Chapter 14. Biological Rhythms, Sleep, and Dreaming
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By Christie Wilcox Venomous cone snails have been a gift to biomedical researchers. Over the past 50 years, scientists have isolated compounds from these predatory marine animals that do everything from stop pain to protect cells during a heart attack. Now, researchers have isolated a cone snail compound that does something unexpected: It puts mice to sleep. All of these compounds belong to a group of ion channels modifiers known as conotoxins. In the wild, the snails use these toxins for capturing prey, and typically when researchers inject them into mice, the rodents either have no response or become paralyzed. In the new study, published this month in Toxicon, researchers isolated and sequenced 14 novel peptide toxins from the venom of the cobweb cone, Conus araneosus (pictured above with its dissected venom gland). When they injected five of them into mice, one put the rodents to sleep for several hours, whereas the others had no effect. The team says the discovery expands the range of therapeutic uses for conotoxins, and could lead to drugs to treat sleep disorders. © 2015 American Association for the Advancement of Science
By Karen Weintraub Can I ever re-pay my sleep debt? (I estimate it at 15 years of poor sleep.) It is unclear whether you can make up a long-term sleep debt, because most studies have looked at the effects of sleep loss and recovery only over a few nights or weeks, said Dr. Matt T. Bianchi, the chief of the division of sleep medicine at Massachusetts General Hospital and an assistant professor of neurology at Harvard Medical School. Simulated driving performance and reaction times are affected by just one sleepless night, research has shown. There’s no doubt that sleeping just four hours a night catches up to people within a few nights, leading to impairments of attention, learning and memory and worse performance in school and at work. And making up for lost sleep over the weekend doesn’t work. Five brief nights quickly add up to a shortfall of 20 hours, but people don’t sleep more than five to 10 extra hours to compensate, Dr. Bianchi said. “The interpretation has been you can’t pay off your sleep debt, you just carry it with you,” though it’s also possible that people don’t sleep an extra 20 hours because they don’t need it, Dr. Bianchi said. He cited research by Jim Horne of Loughborough University in Britain showing that a timely nap of less than 20 minutes can equate to an extra hour of nighttime sleep. Different people need somewhat different amounts of sleep, but anything less than six hours a night is definitely not enough, said Dr. Charles Czeisler, a professor of sleep medicine at Harvard. © 2015 The New York Times Company
Link ID: 21214 - Posted: 07.25.2015
by Bethany Brookshire For some of us, a weekly case of the Mondays isn’t just because of traffic, work pileups or our soulless office space. It’s because we had to get up early, and sleeping in on the weekend was so incredibly glorious. Besides, because we slept in on Sunday, we didn’t get to the gym until the afternoon, we cooked a late dinner for a friend and then we couldn’t fall asleep at all and so stayed up playing around on the Internet. OK, maybe that’s just me. But you get the general idea. Our obligations — work, family and friends — often don’t line up with when our bodies want to sleep. Scientists call this phenomenon social jetlag. And it may make for more than just miserable Mondays. Social jetlag may also be associated with wider waistlines. As we learn more about how our body clocks work, it might help to think about how our own schedules can shift. Some of us love late nights and can’t help glaring at those who hop out of bed for a 5 a.m. workout (again, maybe that’s just me). But in fact our chronotypes aren’t a result of willpower. Instead they fall in a natural curve. About two-thirds of people are neutral, but a few fall at each end of the spectrum, rising extra early, or staying up until the wee hours. But even those in the middle are still getting up a little bit too early and staying up a little bit too late. We try to make up for it on days off, sleeping in or falling asleep early for a few extra hours of rest. But the result of that shift in sleep schedule? Jetlag. “It’s the equivalent of taking a flight one direction every Friday and going back every Sunday,” says Michael Parsons, a behavioral geneticist at the Medical Research Council Harwell in England. © Society for Science & the Public 2000 - 2015
