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Chapter 10. Biological Rhythms and Sleep
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Jon Hamilton During deep sleep, the brain appears to wash away waste products that increase the risk for Alzheimer's disease. A host of new research studies suggest that this stage of sleep — when dreams are rare and the brain follows a slow, steady beat – can help reduce levels of beta-amyloid and tau, two hallmarks of the disease. "There is something about this deep sleep that is helping protect you," says Matthew Walker, a professor of neuroscience and psychology at the University of California, Berkeley. The research comes after decades of observations linking poor sleep to long-term problems with memory and thinking, Walker says. "We are now learning that there is a significant relationship between sleep and dementia, particularly Alzheimer's disease." The strongest evidence involves deep sleep, he says. That's when body temperature drops and the brain begins to produce slow, rhythmic electrical waves. So Walker and a team of scientists set out to answer a question: "Can I look into your future and can I accurately estimate how much beta-amyloid you're going to accumulate over the next two years, the next four years, the next six years, simply on the basis of your sleep tonight?" To find out, Walker's team studied 32 people in their 70s who had taken part in a sleep study that looked for the slow electrical waves that signal deep sleep. None of the participants had memory problems. the brain cells of people with Alzheimer's. © 2020 npr
Keyword: Sleep; Alzheimers
Link ID: 27585 - Posted: 11.18.2020
By Catherine Zuckerman It’s 3 a.m. and you’ve been struggling for hours to fall asleep. Morning draws nearer and your anxiety about being exhausted the next day intensifies — yet again. If this sounds familiar, you’re not alone. Among the many disruptions of 2020, insomnia may rank high on the list. Data on how the pandemic has affected sleep is limited because biomedical research can take years to shake out and most studies to date have been small. But evidence from China and Europe suggests that prolonged confinement is altering sleep in adults as well as children. Doctors in the United States are seeing it too. “I think Covid and the election have affected sleep and could be considered a kind of trauma,” said Nancy Foldvary-Schaefer, director of the Cleveland Clinic Sleep Disorders Center. “A lot of people that I talk to — patients and non-patients and colleagues and family — have more anxiety generally now probably because of these two stressors, and high anxiety is clearly associated with insomnia.” Whether you’re suddenly tossing and turning at bedtime or waking up in the middle of the night, the first step toward better sleep is to figure out what’s triggering your insomnia. Once you do that, you can take action to prevent it from becoming chronic — a clinical sleep disorder that should be treated by a sleep-medicine specialist. Stressful and upsetting experiences like the death of a loved one or the loss of a job — two widespread realities of Covid-19 — are known psychological triggers for insomnia. If your insomnia is tied to such an event, the quickest way to get help is to call your doctor. One thing many doctors suggest is cognitive behavioral therapy, or C.B.T. C.B.T., or C.B.T.-I. for insomnia, is a standard treatment for both acute and chronic insomnia and includes a variety of techniques. Meditation, mindfulness and muscle relaxation can help people whose sleep problems are tied to a stressful event. C.B.T. for insomnia typically lasts from six to eight weeks and “works in about two-thirds to three-quarters of patients,” said Jennifer Martin, a psychologist and professor of medicine at the University of California, Los Angeles, David Geffen School of Medicine. © 2020 The New York Times Company
By Nicholas Bakalar Weighted blankets, which have long been popular aids to induce calm, could help reduce insomnia, a new study suggests. Swedish researchers studied 121 patients with depression, bipolar disorder and other psychiatric diagnoses, all of whom had sleep problems. They randomly assigned them to two groups. The first slept with an 18-pound blanket weighted with metal chains, and the second with an identical looking three-pound plastic chain blanket. The study, in the Journal of Clinical Sleep Medicine, used the Insomnia Severity Index, a 28-point questionnaire that measures sleep quality, and participants wore activity sensors on their wrists to measure sleep time, awakenings and daytime activity. More than 42 percent of those using the heavy blanket scored low enough on the Insomnia Severity Index to be considered in remission from their sleep troubles, compared with 3.6 percent of the controls. The likelihood of having a 50 percent reduction on the scale was nearly 26 times greater in the weighted blanket group. The weighted blankets did not have a significant effect on total sleep time, but compared with the controls, the users had a significant decrease in wakenings after sleep onset, less daytime sleepiness and fewer symptoms of depression and anxiety. The senior author, Dr. Mats Adler of the Karolinska Institute in Stockholm, acknowledged that this is only one study and doesn’t provide scientific proof that the blankets work. “I have colleagues using it, and they love it,” he said, “but that’s not proof. This study is an indication that they may work, but more studies should be done.” © 2020 The New York Times Company
