Chapter 11. Emotions, Aggression, and Stress
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Ian Sample, science editor Heartbreak can impair the immune system of older people and make them more prone to infections, researchers have found. Scientists said older people who had suffered a recent bereavement had poorer defences against bacteria, which could leave them more vulnerable to killer infections, such as pneumonia. Blood tests showed that the same group had imbalances in their stress hormones, which are known to have a direct impact on the body's ability to fight off bugs. Anna Phillips, a reader in behavioural medicine at Birmingham University, said the damaging effects of bereavement on the immune system were not seen in younger people, whose defences seemed more resilient. The finding suggests that in the weeks and months after the loss of a loved one, older people should keep in touch with their friends and family, and exercise and eat well, to reduce stress levels and boost their immune systems. "Bereavement is a really key stressor that happens to all of us at some point so it's worth being aware of the negative impact it can have on your health," Phillips said. "It's a key time to look after yourself in terms of your psychological and physical wellbeing. Don't try and cope by staying in, drinking more and exercising less. Try to cope by having social interactions, looking after yourself by keeping a certain level of fitness and eating well," she added. For her study, Phillips recruited people who had lost a loved one, either a spouse or family member, in the past two months. She then looked at how well bacteria-killing immune cells called neutrophils performed. © 2014 Guardian News and Media Limited
Being bullied regularly by a sibling could put children at risk of depression when they are older, a study led by the University of Oxford suggests. Around 7,000 children aged 12 were asked if they had experienced a sibling saying hurtful things, hitting, ignoring or lying about them. The children were followed up at 18 and asked about their mental health. A charity said parents should deal with sibling rivalry before it escalates. Previous research has suggested that victims of peer bullying can be more susceptible to depression, anxiety and self-harm. This study claims to be the first to examine bullying by brothers or sisters during childhood for the same psychiatric problems in early adulthood. Researchers from the Universities of Oxford, Warwick and Bristol and University College London sent questionnaires to thousands of families with 12-year-old children in 2003-04 and went back to them six years later to assess their mental health. If they had siblings they were asked about bullying by brothers and sisters. The questionnaire said: "This means when a brother or sister tries to upset you by saying nasty and hurtful things, or completely ignores you from their group of friends, hits, kicks, pushes or shoves you around, tells lies or makes up false rumours about you." Most children said they had not experienced bullying. Of these, at 18, 6.4% had depression scores in the clinically significant range, 9.3% experienced anxiety and 7.6% had self-harmed in the previous year. The 786 children who said they had been bullied by a sibling several times a week were found to be twice as likely to have depression, self-harm and anxiety as the other children. BBC © 2014
By S. Matthew Liao As many as 20 percent of war veterans return from combat in Afghanistan and Iraq with post-traumatic stress disorder (PTSD) or major depression, according to a 2008 report from the RAND Corporation. Many experience constant nightmares and flashbacks and many can’t live normal lives. For significant number of veterans, available medications do not seem to help. In 2010, at least 22 veterans committed suicide each day, according to the Department of Veterans Affairs. In her book, Demon Camp, the author Jen Percy describes damaged veterans who have even resorted to exorcism to alleviate their PTSD symptoms. As part of President Obama’s BRAIN Initiative, the federal Defense Advanced Research Projects Agency (DARPA) plans to spend more than $70 million over five years to develop novel devices that would address neurological disorders such as PTSD. DARPA is particularly interested in a technology called Deep Brain Stimulation (DBS). DBS involves inserting a thin electrode through a small opening in the skull into a specific area in the brain; the electrode is then connected by an insulated wire to a battery pack underneath the skin; the battery pack then sends electrical pulses via the wire to the brain. About 100,000 people around the world today have a DBS implant to ameliorate the effects of Parkinson’s disease, epilepsy and major depression. There is evidence that DBS can also help with PTSD. Functional neuroimaging studies indicate that amygdala hyperactivity is responsible for the symptoms of PTSD and that DBS can functionally reduce the activity of the amygdala. In animal PTSD models, DBS has been found to be more effective than current treatment using selective serotonin reuptake inhibitors. © 2014 Scientific American
