By JANE E. BRODY How well do you see at night? If you’re over 50, probably not as well as you think, no matter how many carrots you eat. The typical 50-year-old driver needs twice as much light to see as well after dark as a 30-year-old. Yet few of us compensate adequately for the reduction in nighttime acuity that occurs in the aging eye. In a normal healthy eye, light enters through the pupil and passes through the lens, which focuses it and directs it to the retina on the back of the eye, where images form. The retina contains two kinds of photoreceptors: cones and rods. Cones enable us to see when it is light. They give us color vision and allow us to see details like the words on this page. Rods are very sensitive, especially to motion. They provide only black-and-white images and thus are critically important for night vision. If only we had the eyes of a cat. Compared with the human eye, a cat’s eyes have more rods than cones, which helps the cat see in the dark. Cats also have elliptical pupils that open and close faster and can become larger than our round ones. In addition, cats and some other nocturnal animals have a mirrorlike membrane, the tapetum, on the back of their eyes, which reflects the light passing through the rods back through them in the opposite direction. This “double exposure” allows cats to see well in near darkness. Copyright 2007 The New York Times Company

Keyword: Vision
Link ID: 10068 - Posted: 06.24.2010

By NICHOLAS BAKALAR That fat people are jolly is almost certainly a myth, but a study published yesterday has found a strong association between higher body mass index, or B.M.I., and lower risk of suicide. In a 16-year study that followed more than 45,000 male health professionals, researchers found a steady decrease in suicides as B.M.I. increased, even after controlling for variables including smoking, dietary factors, physical activity, marital status and alcohol use. There were 131 suicides during the time of the study. Compared with those in the lowest 20 percent in B.M.I., men in the highest one-fifth were almost 60 percent less likely to kill themselves. “It’s a surprisingly strong relationship,” said Kenneth J. Mukamal, the lead author and an associate professor of medicine at Harvard University. “But even though we see that heavier men are less likely to commit suicide, there are plenty of other studies that link obesity to poor health. Gaining weight is not the best way to improve anyone’s mental health. I hope these findings will provide insight into new strategies to prevent suicide.” The authors, writing in The Archives of Internal Medicine, suggest that B.M.I. could be linked to suicide through circulating levels of insulin, which may have a role in determining mood. Copyright 2007 The New York Times Company

Keyword: Depression; Obesity
Link ID: 10067 - Posted: 06.24.2010

By JOHN TIERNEY So there are these two muffins baking in an oven. One of them yells, “Wow, it’s hot in here!” And the other muffin replies: “Holy cow! A talking muffin!” Did that alleged joke make you laugh? I would guess (and hope) not. But under different circumstances, you would be chuckling softly, maybe giggling, possibly guffawing. I know that’s hard to believe, but trust me. The results are just in on a laboratory test of the muffin joke. Laughter, a topic that stymied philosophers for 2,000 years, is finally yielding to science. Researchers have scanned brains and tickled babies, chimpanzees and rats. They’ve traced the evolution of laughter back to what looks like the primal joke — or, to be precise, the first stand-up routine to kill with an audience of primates. It wasn’t any funnier than the muffin joke, but that’s not surprising, at least not to the researchers. They’ve discovered something that eluded Plato, Aristotle, Hobbes, Kant, Schopenhauer, Freud and the many theorists who have tried to explain laughter based on the mistaken premise that they’re explaining humor. Copyright 2007 The New York Times Company

