Chapter 15. Emotions, Aggression, and Stress
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By Linda Carroll The debate over whether violent movies contribute to real-world mayhem may have just developed a wrinkle: New research suggests they might enhance aggression only in those already prone to it. Using PET scanners to peer into the brains of volunteers watching especially bloody movie scenes, researchers determined that the way a viewer’s brain circuitry responds to violent video depends upon whether the individual is aggressive by nature. The study was published Wednesday in PLOS One. “Just as beauty is in the eye of the beholder, environmental stimuli are in the brain of the beholder,” said Nelly Alia-Klein, the study’s lead author and an associate professor at the Friedman Brain Institute and the Icahn School of Medicine at Mount Sinai Hospital in New York City. To test the importance of personality, Alia-Klein and her colleagues rounded up 54 healthy men, some of whom had a history of getting into physical fights, while the others had no history of aggression. The researchers scanned the volunteers three times: doing nothing, watching emotionally charged video and viewing a violent movie. “It wasn’t the whole [violent] movie,” Alia-Klein said, “just the violent scenes, one after another after another.” Along with the brain scans, the researchers monitored blood pressure and asked about the viewers’ moods every 15 minutes.
Link ID: 20132 - Posted: 09.30.2014
By Erik Parens Will advances in neuroscience move reasonable people to abandon the idea that criminals deserve to be punished? Some researchers working at the intersection of psychology, neuroscience and philosophy think the answer is yes. Their reasoning is straightforward: if the idea of deserving punishment depends upon the idea that criminals freely choose their actions, and if neuroscience reveals that free choice is an illusion, then we can see that the idea of deserving punishment is nonsense. As Joshua Greene and Jonathan Cohen speculated in a 2004 essay: “new neuroscience will undermine people’s common sense, libertarian conception of free will and the retributivist thinking that depends on it, both of which have heretofore been shielded by the inaccessibility of sophisticated thinking about the mind and its neural basis.” Just as we need two eyes that integrate slightly different information about one scene to achieve visual depth perception, we need to view ourselves through two lenses to gain a greater depth of understanding of ourselves. This past summer, Greene and several other colleagues did empirical work that appears to confirm that 2004 speculation. The new work finds that when university students learn about “the neural basis of behavior” — quite simply, the brain activity underlying human actions —they become less supportive of the idea that criminals deserve to be punished. According to the study’s authors, once students are led to question the concept of free will — understood as the idea that humans “can generate spontaneous choices and actions not determined by prior events” — they begin to find the idea of “just deserts” untenable. “When genuine choice is deemed impossible, condemnation is less justified,” the authors write. © 2014 The New York Times Company
By Alyssa Abkowitz If you’re wary of investing in a certain stock or exchange-traded fund, it could be because of the your brain’s physical composition. In a recent study, 61 participants from the Northeastern U.S. were asked to choose between monetary options that differed in the level of risk. Questions included: “Would you prefer a 50 percent chance of receiving $5 or would you rather take a 13 percent chance of winning $50?” and “Would you prefer $10 for sure or a 50 percent chance of receiving $50?” Researchers found that individuals with more gray matter in a specific part of their brains tend to tolerate more financial risks, says Agnieszka Tymula, an economist at the University of Sydney and co-author of the findings. Most of the participants answered questions while their brains were being scanned, while others received MRIs afterward (the timing doesn’t make a difference because the researchers were looking at brain structure, not brain function). The study involved measuring the volume of gray matter, or the outer layer of the brain, in the right posterior parietal region of the cortex. Thicker gray matter corresponded to riskier responses. Tymula worked with researchers from Yale University, University College London, New York University, and the University of Pennsylvania. Their findings, published in the Journal of Neuroscience this month, dovetail with previous work in which Tymula found that adults become more risk-averse as they age. Other neuroscience research shows that people’s cortexes become thinner as they get older, meaning there could be a link between a thinning cortex and risk aversion. ©2014 Bloomberg L.P
by Laura Sanders Earlier this month, a star running back for the Minnesota Vikings was indicted for whipping his young son bloody with a switch. Leaked photographs allegedly showed Adrian Peterson’s 4-year-old son with cuts and bruises on his legs, back, buttocks and scrotum. As details about the incident emerged, Peterson took to Twitter to say that he’s not a perfect parent but what he did was not abuse. It was discipline. “My goal is always to teach my son right from wrong and that’s what I tried to do that day,” he wrote. Many people, and I’m one of them, that think Peterson’s actions were disgusting. There’s no way that hitting 4-year-old with a switch until his body is cut and bruised is a good way to impart values and morals. Peterson’s extreme actions, done in the name of corporal punishment, ignited a ferocious, emotionally fraught debate over whether it’s OK to hit your kid. The debate reflects deep divides in our society, chasms that track along political, religious, regional and racial lines. Half of all U.S. parents say they’ve spanked their kid. Spanking doesn’t just happen in the privacy of homes, either. Nineteen states allow teachers or principals to hit children. Opponents often point to scientific studies as proof that spanking is bad. And I confess, I originally thought this post was going to describe those results that we’ve all heard: how children who have been spanked are more aggressive and have more behavioral problems. But despite the headlines, the science behind spanking is actually quite limited, says clinical psychologist Christopher Ferguson of Stetson University in DeLand, Fla. “Because it’s a culture war issue, I think a lot of what we hear has misrepresented what is very nuanced science,” he says. © Society for Science & the Public 2000 - 2014.