Keyword: Sleep
Link ID: 27524 - Posted: 10.16.2020
By Benedict Carey The swarm of insects — sometimes gnats, sometimes wasps or flying ants — arrived early in this year of nightmares. With summer came equally unsettling dreams: of being caught in a crowd, naked and mask-less; of meeting men in white lab coats who declared, “We dispose of the elders.” Autumn has brought still other haunted-house dramas, particularly for women caring for a vulnerable relative or trying to manage virtual home-schooling. “I am home-schooling my 10-year-old,” one mother told researchers in a recent study of pandemic dreams. “I dreamed that the school contacted me to say it had been decided that his whole class would come to my home and I was supposed to teach all of them for however long the school remained closed.” Deirdre Barrett, a psychologist at Harvard Medical School and the author of “Pandemic Dreams,” has administered dream surveys to thousands of people in the last year, including the one with the home-schooling mother. “At least qualitatively, you see some shifts in content of dreams from the beginning of the pandemic into the later months,” Dr. Barrett said. “It’s an indication of what is worrying people most at various points during the year.” Dr. Barrett is the editor in chief of the journal Dreaming, which in its September issue posted four new reports on how the sleeping brain has incorporated the threat of Covid-19. The findings reinforce current thinking about the way that waking anxiety plays out during REM sleep: in images or metaphors representing the most urgent worries, whether these involve catching the coronavirus (those clouds of insects) or violating mask-wearing protocols. Taken together, the papers also hint at an answer to a larger question: What is the purpose of dreaming, if any? The answers that science has on offer can seem mutually exclusive, or near so. Freud understood dreams as wish fulfillment; the Finnish psychologist Antti Revonsuo saw them as simulations of pending threats. In recent years, brain scientists have argued that REM sleep — the period of sleep during which most dreaming occurs — bolsters creative thinking, learning and emotional health, providing a kind of unconscious psychotherapy. Then again, there is some evidence that dreaming serves little or no psychological purpose — that it is no more than a “tuning of the mind in preparation for awareness,” as Dr. J. Allan Hobson, a Harvard psychiatrist, has said. © 2020 The New York Times Company
By Veronique Greenwood Hummingbirds live a life of extremes. The flitting creatures famously have the fastest metabolisms among vertebrates, and to fuel their zippy lifestyle, they sometimes drink their own body weight in nectar each day. But the hummingbirds of the Andes in South America take that extreme lifestyle a step further. Not only must they work even harder to hover at altitude, but during chilly nights, they save energy by going into exceptionally deep torpor, a physiological state similar to hibernation in which their body temperature falls by as much as 50 degrees Fahrenheit. Then, as dawn approaches, they start to shiver, sending their temperatures rocketing back up to 96 degrees. It’s an intense process, says Andrew McKechnie, a professor of zoology at the University of Pretoria in South Africa. “You’ve got a bird perching on a branch, whose body temp might be 20 degrees Celsius,” or 68 Fahrenheit, he said. “And it’s cranking out the same amount of heat as when it is hovering in front of a flower.” Now, Dr. McKechnie and colleagues reported on Wednesday in Biology Letters that the body temperatures of Andean hummingbirds in torpor and the amount of time they spend in this suspended animation vary among species, with one particular set of species, particularly numerous in the Andes, tending to get colder and go longer than others. They also report one of the lowest body temperatures ever seen in hummingbirds: just under 38 degrees Fahrenheit. On a trip to the Andes about five years ago, Blair Wolf, a professor of biology at the University of New Mexico and an author of the new paper, and his colleagues captured 26 of the little birds for overnight observation. They measured the hummingbirds’ body temperatures as they roosted for the night and found that almost all of them entered torpor, showing a steep decline in temperature partway through the night. © 2020 The New York Times Company
Keyword: Sleep; Miscellaneous
Link ID: 27463 - Posted: 09.09.2020
