Alison Abbott. Anne Churchland had little time for rats. In the course of 13 years' work on decision-making in monkeys, she had never questioned that primate studies were the only way to understand the neurobiology of human cognition. Her work in the lab of Michael Shadlen at the University of Washington, Seattle, had monkeys watch moving dots flitting about on a screen until the animals indicated, with a flick of their eyes, the direction in which most of the dots were going. She recorded from single brain neurons as the monkeys slowly made sense of this 'fuzzy' information — the sort of sophisticated experiment that she did not think was possible in rodents. "I didn't think rats would have the right sorts of brains to contemplate accumulating evidence," says Churchland. And with poor eyesight, and heads that bob around, "I didn't imagine they would be able to convey to us any decision they might be silently making". All that changed a year ago, when Churchland visited Cold Spring Harbor Laboratory in New York. Working with scientists there, she saw that rats could also learn to gather 'fuzzy' sensory information — in this case to decide whether the frequency of a rapid sequence of tones was mostly high or low. And they could convey their decision with a poke of the nose. Churchland was not alone in her earlier scepticism. Neurophysiological research into higher cognitive functions such as decision-making, attention, working memory — even risk-taking — have traditionally been carried out on non-human primates. That seemed an obvious choice, given the closeness of their brain anatomy to that of humans, the sophistication and breadth of their behaviour and their ability to reliably report to experimenters much of what is going on in their minds through eye, hand or other movements. But primate work comes with major downsides: the animals are so expensive, and their use so highly regulated, that a research paper typically relies on data from just a couple of precious animals, which have been used for multiple experiments over their lifetime. This raises concerns that observations could be unique to those animals, rather than a general property of the primate brain. © 2010 Nature Publishing Group

Keyword: Attention; Learning & Memory
Link ID: 14087 - Posted: 06.24.2010

By Diane Mapes Being a “supertaster” may sound like a foodie’s dream come true, but in reality, it’s no picnic. Coffee and alcohol are unpalatable – along with tomatoes, Parmesan cheese, strawberries, condiments and most sweets. “I can’t stand cake,” says Michelle Triplett, a 31-year-old stay-at-home mom and supertaster from Olympia, Wash., who spoke, coincidentally, on her birthday. “It’s too sweet for me. And when I drink beer, I gag. It’s like drinking urine.” Supertasters detect components – like salt or bitterness -- in food that others can’t, says Dr. Alan Hirsch, founder and neurological director of the Smell & Taste Treatment and Research Foundation in Chicago. “[Supertasters] have densities of taste buds that are 10 to 100 times greater than the normal population,” he says. “As a result, supertasters are much more sensitive to spicy foods and they can taste … very mild flavors.” Triplett, whose favorite meals are turkey sandwiches and macaroni and cheese, says the blander the better, since most everything else is, as They Might Be Giants put it in their song “John Lee Supertaster,” simply “too much.” The condition is genetic, tends to affect women more than men and affects 25 percent of the U.S. population; non-tasters (people with a reduced ability to taste) make up another 25 percent with the rest of the population described as medium or normal tasters. © 2010 Microsoft

Keyword: Chemical Senses (Smell & Taste)
Link ID: 14086 - Posted: 06.24.2010

By Katherine Harmon Despite weighty concerns, such as aging, planning for retirement or caring for older friends and family, people in the U.S. seem to get happier with age. A new study reports that these changes are consistent regardless of whether individuals were employed, had young children at home or lived with a partner. General wellbeing (characterized by how people currently felt about their life) fell sharply through the age of 25 and tapered more gradually overall until the ages of 50 to 53. And by the early 70s, that wellbeing was back up to late-teen levels. "As people age, they are less troubled by stress and anger," the researchers noted in their study, which was led by Arthur Stone, of the Department of Psychiatry and Behavioral Science at Stony Brook University and published online May 17 in the Proceedings of the National Academy of Sciences. "And although worry persists, without increasing, until middle age, " they continued, "it too fades after the age of 50." The data come from a 2008 phone survey performed by the Gallup Organization of 340,847 randomly selected adults aged 18 to 85. The respondents represented a fairly average slice of the U.S. population, with about 29 percent holding a college degree and a median monthly average household income between $3,000 and $3,999. During the call, participants were asked to rate how they currently felt their life stood on a scale of 0 ("the worst possible life for you") to 10 ("the best possible life for you"). They were then asked if they had felt different affective states (happiness, enjoyment, stress, sadness, anger and worry) "a lot of the day yesterday." Keeping questions to relatively current periods in time by asking about yesterday as opposed to the previous week, month or year helped the researchers avoid some of the retrospective bias that might have played a role in similar past studies. © 2010 Scientific American,

