Chapter 14. Biological Rhythms, Sleep, and Dreaming
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By PERRI KLASS, M.D. It’s a classic which-came-first question: Is the child not getting enough sleep because of problem behaviors, especially at bedtime, or is the child behaving problematically because of not getting enough sleep? The answers are most likely yes and yes, and the back-and-forth currents can drag a child down developmentally. In an editorial in JAMA Pediatrics in 2015, Michelle M. Garrison, a research assistant professor at the University of Washington in the division of child and adolescent psychiatry, described this intersection of sleep and behavior problems in early childhood as a “feedback whirlpool.” Dr. Garrison was commenting on a longitudinal study of more than 32,000 Norwegian mothers and their children who were followed from birth to age 5; the children with sleep problems at 18 months, including short sleep duration (sleeping 10 hours or less) or frequent nocturnal awakenings (three times a night or more) had more emotional and behavioral problems at the age of 5. This held true even when the researchers adjusted for emotional and behavioral problems already present in the 18-month-olds; compared to children at the same behavioral baseline, the kids with sleep problems ran into more difficulties as they developed. “Sleep really does drive behavior problems and behavior problems are driving sleep problems, it really is bidirectional,” Dr. Garrison said. “A child can start having problems with emotional regulation, melting down more, and that makes it more difficult for the family to do all the things they have to do so the child can get good sleep. Sleep gets worse; behavior gets worse. It can really be an awful cycle for the kid and the family both.” Dr. Oskar Jenni, a professor of developmental pediatrics at Zurich University Children’s Hospital, said that there is a great deal of variation in the individual sleep needs of children at any given age. Parents need to understand their children’s sleep needs and rhythms, since behavior problems can also arise when children are compelled to spend more time in bed than they actually need. “My main message is adjusting bedtime to the needs of the children in both directions,” he said. © 2016 The New York Times Company
Link ID: 22762 - Posted: 10.18.2016
Hannah Devlin Science correspondent Scientists have found the most definitive evidence yet that some people are destined to age quicker and die younger than others - regardless of their lifestyle. The findings could explain the seemingly random and unfair way that death is sometimes dealt out, and raise the intriguing future possibility of being able to extend the natural human lifespan. “You get people who are vegan, sleep 10 hours a day, have a low-stress job, and still end up dying young,” said Steve Horvath, a biostatistician who led the research at the University of California, Los Angeles. “We’ve shown some people have a faster innate ageing rate.” A higher biological age, regardless of actual age, was consistently linked to an earlier death, the study found. For the 5% of the population who age fastest, this translated to a roughly 50% greater than average risk of death at any age. Intriguingly, the biological changes linked to ageing are potentially reversible, raising the prospect of future treatments that could arrest the ageing process and extend the human lifespan. “The great hope is that we find anti-ageing interventions that would slow your innate ageing rate,” said Horvath. “This is an important milestone to realising this dream.” Horvath’s ageing “clock” relies on measuring subtle chemical changes, in which methyl compounds attach or detach from the genome without altering the underlying code of our DNA. © 2016 Guardian News and Media Limited
By Michael Price A deadly disease known as African sleeping sickness has puzzled doctors for decades. It would disappear from villages without a trace, only to re-emerge weeks or months later with no known cause. Frustrated health officials wondered how sleeping sickness could persist when not a single villager or animal—the disease’s only carriers—tested positive for the insect-borne parasite that causes it. Now, scientists may have an answer at last: They’ve discovered the disease was hiding in plain sight this whole time, living in and even transmitting via human skin. African sleeping sickness, also known as African trypanosomiasis, is caused by a microscopic wormlike parasite spread exclusively by the tsetse fly. As such, it’s limited by the fly’s range to sub-Saharan Africa. Locals avoid places where the flies are numerous, but political unrest can displace residents and force them into the path of the disease. Once infected, people have anywhere from weeks to years before the parasite crashes into the brain, causing headaches, tremors, confusion, and paralysis. Those infected also suffer from a disrupted sleep cycle, bouts of random sleepiness and wakefulness that gives the disease its name. Without treatment—toxic drugs that keep patients bedridden for weeks—those infected nearly always slip into a coma and die. In the 1950s and 1960s, health officials got the number of reported cases down to a few thousand per year and were on track to eradicate it, says parasitologist Annette MacLeod of the University of Glasgow in the United Kingdom, who led the new discovery. But despite their best efforts, they could never get rid of the last few thousand cases. © 2016 American Association for the Advancement of Science.