MICHELLE STARR In many parts of the world, people collectively reset their clocks twice a year. Depending on the season, clocks are either wound an hour forwards, or an hour backwards - a practice designed to maximise the overlap between our waking hours and the available daylight. Now, members of the American Academy of Sleep Medicine (AASM) Public Safety Team and Board of Directors have published an advisory calling for the practice of daylight saving to be abolished. "Daylight saving time is less aligned with human circadian biology - which, due to the impacts of the delayed natural light/dark cycle on human activity, could result in circadian misalignment, which has been associated in some studies with increased cardiovascular disease risk, metabolic syndrome and other health risks," they write in the Journal of Clinical Sleep Medicine. "It is, therefore, the position of AASM that these seasonal time changes should be abolished in favour of a fixed, national, year-round standard time." Their paper is focused on the US, citing health statistics connected with the changing of the clocks in spring - from standard time to daylight saving time. This is when the clocks are wound back an hour, so that everyone loses an hour, usually from their sleep schedule. Ostensibly, the major economic reason for daylight saving time (DST) is to reduce energy usage, an effect that has been found to result in savings from 0.5 to 1 percent to a potential energy use increase in some areas as dependence on home heating and cooling rises.
Keyword: Biological Rhythms; Sleep
Link ID: 27458 - Posted: 09.07.2020
By Charlotte Hartley “I was at home and that scary red monster thing from that stupid Looney Tunes show was hanging around,” reads the dream diary of Izzy, a teenage girl. “There were lots of them trying to get in and I was scared to death.” Like many people, Izzy dreams about strange characters in unlikely situations. But according to a new study, in which researchers analyzed thousands of dreams with an automated tool, Izzy’s dream is probably just an expression of her adolescent anxieties—a funhouse reflection of her everyday experiences. The researchers say the tool, which identifies and quantifies the characters, interactions, and emotions of dreams, could help psychologists quickly identify potential stressors and mental health issues among their patients. Throughout history, people have tried to extract hidden meaning from dreams. Ancient Babylonians believed dreams contained prophecies, whereas ancient Egyptians revered them as messages from the gods. In the 1890s, Sigmund Freud assigned symbolic meanings to dream characters, objects, and scenarios—with an emphasis on sex and aggression. Today, however, most psychologists support the “continuity hypothesis,” which posits that dreams are a continuation of what happens in waking life. Indeed, numerous studies have shown that dreams often reflect day-to-day activities and can act as a sort of nocturnal therapist, helping people process experiences and prepare for real-life problems. “If we can understand our dreams better at scale, then maybe we can also tailor technologies that improve our waking life,” says Luca Maria Aiello, a computational social scientist at Nokia Bell Labs and co-author of the study. © 2020 American Association for the Advancement of Science
Keyword: Sleep
Link ID: 27434 - Posted: 08.26.2020
By Gretchen Reynolds People who are evening types go to bed later and wake up later than morning types. They also tend to move around far less throughout the day, according to an interesting new study of how our innate body clocks may be linked to our physical activity habits. The study, one of the first to objectively track daily movements of a large sample of early birds and night owls, suggests that knowing our chronotype might be important for our health. In recent years, a wealth of new science has begun explicating the complex roles of cellular clocks and chronotypes in our health and lifestyles. Thanks to this research, we know that each of us contains a master internal body clock, located in our brains, that tracks and absorbs outside clues, such as ambient light, to determine what time it is and how our bodies should react. This master clock directs the rhythmic release of hormones, such as melatonin, and other chemicals that affect sleep, wakefulness, hunger and many other physiological systems. Responding in part to these biochemical signals, as well as our genetic inclinations and other factors, we each develop a chronotype, which is our overall biological response to the daily passage of time. Chronotypes are often categorized into one of three groups: morning, day or night. Someone with a morning chronotype will naturally wake early; feel most alert and probably hungry in the morning; and be ready for bed before Colbert comes on. Day types tend to wake a bit later and experience peak alertness a few hours deeper into the day. And evening types rise as late as possible and remain vampirically wakeful well past dark. Our chronotypes are not immutable, though. Research shows that they have a yearslong rhythm of their own, with most people harboring a morning or day chronotype when young, an evening version during adolescence and young adulthood, and a return to a day or morning type by middle age. But some people remain night owls lifelong. Our shifting chronotypes are known to affect our health, especially if someone is an evening type. In past studies, people identified as evening types were more likely to develop heart disease, obesity, diabetes and other metabolic conditions than people with other chronotypes. They also tended to exercise less and sit far more, which some researchers suspect contributes to their risks for health problems. © 2020 The New York Times Company