|By Corinne Iozzio Albert “Skip” Rizzo of the University of Southern California began studying virtual reality (VR) as psychological treatment in 1993. Since then, dozens of studies, his included, have shown the immersion technique to be effective for everything from post-traumatic stress disorder (PTSD) and anxiety to phobias and addiction. But a lack of practical hardware has kept VR out of reach for clinicians. The requirements for a VR headset seem simple—a high-resolution, fast-reacting screen, a field of vision that is wide enough to convince patients they are in another world and a reasonable price tag— yet such a product has proved elusive. Says Rizzo, “It’s been 20 frustrating years.” In 2013 VR stepped into the consumer spotlight in the form of a prototype head- mounted display called the Oculus Rift. Inventor Palmer Luckey’s goal was to create a platform for immersive video games, but developers from many fields—medicine, aviation, tourism—are running wild with possibilities. The Rift’s reach is so broad that Oculus, now owned by Facebook, hosted a conference for developers in September. The Rift, slated for public release in 2015, is built largely from off- the-shelf parts, such as the screens used in smartphones. A multi- axis motion sensor lets the headset refresh imagery in real time as the wearer’s head moves. The kicker is the price: $350. (Laboratory systems start at $20,000.) Rizzo has been among the first in line. His work focuses on combat PTSD. In a 2010 study, he placed patients into controlled traumatic scenarios, including a simulated battlefield, so they could confront and process emotions triggered in those situations. © 2014 Scientific American
By Maria Konnikova At the turn of the twentieth century, Ivan Pavlov conducted the experiments that turned his last name into an adjective. By playing a sound just before he presented dogs with a snack, he taught them to salivate upon hearing the tone alone, even when no food was offered. That type of learning is now called classical—or Pavlovian—conditioning. Less well known is an experiment that Pavlov was conducting at around the same time: when some unfortunate canines heard the same sound, they were given acid. Just as their luckier counterparts had learned to salivate at the noise, these animals would respond by doing everything in their power to get the imagined acid out of their mouths, each “shaking its head violently, opening its mouth and making movements with its tongue.” For many years, Pavlov’s classical conditioning findings overshadowed the darker version of the same discovery, but, in the nineteen-eighties, the New York University neuroscientist Joseph LeDoux revived the technique to study the fear reflex in rats. LeDoux first taught the rats to associate a certain tone with an electric shock so that they froze upon hearing the tone alone. In essence, the rat had formed a new memory—that the tone signifies pain. He then blunted that memory by playing the tone repeatedly without following it with a shock. After multiple shock-less tones, the animals ceased to be afraid. Now a new generation of researchers is trying to figure out the next logical step: re-creating the same effects within the brain, without deploying a single tone or shock. Is memory formation now understood well enough that memories can be implanted and then removed absent the environmental stimulus?
by Bob Holmes THERE'S something primal in a mother's response to a crying infant. So primal, in fact, that mother deer will rush protectively to the distress calls of other infant mammals, such as fur seals, marmots and even humans. This suggests such calls might share common elements – and perhaps that these animals experience similar emotions. Researchers – and, indeed, all pet owners – know that humans respond emotionally to the distress cries of their domestic animals, and there is some evidence that dogs also respond to human cries. However, most people have assumed this is a by-product of domestication. However, Susan Lingle, a biologist at the University of Winnipeg, Canada, noticed that the infants of many mammal species have similar distress calls: simple sounds with few changes in pitch. She decided to test whether cross-species responses occur more widely across the evolutionary tree. So, Lingle and her colleague Tobias Riede, now at Midwestern University in Glendale, Arizona, recorded the calls made by infants from a variety of mammal species when separated from their mother or otherwise threatened. They then played the recordings through hidden speakers to wild mule deer (Odocoileus hemionus) out on the Canadian prairies. They found that deer mothers quickly moved towards the recordings of infant deer, but also towards those of infant fur seals, dogs, cats and humans, all of which call at roughly the same pitch. Even the ultrasonic calls of infant bats attracted the deer mothers if Lingle used software to lower their pitch to match that of deer calls. In contrast, they found the deer did not respond to non-infant calls such as birdsong or the bark of a coyote (American Naturalist, DOI: 10.1086/677677). © Copyright Reed Business Information Ltd.