Keyword: Emotions
Link ID: 10066 - Posted: 06.24.2010

NEW YORK (Reuters Health) - High rates of mental health disorders are being diagnosed among US military personnel soon after being released from duty in Iraq and Afghanistan, according to investigators in San Francisco. They estimate that out of 103,788 returning veterans, 25 percent had a mental health diagnosis, and more than half of these patients had two or more distinct conditions. Those most at risk were the youngest soldiers and those with the most combat exposure, Dr. Karen H. Seal at the Veterans Administration Medical Center and associates report in the Archives of Internal Medicine. Seal's group based their findings on records of US veterans deployed in Iraq and Afghanistan who were seen at VA health care facilities between September 2001 and September 2005. In addition to the high rate of mental health disorders, about one in three (31 percent) were affected by at least one psychosocial diagnosis. The most frequent diagnosis was post-traumatic stress disorder. Other diagnoses included anxiety disorder, depression, substance use disorder, or other behavioral or psychosocial problem. SOURCE: Archives of Internal Medicine, March 12, 2007. © 1996-2007 Scientific American, Inc

Keyword: Stress
Link ID: 10065 - Posted: 06.24.2010

Jennifer Viegas, Discovery News — Exposure to attractive, flirtatious women may cause men to hold their current mates in lower esteem after such encounters, suggest the results of a provocative new study. The paper, which has been accepted for publication in the journal Evolution and Human Behavior, is the first to show that one woman's behavior can affect how a man views other women, including his own partner. The researchers believe the findings may explain why men who are chronically exposed to attractive, young women at work — such as male high school teachers and college professors — have an unusually high incidence of divorce. Prior studies suggest a woman may downgrade her current mate after being exposed to an attractive man who possesses greater wealth or status than her present partner. Lead author Sandeep Mishra told Discovery News that biology could explain all of these tendencies. "High male reproductive success, or biological fitness, is contingent on finding and mating with a large number of females," he said. "Females, on the other hand, benefit most from being choosy and looking for quality, as mating with a number of partners at any given time will still only produce one offspring (over the course of nine months)." © 2007 Discovery Communications Inc.

Keyword: Sexual Behavior
Link ID: 10064 - Posted: 06.24.2010

Roxanne Khamsi Embryonic and adult stem cells offer similar protection against neurodegenerative disease, according to a landmark study in mice which has achieved a number of firsts with human stem cells. For the first time, rodents genetically predisposed to disease lived longer and healthier lives after receiving injections of the human cells, researchers claim. “We have been talking about stem cells for a decade and no one had cured anything with stem cells before this,” comments Eva Mezey, a researcher at the National Institutes of Health in Bethesda, Maryland, US, who was not involved in the work. In the new study, Evan Snyder of the Burnham Institute for Medical Research in La Jolla, California, US, and colleagues studied mice with a mutation in a gene called Hex. This mutation leads to a deficiency in an enzyme that breaks down fatty substances called lipids. As a result, these lipid molecules accumulate in the brain and spinal cord, destroying cells and causing the loss control over body movement. Mice with the disorder die prematurely, at around 120 days of age. In humans, similar mutations in the Hex gene lead to illnesses such as Tay Sachs disease and Sandhoff’s disease, which lead to death within the first few years of life because no treatment exists. © Copyright Reed Business Information Ltd

Keyword: Stem Cells; Regeneration
Link ID: 10063 - Posted: 06.24.2010

Kerri Smith A single, specific memory has been wiped from the brains of rats, leaving other recollections intact. The study adds to our understanding of how memories are made and altered in the brain, and could help to relieve sufferers of post-traumatic stress disorder (PTSD) of the fearful memories that disrupt their lives. The results are published in Nature Neuroscience1. The brain secures memories by transferring them from short-term to long-term storage, through a process called reconsolidation. It has been shown before that this process can be interrupted with drugs. But Joseph LeDoux of the Center for Neural Science at New York University and his colleagues wanted to know how specific this interference was: could the transfer of one specific memory be meddled with without affecting others? To find out, they trained rats to fear two different musical tones, by playing them at the same time as giving the rats an electric shock. Then, they gave half the rats a drug known to cause limited amnesia (U0126, which is not approved for use in people), and reminded all the animals, half of which were still under the influence of the drug, of one of their fearful memories by replaying just one of the tones. ©2007 Nature Publishing Group