Link ID: 22691 - Posted: 09.24.2016
By PAGAN KENNEDY In 1914, The Lancet reported on a clergyman who was found dead in a pool; he had left behind this suicide note: “Another sleepless night, no real sleep for weeks. Oh, my poor brain, I cannot bear the lengthy, dark hours of the night.” I came across that passage with a shock of recognition. Many people think that the worst part of insomnia is the daytime grogginess. But like that pastor, I suffered most in the dark hours after midnight, when my desire for sleep, my raging thirst for it, would drive me into temporary insanity. On the worst nights, my mind would turn into a mad dog that snapped and gnawed itself. Though one in 10 American adults suffer from chronic insomnia, we have yet to answer the most fundamental questions about the affliction. Scientists are still arguing about the mechanisms of sleep and the reasons it fails in seemingly healthy people. There are few — if any — reliable treatments for insomnia. At the same time, medical journals warn that bad sleep can fester into diseases like cancer and diabetes. Deep in the night, those warnings scuttle around my mind like rats. About 18 months ago, during a particularly grueling period, I felt so desperate that I consulted yet another doctor — but all he did was suggest the same drugs that had failed me in the past. I was thrown back once again on my own ways of coping. As a child, I had invented mental games to distract myself. For instance, I would compile a list of things and people that made me happy, starting with words that began with A and moving through the alphabet. One night, I was in the Qs, trying to figure out what to add to quesadillas, queer theory and Questlove. Then, suddenly, the game infuriated me — why, why, why did I have to spend hours doing this? In the red glare of the digital clock, my brain rattled its cage. I prepared for a wave of lunacy. But instead of a meltdown, I had a wild idea: What if there was another, easier, way to drive the miserable thoughts from my mind? I began to fantasize about a machine that would do the thinking for me. I pictured it like another brain that would fit on top of my head. The next day, I cobbled together my first insomnia machine. © 2016 The New York Times Company
Link ID: 22667 - Posted: 09.19.2016
Napping for more than an hour during the day could be a warning sign for type-2 diabetes, Japanese researchers suggest. They found the link after analysing observational studies involving more than 300,000 people. UK experts said people with long-term illnesses and undiagnosed diabetes often felt tired during the day. But they said there was no evidence that napping caused or increased the risk of diabetes. The large study, carried out by scientists at the University of Tokyo, is being presented at a meeting of the European Association for the Study of Diabetes in Munich. Their research found there was a link between long daytime naps of more than 60 minutes and a 45% increased risk of type-2 diabetes, compared with no daytime napping - but there was no link with naps of less than 40 minutes. The researchers said long naps could be a result of disturbed sleep at night, potentially caused by sleep apnoea. And this sleeping disorder could increase the risk of heart attacks, stroke, cardiovascular problems and other metabolic disorders, including type-2 diabetes. Sleep deprivation, caused by work or social life patterns, could also lead to increased appetite, which could increase the risk of type-2 diabetes. But it was also possible that people who were less healthy or in the early stages of diabetes were more likely to nap for longer during the day. Shorter naps, in contrast, were more likely to increase alertness and motor skills, the authors said. © 2016 BBC.