By James Gallagher Health editor, BBC News website Irregular sleeping patterns have been "unequivocally" shown to lead to cancer in tests on mice, a study suggests. The report, in Current Biology, lends weight to concerns about the damaging impact of shift work on health. The researchers said women with a family risk of breast cancer should never work shifts, but cautioned that further tests in people were needed. The data also indicated the animals were 20% heavier despite eating the same amount of food. Studies in people have often suggested a higher risk of diseases such as breast cancer in shift workers and flight attendants. One argument is disrupting the body's internal rhythm - or body clock - increases the risk of disease. However, the link is uncertain because the type of person who works shifts may also be more likely to develop cancer due to factors such as social class, activity levels or the amount of vitamin D they get. Mice prone to developing breast cancer had their body clock delayed by 12 hours every week for a year. Normally they had tumours after 50 weeks - but with regular disruption to their sleeping patterns, the tumours appeared eight weeks earlier. The report said: "This is the first study that unequivocally shows a link between chronic light-dark inversions and breast cancer development." Interpreting the consequences for humans is fraught with difficulty, but the researchers guesstimated the equivalent effect could be an extra 10kg (1st 8lb) of body weight or for at-risk women getting cancer about five years earlier. "If you had a situation where a family is at risk for breast cancer, I would certainly advise those people not to work as a flight attendant or to do shift work," one of the researchers, Gijsbetus van der Horst, from the Erasmus University Medical Centre, in the Netherlands, said. © 2015 BBC.
Austin Frakt It’s a Catch-22 that even those with a common cold experience: Illness disrupts sleep. Poor sleep makes the symptoms of the illness worse. What’s true for a cold also holds for more serious conditions that co-occur with insomnia. Depression, post-traumatic stress disorder, alcohol dependence, fibromyalgia, cancer and chronic pain often give rise to insomnia, just as sleeplessness exacerbates the symptoms of these diseases. Historically, insomnia was considered a symptom of other diseases. Today it is considered an illness in its own right and recognized as an amplifier of other mental and physical ailments. When a person is chronically tired, pain can be more painful, depression deeper, anxiety heightened. What should doctors address first, insomnia or the co-occurring condition? How about both at the same time? A new study suggests that a therapy that improves sleep also reduces symptoms of other illnesses that often disrupt it. The study published in JAMA Internal Medicine examined the effect of cognitive behavioral therapy for insomnia in patients with serious mental and physical conditions. As its name suggests, C.B.T.-I. is a treatment that works through the mind. As I wrote about a few weeks ago, the therapy treats insomnia without medications, combining good sleep hygiene techniques with more consistent wake times, relaxation techniques and positive sleep attitudes and thoughts. Several clinical trials have shown that C.B.T.-I. provides as good or better relief of symptoms of insomnia than prescription drugs, with improvements in sleep that are more durable. C.B.T.-I. can usually be delivered relatively inexpensively through an online course costing about $40. Compared with those who didn’t receive C.B.T.-I., patients who did increased the time asleep in bed by about 12 percentage points, fell asleep about 25 minutes faster and decreased the amount of time awake in the middle of the night by about 45 minutes, according to Jade Wu, lead study author and a Boston University doctoral student in psychology. © 2015 The New York Times Company
Link ID: 21181 - Posted: 07.18.2015