Keyword: Sleep
Link ID: 27425 - Posted: 08.18.2020
By Helen Macdonald I found a dead common swift once, a husk of a bird under a bridge over the River Thames, where sunlight from the water cast bright scribbles on the arches above. I picked it up, held it in my palm, saw the dust in its feathers, its wings crossed like dull blades, its eyes tightly closed, and realized that I didn’t know what to do. This was a surprise. Encouraged by books, I’d always been the type of Gothic amateur naturalist who preserved interesting bits of the dead. I cleaned and polished fox skulls; disarticulated, dried and kept the wings of roadkill birds. But I knew, looking at the swift, that I could not do anything like that to it. The bird was suffused with a kind of seriousness very akin to holiness. I didn’t want to leave it there, so I took it home, swaddled it in a towel and tucked it in the freezer. It was in early May the next year, as soon as I saw the first returning swifts flowing down from the clouds, that I knew what I had to do. I went to the freezer, took out the swift and buried it in the garden one hand’s-width deep in earth newly warmed by the sun. Swifts are magical in the manner of all things that exist just a little beyond understanding. Once they were called the “Devil’s bird,” perhaps because those screaming flocks of black crosses around churches seemed pulled from darkness, not light. But to me, they are creatures of the upper air, and of their nature unintelligible, which makes them more akin to angels. Unlike all other birds I knew as a child, they never descended to the ground. When I was young, I was frustrated that there was no way for me to know them better. They were so fast that it was impossible to focus on their facial expressions or watch them preen through binoculars. They were only ever flickering silhouettes at 30, 40, 50 miles an hour, a shoal of birds, a pouring sheaf of identical black grains against bright clouds. There was no way to tell one bird from another, nor to watch them do anything other than move from place to place, although sometimes, if the swifts were flying low over rooftops, I’d see one open its mouth, and that was truly uncanny, because the gape was huge, turning the bird into something uncomfortably like a miniature basking shark. Even so, watching them with the naked eye was rewarding in how it revealed the dynamism of what before was merely blankness. Swifts weigh about 1½ ounces, and their surfing and tacking against the pressures of oncoming air make visible the movings of the atmosphere. © 2020 The New York Times Company
Keyword: Sleep; Evolution
Link ID: 27391 - Posted: 07.29.2020
By Baland Jalal Imagine waking up in the middle of the night to an unearthly figure with blood dripping down its fangs. You try to scream, but you can’t. You can’t move a single muscle! If this sounds familiar, you’ve probably experienced an episode of sleep paralysis, which involves the inability to move or speak upon falling asleep or awakening and is often coupled with hallucinations. About one in five people have had sleep paralysis at least once. But despite its prevalence, it has largely remained a mystery. For centuries, cultures across the world have attributed these hallucinations to black magic, mythical monsters, even paranormal activity. Scientists have since dismissed such explanations, yet these cultural beliefs persist. In fact, my and my colleagues’ research, conducted over roughly a decade in six different countries, suggests that beliefs about sleep paralysis can dramatically shape the physical and psychological experience, revealing a striking type of mind-body interaction. Sleep paralysis is caused by what appears to be a basic brain glitch at the interface between wakefulness and rapid eye movement (REM) sleep. During REM, you have intensely lifelike dreams. To prevent you from acting out these realistic dreams (and hurting yourself!), your brain has a clever solution: it temporarily paralyzes your entire body. Indeed, your brain has a “switch” (a handful of neurochemicals) that tilts you between sleep and wakefulness. Sometimes the “switch” fails, however—your brain inadvertently wakes up while your body is still under the “spell” of REM paralysis, leaving you stuck in a paradoxical state between parallel realities: wakefulness and REM sleep. During sleep paralysis, the crisp dreams of REM “spill over” into waking consciousness like a dream coming alive before your eyes—fanged figures and all. © 2020 Scientific American
Keyword: Sleep
Link ID: 27367 - Posted: 07.16.2020