By Krystnell A. Storr This one goes out to the head bobbers, the window seat sleepers, and the open-mouth breathers — there is no shame in being able to fall asleep anywhere, and at any time. Be proud, and, if you can’t help it, snore loud. Scientists have come to a consensus that our bodies definitely need sleep, but we don’t all need the same amount. The next step for them is to figure out where the process of sleep starts and ends in the body. And, like a good movie, one revelation about sleep only leads to another. Think of yourself as a very minor character in the scientific story of fatigue. The real star of this cozy mystery is the fruit fly, an A-lister in sleep science. Thanks to fruit flies, we understand two of the basic factors that govern sleep: a biological clock, which scientists know a lot about, and a homeostatic switch, which they only just discovered and are beginning to understand. Let’s start with this biological clock. The clock that is connected to sleep is controlled by a circadian rhythm and uses environmental cues such as sunlight to tell the body when to wake up. This sun-sleep connection in humans and flies alike got scientists like Russell Foster, a professor at Oxford University in the United Kingdom, asking questions such as: What happens when we don’t have the mechanisms in our eye to distinguish dawn from dusk and send that message to the brain? Why can we still fall asleep according to the circadian rhythm? The answer, Foster said, is that mammals have a third layer of photoreceptors in the eye. It used to be that scientists thought rods and cones, cells that help us process images, were the only ones in the eye that worked to detect light. But when they removed these cells in mice, they noticed that the mice could still keep up with the circadian rhythm. The hidden cells, they found, were intrinsically sensitive to light and acted as a backup measure to keep us on our sleep schedule, whether we can see that the sun is up or not.
By Rachel Feltman In the age of the quantified self, products that promise to track your habits and fix your behavior are a dime a dozen. Find out how much you walk; do that more. Find out how much junk you eat; do that less. Correct your posture in real time, and get feedback as you strengthen your pelvic floor muscles. More and more companies are built on the notion that any problem can be solved if you get enough numbers to find a pattern. In that sense, Sense — a sleep tracker made by the start-up Hello — isn't all that unusual. But the company's new lead scientist is just getting his hands on two years of user sleep data, and he seems particularly passionate about using it for good. Matthew Walker, a professor of neuroscience and psychology at the University of California in Berkeley, and director of the U.C. Berkeley Sleep and Neuroimaging Laboratory, does not mince words when it comes to snoozing. "It’s very clear right now that the sleep-loss epidemic is the greatest public health crisis in First World nations of the 21st century," Walker told The Washington Post. "Every disease that is killing us, in First World countries, can be linked to loss of sleep." Indeed, the Centers for Disease Control and Prevention states that lack of sleep — in addition to causing fatal accidents and injuries — has been linked to an increase risk of hypertension, diabetes, depression, obesity and even cancer. Just about all scientists and medical professionals agree that good sleep helps keep the body healthy. © 1996-2016 The Washington Post
Link ID: 22655 - Posted: 09.15.2016
Susan Milius Contrary to many adorable children’s stories, hibernation is so not sleeping. And most animals can’t do both at the same time. So what’s with Madagascar’s dwarf lemurs? The fat-tailed dwarf lemur slows its metabolism into true hibernation, and stays there even when brain monitoring shows it’s also sleeping. But two lemur cousins, scientists have just learned, don’t multitask. Like other animals, they have to rev their metabolisms out of hibernation if they want a nap. Hibernating animals, in the strictest sense, stop regulating body temperature, says Peter Klopfer, cofounder of the Duke Lemur Center in Durham, N.C. “They become totally cold-blooded, like snakes.” By this definition, bears don’t hibernate; they downregulate, dropping their body temperatures only modestly, even when winter den temperatures sink lower. And real hibernation lasts months, disqualifying short-termers such as subtropical hummingbirds. The darting fliers cease temperature regulation and go truly torpid at night. “You can pick them out of the trees,” Klopfer says. The fat-tailed dwarf lemur, Cheirogaleus medius, was the first primate hibernator discovered, snuggling deep into the softly rotting wood of dead trees. “You’d think they’d suffocate,” he says. But their oxygen demands plunge to somewhere around 1 percent of usual. As trees warm during the day and cool at night, so do these lemurs. When both a tree and its inner lemur heat up, the lemur’s brain activity reflects mammalian REM sleep. |© Society for Science & the Public 2000 - 2016