Link ID: 20039 - Posted: 09.06.2014
By Jonathan Webb Science reporter, BBC News Monkeys at the top and bottom of the social pecking order have physically different brains, research has found. A particular network of brain areas was bigger in dominant animals, while other regions were bigger in subordinates. The study suggests that primate brains, including ours, can be specialised for life at either end of the hierarchy. The differences might reflect inherited tendencies toward leading or following, or the brain adapting to an animal's role in life - or a little of both. Neuroscientists made the discovery, which appears in the journal Plos Biology, by comparing brain scans from 25 macaque monkeys that were already "on file" as part of ongoing research at the University of Oxford. "We were also looking at learning and memory and decision-making, and the changes that are going on in your brain when you're doing those things," explained Dr MaryAnn Noonan, the study's first author. The decision to look at the animals' social status produced an unexpectedly clear result, Dr Noonan said. "It was surprising. All our monkeys were of different ages and different genders - but with fMRI (functional magnetic resonance imaging) you can control for all of that. And we were consistently seeing these same networks coming out." BBC © 2014
|By Madhuvanthi Kannan We humans assume we are the smartest of all creations. In a world with over 8.7 million species, only we have the ability to understand the inner workings of our body while also unraveling the mysteries of the universe. We are the geniuses, the philosophers, the artists, the poets and savants. We amuse at a dog playing ball, a dolphin jumping rings, or a monkey imitating man because we think of these as remarkable acts for animals that, we presume, aren’t smart as us. But what is smart? Is it just about having ideas, or being good at language and math? Scientists have shown, time and again, that many animals have an extraordinary intellect. Unlike an average human brain that can barely recall a vivid scene from the last hour, chimps have a photographic memory and can memorize patterns they see in the blink of an eye. Sea lions and elephants can remember faces from decades ago. Animals also have a unique sense perception. Sniffer dogs can detect the first signs of colon cancer by the scents of patients, while doctors flounder in early diagnosis. So the point is animals are smart too. But that’s not the upsetting realization. What happens when, for just once, a chimp or a dog challenges man to one of their feats? Well, for one, a precarious face-off – like the one Matt Reeves conceived in the Planet of the Apes – would seem a tad less unlikely than we thought. In a recent study by psychologists Colin Camerer and Tetsuro Matsuzawa, chimps and humans played a strategy game – and unexpectedly, the chimps outplayed the humans. Chimps are a scientist’s favorite model to understand human brain and behavior. Chimp and human DNAs overlap by a whopping 99 percent, which makes us closer to chimps than horses to zebras. Yet at some point, we evolved differently. Our behavior and personalities, molded to some extent by our distinct societies, are strikingly different from that of our fellow primates. Chimps are aggressive and status-hungry within their hierarchical societies, knit around a dominant alpha male. We are, perhaps, a little less so. So the question arises whether competitive behavior is hard-wired in them. © 2014 Scientific American
|By Jill U. Adams Our noses are loaded with bitter taste receptors, but they're not helping us taste or smell lunch. Ever since researchers at the University of Iowa came to this conclusion in 2009, scientists have been looking for an explanation for why the receptors are there. One speculation is that they warn us of noxious substances. But they may play another role too: helping to fight infections. In addition to common bitter compounds, the nose's bitter receptors also react to chemicals that bacteria use to communicate. That got Noam Cohen, a University of Pennsylvania otolaryngologist, wondering whether the receptors detect pathogens that cause sinus infections. In a 2012 study, his team found that bacterial chemicals elicited two bacteria-fighting responses in cells from the nose and