Keyword: Learning & Memory; Emotions
Link ID: 10062 - Posted: 06.24.2010

Michael Hopkin Exposure to widely used anaesthetic drugs increases production of a brain protein thought to cause Alzheimer's disease, a study of mice has shown. The research feeds concern that general anaesthesia may be linked to dementia in humans. Inhaled doses of halothane, one of a class of drugs called volatile anaesthetics, increase the amount of a protein called amyloid beta in mouse brains, researchers at the University of Pennsylvania in Philadelphia have found. Some 60 million people worldwide are given volatile anaesthetics each year. The drugs are known to cause 'post-operative cognitive decline' in many cases, which can last for days, weeks or years. If these drugs boost production of amyloid beta, they may also be linked to long-term dementias such as Alzheimer's. The brains of Alzheimer's patients contain high levels of amyloid beta, although the molecule's links with disease are still unknown. There are no data on whether the effect occurs in humans. Until such information is gathered, it will be difficult to say whether anaesthetists should stop using volatile anaesthetics, including halothane and the related isoflurane, the most widely used of the group. ©2007 Nature Publishing Group

Keyword: Alzheimers; Sleep
Link ID: 10061 - Posted: 06.24.2010

PHILADELPHIA – Researchers at the University of Pennsylvania's School of Medicine have discovered that common inhaled anesthetics increase the number of amyloid plaques in the brains of animals, which might accelerate the onset of neurodegenerative diseases like Alzheimer's. Roderic Eckenhoff, MD, Vice Chair of Research in the University of Pennsylvania's Department of Anesthesia and Critical Care, and his co-authors, report their findings in the March 7th online edition of Neurobiology of Aging. Every year over 100 million people undergo surgery worldwide, most under general anesthesia with an inhaled drug. These drugs clearly affect cognitive ability at least in the short term, but the growing concern is that inhaled anesthetics may affect a person well beyond the perioperative period, even permanently. Several factors appear to play a role in this subtle loss of cognitive ability, most notably age. A specific effect of these drugs on dementias like Alzheimer's disease, though suspected for many years, has only been recently supported by data. In 2003, Eckenhoff's group showed that the inhaled anesthetics enhance the aggregation and cytotoxicity of the amyloid beta peptide. Just last month, a study reported that these drugs also enhance the production of amyloid beta in isolated cells. But these protein and cell culture studies are a long way from showing that an effect occurs in vivo. This new study provides the first evidence that the predicted effect occurs in animals.

Keyword: Alzheimers
Link ID: 10060 - Posted: 06.24.2010

More than a third of Britons are losing two years of sleep in a lifetime because of their partner's snoring, a survey suggests. Slumbering next to a snorer robs a person of about two hours sleep per night, according to the British Snoring and Sleep Apnoea Association (BSSAA). With an average relationship lasting 24 years, this would equate to a loss of two years' sleep for 15 million Brits. Half of 2,000 adults polled said snoring affected their sex lives. And 85% said their relationship would be better if their partner's snoring problem was resolved. Marianne Davey, co-founder of the BSSAA, said: "Snoring can have a very negative impact on the people who have to live with it." A spokesman from the British Sleep Society said: "You need to get the right amount of sleep, so each night that is disturbed is going to have a profound effect. (C)BBC

Keyword: Sleep
Link ID: 10059 - Posted: 03.10.2007

By MINDY SINK DENVER, March 8 — A woman who has been in a coma-like state for more than six years awoke for three days this week to talk with family members and eat her favorite foods before relapsing. “She was smiling and grinning and told my staff she wanted to go to a club, even doing a little chair dance in her wheelchair,” said one of her doctors, Randall Bjork. The woman, Christa Lilly, 49, suffered a cardiac arrest in November 2000. Since then, her mother, Minnie Smith, has been caring for her at home. Ms. Smith said Ms. Lilly had awakened five times, sometimes for hours, then for days. “We may have to rethink these people that have been called vegetative in nursing homes who may have some awareness of their horrible circumstances,” said Dr. Bjork. “It goes against the grain of what we thought.” Ms. Lilly, who has four daughters, including a 12-year-old, and three grandchildren, awakens without warning. On Sunday her mother, 74, said the same thing to her that she does every day, “Hi, baby; how you doing?” And this time Ms. Lilly replied, “I’m fine.” Although Ms. Lilly is fed through a tube when not awake, Ms. Smith said she took her daughter out for her favorite foods this week — catfish, hush puppies, cake and ice cream. Copyright 2007 The New York Times Company