By Nicholas Bakalar Artificial outdoor light at night may disrupt adolescents’ sleep and raise the risk for psychiatric disorders, a new study suggests. Researchers tracked the intensity of outdoor light in representative urban and rural areas across the country using satellite data from the National Oceanic and Atmospheric Administration. They interviewed more than 10,123 adolescents living in these neighborhoods about their sleep patterns, and assessed mental disorders using well-validated structured scales. They also interviewed the parents of more than 6,000 of the teenagers about their children. The study, in JAMA Psychiatry, found that the more intense the lighting in your neighborhood, the more sleep was disrupted and the greater the risk for depression and anxiety. After adjustment for other factors such as sex, race, parental education and population density, they found that compared with the teenagers in the one-quarter of neighborhoods with the lowest levels of outdoor light, those in the highest went to bed, on average, 29 minutes later and reported 11 fewer minutes of sleep. Adolescents living in the most intensely lit neighborhoods had a 19 percent increased risk for bipolar illness, and a 7 percent increased risk for depression. The study is observational, and does not prove cause and effect. The senior author, Kathleen R. Merikangas, a senior investigator with the National Institute of Mental Health, said that future policy changes could make a difference. In the meantime, she said, “At least as individuals, we ought to try to minimize exposure to light at night.” © 2020 The New York Times Company
Keyword: Sleep; Biological Rhythms
Link ID: 27362 - Posted: 07.15.2020
By Anna Goldfarb It’s understandable that you may be struggling to fall asleep these days. Our world has been turned upside down, so it is especially hard to unplug from the day and get the high-quality sleep your body needs. “Almost every single patient I’m speaking with has insomnia,“ said Dr. Alon Y. Avidan, a professor and vice chair in the department of neurology at the David Geffen School of Medicine at the University of California, Los Angeles, and director of the U.C.L.A. Sleep Disorders Center. “Especially now with Covid-19, we have an epidemic of insomnia. We call it Covid-somnia.” An increase in anxiety in both children and adults is affecting our ability to fall asleep. Additionally, our lifestyles have changed drastically as people observe sheltering in place guidelines. With more people staying indoors, it can mean they are not getting enough light exposure. “Without light exposure in the morning,” Dr. Avidan said, people “lose the circadian cues that are so fundamentally important in setting up appropriate and normal sleep-wake time.” There are nonmedical ways to help you sleep better: Meditation, turning off screens early in the night, warm showers and cool bedrooms can help your body rest better. But if these options don’t work, or if you are ready for the next step, you may have considered trying melatonin supplements. These pills are commonplace enough that you have most likely heard of them and seen them in your local pharmacy. Here’s what you need to know about the pros and cons of using melatonin supplements for sleeping difficulties. What is melatonin? Melatonin is a hormone that helps regulate sleep timing. It is produced in the pea-size pineal gland, which is nestled in the middle of your brain and syncs melatonin production with the rising and setting of the sun. According to the National Sleep Foundation, the gland remains inactive during the day but switches on around 9 p.m. (when it’s generally dark) to flood the brain with melatonin for the next 12 hours. © 2020 The New York Times Company
Keyword: Sleep; Biological Rhythms
Link ID: 27360 - Posted: 07.14.2020
Research shows that adolescents who live in areas that have high levels of artificial light at night tend to get less sleep and are more likely to have a mood disorder relative to teens who live in areas with low levels of night-time light. The research was funded by the National Institute of Mental Health (NIMH), part of the National Institutes of Health, and is published in JAMA Psychiatry. “These findings illustrate the importance of joint consideration of both broader environmental-level and individual-level exposures in mental health and sleep research,” says study author Diana Paksarian, Ph.D., a postdoctoral research fellow at NIMH. Daily rhythms, including the circadian rhythms that drive our sleep-wake cycles, are thought to be important factors that contribute to physical and mental health. The presence of artificial light at night can disrupt these rhythms, altering the light-dark cycle that influences hormonal, cellular, and other biological processes. Researchers have investigated associations among indoor artificial light, daily rhythms, and mental health, but the impact of outdoor artificial light has received relatively little attention, especially in teens. In this study, Paksarian, Kathleen Merikangas, Ph.D., senior investigator and chief of the Genetic Epidemiology Research Branch at NIMH, and coauthors examined data from a nationally representative sample of adolescents in the United States, which was collected from 2001 to 2004 as part of the National Comorbidity Survey Adolescent Supplement (NCS-A). The dataset included information about individual-level and neighborhood-level characteristics, mental health outcomes, and sleep patterns for a total of 10,123 teens, ages 13 to 18 years old.