upper airways: movement of the cells' projections that divert noxious things out of the body and release of nitric oxide, which kills bacteria. The findings may have clinical applications. When Cohen recently analyzed bitter taste receptor genes from his patients with chronic sinus infections, he noticed that practically none were supertasters, even though supertasters make up an estimated 25 percent of the population. Supertasters are extra sensitive to bitter compounds in foods. People are either supertasters or nontasters, or somewhere in between, reflecting the genes they carry for a receptor known as T2R38. Cohen thinks supertasters react vigorously to bacterial bitter compounds in the nose and are thus resistant to sinus infections. In nontasters the reaction is weaker, bacteria thrive and sinus infections ensue. These results suggest that a simple taste test could be used to predict who is at risk for recurrent infections and might need more aggressive medical treatment. © 2014 Scientific American
Carl Zimmer An unassuming single-celled organism called Toxoplasma gondii is one of the most successful parasites on Earth, infecting an estimated 11 percent of Americans and perhaps half of all people worldwide. It’s just as prevalent in many other species of mammals and birds. In a recent study in Ohio, scientists found the parasite in three-quarters of the white-tailed deer they studied. One reason for Toxoplasma’s success is its ability to manipulate its hosts. The parasite can influence their behavior, so much so that hosts can put themselves at risk of death. Scientists first discovered this strange mind control in the 1990s, but it’s been hard to figure out how they manage it. Now a new study suggests that Toxoplasma can turn its host’s genes on and off — and it’s possible other parasites use this strategy, too. Toxoplasma manipulates its hosts to complete its life cycle. Although it can infect any mammal or bird, it can reproduce only inside of a cat. The parasites produce cysts that get passed out of the cat with its feces; once in the soil, the cysts infect new hosts. Toxoplasma returns to cats via their prey. But a host like a rat has evolved to avoid cats as much as possible, taking evasive action from the very moment it smells feline odor. Experiments on rats and mice have shown that Toxoplasma alters their response to cat smells. Many infected rodents lose their natural fear of the scent. Some even seem to be attracted to it. Manipulating the behavior of a host is a fairly common strategy among parasites, but it’s hard to fathom how they manage it. A rat’s response to cat odor, for example, emerges from complex networks of neurons that detect an odor, figure out its source and decide on the right response in a given moment. © 2014 The New York Times Company
By JAMIE EDGIN and FABIAN FERNANDEZ LAST week the biologist Richard Dawkins sparked controversy when, in response to a woman’s hypothetical question about whether to carry to term a child with Down syndrome, he wrote on Twitter: “Abort it and try again. It would be immoral to bring it into the world if you have the choice.” In further statements, Mr. Dawkins suggested that his view was rooted in the moral principle of reducing overall suffering whenever possible — in this case, that of individuals born with Down syndrome and their families. But Mr. Dawkins’s argument is flawed. Not because his moral reasoning is wrong, necessarily (that is a question for another day), but because his understanding of the facts is mistaken. Recent research indicates that individuals with Down syndrome can experience more happiness and potential for success than Mr. Dawkins seems to appreciate. There are, of course, many challenges facing families caring for children with Down syndrome, including a high likelihood that their children will face surgery in infancy and Alzheimer’s disease in adulthood. But at the same time, studies have suggested that families of these children show levels of well-being that are often greater than those of families with children with other developmental disabilities, and sometimes equivalent to those of families with nondisabled children. These effects are prevalent enough to have been coined the “Down syndrome advantage.” In 2010, researchers reported that parents of preschoolers with Down syndrome experienced lower levels of stress than parents of preschoolers with autism. In 2007, researchers found that the divorce rate in families with a child with Down syndrome was lower on average than that in families with a child with other congenital abnormalities and in those with a nondisabled child. © 2014 The New York Times Company