Keyword: Attention; Stroke
Link ID: 10058 - Posted: 06.24.2010

NEW YORK (Reuters Health) - The development of tiny fat clots in the brain during joint replacement surgery is not clearly associated with the decline in mental function that may follow, according to a study. Given the fact that cognitive decline is well known to occur after joint replacement procedures, "we were quite surprised" to not find any ties between fat clots and cognitive outcome," Dr. Sebastian Koch from University of Miami, Miller School of Medicine, Florida told Reuters Health. Koch and associates examined 24 patients age 65 years and older following hip or knee replacement. All 24 patients developed clots during surgery. Three-quarters of the patients had cognitive decline at discharge, the results indicate, and 10 of 22 patients continued to have cognitive decline at 3 months. There were no significant differences in tiny clots or "microemboli" between patients with and without cognitive deficits at any time studied, the researchers note. "A question remaining is if we captured all the emboli possible," Koch said, noting that patients were monitored only during surgery. Some patients may develop clots once surgery is completed. "This is something that may be worth looking into further," Koch said. © 1996-2007 Scientific American, Inc.

Keyword: Stroke
Link ID: 10057 - Posted: 06.24.2010

Patrick L. Barry Scientists have known since the 1930s that mice and other animals live 30 to 50 percent longer when placed on a diet that's low in calories yet nutritionally complete. The unanswered question has been whether calorie restriction has the same life-extending effect on people. Direct proof of a payoff for human longevity would take decades. But scientists have now shown that people on a calorie-restricted diet experience many of the cellular changes reported in mouse studies. "The experimental results [in mice] mirror the results we found," says Anthony E. Civitarese of the Pennington Biomedical Research Center in Baton Rouge, La. Whether those changes would extend a person's life remains uncertain, he notes. As people get older, energy-converting organelles called mitochondria decrease in number and generate greater amounts of harmful by-products called free radicals. Many scientists hypothesize that DNA damage from these by-products can cause chronic diseases of old age such as cancer. Civitarese and his colleagues randomly assigned 36 overweight people to one of three groups. The first group was instructed to follow a diet with 25 percent fewer calories than the individuals' initial energy expenditures. Each participant in the second group followed a diet with 12.5 percent fewer calories than he or she had initially expended, while exercising to burn another 12.5 percent. Both diets contained adequate nutrition. People in the third group ate a weight-maintenance diet, the researchers report in the March PLoS Medicine. ©2007 Science Service.

Keyword: Obesity
Link ID: 10056 - Posted: 06.24.2010

Jennifer Viegas, Discovery News — Most mammals, including humans, experience moments of overwhelming desire — be it for food, sex or other things — that can be followed by seemingly magical feelings of satisfaction and bliss if the desire is met. But scientists have found that, thanks to brain circuitry, we're often likely to be left wanting rather than satisfied. According to a study recently published in the Journal of Neuroscience, wanting and liking are separate urges in the brain that are controlled by different circuits. When these urges occur in sync, the impact on the brain is very powerful. But there’s a catch. Mammal brains appear to have fewer mechanisms for pleasure than they do for desire. "Our results suggest we all are inherently susceptible to wanting more than we’ll actually enjoy, at least in certain situations," co-author Kent Berridge told Discovery News. Berridge, a University of Michigan psychology researcher, added, "If separable brain circuits exist for liking and wanting, then a person who had selective activation of the wanting circuit would want more without liking more." Such want/like dissociations can lead to addictions with drugs, sex, food, gambling and more, the researchers believe. Some people also appear to be prone to experiencing the out-of-sync phases. © 2007 Discovery Communications Inc.

