional response, attentiveness and memory function are all measured. An electroencephalogram or EEG, a painless brain scan, allows researchers to track the electrical impulses across the surface of the brain. I volunteered as a guinea pig to see how it works. EEG's have been around for roughly ninety years and are regularly used in medical applications for diagnosing epilepsy. In the last two decades the technology has moved on. Activity used to be recorded using pens on moving paper, now it can be digitised instantaneously into graphs. The equipment has also recently become a lot smaller and more portable so the marketing experts now believe it can be used more widely as a tool for studying the reactions of potential consumers. In the demonstration of the technique, I was fitted with something that looked a bit like a swimming cap full of holes. Sensors which capture brainwave activity 2,000 times a second were plugged into the holes. A gel was squeezed into the holes to allow my brain's electrical signals to be picked up. As the sensors were fastened in place in the cap and two put by my eye to monitor blinking, Darren Bridger, director of lab operations at Neurofocus Europe, explained the basics. (C)BBC

Keyword: Emotions
Link ID: 13887 - Posted: 03.18.2010

Janet Fang In pipefish, pregnant males give birth to more young from attractive mates, new research shows. Pipefish, sea horses, and sea dragons belong to a family in which the males get pregnant. In some of these species, the females court and compete for males. The pair then do a dance, which includes "twitching at each other and spiralling together, like a double helix", says lead author Kimberly Paczolt from Texas A&M University in College Station. As they spiral around each other, the female transfers the eggs into two rows along its mate's body. The male then fertilizes the eggs, and the brood pouch — which consists of two flaps — glues itself together in the middle. Weeks later, the seam breaks apart, tiny versions of the adults swim out, and the males are free to be impregnated again in as little as an hour. The male's pouch protects the embryos and gives them oxygen and nutrients. But, Paczolt says, the male doesn't care for the babies with utter abandon. Rather, he tempers how much he invests in the eggs according to how large the female is. In their study, published in Nature today, Paczolt and her colleague Adam Jones mated 22 male Gulf pipefish (Syngnathus scovelli) with two females each, in separate broods1. They found that the males preferred to mate with larger females, and that these more 'attractive' females transfer more eggs to the male and more of her young survive. © 2010 Nature Publishing Group

Keyword: Sexual Behavior; Evolution
Link ID: 13886 - Posted: 06.24.2010

By Jennifer Viegas Human friends may come and go, but a horse could be one of your most loyal, long-term buddies if you treat it right, suggests a new study. Horses also understand words better than expected, according to the research, and possess "excellent memories," allowing horses to not only recall their human friends after periods of separation, but also to remember complex, problem-solving strategies for ten years or more. The bond with humans likely is an extension of horse behavior in the wild, since horses value their own horse relatives and friends, and are also open to new, non-threatening acquaintances. "Horses maintain long-term bonds with several members of their family group, but they also interact temporarily with members of other groups when forming herds," explained Carol Sankey, who led the research, and her team. "Equid social relationships are long-lasting and, in some cases, lifelong," added the scientists, whose paper has been accepted for publication in the journal Animal Behavior. Ethologist Sankey of the University of Rennes and her colleagues studied 20 Anglo-Arabian and three French Saddlebred horses stabled in Chamberet, France. The scientists tested how well the horses remembered a female trainer and her instructions after she and the horses had been separated up to eight months. © 2010 Discovery Communications, LLC

Keyword: Learning & Memory
Link ID: 13885 - Posted: 06.24.2010

by Jeff Hecht Attracting the opposite sex is not the only reason some birds have elaborate head ornamentation. Avoiding things that might bump your head in the dark is also important, at least for crested and whiskered auklets – seabirds famed for their decorative head feathers. Charles Darwin suggested that elaborate display feathers were involved in sexual selection, and subsequent experiments confirmed his idea. In fact, elaborate feathers may have first evolved for touch sensing, with sexual selection coming later, says Ian Jones of Memorial University in St John's, Newfoundland, Canada, who did the research with Sampath Seneviratne, now at the University of British Columbia in Vancouver, Canada. Crested and whiskered auklets nest in hollows on rocky islands in the remote northern Pacific Ocean. To see if their elaborate headdresses helped the birds make their way through the rocks to their nests at night, Jones and Seneviratne went to the Aleutian Islands, captured wild birds and put them in a darkened maze – but first they taped down some birds' decorative feathers. Infrared camera recordings (see video) showed that whiskered auklets (Aethia pygmaea) bumped their heads nearly three times more often if their long head feathers were taped down. Crested auklets (A. cristatella), suffered similarly with their crests taped down, but adding an artificial crest to the naturally unadorned least auklet (A. pusilla) – which also nests on the islands but in more open areas – didn't help these birds avoid bumps. Moreover, Sereviratne says, "birds with longer crests had greater difficulty in navigating inside the maze" when their crests were taped down. © Copyright Reed Business Information Ltd