By Christof Koch Flies, birds, mice, dogs, monkeys and people all need to sleep. That is, they show daily periods of relative immobility and lack of response to external stimuli, such as light, sound or touch. This reduced sensitivity to external events distinguishes sleep from quiet resting, whereas the capacity to awaken from slumber distinguishes sleep from coma. Why sleep should be such a prominent feature of daily life across the animal kingdom, despite the fact that it leaves the sleeper unable to confront potential threats, remains mysterious. Still, much progress in characterizing the physiology and capabilities of the sleeping brain has occurred over the past century, driven by the ability to record electrical activity of the brain (via electroencephalography, or EEG, on the surface of the skull), of the eyes (via electrooculography, or EOG), and of facial or other muscles (via electromyography, or EMG). For scientists, it is this triad of simultaneous measurements that operationally defines the state of sleep, leading to both surprising and counterintuitive insights. Even without these tools, there are some basic things we do know about sleep. It is essential for our brain to function properly. Most of us have pulled all-nighters or have wanted to sleep but could not, unable to switch off our mind. The next day we are irritable, have trouble keeping our eyes open, and are terrible at tasks that demand sustained attention. Indeed, sleep deprivation causes many traffic accidents—the reason countries have laws that mandate a minimum rest period and maximum working hours for truck drivers. © 2016 Scientific American,
By Alice Callahan As new parents, Penn State researcher Doug Teti and his wife were co-sleepers, sharing their bed at night with all three of their children, now grown. So when Dr. Teti, a professor of human development and family studies, embarked on an usual study of co-sleeping, bringing cameras into the bedrooms of 139 Pennsylvania couples, he did not expect to see co-sleeping associated with family stress. But to his surprise, many of the parents in the study who co-slept with their children beyond 6 months of age, a group he called “persistent co-sleepers,” did show signs of stress, particularly the mothers. Dr. Teti emphasized that the research isn’t an indictment against co-sleeping, but does suggest that a number of factors, including cultural pressures and an unsupportive spouse, can make longer-term co-sleeping a more stressful experience for some families. “Co-sleeping is simply a practice, just like solitary sleep is a practice,” he said. “It is important for parents to be on the same page about whatever practices with their children they choose to put into effect.” The study, published this month in the journal Developmental Psychology, was unusual in that it tracked 139 couples, mostly married or living together, who generously allowed researchers to peek into their bedrooms with video cameras, recording nighttime interactions with their new babies at five time points in the first year of life. Co-sleeping — defined in this study as room-sharing or bed-sharing, often a mix of the two — was surprisingly common in early infancy. Nearly 75 percent of the parents co-slept with infants early on, and about half were still co-sleeping three months after the birth. But once the babies reached 6 months of age, only one in four babies continued to share a bed or a room with their parents. © 2016 The New York Times Company
Link ID: 22598 - Posted: 08.25.2016
Ian Sample Science editor For Jules Verne it was the friend who keeps us waiting. For Edgar Allan Poe so many little slices of death. But though the reason we spend a third of our lives asleep has so far resisted scientific explanation, research into the impact of sleepless nights on brain function has shed fresh light on the mystery - and also offered intriguing clues to potential treatments for depression. In a study published on Tuesday, researchers show for the first time that sleep resets the steady build-up of connectivity in the human brain which takes place in our waking hours. The process appears to be crucial for our brains to remember and learn so we can adapt to the world around us. The loss of a single night’s sleep was enough to block the brain’s natural reset mechanism, the scientists found. Deprived of rest, the brain’s neurons seemingly became over-connected and so muddled with electrical activity that new memories could not be properly laid down. Lack of sleep alters brain chemicals to bring on cannabis-style 'munchies' But Christoph Nissen, a psychiatrist who led the study at the University of Freiburg, is also excited about the potential for helping people with mental health disorders. One radical treatment for major depression is therapeutic sleep deprivation, which Nissen believes works through changing the patient’s brain connectivity. The new research offers a deeper understanding of the phenomenon which could be adapted to produce more practical treatments. © 2016 Guardian News and Media Limited