By Tori Rodriguez Many studies have examined the effects of sufficient versus insufficient sleep on mental health. A new study, published in February in the Journal of Youth and Adolescence, takes a more nuanced look, attempting to determine just how much each hour less per night really costs—where teenagers are concerned. The researchers surveyed an ethnically diverse sample of 27,939 suburban high school students in Virginia. Although teenagers need about nine hours of sleep a night on average, according to the National Institutes of Health, only 3 percent of students reported getting that amount, and 20 percent of participants indicated that they got five hours or less. The average amount reported was 6.5 hours every weekday night. After controlling for background variables such as family status and income, the researchers determined that each hour of lost sleep was associated with a 38 percent increase in the odds of feeling sad and hopeless, a 42 percent increase in considering suicide, a 58 percent increase in suicide attempts and a 23 percent increase in substance abuse. These correlational findings do not prove that lack of sleep is causing these problems. Certainly the reverse can be true: depression and anxiety can cause insomnia. “But the majority of the research evidence supports the causal direction being lack of sleep leading to problems rather than the other way around,” says study co-author Adam Winsler, a psychology professor at George Mason University. © 2015 Scientific American
Tina Hesman Saey The Earth has rhythm. Every 24 hours, the planet pirouettes on its axis, bathing its surface alternately in sunlight and darkness. Organisms from algae to people have evolved to keep time with the planet’s light/dark beat. They do so using the world’s most important timekeepers: daily, or circadian, clocks that allow organisms to schedule their days so as not to be caught off guard by sunrise and sunset. A master clock in the human brain appears to synchronize sleep and wake with light. But there are more. Circadian clocks tick in nearly every cell in the body. “There’s a clock in the liver. There’s a clock in the adipose [fat] tissue. There’s a clock in the spleen,” says Barbara Helm, a chronobiologist at the University of Glasgow in Scotland. Those clocks set sleep patterns and meal times. They govern the flow of hormones and regulate the body’s response to sugar and many other important biological processes (SN: 4/10/10, p. 22). Having timekeepers offers such an evolutionary advantage that species have developed them again and again throughout history, many scientists say. But as common and important as circadian clocks have become, exactly why such timepieces arose in the first place has been a deep and abiding mystery. Many scientists favor the view that multiple organisms independently evolved their own circadian clocks, each reinventing its own wheel. Creatures probably did this to protect their fragile DNA from the sun’s damaging ultraviolet rays. But a small group of researchers think otherwise. They say there had to be one mother clock from which all others came. That clock evolved to shield the cell from oxygen damage or perhaps provide other, unknown advantages. © Society for Science & the Public 2000 - 2015
By Maria Konnikova This is the third piece in a three-part series on sleep. Read part one, on falling asleep, and part two, on sleeping and dreaming. Did you get enough sleep last night? Are you feeling fully awake, like your brightest, smartest, and most capable self? This, unfortunately, is a pipe dream for the majority of Americans. “Most of us are operating at suboptimal levels basically always,” the Harvard neurologist and sleep medicine physician Josna Adusumilli told me. Fifty to seventy million Americans, Adusumilli says, have chronic sleep disorders. In a series of conversations with sleep scientists this May, facilitated by a Harvard Medical School Media Fellowship, I learned that the consequences of lack of sleep are severe. While we all suffer from sleep inertia (a general grogginess and lack of mental clarity), the stickiness of that inertia depends largely on the quantity and quality of the sleep that precedes it. If you’re fully rested, sleep inertia dissipates relatively quickly. But, when you’re not, it can last far into the day, with unpleasant and even risky results. Many of us have been experiencing the repercussions of inadequate sleep since childhood. Judith Owens, the director of the Center for Pediatric Sleep Disorders at Boston Children’s Hospital, has been studying the effects of school start times on the well-being of school-age kids—and her conclusions are not encouraging. Most adults are fine with about eight hours of sleep, but toddlers need around thirteen hours, including a daytime nap. Teens need around nine and a half hours; what’s more, they tend to be night owls, whose ideal circadian rhythm has them going to bed and waking up late. As schools have pushed their start times earlier and earlier—a trend that first started in the sixties, Owens says—the health effects on students have been severe.