By JAMES GORMAN Are chimpanzees naturally violent to one another, or has the intrusion of humans into their environment made them aggressive? A study published Wednesday in Nature is setting off a new round of debate on the issue. The study’s authors argue that a review of all known cases of when chimpanzees or bonobos in Africa killed members of their own species shows that violence is a natural part of chimpanzee behavior and not a result of actions by humans that push chimpanzee aggression to lethal attacks. The researchers say their analysis supports the idea that warlike violence in chimpanzees is a natural behavior that evolved because it could provide more resources or territory to the killers, at little risk. But critics say the data shows no such thing, largely because the measures of human impact on chimpanzees are inadequate. While the study is about chimpanzees, it is also the latest salvo in a long argument about the nature of violence in people. In studying chimpanzee violence, “we’re trying to make inferences about human evolution,” said Michael L. Wilson, an anthropologist at the University of Minnesota and a study organizer. There is no disagreement about whether chimpanzees kill one another, or about some of the claims that Dr. Wilson and his 29 co-authors make. The argument is about why chimpanzees kill. Dr. Wilson and the other authors, who contributed data on killings from groups at their study sites, say the evidence shows no connection between human impact on the chimpanzee sites and the number of killings. He said the Ngogo group of chimpanzees in Uganda “turned out to be the most violent group of chimpanzees there is,” even though the site was little disturbed by humans. They have a pristine habitat, he said, and “they go around and kill their neighbors.” © 2014 The New York Times Company
By John Horgan On this blog, in my book The End of War and elsewhere (see Further Reading and Viewing), I have knocked the deep roots theory of war, which holds that war stems from an instinct deeply embedded in the genes of our male ancestors. Inter-community killings are rare among chimpanzees and non-existent among bonobos, according to a new report in Nature, undercutting the theory that the roots of war extend back to the common ancestor of humans and chimps. Proponents of this theory—notably primatologist Richard Wrangham—claim it is supported by observations of inter-community killings by chimpanzees, Pan troglodytes, our closest genetic relatives. Skeptics, including anthropologists Robert Sussman and Brian Ferguson, have pointed out that chimpanzee violence might be not an adaptation but a response to environmental circumstances, such as human encroachment. This “human impacts” hypothesis is rejected in a new report in Nature by a coalition of 30 primatologists, including Wrangham and lead author Michael Wilson. In “Lethal aggression in Pan is better explained by adaptive strategies than human impacts,” Wilson et al. analyze 152 killings in 18 chimpanzee communities and find “little correlation with human impacts.” Given that the primary interest in chimp violence is its alleged support of the deep-roots theory, it might seem odd, at first, that Wilson et al. do not mention human warfare. Actually, this omission is wise, because the Nature report undermines the deep-roots theory of war, and establishes that the “human impact” issue is a red herring. © 2014 Scientific American,
|By Daniel A. Yudkin If you’re reading this at a desk, do me a favor. Grab a pen or pencil and hold the end between your teeth so it doesn’t touch your lips. As you read on, stay that way—science suggests you’ll find this article more amusing if you do. Why? Notice that holding a pencil in this manner puts your face in the shape of a smile. And research in psychology says that the things we do—smiling at a joke, giving a gift to a friend, or even running from a bear—influence how we feel. This idea—that actions affect feelings—runs counter to how we generally think about our emotions. Ask average folks how emotions work—about the causal relationship between feelings and behavior—and they’ll say we smile because we’re happy, we run because we’re afraid. But work by such psychologists as Fritz Strack, Antonio Damasio, Joe LeDoux shows the truth is often the reverse: what we feel is actually the product, not the cause, of what we do. It’s called “somatic feedback.” Only after we act do we deduce, by seeing what we just did, how we feel. This bodes well, at first blush, for anyone trying to change their emotions for the better. All you’d need to do is act like the kind of person you want to be, and that’s who you’ll become. (Call it the Bobby McFerrin philosophy: “Aren’t happy? Don’t worry. Just smile!”) But new research, published in the Journal of Experimental Social Psychology by Aparna Labroo, Anirban Mukhopadhyay, and Ping Dong suggests there may be limits to our ability to proactively manage our own well-being. The team ran a series of studies examining whether more smiling led to more happiness. One asked people how much smiling they had done that day, and how happy they currently felt. Other studies manipulated the amount of smiling people actually did, either by showing them a series of funny pictures or by replicating a version of the pencil-holding experiment. As expected, across these experiments, the researchers found that the more people smiled, the happier they reported being. © 2014 Scientific American