by Laura Sanders When someone uses the phrase “sleeping like a baby,” it’s obvious that they don’t really know how babies sleep. Many babies, especially newborns, are lousy sleepers, waking up every few hours to rustle around, cry and eat. For creatures who sleep up to 18 hours per 24-hour period, newborns are exhausting. That means that bone-tired parents are often desperate to get their babies to sleep so they can rest too. A study published in the September Pediatrics captured this nightly struggle in the homes of 162 Pennsylvanian families. And the results revealed something disturbing: Despite knowing that they were being videotaped, many parents didn’t put their babies into a safe sleeping spot. The risk of sleep-related infant deaths, including those caused by strangulation or sudden infant death syndrome, goes up when babies are put in unsafe sleeping positions or near suffocation hazards. Babies should be on their back on a firm mattress free of any objects. But that wasn’t the case for the majority of babies in the study, says Ian Paul, a pediatrician at Penn State. As a parent to three, Paul is sympathetic to the difficulties of soothing babies to sleep. “The first few months are really exhausting,” he says. But as a pediatrician, he also sees the risks of ignoring safe sleep guidelines. “Parents need to realize that these risks are real and might happen to them.” The videos taken for the study revealed that at 1 month of age, nearly all of the babies were put onto a sleep surface that had a loose or ill-advised item. |© Society for Science & the Public 2000 - 2016
By Roni Caryn Rabin We’ve all heard about the power of positive thinking. But will it help me sleep? My problem isn’t falling asleep – it’s staying asleep. This particular form of torture has been dubbed “sleep-maintenance” insomnia. Call me a high-functioning sufferer: I’m usually O.K. once I’ve had my morning coffee. But I worry about the long-term health ramifications of losing sleep. Now several medical organizations have endorsed a treatment known as cognitive behavioral therapy for insomnia or C.B.T.-I. In May the American College of Physicians advised its members that C.B.T.-I. was the first treatment they should offer patients with insomnia. I wanted to try it, but there is a shortage of trained therapists with expertise in C.B.T.-I. I didn’t want to wait for an appointment; I just wanted to solve the problem. So I decided to try an online sleep program. Convincing data that internet-based programs are effective is piling up, and a recent review of clinical trials reported that insomniacs improved their sleep as much after online C.B.T.-I. programs as they did after face-to-face C.B.T.-I. counseling. Internet programs are likely to be cheaper than most therapists, too. I downloaded a five-week course called Conquering Insomnia for $40. Another online C.B.T. program called SHUTi charges $135 for 16 weeks of access to a program, which includes a series of six sessions and follow-up for 10 weeks. Both programs provide individualized feedback on your weekly sleep logs. The developers of these programs say they want them to be accessible to as many people as possible. One in 10 people suffer from insomnia. “The number of clinicians nationally who know how to do C.B.T. for insomnia is a couple of thousand. We need 100,000,” said Dr. Gregg Jacobs, a sleep medicine specialist and assistant professor of psychiatry at the University of Massachusetts Medical School who developed the Conquering Insomnia program. “There are tens of millions of people out there who have insomnia.” © 2016 The New York Times Company
Link ID: 22591 - Posted: 08.24.2016
By Andrea Anderson When we bed down in a new locale, our sleep often suffers. A recent study finds that this so-called first-night effect may be the result of partial wakefulness in one side of the brain—as if the brain is keeping watch. Researchers at Brown University and the Georgia Institute of Technology used neuroimaging and a brain wave–tracking approach called polysomnography to record activity in four brain networks in 11 individuals as they slept on two nights about a week apart. The subjects nodded off at their normal bedtimes, and their brain was scanned for about two hours—the length of a sleep cycle. As participants slept, right hemisphere regions showed consistent slow-wave activity regardless of the night. Yet average slow-wave activity was shallower in their left hemisphere during the first night—an asymmetry that was enhanced in those who took longer to fall asleep. The results, published in May in Current Biology, suggest systems in one side of the brain remain active as people venture into unfamiliar sleep situations—an apparent survival strategy reminiscent of the unihemispheric sleep reported in certain animals. Because the results represent just one sleep cycle, however, it is unclear whether the left side of the brain is always tasked with maintaining attentiveness, explains the study's senior author Yuka Sasaki, a cognitive, linguistic and psychological sciences researcher at Brown. It is possible the right hemisphere takes over guard dog duties at some point in the night. © 2016 Scientific American