Link ID: 21165 - Posted: 07.14.2015
By Nicholas Bakalar A short nap could reduce impulsive behavior and improve the ability to withstand frustration, a small study suggests. Researchers studied 40 people aged 18 to 50. After three nights of normal sleep, the participants took computer-based tests of frustration tolerance — which consisted of trying to complete an impossible task — and completed questionnaires on sleepiness, mood and impulsivity. Then they were randomly assigned to take an hour’s nap, or to watch a nature video. At the end of the process, they were tested again. The study appears in Personality and Individual Differences. Before the nap period, everyone spent about the same amount of time on the unsolvable task, but afterward nappers, who all reported having slept at least part of the time, spent significantly more time working at it than they had before their nap, while non-nappers gave up sooner. Nappers also rated their behavior as less impulsive than non-nappers. The lead author, Jennifer R. Goldschmied, a doctoral student at the University of Michigan, acknowledged that the sample is small, involved mainly college students and may not be applicable to other populations. The sleep calculations also did not use electronic devices to precisely measure sleep and wakefulness. Still, she said, “These results are valuable and have put us on the route to understanding how we can utilize naps. Now people are starting to understand how powerful short bursts of sleep can be.” © 2015 The New York Times Company
By David Robson William’s internal clock is eternally jammed at 13:40 on 14 March 2005 – right in the middle of a dentist appointment. A member of the British Armed Forces, he had returned to his post in Germany the night before after attending his grandfather’s funeral. He had gym in the morning, where he played volleyball for 45 minutes. He then entered his office to clear a backlog of emails, before heading to the dentist’s for root-canal surgery. “I remember getting into the chair and the dentist inserting the local anaesthetic,” he tells me. After that? A complete blank. It is as if all new memories are being written in invisible ink that slowly disappears. Since then, he has been unable to remember almost anything for longer than 90 minutes. So while he can still tell me about the first time he met the Duke of York for a briefing at the Ministry of Defence, he can’t even remember where he’s living now; he wakes up every morning believing he is still in Germany in 2005, waiting to visit the dentist. Without a record of new experiences, the passing of time means nothing to him. Today, he only knows that there is a problem because he and his wife have written detailed notes on his smartphone, in a file labelled “First thing – read this”. It is as if all new memories are being written in invisible ink that slowly disappears. How could minor dental work have affected his brain in such a profound way? This real-life medical mystery offers a rare glimpse at the hidden depths of the brain’s workings. © 2015 BBC.
Keyword: Learning & Memory
Link ID: 21137 - Posted: 07.06.2015
By Gretchen Vogel The 2009 H1N1 influenza pandemic left a troubling legacy in Europe: More than 1300 people who received a vaccine to prevent the flu developed narcolepsy, an incurable, debilitating condition that causes overpowering daytime sleepiness, sometimes accompanied by a sudden muscle weakness in response to strong emotions such as laughter or anger. The manufacturer, GlaxoSmithKline (GSK), has acknowledged the link, and some patients and their families have already been awarded cpmpensation. But how the vaccine might have triggered the condition has been unclear. In a paper in Science Translational Medicine (STM) this week, researchers offer a possible explanation. They show that the vaccine, called Pandemrix, triggers antibodies that can also bind to a receptor in brain cells that help regulate sleepiness. The work strongly suggests that Pandemrix, which was given to more than 30 million Europeans, triggered an autoimmune re action that led to narcolepsy in some people who are genetically at risk. “They put together quite a convincing picture and provide a plausible explanation for what has happened,” says Pasi Penttinen, who heads the influenza program at the European Centre for Disease Prevention and Control in Stockholm. “It’s really the kind of work we’ve been waiting for for 5 years.” But the results still need to be confirmed in a larger study, the authors and other narcolepsy researchers say. A 2013 paper in STM by another group, documenting a different type of vaccine-triggered autoimmune re action, was retracted after the results proved irreproducible (Science, 1 August 2014, p. 498). © 2015 American Association for the Advancement of Science