Link ID: 20085 - Posted: 09.17.2014
By Linda Searing THE QUESTION Benzodiazepines such as Valium, Xanax and Ativan, widely prescribed to relieve anxiety and alleviate insomnia, are known to affect memory and cognition in the short term. Might they also have a more serious, longer-term effect on the brain? THIS STUDY analyzed data on 8,990 adults older than 66, including 1,796 with Alzheimer’s disease. In a five-to-10-year span before the start of the study, 3,767 of the participants (52 percent) had taken benzodiazepines. Overall, those who had taken the drugs were 51 percent more likely to have Alzheimer’s than were those who had never taken benzodiazepines. The longer people took the drugs, the greater their risk for Alzheimer’s. Those who took the drugs for less than 90 days had essentially the same risk as those who never took them. But risk nearly doubled for people who took them for longer than six months. Risk also was greater for longer-acting vs. shorter-acting benzodiazepines. WHO MAY BE AFFECTED? Adults, especially older people, who take benzodiazepines. The drugs have a calming effect on the body and work quickly, unlike antidepressants, which can take weeks to have an effect. The American Geriatrics Society lists benzodiazepines as inappropriate for treating older people for insomnia or agitation because of their negative effect on cognition seen in that age group and an increased likelihood of falls and accidents. However, some recent estimates note that roughly half of older adults take benzodiazepines. CAVEATS Some study participants may have been prescribed benzodiazepines to treat early symptoms of unrecognized dementia, which can include depression, anxiety and sleep disorders; the study authors noted that use of the drugs “might be an early marker of a condition associated with an increased risk of dementia and not the cause.”
by Bethany Brookshire Post-traumatic stress disorder, or PTSD, has many different symptoms. Patients may suffer from anxiety, flashbacks, memory problems and a host of other reactions to a traumatic event. But one symptom is especially common: 70 percent of civilian patients and 90 percent of combat veterans with PTSD just can’t get a decent night’s sleep. Problems with sleep, including rapid-eye movement — or REM — sleep, have long been associated with PTSD. “We know that sleep difficulties in the weeks following trauma predict the development of PTSD, and we know that bad sleep makes PTSD symptoms worse,” says Sean Drummond, a clinical psychologist who studies sleep at the University of California at San Diego. Studies in rats show that exposing the animals to traumatic, fearful experiences such as foot shocks disrupts their REM sleep. Drummond and his research assistant Anisa Marshall wanted to connect those findings to humans. But he soon found out that in humans, it’s not fear that predicts REM sleep. Instead, it’s safety. The scientists tested this in 42 people without PTSD using a measure called fear-potentiated startle. Subjects sit in a comfortable chair with an electrode on their wrists. A screen shows blue squares or yellow squares. If participants see blue squares, they run a high risk of receiving an annoying shock to the wrist. If they see yellow squares, they can relax; no shocks are headed their way. During this time, they will also hear random, loud bursts of white noise. The scientists measure how much the subjects startle in response to the noise by measuring the strength of their eyeblinks in response to the noise. In the presence of the blue squares, the blinks become much stronger, an effect called fear-potentiated startle. With yellow squares, the blinks weaken. © Society for Science & the Public 2000 - 2014.
By Smitha Mundasad Health reporter, BBC News Giving young people Botox treatment may restrict their emotional growth, experts warn. Writing in the Journal of Aesthetic Nursing, clinicians say there is a growing trend for under-25s to seek the wrinkle-smoothing injections. But the research suggests "frozen faces" could stop young people from learning how to express emotions fully. A leading body of UK plastic surgeons says injecting teenagers for cosmetic reasons is "morally wrong". Botox and other versions of the toxin work by temporarily paralysing muscles in the upper face to reduce wrinkling when people frown. Nurse practitioner Helen Collier, who carried out the research, says reality TV shows and celebrity culture are driving young people to idealise the "inexpressive frozen face." But she points to a well-known psychological theory, the facial feedback hypothesis, that suggests adolescents learn how best to relate to people by mimicking their facial expressions. She says: "As a human being our ability to demonstrate a wide range of emotions is very dependent on facial expressions. "Emotions such as empathy and sympathy help us to survive and grow into confident and communicative adults." But she warns that a "growing generation of blank-faced" young people could be harming their ability to correctly convey their feelings. "If you wipe those expressions out, this might stunt their emotional and social development," she says. The research calls for practitioners to use assessment tools to decide whether there are clear clinical reasons for Botox treatment. BBC © 2014
Link ID: 20070 - Posted: 09.13.2014
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