Keyword: Drug Abuse; Emotions
Link ID: 10055 - Posted: 06.24.2010

The brain does register subliminal images even if a person is unaware they have seen them, UK researchers report. The research, in Current Biology, suggests subliminal advertising is probably effective. The practice, which was first used in the 1950s, has been banned in the UK, but is still permitted in the US. Using brain scans, a team from University College, London, showed people only registered the images if the brain had "spare capacity". Subliminal images may be contained in other information, which people are aware of receiving. The researchers sight the example of the film Fight Club, where a character who works as a cinema projectionist inserts a single frame of pornography into the 24 frames of a film shown each second. In the movie, those watching were unaware of the split-second shot, but felt depressed or aggressive afterwards. Although it has long been thought that subliminal images can be detected without people being aware of them, and have been used in techniques such as subliminal advertising, this is the first time researchers have provided physiological evidence of the impact. The seven participants in the study wore red-blue filter glasses that projected faint images of everyday objects, such as an iron, on to one eye and a strong flashing image on the other. The strong flashing image meant the participants were not consciously aware of the faint images projected on to the other eye. (C)BBC

Keyword: Attention
Link ID: 10054 - Posted: 03.09.2007

(HealthDay News) -- Black Americans are more likely than whites to suffer severe, untreated and disabling depression, U.S. research shows. Researchers at the Harvard School of Public Health analyzed data on 6,082 people who took part in a national survey conducted between 2001 and 2003. They found that 17.9 percent of white Americans had depression at some point in their lives, compared with 10.4 percent of blacks of African descent and 12.9 percent of blacks of West Indian or Caribbean descent. Rates of depression in the 12 months before they were surveyed were 7.2 percent for Caribbean blacks; 6.9 percent for whites; and 5.9 percent for blacks of African descent. Among those who reported depression at some point in their lives, rates of depression in the 12 months before they were surveyed were 56.5 percent for blacks of African descent; 56 percent for Caribbean blacks; and 38.6 percent for whites. "Fewer than half of the African Americans (45 percent) and fewer than a quarter (24.3 percent) of the Caribbean blacks who met the criteria (for depression) received any form of major depressive disorder therapy," the study authors wrote. About 57 percent of white Americans with major depression received treatment. © 2007 Scout News LLC. All rights reserved.

Keyword: Depression
Link ID: 10053 - Posted: 06.24.2010

By NICHOLAS WADE One of the more embarrassing mysteries of human evolution is that people are host to no fewer than three kinds of louse while most species have just one. Even bleaker for the human reputation, the pubic louse, which gets its dates and residence-swapping opportunities when its hosts are locked in intimate embrace, does not seem to be a true native of the human body. Its closest relative is the gorilla louse. (Don’t even think about it.) Louse specialists now seem at last to have solved the question of how people came by their superabundance of fellow travelers. And in doing so they have shed light on the two major turning points in the history of fashion: when people lost their body hair, and when they first made clothing. Three kinds of louse call Homo sapiens their home, but each occupies a different niche on the human body. The head louse, Pediculus humanus, lives in the forest of fine hairs on the scalp. Its cousin, the body louse, lives not on the skin but in clothes. And the exclusive territory of the pubic louse, Phthirus pubis, is the coarser hairs of the crotch. Lice are intimately adapted to their hosts and cannot long survive away from the body’s blood and warmth. If their host evolves into two species, the lice will do likewise. So biologists have long been puzzled over the fact that the human head louse is a sister species to the chimpanzee louse, but the pubic louse is closely related to the gorilla louse. Copyright 2007 The New York Times Company