By Dina Fine Maron The game is a contemporary of the original Nintendo but it still appeals to today’s teens and lab monkeys alike—which is a boon for neuroscientists. It offers no lifelike graphics. Nor does it boast a screen. Primate players—whether human or not—are simply required to pull levers and replicate patterns of flashing lights. Monkeys get a banana-flavored treat as a reward for good performance whereas kids get nickels. But the game's creators are not really in it for fun. It was created by toxicologists at the U.S. Food and Drug Administration in the 1980s to study how chronic exposure to marijuana smoke affects the brain. Players with trouble responding quickly and correctly to the game’s commands may have problems with short-term memory, attention or other cognitive issues. The game has since been adapted to address a different question: whether anesthetics used to knock pediatric patients unconscious during surgery and diagnostic tests could affect a youngster's long-term neural development and cognition. Despite 20 years’ worth of experiments in young rodents and monkeys, there have been few definitive answers. To date, numerous studies suggest that being put under with anesthesia early in life seems somehow related to future cognitive problems. But whether this association is causal or merely coincidence is unclear. Researchers do know that the young human brain is exceptionally sensitive. When kids are exposed to certain harmful chemicals in their formative years, that experience can fundamentally alter the brain’s architecture by misdirecting the physical connections between neurons or causing cell deaths. But unraveling whether anesthetics may fuel such long-term damage in humans remains a challenge. © 2015 Scientific American
by Clare Wilson Do you dream of where you'd like to go tomorrow? It looks like rats do. When the animals are shown a food treat at the end of a path they cannot access and then take a nap, the neurons representing that route in their brains fire as they sleep – as if they are dreaming about running down the corridor to grab the grub. "It's like looking at a holiday brochure for Greece the day before you go – that night you might dream about the pictures," says Hugo Spiers of University College London. Like people, rats store mental maps of the world in their hippocampi, two curved structures on either side of the brain. Putting electrodes into rats' brains as they explore their environment has shown that different places are recorded and remembered by different combinations of hippocampal neurons firing together. These "place cells" fire not only when a rat is in a certain location, but also when it sleeps, as if it is dreaming about where it has been in the past. Spiers's team wondered whether this activity during sleep might also reflect where a rat wants to go in future. They placed four rats at the bottom of a T-shaped pathway, with entry to the top bar of the T blocked by a grille. Food was placed at the end of one arm, in a position visible to the animals. Next they encouraged the rats to sleep in a cosy nest and recorded their hippocampus activity with about 50 electrodes each as they rested. Finally they put the rats back into the maze, but now with the grille and the treat removed. © Copyright Reed Business Information Ltd.
Link ID: 21103 - Posted: 06.27.2015
by Colin Barras Bacteria aren't renowned for their punctuality – but perhaps one day they will be. A working circadian clock has been inserted in E. coli that allows the microbes to keep to a 24-hour schedule. The tiny timekeepers could eventually be used in biological computers or for combating the effects of jet lag. Many plants and animals use circadian clocks to regulate their daily activities – but bacterial circadian rhythms are much less well understood. The best studied belongs to photosynthetic cyanobacteria: other common microbes, like E. coli, don't carry clocks at all, says Pamela Silver of Harvard Medical School. The cyanobacterial clock is based around the kaiABC gene cluster and ATP – the molecular fuel that nearly all living cells rely on. During the day, while the cyanobacteria are active, the KaiA protein encourages the KaiC protein to bind to phosphate groups from ATP. At night, the KaiB protein kicks into action, disrupting the activity of KaiA and encouraging KaiC to hand back the phosphate. Silver, her former student Anna Chen and other colleagues have transplanted this kaiABC clock wholesale into E. coli – the first time such a sophisticated clock has been slotted into a new microbe. But would the bacteria use their new clocks to keep time? "That's the cleverest part – and it's down to Anna's genius," says Silver. Chen suggested hooking up the kaiABC clock to a green fluorescent protein so that the phosphorylated KaiC protein would make the E. coli glow. Sure enough, the E. coli became gradually more fluorescent and then returned to a non-fluorescent state over a 24-hour period, proving that the kaiABC clock kept ticking even after it was transplanted. © Copyright Reed Business Information Ltd.