Keyword: Pain & Touch; Evolution
Link ID: 13884 - Posted: 06.24.2010

Babies love a beat, according to a new study that found dancing comes naturally to infants. The research showed babies respond to the rhythm and tempo of music, and find it more engaging than speech. The findings, based on a study of 120 infants between 5 months and 2 years old, suggest that humans may be born with a predisposition to move rhythmically in response to music. "Our research suggests that it is the beat rather than other features of the music, such as the melody, that produces the response in infants," said researcher Marcel Zentner, a psychologist at the University of York in England. "We also found that the better the children were able to synchronize their movements with the music, the more they smiled." To test babies' dancing disposition, the researchers played recordings of classical music, rhythmic beats and speech to infants, and videotaped the results. They also recruited professional ballet dancers to analyze how well the babies matched their movements to the music. During the experiments, the babies were sitting on a parent's lap, though the adults had headphones to make sure they couldn't hear the music and were instructed not to move. The researchers found the babies moved their arms, hands, legs, feet, torsos and heads in response to the music, much more than to speech. © 2010 LiveScience.com

Keyword: Hearing; Development of the Brain
Link ID: 13883 - Posted: 06.24.2010

By Julie Steenhuysen CHICAGO - People with a family history of Alzheimer's disease often have clumps of a toxic protein in their brains even though they are perfectly healthy, researchers said on Monday. They said the findings could lead to new ways to identify people most likely to develop Alzheimer's disease, when there is still time to do something about it. "The hope is to one day be able to diagnose very clearly the Alzheimer's disease process before any symptoms occur, when the brain is still healthy. Then the treatments would have the best chance of success," said Lisa Moscone of New York University Langone Medical Center, whose study appears in the Proceedings of the National Academy of Sciences. The team wants to continue to follow the people in the study to see whether they develop dementia, and they want to replicate the findings in a much larger study. Several teams have been working on better ways to detect early-stage Alzheimer's disease in hopes of developing drugs that can fight it before it causes too much damage. Current treatments cannot reverse the course of Alzheimer's, a mind-robbing form of dementia that affects more than 26 million people globally. Copyright 2010 Reuters.

Keyword: Alzheimers; Brain imaging
Link ID: 13882 - Posted: 06.24.2010

By Kay Lazar Attorney General Martha Coakley’s office joined a federal lawsuit yesterday that contends that Johnson & Johnson paid tens of millions of dollars in kickbacks to get its drugs, especially the powerful antipsychotic Risperdal, prescribed in nursing homes. The action was taken as Coakley’s office disclosed that it is also scrutinizing companies that market antipsychotics to Massachusetts nursing homes. These drugs are widely used in some homes for residents suffering from dementia, a condition that puts them at greater risk of death when given antipsychotics. Antipsychotics were approved to treat people with severe mental illnesses, such as schizophrenia, but it is legal for physicians to prescribe them “off label’’ to treat people with dementia. Pharmaceutical companies are prohibited from marketing or promoting off-label uses of their products. “The inappropriate off-label marketing of antipsychotic drugs to nursing homes is a significant health and safety issue for our seniors,’’ Coakley said in a statement released by her office. “We have taken strong action on this issue in the past and are continuing to monitor it very closely moving forward.’’ Coakley’s office declined further comment, citing the pending litigation. The Globe reported Monday that 28 percent of Massachusetts nursing home residents were given antipsychotics last year. © 2010 NY Times Co.

Keyword: Schizophrenia; Alzheimers
Link ID: 13881 - Posted: 06.24.2010

By Liam Creedon, Press Association A soldier blinded by a grenade in Iraq today described how his life has been transformed by ground-breaking technology that enables him to "see" with his tongue. Lance Corporal Craig Lundberg, 24, from Walton, Liverpool, can read words, identify shapes and walk unaided thanks to the BrainPort device, despite being totally blind. The Liverpool fan, who plays blind football for England, lost his sight after being struck by a rocket propelled grenade while serving in Basra in 2007. He was faced with the prospect of relying on a guide dog or cane for the rest of his life. But he was chosen by the Ministry of Defence (MoD) to be the first person to trial a pioneering device - the BrainPort, which could revolutionise treatment for the blind. The BrainPort converts visual images into a series of electrical pulses which are sent to the tongue. The different strength of the tingles can be read or interpreted so the user can mentally visualise their surroundings and navigate around objects. The device is a tiny video camera attached to a pair of sunglasses which are linked to a plastic "lolly pop" which the user places on their tongue to read the electrical pulses. L/Cpl Lundberg explained: "It feels like licking a nine volt battery or like popping candy. ©independent.co.uk