By PAM BELLUCK Memories and the feelings associated with them are not set in stone. You may have happy memories about your family’s annual ski vacation, but if you see a tragic accident on the slopes, those feelings may change. You might even be afraid to ski that mountain again. Now, using a technique in which light is used to switch neurons on and off, neuroscientists at the Massachusetts Institute of Technology appear to have unlocked some secrets about how the brain attaches emotions to memories and how those emotions can be adjusted. Their research, published Wednesday in the journal Nature, was conducted on mice, not humans, so the findings cannot immediately be translated to the treatment of patients. But experts said the experiments may eventually lead to more effective therapies for people with psychological problems such as depression, anxiety or post-traumatic stress disorder. “Imagine you can go in and find a particular traumatic memory and turn it off or change it somehow,” said David Moorman, an assistant professor of psychological and brain sciences at the University of Massachusetts Amherst, who was not involved in the research. “That’s still science fiction, but with this we’re getting a lot closer to it.” The M.I.T. scientists labeled neurons in the brains of mice with a light-sensitive protein and used pulses of light to switch the cells on and off, a technique called optogenetics. Then they identified patterns of neurons activated when mice created a negative memory or a positive one. A negative memory formed when mice received a mild electric shock to their feet; a positive one was formed when the mice, all male, were allowed to spend time with female mice. © 2014 The New York Times Company
by Penny Sarchet Memory is a fickle beast. A bad experience can turn a once-loved coffee shop or holiday destination into a place to be avoided. Now experiments in mice have shown how such associations can be reversed. When forming a memory of a place, the details of the location and the associated emotions are encoded in different regions of the brain. Memories of the place are formed in the hippocampus, whereas positive or negative associations are encoded in the amygdala. In experiments with mice in 2012, a group led by Susumo Tonegawa of the Massachusetts Institute of Technology managed to trigger the fear part of a memory associated with a location when the animals were in a different location. They used a technique known as optogenetics, which involves genetically engineering mice so that their brains produce a light-sensitive protein in response to a certain cue. In this case, the cue was the formation of the location memory. This meant the team could make the mouse recall the location just by flashing pulses of light down an optical fibre embedded in the skull. The mice were given electric shocks while their memories of the place were was being formed, so that the animals learned to associate that location with pain. Once trained, the mice were put in a new place and a pulse of light was flashed into their brains. This activated the neurons associated with the original location memory and the mice froze, terrified of a shock, demonstrating that the emotion associated with the original location could be induced by reactivating the memory of the place. © Copyright Reed Business Information Ltd.
Erin Allday It's well established that chronic pain afflicts people with more than just pain. With the pain come fatigue and sleeplessness, depression and frustration, and a noticeable disinterest in so many of the activities that used to fill a day. It makes sense that chronic pain would leave patients feeling weary and unmotivated - most people wouldn't want to go to work or shop for a week's worth of groceries or even meet friends for dinner when they're exhausted and in pain. But experts in pain and neurology say the connection between chronic pain and a lousy mood may be biochemical, something more complicated than a dour mood brought on from persistent, long-term discomfort alone. Now, a team of Stanford neurologists have found evidence that chronic pain triggers a series of molecular changes in the brain that may sap patients' motivation. "There is an actual physiologic change that happens," said Dr. Neil Schwartz, a post-doctoral scientist who helped lead the Stanford research. "The behavior changes seem quite primary to the pain itself. They're not just a consequence of living with it." Schwartz and his colleagues hope their work could someday lead to new treatments for the behavior changes that come with chronic pain. In the short term, the research improves understanding of the biochemical effects of chronic pain and may be a comfort to patients who blame themselves for their lack of motivation, pain experts said. © 2014 Hearst Communications, Inc.