Keyword: Biological Rhythms
Link ID: 21055 - Posted: 06.16.2015
Hannah Devlin Science correspondent When Lucy Tonge started drifting off in front of the television as a 13-year-old, her parents put it down to typical teenage lethargy. And when she developed a strange habit of slumping forward when she laughed, her mum told her: “Stop doing that stupid thing when you laugh. It makes you look silly.” But she couldn’t. It was only when she started collapsing with no warning that her family sought medical advice that led to a diagnosis of narcolepsy. Soon afterwards, Tonge discovered that her sleeping disorder was very likely to have been triggered by the swine flu vaccine, which she had received in 2009 a couple of months before her symptoms first emerged. Swine flu vaccine can trigger narcolepsy, UK government concedes The government has acknowledged the rare side-effect of the Pandemrix jab, which was given to 6 million people in Britain during the 2009 and 2010 swine flu pandemic, but the Department for Work and Pensions (DWP)has rejected the compensation claims of about 80 people including Tonge on the grounds that their disabilities were not “severe”. This week, the group was given fresh hope that the challenges they face will be acknowledged after a tribunal ordered the government to pay £120,000 in damages to a 12-year-old boy whose narcolepsy was also linked to Pandemrix. © 2015 Guardian News and Media Limited
Link ID: 21052 - Posted: 06.15.2015
By David Noonan Every night, before he goes to sleep, Al Pierce, whose thunderous snoring used to drive his wife out of their bedroom, uses a small remote control to turn on an electronic sensor implanted in his chest. The sensor detects small changes in his breathing pattern—early signs that Pierce's airway is beginning to collapse on itself. When the device senses these changes, it triggers a mild jolt of electricity that travels through a wire going up his neck. The wire ends at a tiny electrode wrapped around a nerve that controls muscles in his tongue. The nerve, stimulated by the charge, activates muscles that thrust Pierce's tongue forward in his mouth, which pulls his airway open. Throughout the night the 65-year-old plumber in Florence, S.C., gets hundreds of little jolts, yet he sleeps quietly. In the morning, rested and refreshed, Pierce uses the remote to turn off the device. This new technology, called upper-airway electronic stimulation and approved by the U.S. Food and Drug Administration last summer, offers much more than relief from an annoying noise. Pierce's loud snoring was the most obvious symptom of obstructive sleep apnea, a drastically underdiagnosed disorder shared by an estimated 25 million Americans. It can lead to high blood pressure, heart disease, diabetes, depression and an impaired ability to think clearly. Overall, people with severe sleep apnea have triple the risk of death from all causes as compared with those without the disorder. © 2015 Scientific American
Link ID: 21035 - Posted: 06.10.2015
Austin Frakt One weekend afternoon a couple of years ago, while turning a page of the book I was reading to my daughters, I fell asleep. That’s when I knew it was time to do something about my insomnia. Data, not pills, was my path to relief. Insomnia is common. About 30 percent of adults report some symptoms of it, though less than half that figure have all symptoms. Not all insomniacs are severely debilitated zombies. Consistent sleeplessness that causes some daytime problems is all it takes to be considered an insomniac. Most function quite well, and the vast majority go untreated. I was one of the high-functioning insomniacs. In fact, part of my problem was that I relished the extra time awake to work. My résumé is full of accomplishments I owe, in part, to my insomnia. But it took a toll on my mood, as well as my ability to make it through a children’s book. Insomnia is worth curing. Though causality is hard to assess, chronic insomnia is associated with greater risk of anxiety, depression, hypertension, diabetes, accidents and pain. Not surprisingly, and my own experience notwithstanding, it is also associated with lower productivity at work. Patients who are successfully treated experience improved mood, and they feel healthier, function better and have fewer symptoms of depression. Which remedy would be best for me? Lunesta, Ambien, Restoril and other drugs are promised by a barrage of ads to deliver sleep to minds that resist it. Before I reached for the pills, I looked at the data. © 2015 The New York Times Company
Link ID: 21031 - Posted: 06.09.2015