Keyword: Biological Rhythms; Depression
Link ID: 27348 - Posted: 07.08.2020
By Richard Sandomir Dr. William Dement, whose introduction to the mysteries of slumber as a postgraduate student in the 1950s led him to become an eminent researcher of sleep disorders and to preach the benefits of a good night’s sleep, died on June 17 in Stanford, Calif. He was 91. His son, Nick, a physician, said the cause was complications of a heart procedure. Dr. Dement spent his working life as a popular professor in the department of psychiatry at Stanford University, where he started what is believed to be the world’s first successful sleep disorders clinic. He taught a class on sleep and dreams that drew as many as 1,200 students. When he awakened dozing students with spritzes from a water gun, Dr. Dement gave them extra credit if they recovered and shouted, “Drowsiness is red alert!” — his rallying cry to make sleep deprivation a public health priority. Drowsiness was the last step before falling asleep, he often said. Sleep deprivation put people at a higher risk of an accident on the road, diminished their productivity, increased the likelihood of their making mistakes, made them irritable and actually hurt their ability to fall asleep. “Bill Dement was an evangelist about sleep,” Dr. Rafael Pelayo, a Stanford psychiatry professor who succeeded Dr. Dement in leading the sleep class, said in a phone interview. “He felt that not enough people knew about sleep disorders, and he thought of his students as multipliers who would tell the world about them.” Dr. Dement’s expertise led to his appointment as chairman of a federal commission on sleep disorders. The commission reported in 1992 that 40 million Americans had undiagnosed, untreated, mistreated or chronic sleep problems — findings that led Congress to establish the National Center on Sleep Disorders Research, within the National Institutes of Health, in 1993. When Dr. Dement testified on Capitol Hill five years later about the sleep center’s progress, he said he was pleased with its research but disappointed that the government had not sounded loud enough alarms about the serious, sometimes fatal, consequences of unhealthful sleep. © 2020 The New York Times Company
Keyword: Sleep
Link ID: 27333 - Posted: 06.29.2020
Kerry Grens William Dement, whose research and leadership were integral to the expansion of sleep science and medicine in the 20th century, died June 17 at age 91. He made fundamental contributions to understanding the phases of sleep and the array of sleep disorders people experience. In 1970, he launched one of the first sleep disorders clinic in the world. “William Dement was a force of nature. A pioneering researcher and clinician, and a legendary teacher, his passion to uncover sleep’s secrets and to share these discoveries was unquenchable,” Lloyd Minor, the dean of Stanford University School of Medicine, where Dement was a faculty member for half a century, says in a university obituary. “Not only did he make great contributions to Stanford, but his efforts directly led to the birth and development of the field of sleep medicine.” Dement was born in Wenatchee, Washington, in 1928. He served in the US Army in Japan and earned his bachelor’s degree from the University of Washington. At the University of Chicago, where he received a PhD and an MD, Dement worked with Nathaniel Kleitman to describe the physiology of rapid eye movement (REM) sleep and its relationship to dreaming. “The groundbreaking research and use of polysomnography by Kleitman, [Eugene] Aserinsky, and Dement in the U.S., and by Michel Jouvet in France, laid the foundation for the fields of sleep and circadian science and clinical sleep medicine,” according to a memoriam by the American Academy of Sleep Medicine (AASM), the first professional organization for sleep disorders that Dement helped launch in 1975. © 1986–2020 The Scientist.