Keyword: Emotions; Development of the Brain
Link ID: 14085 - Posted: 06.24.2010

by Sandrine Ceurstemont A simple animation has been found to offer our brains many possible interpretations. Jan Kremláček from Charles University in Hradec Králové, Czech Republic, discovered six different ways of perceiving a moving sine graph drawn with dots. The curves often seem to undulate like two ribbons, but the animation can also seem to have depth, with one curve seeming to be further back than the other. The dotted arcs can also look like a spindle shape that revolves and snakes along. If you keep staring, the curves can seem to revolve vertically around a static rod, first in one direction, then the other. The animation can also look like a series of bouncing dots, but this is very hard to perceive without overlaying vertical bars on top of it. "Our brain is able to reconstruct different learned interpretations, but only one can be perceived at a time," says Kremláček. He came across the illusion by chance while preparing graphs for a lecture in signal processing. © Copyright Reed Business Information Ltd.

Keyword: Vision
Link ID: 14084 - Posted: 06.24.2010

by Carl Zimmer Your nose is a paradox. In some ways the human sense of smell is astonishingly precise. For example, natural gas companies add a smelly molecule called n-butyl mercaptan to natural gas, which is odorless by itself, so that people can sniff gas leaks. All it takes is one n-butyl mercaptan molecule for every 10 billion molecules of methane to do the trick. To put this precision in perspective, imagine you are standing in front of two Olympic-size swimming pools. One of them contains a grand total of three drops of n-butyl mercaptan, and the other has none. Your nose could tell the difference. But don’t get too smug, because in other ways your sense of smell is practically useless. To judge for yourself, find someone to help you run a simple experiment. Close your eyes while your partner raids your refrigerator and then holds different foods under your nose. Try to name each scent. If you’re like most people, you’ll bomb. In a number of studies, scientists have found that people tested on items in their own kitchens and garages give the wrong answer at least half the time. And as bad as we normally are at identifying smells, we can easily be fooled into doing worse. If orange food coloring is added to cherry-flavored soda, for example, people are more likely to say that it smells like oranges. Noam Sobel of the Weizmann Institute of Science in Israel and his colleagues have been puzzling over this paradox for the past several years. What has been missing in the science of smell, they argue, is a meaningful way to measure it—an olfactory yardstick. Now they have built one.

Keyword: Chemical Senses (Smell & Taste)
Link ID: 14083 - Posted: 06.24.2010

By Nathan Seppa Elderly people who care for a spouse who has dementia are at increased risk of developing dementia themselves, a study finds. The stress of attending to a mentally incapacitated spouse may somehow contribute to the added risk, scientists report in the May Journal of the American Geriatrics Society. Previous studies have shown that chronic stress leads to increased levels of the hormone cortisol in the body, which can suppress immunity, says study coauthor Peter Rabins, a psychiatrist at Johns Hopkins School of Medicine in Baltimore who teamed with researchers at Utah State University in Logan to do this study. “It’s long been thought that this might have adverse outcomes psychologically and physiologically.” Taking care of a spouse with dementia takes a toll in other ways as well, Rabins says. “Caregivers often complain that they lose their friends,” he says, because they don’t have time to socialize. But the biological mechanisms that might link these challenges to heightened dementia risk remain unclear. In the new study, the researchers assessed the mental status of 1,221 Utah couples who had agreed to be part of a community-wide health study that started in 1995. The men averaged age 76 and the women 73 at that point, and 95 percent had been married for more than 20 years. Researchers tracked these couples’ mental status with up to four exams over the next decade with a median follow-up of 3.3 years. No participants in this analysis had dementia at the start. © Society for Science & the Public 2000 - 2010