Keyword: Vision; Robotics
Link ID: 13880 - Posted: 06.24.2010

By Diane Daniel When Claudette Broyles tries to describe to friends how she feels, she likens herself to a balloon on a string, tied to a post. "I'm constantly rocking and swaying, but the level changes," said Broyles, 60, of Woodstock, Va. "If I'm having an average day, then it's like I'm a balloon in a mild breeze. If I'm having a bad day, it's like it's really windy." I hadn't heard the balloon analogy before, but I could relate. Broyles and I suffer from mal de debarquement syndrome (MdDS), an uncommon balance disorder that one researcher describes as "motion hallucination." For weeks, months or even years at a time, we feel that we are rocking, bobbing, swaying, even though diagnostic tests for balance, hearing and vision show up normal. The name for the illness is French for "disembarkation sickness," so called because it most frequently occurs after being on a boat. Of course, many people have experienced the swaying sensations that occur just after a boat trip. But for those with MdDS, that feeling doesn't let up; it persists with varying degrees of severity, causing everything from clumsiness to the inability to walk without some kind of support. Just how many sufferers there are is unknown, says neurologist Yoon-Hee Cha, who this year launched a study funded in part by the National Institutes of Health, the first time federal money has been used for research into the syndrome. © 2010 The Washington Post Company

Keyword: Miscellaneous
Link ID: 13879 - Posted: 06.24.2010

By HARRIET BROWN As a woman whose height and weight put me in the obese category on the body-mass-index chart, I cringed when Michelle Obama recently spoke of putting her daughters on a diet. While I’m sure the first lady’s intentions are good, I’m also sure that her comments about childhood obesity will add yet another layer to the stigma of being overweight in America. Last August, Dr. Delos M. Cosgrove, a cardiac surgeon and chief executive of the prestigious Cleveland Clinic, told a columnist for The New York Times that if he could get away with it legally, he would refuse to hire anyone who is obese. He probably could get away with it, actually, because no federal legislation protects the civil rights of fat workers, and only one state, Michigan, bans discrimination on the basis of weight. Dr. Cosgrove may be unusually blunt, but he is far from alone. Public attitudes about fat have never been more judgmental; stigmatizing fat people has become not just acceptable but, in some circles, de rigueur. I’ve sat in meetings with colleagues who wouldn’t dream of disparaging anyone’s color, sex, economic status or general attractiveness, yet feel free to comment witheringly on a person’s weight. Over the last few years, fat people have become scapegoats for all manner of cultural ills. “There’s an atmosphere now where it’s O.K. to blame everything on weight,” said Dr. Linda Bacon, a nutrition researcher and the author of “Health at Every Size: The Surprising Truth About Your Weight” (Benbella, 2008). “If we’re worried about climate change, someone comes out with an article about how heavier people weigh more, so they require more fuel, and they blame the climate change crisis on fatter people. We have this strong belief system that it’s their fault, that it’s all about gluttony or lack of exercise.” Copyright 2010 The New York Times Company

Keyword: Obesity
Link ID: 13878 - Posted: 06.24.2010

by Helen Thomson HORROR films are simply a disconcerting watch for the majority of us, but for Jane Barrett they are literally torturous. She writhes in agony whenever the actors on the screen feel pain. "When I see violence in films I have an extreme reaction," she says. "I simply have to close my eyes. I start to feel nauseous and have to breathe deeply." She is just one of many people who suffer from a range of disorders that give rise to "extreme empathy". Some of these people, like Barrett, empathise so strongly with others that they experience the same physical feelings - whether it's the tickle of a feather or the cut of a knife. Others, who suffer from a disorder known as echopraxia, just can't help immediately imitating the actions of others, even in inappropriate situations. Far from being mere curiosities, understanding these conditions could have many pay-offs for neuroscience, such as illuminating conditions like phantom pain. They may even help answer the age-old question of whether empathy really is linked to compassion. There is a general consensus that empathy-linked conditions arise from abnormalities in the common mechanisms for empathy found in all humans: although few of us experience sensations as powerful as Barrett's, we all wince at a brutal foul on the football field and feel compassion for someone experiencing grief. Many studies have suggested that our capacity for empathy arises from a specific group of neurons, labelled mirror neurons. First discovered in macaque monkeys, they are situated in and around the premotor cortex and parietal lobe - regions that span the top of the brain near the middle of the head. These neurons fire both when you perform an action and when you see someone else perform that action. © Copyright Reed Business Information Ltd