Keyword: Evolution; Sexual Behavior
Link ID: 10052 - Posted: 06.24.2010

By Gisela Telis Already famous for swimming through sewers and surviving under subway rails, rats can now claim a more sophisticated talent: thinking about thinking. It's not epistemology, but a study published today in Current Biology reports the first evidence that rats know the limits of their own knowledge--a capacity long thought to belong only to the animal kingdom's top brains. People experience metacognition, or gauging their own knowledge, on a daily basis; anyone who's ever had a sinking feeling during an exam knows it well. But attempts to detect metacognition in animals have met with little success, in large part because animals can't tell researchers what they're thinking. Scientists must instead rely on behavioral clues: Monkeys place lower bets on their answers when given a difficult test, for example, and dolphins waver when asked to distinguish between two similar sounds. Thus far, however, smaller-brained animals, such as pigeons, have shown no signs of metacognition in the lab. Would rats be any different? Neuroscientist Jonathon Crystal of the University of Georgia in Athens and his graduate student, Allison Foote, put the rodents to the self-knowledge test by asking them to classify sounds. First, the researchers trained the rats to associate a short burst of static--lasting about 2 seconds--with one lever, and a long burst of static--lasting about 8 seconds--with another lever. Pushing the correct lever yielded a tasty reward of six food pellets; pushing the incorrect lever yielded no food and no chance to try again. The rats also learned that they could get half the reward without making a choice, by poking their nose into a food trough. © 2007 American Association for the Advancement of Science

Keyword: Intelligence
Link ID: 10051 - Posted: 06.24.2010

By Greg Miller Chimpanzees and bonobos are our closest primate relatives, but the two apes have very different personalities. While primatologists have often noted nasty, competitive behavior among power-hungry chimps, bonobos have a reputation as free-loving peaceniks. Now, a behavioral study that directly compares the two apes suggests that the bonobos' more cordial nature enables them to cooperate more successfully than chimps in some situations. Most researchers believe that humans shared a common ancestor with chimpanzees and bonobos between 5 million and 7 million years ago (for a different take, see ScienceNOW, 27 February). Both of these apes may have something to tell us about the evolution of human behavior, yet most research has focused on chimps, in large part because bonobos are endangered--perhaps as few as 10,000 remain. In the new study, researchers worked with bonobos at a sanctuary in the Democratic Republic of Congo and with chimps at a Ugandan sanctuary. The different natures of the two apes became clear when the researchers, led by Brian Hare, a biological anthropologist at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, presented pairs of bonobos and pairs of chimps with plates of fruit. Bonobo pairs reacted by playing with each other and even rubbing genitals--a frequent stress-reliever in bonobo society. They also shared the bounty more often than not. Chimps, on the other hand, generally avoided their partner and shared food less than half of the time. © 2007 American Association for the Advancement of Science

Keyword: Aggression; Evolution
Link ID: 10050 - Posted: 06.24.2010

Roxanne Khamsi How well people perform on tests after being deprived of sleep depends in part on their genes, new research suggests. After staying awake all night, individuals with a long version of the PER3 gene only scored half as well on cognitive tests as subjects with a short version. What is more, the greatest differences in performance were seen during the small hours – the time when most tiredness-related accidents happen and when shift-workers have most trouble staying awake. “It may be there are people who are genetically predisposed against shift work,” says Malcolm von Schantz, at the University of Surrey, UK. But he emphasises that gene tests should not be used to discriminate against such individuals. It is very possible that carriers of the long PER3 gene have advantages at other times, he notes. Von Schantz and his colleagues recruited 12 volunteers who carried two copies of the long version of PER3 and another dozen with two copies of the short version. Using electroencephalogram machines to record brain activity, researchers monitored the participants' sleep patterns. The recordings revealed that although both groups slept for about the same amount of time, subjects with the short PER3 gene spent roughly 15% of this time in deep sleep, also known as slow-wave sleep. Their counterparts with the long PER3, meanwhile, spent about 22% in this restorative sleep stage. © Copyright Reed Business Information Ltd

Keyword: Sleep; Genes & Behavior
Link ID: 10049 - Posted: 06.24.2010