Keyword: Alzheimers; Stress
Link ID: 14082 - Posted: 06.24.2010

Newborn infants are capable of a simple form of learning while they’re asleep, according to a study by researchers funded by the National Institutes of Health. The finding may one day lead to a test that can identify infants at risk for developmental disorders that do not become apparent until later in childhood. The study was confined to newborns, so the researchers do not know whether older children or adults are capable of learning during sleep. Funding for the study was provided by the NIH’s Eunice Kennedy Shriver National Institute of Child Health and Human Development. Additional funding was provided by the National Institute of Mental Health. Conducted by William Fifer, Ph.D. and his colleagues at Columbia University in New York, the study was published today online in the Proceedings of the National Academy of Sciences. Researchers used an electroencephalogram, a machine that records the brain’s electrical activity and converts it into patterns, to record the brain activity of each sleeping infant. A video camera recorded each infant’s facial expressions. The researchers played a tone, while a machine blew a faint puff of air at each sleeping infant’s eyelids. In response to the air puff, the infants reflexively squeezed their closed lids tighter. The researchers repeated this nine times, each time pairing the air puff with the tone. For the tenth time in the sequence, however, the researchers played the tone without the air puff. This sequence was repeated over and over again. After roughly 20 minutes, most of the infants (24 out of 26) would scrunch their faces in response to the tone that was not accompanied by the air puff. Moreover, the electroencephalogram detected changes in brain wave activity that occurred simultaneously with the tone, which the researchers interpret as further evidence that the infants had learned to associate the tone with the air puff.

Keyword: Sleep; Learning & Memory
Link ID: 14081 - Posted: 06.24.2010

By Emily Sohn Teenagers do crazy things, and the chemistry of their brains might explain why. In a new study, scientists found that the adolescent brain is extra sensitive to the rewarding signals it gets when something better than expected happens. The discovery might help explain why teens take risks that don't seem worth it to adults -- from driving too fast to experimenting with drugs. "Teenagers seek out these sorts of rewarding experiences, and this provides a little explanation for that," said Russell Poldrack, a cognitive neuroscientist at the University of Texas, Austin. "In the long run, it may help us understand how addictions start and develop." To zero in on the neuroscience behind risk-taking behavior in adolescents, Poldrack and colleagues focused on a concept called prediction error, which describes the difference between what a person expects to happen and what actually happens. If you anticipate a rich sip of full-bodied espresso, for example, but you end up gulping weak, watery, and burnt coffee, that's a negative prediction error. If you expect nothing from a friend for your birthday but he gives you $20, that's a positive error -- far better than expected. To test the brain's reaction to positive prediction errors at different stages of life, the scientists enlisted 45 people, ranging in age from 8 to 30. Each participant was shown a series of abstract kaleidoscopic images and challenged to categorize the figures as logos belonging to one of two fictional colleges. © 2010 Discovery Communications, LLC.

Keyword: Development of the Brain; Drug Abuse
Link ID: 14080 - Posted: 06.24.2010

By JoNel Aleccia Exposure to pesticides used on common kid-friendly foods — including frozen blueberries, fresh strawberries and celery — appears to boost the chances that children will be diagnosed with attention deficit hyperactivity disorder, or ADHD, new research shows. Youngsters with high levels of pesticide residue in their urine, particularly from widely used types of insecticide such as malathion, were more likely to have ADHD, the behavior disorder that often disrupts school and social life, scientists in the United States and Canada found. Kids with higher-than-average levels of one pesticide marker were nearly twice as likely to be diagnosed with ADHD as children who showed no traces of the poison. “I think it's fairly significant. A doubling is a strong effect,” said Maryse F. Bouchard, a researcher at the University of Montreal in Quebec and lead author of the study published Monday in the journal Pediatrics. The take-home message for parents, according to Bouchard: “I would say buy organic as much as possible,” she said. “I would also recommend washing fruits and vegetables as much as possible.” Diet is a major source of pesticide exposure in children, according to the National Academy of Sciences, and much of that exposure comes from favorite fruits and vegetables. In 2008, detectable concentrations of malathion were found in 28 percent of frozen blueberry samples, 25 percent of fresh strawberry samples and 19 percent of celery samples, a government report found. © 2010 msnbc.com