By ANNA NORTH “You can learn a lot from what you see on a screen,” said Yalda T. Uhls. However, she told Op-Talk, “It’s not going to give you context. It’s not going to give you the big picture.” Ms. Uhls, a researcher at the Children’s Digital Media Center in Los Angeles, was part of a team that looked at what happened when kids were separated from their screens — phones, iPads, laptops and the like — for several days. Their findings may have implications for adults’ relationship to technology, too. For a paper published in the journal Computers in Human Behavior, the researchers studied 51 sixth-graders who attended a five-day camp where no electronic devices were allowed. Before and after the camp, they tested the kids’ emotion-recognition skills using photos of facial expressions and sound-free video clips designed to measure their reading of nonverbal cues. The kids did significantly better on both tests after five screen-free days; a group of sixth-graders from the same school who didn’t go to camp showed less or no improvement. Ms. Uhls, who also works for the nonprofit Common Sense Media, told Op-Talk that a number of factors might have been at play in the campers’ improvement. For instance, their time in nature might have played a role. But to her, the most likely explanation was the sheer increase in face-to-face interaction: “The issue really is not that staring at screens is going to make you bad at recognizing emotions,” she said. “It’s more that if you’re looking at screens you’re not looking at the world, and you’re not looking at people.” Many adults have sought out the same Internet-free experience the kids had, though they usually don’t go to camp to get it. The novelist Neil Gaiman took a “sabbatical from social media” in 2013, “so I can concentrate on my day job: making things up.” © 2014 The New York Times Company
Link ID: 20006 - Posted: 08.28.2014
By Michael Balter Humans are generally highly cooperative and often impressively altruistic, quicker than any other animal species to help out strangers in need. A new study suggests that our lineage got that way by adopting so-called cooperative breeding: the caring for infants not just by the mother, but also by other members of the family and sometimes even unrelated adults. In addition to helping us get along with others, the advance led to the development of language and complex civilizations, the authors say. Cooperative breeding is not unique to humans. Up to 10% of birds are cooperative breeders, as are meerkats and New World monkeys such as tamarins and marmosets. But our closest primate relatives, great apes such as chimpanzees, are not cooperative breeders. Because the human and chimpanzee lineages split between 5 million and 7 million years ago, and humans are the only apes that engage in cooperative breeding, researchers have puzzled over how this helping behavior might have evolved all over again on the human line. In the late 1990s, Sarah Blaffer Hrdy, now an anthropologist emeritus at the University of California, Davis, proposed the cooperative breeding hypothesis. According to her model, early in their evolution humans added cooperative breeding behaviors to their already existing advanced ape cognition, leading to a powerful combination of smarts and sociality that fueled even bigger brains, the evolution of language, and unprecedented levels of cooperation. Soon after Hrdy’s proposal, anthropologists Carel van Schaik and Judith Burkart of the University of Zurich in Switzerland began to test some of these ideas, demonstrating that cooperatively breeding primates like marmosets engaged in seemingly altruistic behavior by helping other marmosets get food with no immediate reward to themselves. © 2014 American Association for the Advancement of Science.
by Bethany Brookshire When a laboratory mouse and a house mouse come nose to nose for the first time, each one is encountering something it has never seen before. They are both Mus musculus. But the wild mouse is facing a larger, fatter, calmer and less aggressive version of itself that’s the result of brother-to-sister inbreeding for generations, resulting in mice that are almost completely genetically identical. Laboratory mice are incredibly valuable tools for research into diseases from Alzheimer’s to Zellweger syndrome. Scientists have a deep understanding of lab mouse DNA, and can use that knowledge to study how specific genes may control certain behaviors and underlie disease. But with all the inbreeding comes some traits that, while desirable in a lab mouse, may not reflect the behavior of an animal in the wild. So for some questions, and some behaviors, scientists might need something a bit wilder. A new study takes lab mice back to their roots and along the way uncovers a new gene function. Lea Chalfin and colleagues at the Weizmann Institute of Science in Rohovot, Israel, bred laboratory mice with wild mice for 10 generations. The result was a mouse with wild mouse genes and wild mouse behavior — with a few important lab mouse genes mixed in. The technique allows scientists to place specific mutations in a wild mouse. The results have interesting implications for studying the mouse species, and might provide some new ways to study human disease as well. Chalfin and her colleagues were especially interested in behaviors linked to female aggression. © Society for Science & the Public 2000 - 2013