Keyword: Emotions
Link ID: 13877 - Posted: 06.24.2010

By Lisa Grossman The molecule that lets snakes sense heat is the same one that makes wasabi feel fiery. Scientists have known for decades that some snakes use specialized holes called pit organs to “see” the heat radiating from prey. Now, molecular biologists have pinpointed the protein that gives pit-bearing snakes — vipers, boas and pythons — this sixth sense. The culprit is called TRPA1, a protein whose human counterpart is known as the “wasabi receptor” for its role in sensing the potent condiment. The results are reported online March 14 in Nature. “This is one of the first really interesting new findings in that species” in 20 years, comments snake-sense specialist Ken Catania of Vanderbilt University in Nashville, who was not associated with the study. “It’s the kind of paper that makes me have to go and revise my class lectures.” Scientists had thought that snakes’ sensitivity to heat comes from the exceptionally thin tissue in pit organs. Just as it takes less heat to boil a cup of water than a pot, it takes less heat to stimulate pit organ tissue than a mammal’s skin. But what was happening on a molecular level had never been explored. “We’ve been trying to address this question for a long time, several years,” says study coauthor David Julius of the University of California, San Francisco. “The technology wasn’t really right for us to do that until recently.” Recent advances in high-throughput genetic screening that can sift through hundreds of genes quickly made the study possible. © Society for Science & the Public 2000 - 2010

Keyword: Chemical Senses (Smell & Taste); Vision
Link ID: 13876 - Posted: 06.24.2010

By Rossella Lorenzi An international team of researchers has identified intact neurons and cerebral cells in a mummified medieval brain, according to a study published in the journal Neuroimage. Found inside the skull of a 13th century A.D. 18-month-old child from northwestern France, the brain had been fixed in formalin solution since its discovery in 1998. "Although reduced by about 80 percent of its original weight, it has retained its anatomical characteristics and most of all, to a certain degree its cell structures," anatomist and palaeopathologist Frank Ruhli, head of the Swiss Mummy Project at the University of Zurich, Switzerland, told Discovery News. The brain was the only tissue preserved in the infant's skeletonized body. "It is a unique case of naturally-occurring preservation of human brain tissue in the absence of other soft tissues," Ruhli said. The brain appeared almost intact. The grooves and furrows -- gyri and sulci -- that make up the surface of the brain's cerebral cortex were still clearly visible, as well the frontal, temporal and occipital lobe. Amazingly, the cellular structure had also been preserved to a certain degree. Microscopic examination of the tissue revealed gray and white matter, blood vessels and large neurons near the the hippocampus area, the memory-making region of the brain. The cells had mostly retained their original shape as well as the dendrites, the short, branched fibers that extend from the cell body of a neuron. © 2010 Discovery Communications, LLC.

Keyword: Miscellaneous
Link ID: 13875 - Posted: 06.24.2010

By Vilayanur S. Ramachandran and Diane Rogers-Ramachandran Although our perception of the world seems effortless and instantaneous, it actually involves considerable image processing, as we have noted in many of our previous columns. Curiously enough, much of the current scientific understanding of that process is based on the study of visual illusions. Analysis and resolution of an image into distinct features begin at the earliest stages of visual processing. This was discovered in cats and monkeys by a number of techniques, the most straightforward of which was to use tiny needles—microelectrodes—to pick up electrical signals from cells in the retina and the areas of the brain associated with vision (of which there are nearly 30). By presenting various visual targets to monitored animals, investigators learned that cells in early-processing brain areas are each sensitive mainly to changes in just one visual parameter, not to others. For instance, in the primary visual cortex (V1, also called area 17), the main feature extracted is the orientation of edges. In the area known as V4 in the temporal lobes, cells react to color (or, strictly speaking, to wavelengths of light, with different cells responding to different wavelengths). Cells in the area called MT are mainly interested in direction of movement. One characteristic of these cells that may seem surprising is that their activity when stimulated is not constant. A neuron that responds to red, for instance, will initially fire vigorously but taper off over time as it adapts, or “fatigues,” from steady exposure. Although part of this adaptation may result from depletion of neurotransmitters, it also likely reflects the evolutionary logic that the goal of the cell is to signal change rather than a steady state (that is, if nothing changes, there is literally nothing for the cell to get excited about). © 2010 Scientific American,

Keyword: Vision
Link ID: 13874 - Posted: 06.24.2010