Keyword: ADHD; Neurotoxins
Link ID: 14079 - Posted: 06.24.2010

By Judy Foreman The symptoms of restless legs syndrome sound so bizarre — creepy-crawly feelings and an uncontrollable urge to move the legs, especially at bedtime — that until recently, many people who experienced it simply weren’t believed when they described it to others. Betsy Dunn, an 85-year-old Cambridge businesswoman who has had restless legs for nearly 30 years, remembers a doctor saying she must be depressed. “I walked out and never went back,’’ she says. “All I needed him to say was, ‘I don’t know what this is, but together we will find out.’ ’’ In severe cases, like that of Donald Loveland, 75, a retired Duke University computer scientist now living in Dennis, the urge to move the legs overwhelms everything else, including pain. Right after back surgery, he recalls, “it was actually painful to be up but I had to get up anyway.’’ Ron Blum, 38, a Jamaica Plain e-mail marketer who first noticed his symptoms as a 7-year-old, recalls that the minute he lay down and tried to sleep, “my left leg felt like it had to go for a walk.’’ Though he never told his parents, he’d get up and walk for hours in circles. It wasn’t until years later that a friend heard about RLS. “He called me up and said, ‘Ron, I know what you have. It has a name.’ ’’ It also has growing recognition. RLS may affect some 12 million Americans, according to the National Institute of Neurological Disorders and Stroke, as reported on the National Institutes of Health website (www.ninds.nih.gov/disorders). The NIH supports research into the condition at major medical institutions across the country, as well as within its own labs. © 2010 NY Times Co.

Keyword: Movement Disorders
Link ID: 14078 - Posted: 06.24.2010

By Laura Sanders A quick flash of light has confirmed the key assumption justifying the use of functional magnetic resonance imaging to reveal the inner workings of living brains. In a study appearing online May 16 in Nature, researchers used light to activate nerve cells and then saw the telltale fMRI signal, demonstrating that nerve cell activity is indeed responsible for the colorful splotches appearing on fMRI images. The new technique, called optogenetic fMRI, may lead to a much deeper understanding of how information travels through the brain. These results “put the fMRI field on firm footing,” by showing unambiguously that neuron activity can cause the fMRI signal, says study coauthor Karl Deisseroth of Stanford University. One of the most common versions of fMRI doesn’t directly measure the activity of nerve cells, or neurons, in the brain (SN: 12/19/09, p. 16). Instead, the typical method, called BOLD (for blood oxygen level-dependent), tallies slight changes in oxygen levels in the blood that surrounds neurons. Presumably, as neurons become active, they need more energy and consume more oxygen. These tiny fluctuations in oxygen serve as a proxy for brain activity. But direct evidence for this causal relationship has been lacking. Deisseroth and colleagues used a technique pioneered in their lab called optogenetics, in which light-responsive molecules are used to control particular cells (SN: 1/30/10, p. 18). To directly test the relationship between neuron activity and BOLD signal, the researchers inserted a molecule that responds to a pulse of blue light into neurons in the motor cortex of rats. Under normal conditions, these neurons activate and send the “go” signal when the rat wants to move a leg. With the addition of the light-responsive molecule, these neurons also fire when a pulse of blue light strikes. Armed with the ability to activate select groups of neurons at will, Deisseroth and colleagues could play with the switch and see when BOLD signals were made. © Society for Science & the Public 2000 - 2010