Link ID: 22580 - Posted: 08.22.2016
By Melinda Wenner Moyer The science of sleep is woefully incomplete, not least because research on the topic has long ignored half of the population. For decades, sleep studies mostly enrolled men. Now, as sleep researchers are making a more concerted effort to study women, they are uncovering important differences between the sexes. Hormones are a major factor. Estrogen, progesterone and testosterone can influence the chemical systems in the brain that regulate sleep and arousal. Moreover, recent studies indicate that during times of hormonal change—such as puberty, pregnancy and menopause—women are at an increased risk for sleep disorders such as obstructive sleep apnea, restless legs syndrome and insomnia. Women also tend to report that they have more trouble sleeping before and during their menstrual periods. And when women do sleep poorly, they may have a harder time focusing than sleep-deprived men do. In one recent study, researchers shifted the sleep-wake cycles of 16 men and 18 women for 10 days. Volunteers were put on a 28-hour daily cycle involving nearly 19 hours of awake time followed by a little more than nine hours of sleep. During the sleep-shifted period, the women in the group performed much less accurately than the men on cognitive tests. The findings, published in April of this year in the Proceedings of the National Academy of Sciences USA, may help explain why women are more likely than men to get injured working graveyard shifts. In addition, a study conducted in 2015 in teenagers reported that weekday sleep deprivation affects cognitive ability more in girls than in boys. © 2016 Scientific American
By Karen Weintraub There’s been lots of coverage lately about meeting exercise recommendations by completing small chunks of exercise throughout the day rather than one, continuous session. Does the same hold true for meeting sleep recommendations? No. Unfortunately, sleep does not work that way. Substituting periodic naps for one consolidated night of sleep creates severe sleep deprivation, said Dr. Daniel Buysse, a sleep expert and professor of psychiatry at the University of Pittsburgh. He and his colleagues once did an experiment in which volunteers agreed to alternate 30 minutes of sleep with 60 minutes of wakefulness for two and a half days straight. They ended up sleep deprived, he said, because sound sleep is not equally likely at all times of day. People have a better chance of falling quickly into deep, restful sleep at night than midday, even if they feel as though they could fall asleep at any time. “Our biological clocks do not allow us to sleep as well during the day as at night,” he said. “All sleep is not necessarily equal.” That’s why night workers get less sleep on average than people who work other shifts – and suffer health consequences as a result, he said. But it’s always a good idea to make up for lost sleep, regardless of the time of day, said Dr. Ruth Benca, a professor of psychiatry and director of the Center for Sleep Medicine and Sleep Research at the University of Wisconsin-Madison. People used to think that it was better to pull an all-nighter than to break it up with a short nap, but that isn’t true, she said. On the other hand, it may be helpful, she said, to take an afternoon nap to compensate for a short night of sleep, bringing a six-and-a-half hour night up to seven, for instance. “If you have to stay awake for a prolonged period, you can mitigate that a little bit by taking some naps, but you can’t live your life like that,” Dr. Benca said. “Any sleep is better than no sleep, and more sleep is better than less sleep.” © 2016 The New York Times Company
Link ID: 22567 - Posted: 08.18.2016
By Sunpreet Singh Every day people are exposed to hours of artificial light from a variety of sources – computers, video games, office lights and, for some, 24-hour lighting in hospitals and nursing homes. Now new research in animals shows that excessive exposure to “light pollution” may be worse for health than previously known, taking a toll on muscle and bone strength. Researchers at Leiden University Medical Center in the Netherlands tracked the health of rats exposed to six months of continuous light compared to a control group of rats living under normal light-dark conditions — 12 hours of light, followed by 12 hours of dark. During the study, the rats exposed to continuous light had less muscle strength and developed signs of early-stage osteoporosis. They also got fatter and had higher blood glucose levels. Several markers of immune system health also worsened, according to the report published in the medical journal Current Biology. While earlier research has suggested excessive light exposure could affect cognition, the new research was surprising in that it showed a pronounced effect on muscles and bones. While it’s not clear why constant light exposure took a toll on the motor functions of the animals, it is known that light and dark cues influence a body’s circadian rhythms, which regulate many of the body’s physiological processes. “The study is the first of its kind to show markers of negatively-affected muscle fibers, skeletal systems and motor performances due to the disruption of circadian clocks, remarkably in only a few months,” said Chris Colwell, a psychiatry professor and sleep specialist at the University of California, Los Angeles, who was not part of the study. “They found that not only did motor performance go down on tests, but the muscles themselves just atrophied, and mice physically became weaker under just two months under these conditions.” © 2016 The New York Times Company