Keyword: Sleep
Link ID: 27322 - Posted: 06.26.2020
by Laura Dattaro Children with autism are more likely than typical children to have had problems falling asleep as infants, according to a new study1. These infants also have more growth in the hippocampus, the brain’s memory hub, from age 6 to 24 months. The study is the first to link sleep problems to altered brain development in infants later diagnosed with autism. Sleep difficulties are common in autistic children: Nearly 80 percent of autistic preschoolers have trouble sleeping2. But little is known about the interplay between sleep and brain development in early life, says lead investigator Annette Estes, director of the UW Autism Center at the University of Washington in Seattle. The researchers examined the sleep patterns and brain scans of infants who have autistic older siblings, a group known as ‘baby sibs.’ Baby sibs are 20 times as likely to be diagnosed with autism as are children in the general population, and they often show signs of autism early in life. The study shows an association between sleep problems and brain structure in babies who have autism. But it is too early to say whether sleep troubles contribute to brain changes and autism traits or vice versa, or whether some common factor underlies all three, Estes says. It is also not clear what, if any, connection exists between these findings and the well-documented sleep problems in older autistic children. © 2020 Simons Foundation
By Simon Makin on June 15, 2020 A well-worn science-fiction trope imagines space travelers going into suspended animation as they head into deep space. Closer to reality are actual efforts to slow biological processes to a fraction of their normal rate by replacing blood with ice-cold saline to prevent cell death in severe trauma. But saline transfusions or other exotic measures are not ideal for ratcheting down a body’s metabolism because they risk damaging tissue. Coaxing an animal into low-power mode on its own is a better solution. For some animals, natural states of lowered body temperature are commonplace. Hibernation is the obvious example. When bears, bats or other animals hibernate, they experience multiple bouts of a low-metabolism state called torpor for days at a time, punctuated by occasional periods of higher arousal. Mice enter a state known as daily torpor, lasting only hours, to conserve energy when food is scarce. The mechanisms that control torpor and other hypothermic states—in which body temperatures drop below 37 degrees Celsius—are largely unknown. Two independent studies published in Nature on Thursday identify neurons that induce such states in mice when they are stimulated. The work paves the way toward understanding how these conditions are initiated and controlled. It could also ultimately help find methods for inducing hypothermic states in humans that will prove useful in medical settings. And more speculatively, such methods might one day approximate the musings about suspended animation that turn up in the movies. One of the two studies was conducted by neuroscientist Takeshi Sakurai of the University of Tsukuba in Japan and his colleagues. It began with a paradoxical finding about a peptide called QRFP. The team showed that injecting it into animals actually increased their activity. But when the researchers switched on neurons that were making the peptide in mice, they got a surprise. “The mice stayed still and were very cold: the opposite to what they expected,” says Genshiro Sunagawa, of the RIKEN Center for Biosystems Dynamics Research in Japan, who co-led the study. The animals’ metabolic rate (measured by oxygen consumption), body temperature, heart rate and respiration all dropped. © 2020 Scientific American,
Keyword: Sleep
Link ID: 27307 - Posted: 06.17.2020
Ruth Williams Research teams in the US and Japan have each discovered independently and by unrelated routes a population of hypothalamic neurons in mice that induce the low body temperature, reduced metabolism, and inactivity characteristic of hibernation and torpor. The two papers are published today (June 11) in Nature. “Trying to pin down which neurons are involved with initiating torpor and hibernation . . . is certainly something that biologists have been interested in for several years now,” says biologist Steven Swoap of Williams College who was not involved in the research. “Both of [the teams] come at it from a different angle and almost end up in the same place, so they complement each other in that way, which is pretty nice,” he adds. Hibernation and daily torpor are both forms of mammalian suspended animation and share a number of features. Both involve significant, but regulated, drops in body temperature, metabolism, heart rate, breathing rate, and activity, and both are thought to be ways of preserving energy when food is scarce. While hibernation lasts for weeks or months, however, daily torpor lasts several hours each day. Why some mammals such as bears and certain primates and rodents have the ability to enter periods of dormancy while others don’t is unknown. But the diversity of hibernator species suggests that the biological mechanisms controlling such states may also be preserved, albeit unused, in non-hibernating species. This tantalizing possibility sparks ideas of sending dormant astronauts on extended space journeys as well as more down-to-earth notions of temporarily lowering body temperature and metabolism to preserve tissues in patients with, for example, traumatic injuries. © 1986–2020 The Scientist.