Keyword: Brain imaging
Link ID: 14077 - Posted: 06.24.2010

By Cristen Conger A debate is brewing in the bat research community over one of the winged mammal’s senses. No, it has nothing to do with vision. Despite the tiny eyes and nocturnal lifestyle, none of the roughly 1,100 bat species is blind. “All bats can see and all bats are sensitive to changing light levels because this is the main cue that they use to sense when it is (night time) and time to become active,” said Paul Faure, of McMaster University’s Bat Lab. Instead, researchers can’t agree on a certain aspect of the mammal’s sonar sight, called echolocation. To track down prey, avoid predators and find their way home in the dark, most bats depend on echolocation. They broadcast high-pitched sonar signals and listen for the echoes of sound waves bouncing off objects they’re looking for or obstacles in their path. Bats’ brains then process the auditory information within those echoes as visual maps. Scientists know a lot about the finer points of how echolocation works, but they differ on whether that sense evolved before or after bat’s ability to fly. “Some question whether echolocation 60 million years ago would’ve been too sophisticated,” said Brock Fenton, of the University of Western Ontario. The scientists who discovered Onychonycteris finneyi, the oldest known bat fossil (above), concluded that the prehistoric species could fly but that the sonar sense didn't evolve until later. © 2010 Discovery Channel

Keyword: Hearing; Evolution
Link ID: 14076 - Posted: 06.24.2010

By Jeremy Laurence, A blood test to assess the risk of brain damage in vulnerable newborn babies could save lives and prevent disability, scientists say. The test, carried out on blood taken from the umbilical cord immediately after birth, measures its acidity (the pH level). Blood with a low pH (more acid) indicates a lack of oxygen at birth, which is the commonest cause of brain damage, cerebral palsy and death. Current guidelines suggest that measuring the pH level of umbilical cord blood is worthless as a predictor of how the baby will fare, because the association is inconsistent. But doctors based in Birmingham reviewed 51 studies involving almost 500,000 babies and found a low pH in the cord blood was strongly linked with serious outcomes. Based on their findings, published in the British Medical Journal, they call for increased surveillance of babies born with low cord blood pH and for further research to explore the cost effectivenees of doing the test on all babies. In an accompanying editorial, James Neilson, professor of obstetrics and gynaecology at the University of Liverpool, said: "We should aim to reduce the number of babies born with a low cord pH, without increasing unnecessary obstetric intervention." Andy Shennan, professor of obstetrics at St Thomas' Hospital in London welcomed the study into the relationship between low pH and future health. "Lack of oxygen to the baby during labour will result in a low pH in the umbilical cord," he said. "If it is prolonged, irreversible neurological damage can occur, although this is rare." ©independent.co.uk

Keyword: Development of the Brain
Link ID: 14075 - Posted: 06.24.2010

by Leigh Krietsch Boerner Even if a mouse has never seen a cat before, he’ll turn tail when one is nearby. Researchers suspected that the rodents somehow sniff out their would-be assassins, but exactly what they smelled was unclear. Now scientists have isolated the compound, one of a class of urinary proteins that are secreted by cats, snakes, and a variety of other predators. Mice have two different ways to pick up scents: their nose and a specialized organ inside their nose called the vomeronasal organ (VNO), which helps them detect other mouse pheromones. Suspecting that VNO might help the rodents sniff out predators as well, neurobiologist Lisa Stowers of The Scripps Research Institute in San Diego, California, dropped cotton balls laced with either cat saliva, rat urine, or snake skin essence into the cages of both normal and mutant mice with inactive VNOs. The normal mice cowered in the corner, as if a predator were present. Meanwhile, the mutants weren’t afraid at all, even when an anesthetized rat was placed in their cage. “Some of the subjects were so relaxed that they actually curled up and went to sleep next to the rat,” Stowers says. In addition, using dyes that light up when neurons are activated, the team saw neurons associated with VNOs turn on in response to the scents. These mice were inbred in labs for hundreds of generations, none of them having ever seen a predator, Stowers notes. “This isn’t the mouse learning to recognize these cues,” she says, “he’s born with the ability to detect them.” © 2010 American Association for the Advancement of Science.