David Shariatmadari Maybe we should ask the duck-billed platypus. Back in the 1950s, scientists working on humans identified a state marked by increased brain activation, accelerated breathing and heart rate, and muscular paralysis. But perhaps the most remarkable feature was a flickering of the eyes beneath closed eyelids – because all these physiological changes took place while the subjects were fast asleep. What the researchers had discovered became known as the “rapid eye movement” (REM) phase. Under normal circumstances, it recurs every 90 minutes or so, and takes up around 25% of our total time spent sleeping. It quickly became clear that people woken during REM had much better recall of their dreams; in fact, they would often say they’d just that moment been dreaming. As a result, the scientific community began to think of REM as the outward manifestation of the dream state. For the first time in human history, the most extraordinary and fantastical part of our lives had been subject to experimental observation. Not only that, but animals were found to experience REM as well – some of them more often and for longer than humans. We now know that the REM-iest mammal of them all is, bizarrely enough, Ornithorhynchus anatinus, known to you and me as the duck-billed platypus. Perhaps we shouldn’t be surprised, since, as Nature notes, “an account from as long ago as 1860, before REM sleep was discovered, reported that young platypus showed ‘swimming’ movements of their forepaws while asleep”. © 2015 Guardian News and Media Limited
by Penny Sarchet The common pet budgerigar (or parakeet) is loved for its ability to mimic its owners. But it has another special trick – it can catch yawns from other budgies, suggesting it has some kind of empathy. "Practically all vertebrates yawn," says Ramiro Joly-Mascheroni of City University, London. In 2008, he showed that dogs can catch yawns from humans. The only other species shown to yawn contagiously are humans, chimpanzees and a type of rodent called the high-yawning Sprague-Dawley rat. But Andrew Gallup of the State University of New York and his colleagues have now shown for the first time that the same happens for a species of non-mammals. To see whether budgies, a sociable parrot species, can make each other yawn, his team designed two experiments. In the first, budgies were placed in adjacent cages, either with a barrier between them, or with nothing obstructing their view of each other. They found that, when budgies could see each other, they were around three times as likely to yawn within five minutes of a yawn from their neighbour. In their second experiment, budgies were shown a video – either one that showed clips of budgies yawning, or one that had no yawning at all. Every bird that watched the yawning video also yawned, while fewer than half of the birds shown the other video yawned. "Thus far, yawning has been demonstrated to be contagious in a few highly social species," said Gallup. "To date, this is the first experimental evidence of contagious yawning in a non-mammalian species." © Copyright Reed Business Information Ltd
Link ID: 20997 - Posted: 05.30.2015
By Tara Haelle Thousands of infants each year die in their cribs from sudden infant death syndrome (SIDS) for reasons that have remained largely a mystery. A study published May 25 provides strong evidence that oxygen deprivation plays a big role. One reason the cause of SIDS has been so difficult to study is the sheer number of variables researchers have had to account for: whether the infant sleeps face down, breathes secondhand smoke or has an illness as well as whether the child has an unidentified underlying susceptibility. To isolate the effects of oxygen concentration, researchers from the University of Colorado compared the rate of SIDS in infants living at high altitudes, where the air is thin, to those living closer to sea level. Infants at high altitudes, they found, were more than twice as likely to die from SIDS. It was “very clever of the authors,” says Michael Goodstein, a pediatrician and member of the 2010–2011 Task Force on Sudden Infant Death Syndrome who was not involved in the study. “The authors did a good job controlling for other variables,” he adds. Beyond the risk of living at high altitudes, the study suggests a common link among different risk factors about the causes of SIDS. For example, the authors note that sleeping on the stomach and exposure to tobacco smoke can also contribute to hypoxia—insufficient oxygen reaching the tissues. Similarly, past research has suggested that sleeping on soft surfaces may shift the chin down, partly obstructing the airway, which might cause an infant to breathe in less oxygen. It’s unclear how hypoxia might contribute to SIDS but it could have to do with a buildup of carbon dioxide in the tissues when a child does not wake up. © 2015 Scientific American