Keyword: Sleep
Link ID: 27300 - Posted: 06.13.2020
Ruth Williams In the hippocampus of the adult mouse brain, newly formed cells that become activated by a learning experience are later reactivated in the REM phase of sleep, according to a study in Neuron today (June 4). The authors show this reactivation is necessary for fortifying the encoding of the memory. “It is a very cool paper,” writes neuroscientist Sheena Josselyn of the University of Toronto in an email to The Scientist. “This is the first study to causally link new neurons to sleep-dependent memory consolidation. I am sure it will have a broad impact on scientists studying memory, sleep as well as those interested in adult neurogenesis,” she says. Josselyn was not involved in the study. In the adult mammalian brain, most cells do not replicate. But, deep in the center of the organ, in a particular region of the hippocampus called the dentate gyrus, new neurons continue to be born at a slow rate throughout the lifetime of the animal. This neurogenesis is thought to be important for memory formation among other cognitive tasks. Indeed, if the activities of mouse adult-born neurons (ABNs) are perturbed during a learning experience, the animal will not memorize the event as effectively as it does when these cells are left alone. Learning is just one part of forming a memory, however. For memories to last, sleep, and in particular REM sleep, is essential. “Sleep deprivation generally decreases neurogenesis,” writes neuroscientist Masanori Sakaguchi of the International Institute for Integrative Sleep Medicine at the University of Tsukuba in an email to The Scientist. The question was, says Sakaguchi, “is there any function of adult-born neurons during sleep?” To find out, Sakaguchi’s team first examined the activity of mouse ABNs after a learning experience—a contextual fear conditioning in which the animals’ feet were shocked as they explored a particular cage—and during subsequent sleep. Using miniaturized microscopes attached to the skulls of freely moving mice and fluorescent markers to track ABN activities, the team showed that the ABNs that had been activated after the context-shock learning event were more likely to then be reactivated during the animals’ next REM phases of sleep. © 1986–2020 The Scientist
Keyword: Neurogenesis; Sleep
Link ID: 27298 - Posted: 06.10.2020
By Lisa Sanders, M.D. “I know what Danny has,” said the boy’s aunt to the boy’s mother, her sister-in-law. Her voice on the phone cracked with excitement. “I saw someone just like him on TV!” This was last fall, and Danny was 18. He had been a medical mystery since he was 7 months old. His mother recalled that she had just finished changing his diaper and picked him up when she heard him make a strange clicking noise, his mouth opening and closing oddly. And then his head flopped back as she held him. She hurried to the living room of their Queens home to show her husband, but by the time she got there, Danny was fine. Those sudden episodes of clicking and collapse happened again and again, eventually occurring more than 100 times a day. His first doctors thought these episodes could be tiny seizures. But none of the antiseizure medications they prescribed helped. Then, when Danny was 8, and almost too big for his mother to catch when he slow-motion slumped to the floor, his parents found a doctor who was willing to explore a different diagnosis and treatment. Could this be a rare disease known as cataplexy? In this disorder, patients have episodes of sudden weakness in the skeletal muscles of the body. In some, cataplexy may affect only the face or neck, causing the eyelids to droop or the head to fall forward. But in others, it can also affect the entire body. These episodes are often triggered by strong emotion, which was the case for Danny. Cataplexy is usually part of another rare disorder, narcolepsy, in which the normal control of sleep and wakefulness is somehow lost. Those with narcolepsy have sudden episodes of sleep that invade their waking hours and transient periods of wakefulness that disrupt their sleep. © 2020 The New York Times Company