Keyword: Chemical Senses (Smell & Taste); Emotions
Link ID: 14074 - Posted: 06.24.2010

By Katherine Harmon Even cobras need to defend themselves sometimes. These venomous snakes keep adversaries at bay by spitting a neurotoxin or other substance into their perceived enemy's eyes, causing severe pain and sometimes blindness. And they are incredibly accurate in hitting their target—even though it is often moving and more than a meter away. But how can a cobra be so adept at adjusting its venom trajectory (usually launched straight from openings in the fangs) to different scenarios, when fang and venom-opening sizes remain the same? "Basic fluid dynamics would lead you to think that the pattern of the fluid should be fixed," Bruce Young, of the Department of Physical Therapy at the University of Massachusetts Lowell and co-author of a new study, said in a prepared statement. To find out, Young and his colleagues headed into the snake-filled labs of Horst Bleckmann at the University of Bonn Institute of Zoology to taunt some cobras. After donning proper protection, Young met his experimental partners: red spitting cobras (Naja pallida), black-necked spitting cobras (Naja nigricollis) and black-and-white spiting cobras (Naja siamensis). "I just put on the goggles and the cobras start spitting all over," Young said. He was also outfitted with accelerometers on his head, and his human colleagues used high-speed video to film cobras spitting and then compared the movements of the two. The results were published online May 14 in The Journal of Experimental Biology. © 2010 Scientific American

Keyword: Neurotoxins; Vision
Link ID: 14073 - Posted: 06.24.2010

by Teresa Shipley I always knew we women had the magic touch. Turns out that now science can prove it. As babies, we're touched a lot by our mothers, and we actually take a lot of risks. When we took our first steps, tasted new things or explored unknown places, our mothers were there to hold our hands, pick us up and dust us off. They made us feel safer and therefore more likely to keep exploring. Two researchers at Columbia University were curious whether the comforted, secure feelings we have as babies would transfer to adults when they were faced with making a risky choice. They designed an experiment where participants were greeted by either a female or male experimenter and then tested to see if they would take financial risks, such as investing money or gambling. It turns out that the type of touch mattered as much as who was giving it. When a female experimenter touched a participant on the back of the shoulder, that person was much more likely to risk money. If she shook their hands or just spoke to them, however, there was no effect. At the end of the experiment, participants filled out surveys that asked how secure they felt. Those who were touched by the woman, especially if it was on the back, said they felt safer and took bigger risks than those who weren't. But those who were touched by the man didn't show any extra feelings of security. © 2010 Discovery Communications, LLC.

Keyword: Pain & Touch; Emotions
Link ID: 14072 - Posted: 06.24.2010

by Jim Giles Studying animal conflicts could help shed light on human wars – that is the hope from a study of the choices that monkeys make when deciding to fight or remain at peace. Competition for resources is often assumed to be a main cause of conflict in both humans and other animals, says Jessica Flack at the Santa Fe Institute in New Mexico, but that might be wrong. "We find that fighting is based on memories of what other individuals did last." Flack and colleagues Simon DeDeo and David Krakauer analysed data from 160 days of field observations of a group of 84 pigtailed macaques at the Yerkes National Primate Research Center in Lawrenceville, Georgia. The team paid particular attention to which animals fought and how long each fight lasted. Instead of explaining the monkey's fighting ways by dreaming up a strategy based, for example, on the reward value of winning a fight for food or a mate, Flack and colleagues decided to look for strategies suggested by the data alone. They made no assumption about the reasons for the monkeys' behaviour and looked only at patterns of behaviour leading up to fights. This allowed them to determine the relative importance of the factors that led up to a fight. They found that the strategy that best explained involvement in a fight was one in which decisions were based on the presence or absence of pairs of other monkeys. This suggests that social dynamics play a central role. © Copyright Reed Business Information Ltd.