|By Christie Nicholson Children who experience neglect, abuse and poverty have a tougher time as adults than do well-cared-for kids. Now there’s evidence that such stress can actually change the size of brain structures responsible for learning, memory and processing emotion. The finding is in the journal Biological Psychiatry. [Jamie L. Hanson et al, Behavioral Problems After Early Life Stress: Contributions of the Hippocampus and Amygdala] Researchers took images of the brains of 12-year-olds who had suffered either physical abuse or neglect or had grown up poor. From the images the scientists were able to measure the size of the amygdala and hippocampus—two structures involved in emotional processing and memory. And they compared the sizes of these structures with those of 12-year-old children who were raised in middle-class families and had not been abused. And they found that the stressed children had significantly smaller amygdalas and hippocampuses than did the kids from the more nurturing environments. Early stress has been associated with depression, anxiety, cancer and lack of career success later on in adulthood. This study on the sizes of brain regions may offer physiological clues to why what happens to toddlers can have such a profound impact decades later. © 2014 Scientific American
Greta Kaul It was a rainy day, and earthworms wriggled out of the ground and began to arrange themselves on the pavement as Julian Plumadore walked to his community college zoology class in 1991. They spelled out messages only he could read. "I was very frightened to be a custodian of that kind of cosmic information and be able to do absolutely nothing about it," Plumadore said. Other times, there were voices - demons screaming - telling him he was going to hell. Plumadore was eventually diagnosed as having schizoaffective disorder, a psychosis that combines the hallucinations of schizophrenia with a mood disorder like depression. People with psychotic disorders, of which schizophrenia is the most severe, have hallucinations, like the voices Plumadore was hearing, that are divorced from reality. Now, a Stanford researcher suggests that the voices he experienced might have been different if he had grown up somewhere other than the U.S. If he were from India, he might have heard family members telling him to do household chores. If he were from Ghana, he might have heard the voice of God guiding him. For a study published in June, Tanya Luhrmann, a Stanford anthropologist, and other researchers interviewed 60 people who met the criteria for schizophrenia: 20 from in and around San Mateo, 20 from India and 20 from Ghana. Though the patients heard both positive and negative voices no matter where they were from, those in India and in Ghana tended to have less negative experiences than Americans: They could more often identify who was talking to them and had less violent hallucinations. Though the study isn't conclusive, Luhrmann believes the differences in voice-hearing between cultures may be a clue into how social expectations and environment shape the way people hear those imaginary voices. © 2014 Hearst Communications, Inc.
By NATALIE ANGIER SOUTH LUANGWA NATIONAL PARK, ZAMBIA — We saw the impala first, a young buck with a proud set of ridged and twisted horns, like helical rebar, bounding across the open plain at full, desperate gallop. But why? A moment later somebody in our vehicle gasped, and the answer became clear. Rising up behind the antelope, as though conjured on movie cue from the aubergine glow of the late afternoon, were six African wild dogs, running in single file. They moved with military grace and precision, their steps synchronized, their radio-dish ears cocked forward, their long, puppet-stick legs barely skimming the ground. Still, the impala had such a jump on them that the dogs couldn’t possibly catch up — could they? We gunned the engine and followed. The pace quickened. The dogs’ discipline held steady. They were closing the gap and oh, no, did I really want to watch the kill? To my embarrassed relief, the violence was taken off-screen, when prey and predators suddenly dashed up a hill and into obscuring bushes. By the time we reached the site, the dogs were well into their communal feast, their dark muzzles glazed with bright red blood, their white-tipped tails wagging in furious joy. “They are the most enthusiastic animals,” said Rosie Woodroffe of the Institute of Zoology in London, who has studied wild dogs for the last 20 years. “Other predators may be bigger and fiercer, but I would argue that there is nothing so enthusiastic as a wild dog,” she said. “They live the life domestic dogs wish they could live.” In 1997, while devising an action plan to help save the wild dog species, Lycaon pictus, Dr. Woodroffe felt anything but exuberant. Wild dogs were considered among the most endangered of Africa’s mammals; Dr. Woodroffe had yet to see one in the wild, and she feared she never would. © 2014 The New York Times Company