Keyword: Biological Rhythms
Link ID: 22556 - Posted: 08.13.2016
Rachel Ehrenberg Pulling consecutive all-nighters makes some brain areas groggier than others. Regions involved with problem solving and concentration become especially sluggish when sleep-deprived, a new study using brain scans reveals. Other areas keep ticking along, appearing to be less affected by a mounting sleep debt. The results might lead to a better understanding of the rhythmic nature of symptoms in certain psychiatric or neurodegenerative disorders, says study coauthor Derk-Jan Dijk. People with dementia, for instance, can be afflicted with “sundowning,” which worsens their symptoms at the end of the day. More broadly, the findings, published August 12 in Science, document the brain’s response to too little shut-eye. “We’ve shown what shift workers already know,” says Dijk, of the University of Surrey in England. “Being awake at 6 a.m. after a night of no sleep, it isn’t easy. But what wasn’t known was the remarkably different response of these brain areas.” The research reveals the differing effects of the two major factors that influence when you conk out: the body’s roughly 24-hour circadian clock, which helps keep you awake in the daytime and put you to sleep when it’s dark, and the body’s drive to sleep, which steadily increases the longer you’re awake. Dijk and collaborators at the University of Liege in Belgium assessed the cognitive function of 33 young adults who went without sleep for 42 hours. Over the course of this sleepless period, the participants performed some simple tasks testing reaction time and memory. The sleepy subjects also underwent 12 brain scans during their ordeal and another scan after 12 hours of recovery sleep. Throughout the study, the researchers also measured participants’ levels of the sleep hormone melatonin, which served as a way to track the hands on their master circadian clocks. |© Society for Science & the Public 2000 - 2016
Link ID: 22548 - Posted: 08.12.2016
By Alice Klein Rise and shine! Neuronal switches have been discovered that can suddenly rouse flies from slumber – or send them into a doze. There are several parallels between sleep in flies and mammals, making fruit flies a good choice for investigating how we sleep. One way to do this is to use optogenetics to activate specific neurons to see what they do. This works by using light to turn on cells genetically modified to respond to certain wavelengths. Gero Miesenböck at the University of Oxford and his team have discovered how to wake flies up. Using light as the trigger the team stimulated neurons that release a molecule called dopamine. The dopamine then switched off sleep-promoting neurons in what’s called the dorsal fan-shaped body, waking the flies. Meanwhile, Fang Guo at Brandeis University in Waltham, Massachusetts, and his team have found that activating neurons that form part of a fly’s internal clock will send it to sleep. When stimulated, these neurons released glutamate, which turned off activity-promoting neurons in the master pacemaker area of the brain. While human and fly brains are obviously very different in structure, being asleep or awake are similar states regardless of the kind of brain an animal has, says Bruno van Swinderen at the University of Queensland, Australia. © Copyright Reed Business Information Ltd.
By Sarah Kaplan Sleep just doesn't make sense. "Think about it," said Gero Miesenböck, a neuroscientist at the University of Oxford. "We do it. Every animal with a brain does it. But obviously it has considerable risks." Sleeping animals are incredibly vulnerable to attacks, with no obvious benefit to make up for it — at best, they waste precious hours that could be used finding food or seducing a mate; at worst, they could get eaten. "If evolution had managed to invent an animal that doesn’t need to sleep ... the selective advantage for it would be immense," Miesenböck said. "The fact that no such animal exists indicates that sleep is really vital, but we don't know why." But Miesenböck is part of team of sleep researchers who believe they are inching closer to to an answer. In a paper published in the journal Nature on Wednesday, they describe a cluster of two dozen brain cells in fruit flies that operate as a homeostatic sleep switch, turning on when the body needs rest and off again when it's time to wake up. "It's like a thermostat," Miesenböck said of the switch, "But instead of responding to temperature it responds to something else." If he and his colleagues could find out what that "something" is, "we might have the answer to the mystery of sleep."