Keyword: Aggression
Link ID: 14071 - Posted: 06.24.2010

by Dan Ferber Brain cells thought to underlie our ability to understand one another work just fine in people with autism spectrum disorders (ASD), according to the authors of a controversial new study. Other researchers had proposed that these cells, called mirror neurons, malfunction in people with ASD, disrupting their ability to understand what someone else is experiencing. If the results hold up, researchers will need another way to explain the social deficits that characterize the disorder. First identified in monkeys, mirror neurons fire when an animal performs particular movements but also when it sees another monkey or a person perform the same movement. Such neurons allow monkeys—and presumably humans—to learn actions by imitating others, and, some researchers believe, to understand other people and empathize with them. People on the autism spectrum struggle to understand what’s happening in other people’s minds, which makes it hard for them to connect socially. Some neuroscientists had proposed that mirror neuron deficits were at the root of their social problems. Several groups had found evidence supporting the mirror neuron hypothesis; for example, neuroscientist Marco Iacoboni of the University of California, Los Angeles, and colleagues reported in 2005 that children with ASD show reduced mirror neuron activity compared with healthy controls when they watch and imitate others making faces. But neuroscientists Ilan Dinstein and David Heeger of New York University and their colleagues considered the previous results in humans inconsistent and inconclusive and designed what they considered “a more in-depth test,” Dinstein says. © 2010 American Association for the Advancement of Science.

Keyword: Autism
Link ID: 14070 - Posted: 06.24.2010

by Gretchen Vogel If you’re reading this at night, beware: You may be affecting your body’s internal clock. Humans, like other animals, rely on light cues to set their body's daily cycle of activity, or circadian rhythm. Now a new study shows that some wavelengths of light, such as those from computer screens, have an unexpectedly strong influence on these rhythms, keeping us awake, for example, when we should be sleeping. In mammals, a well-tuned system of light-sensing cells regulates the area of the brain that controls circadian rhythms, including those governing alertness and hunger. In diurnal animals, for example, light suppresses the production of the hormone melatonin, which is released during the night and promotes sleep. Researchers once thought that the eye’s rod and cone cells, which allow us to see, were responsible for detecting these light cues. But in some blind mice and blind people, circadian rhythms respond normally to changes in light exposure. Scientists now suspect that neurons in the retina that contain melanopsin, a pigment that is sensitive to short-wavelength blue light, drive circadian signals; these cells are still functional in blind people whose body clocks respond to light and dark signals. As a result, some researchers have recommended blue-light therapy for seasonal affective disorder, a type of depression triggered by winter’s short days. Others have developed blue light-blocking goggles to help insomniacs sleep better. But a new study of the specific effects of blue and green light suggests that the real story is more complicated. Neuroscientist Steven Lockley of Brigham and Women’s Hospital in Boston and his colleagues studied how exposure to different levels of light affected the sleep of healthy human volunteers, too. © 2010 American Association for the Advancement of Science

Keyword: Biological Rhythms; Vision
Link ID: 14069 - Posted: 06.24.2010

by Wendy Zukerman Having trouble picking out the guilty party? A brain scan won't help. Jesse Rissman and his team at Stanford University in California have found that monitoring brain activity of witnesses reveals no more than what they say they remember. The study comes amid controversy over whether to admit functional MRI scans as evidence in US courts. Last week, an attorney in New York City attempted to use a brain scan to demonstrate the truthfulness of a witness in an employment case, but failed on a separate legal technicality. And this week, a judge in a federal case in Tennessee was due to decide whether to admit fMRI evidence in a fraud case; if successful, this would be the first time a court anywhere in the world accepted this type of scan. The Stanford team asked 16 volunteers to view 200 mugshots. An hour later, they were again shown pictures of faces, some of which they had seen before and others that were new. The researchers recorded fMRI scans of the volunteers' brains as they reported which faces they recognised. While the brain scans matched the volunteers' decisions on whether the faces were familiar, they could not predict if the recollection was accurate. The team also don't know how easily a witness could cheat the system: remembering a recent event or fabricating a lie may look the same to the scanner. Journal reference: Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.1001028107 © Copyright Reed Business Information Ltd.

Keyword: Brain imaging; Learning & Memory
Link ID: 14068 - Posted: 06.24.2010