Helen Shen Most people gradually recover from trauma, but a small fraction of individuals develop post-traumatic stress disorder (PTSD) — prompting scientists to look for the biological underpinnings of this extreme response to traumatic situations such as warfare, car accidents and natural disasters. Research published on 11 August in Proceedings of the National Academy of Sciences identifies up to 334 genes that may be involved in vulnerability to post-traumatic stress in rats1. Most animal studies of stress use intense stimuli such as electric shocks, designed to produce large, group differences between exposed and unexposed animals. But Nikolaos Daskalakis and his colleagues tried a subtler approach to elicit a wide range of individual responses in rats that had all experienced the same trauma — more closely mimicking the variability of human responses to disturbing events. "We wanted to capture the differences between a susceptible individual and one that is not susceptible to the same experience," says Daskalakis, a neuroendocrinologist at the Icahn School of Medicine at Mount Sinai in New York. The researchers exposed around 100 rats to soiled cat litter — which evokes a feared predator — and tested the animals one week later for lingering effects of the trauma. About one-quarter of the exposed animals were classified as 'extreme' responders, showing high levels of anxiety and startling easily on hearing loud noises. Another quarter of the animals were 'minimal' responders, and exhibited anxiety levels similar to those of non-exposed rats. © 2014 Nature Publishing Group
By DANIEL J. LEVITIN THIS month, many Americans will take time off from work to go on vacation, catch up on household projects and simply be with family and friends. And many of us will feel guilty for doing so. We will worry about all of the emails piling up at work, and in many cases continue to compulsively check email during our precious time off. But beware the false break. Make sure you have a real one. The summer vacation is more than a quaint tradition. Along with family time, mealtime and weekends, it is an important way that we can make the most of our beautiful brains. Every day we’re assaulted with facts, pseudofacts, news feeds and jibber-jabber, coming from all directions. According to a 2011 study, on a typical day, we take in the equivalent of about 174 newspapers’ worth of information, five times as much as we did in 1986. As the world’s 21,274 television stations produce some 85,000 hours of original programming every day (by 2003 figures), we watch an average of five hours of television per day. For every hour of YouTube video you watch, there are 5,999 hours of new video just posted! If you’re feeling overwhelmed, there’s a reason: The processing capacity of the conscious mind is limited. This is a result of how the brain’s attentional system evolved. Our brains have two dominant modes of attention: the task-positive network and the task-negative network (they’re called networks because they comprise distributed networks of neurons, like electrical circuits within the brain). The task-positive network is active when you’re actively engaged in a task, focused on it, and undistracted; neuroscientists have taken to calling it the central executive. The task-negative network is active when your mind is wandering; this is the daydreaming mode. These two attentional networks operate like a seesaw in the brain: when one is active the other is not. © 2014 The New York Times Company
Simon Makin Fish that have been exposed to a common anti-anxiety drug are more active and have better chances of survival than unexposed fish, researchers report in Environmental Research Letters1. The results suggest that standard methods for assessing the environmental impact of pharmaceuticals in waterways might miss some of the drugs' effects because they focus exclusively on harms, according to the authors. In the study, researchers led by Jonatan Klaminder at Umeå University in Sweden exposed Eurasian perch (Perca fluviatilis) to oxazepam, one of a widely used class of anti-anxiety drugs called benzodiazepines. Standard ecotoxicology experiments use unstressed, healthy fish that have been bred in labs. Control groups are designed to have 100% survival rates so that decreases in survival in the test group are easy to detect by comparison. But it is difficult to detect any increase in survival rates when the control group already has nearly complete survival. So Klaminder and his colleagues used the opposite approach. They exposed fish to the drug at two sensitive life stages: two-year-old wild fish taken from a Swedish lake that had only recently thawed after winter, and strings of roes — fish eggs that contain embryos undergoing development. These are more realistic conditions, the researchers say, as animals in the wild often experience high mortality. The researchers used oxazepam at a high concentration of 1,000 micrograms per litre and at a low concentration of 1 μg l−1. The low dose is relevant to aquatic environments in urban areas, because oxazepam concentrations of 1.9 μg l−1 have been measured in effluents from wastewater treatment plants. © 2014 Nature Publishing Group,
Link ID: 19928 - Posted: 08.09.2014