Chapter 10. Biological Rhythms and Sleep

Follow us on Facebook or subscribe to our mailing list, to receive news updates. Learn more.


Links 1 - 20 of 1833

By Elissa Welle A new study suggests that the brain clears less waste during sleep and under anesthesia than while in other states—directly contradicting prior results that suggest sleep initiates that process. The findings are stirring fresh debate on social media and elsewhere over the glymphatic system hypothesis, which contends that convective flow of cerebrospinal fluid clears the sleeping brain of toxins. The new work, published 13 May in Nature Neuroscience, proposes that fluid diffusion is responsible for moving waste throughout the brain. It uses a different method than the earlier studies—injecting tracers into mouse brain tissue instead of cerebrospinal fluid—which is likely a more reliable way to understand how the fluid moves through densely packed neurons, says Jason Rihel, professor of behavioral genetics at University College London, who was not involved in any of the studies on brain clearance. The findings have prompted some sleep researchers, including Rihel, to question the existence of a glymphatic system and whether brain clearance is tied to sleep-wake states, he says. But leading proponents of the sleep-induced clearance theory are pushing back against the study’s techniques. The new study is “misleading” and “extremely poorly done,” says Maiken Nedergaard, professor of neurology at the University of Rochester Medical Center, whose 2013 study on brain clearance led to the hypothesis of a glymphatic system. She says she plans to challenge the work in a proposed Matters Arising commentary for Nature Neuroscience. Inserting needles into the brain damages the tissue, and injecting fluid, as the team behind the new work did, increases intracranial pressure, says Jonathan Kipnis, professor of pathology and immunology at Washington University School of Medicine in St. Louis. Kipnis and his colleagues published a study in February in support of the glymphatic system hypothesis that suggests neural activity facilitates brain clearance. “You disturb the system when you inject into the brain,” Kipnis says, “and that’s why we were always injecting in the CSF.” © 2024 Simons Foundation

Keyword: Sleep
Link ID: 29327 - Posted: 05.25.2024

By Carl Zimmer Earlier this month, millions of Americans looked up at the sky to witness a total eclipse. Now, another cyclical marvel has arrived, this time at our feet. Trillions of noisy, red-eyed insects called cicadas are emerging from the earth after more than a decade of feeding on tree roots. The United States is home to 15 cicada broods, and in most years at least one of them emerges. This spring, Brood XIX, known as the Great Southern Brood, and Brood XIII, or the Northern Illinois Brood, are emerging simultaneously. Cicada watchers have spotted the first insects coming out of the ground, reporting their sightings to apps such as iNaturalist and Cicada Safari. The Great Southern Brood, which emerges across the South and the Midwest every 13 years, has been seen at sites scattered from North Carolina to Georgia. The Northern Illinois Brood, which appears every 17 years in the Midwest, is expected to appear in the next month, as temperatures there warm. How cicadas manage to rise en masse after spending so long underground remains largely a mystery. “There’s surprisingly little information about cicadas that you’d like to know,” said Raymond Goldstein, a physicist at the University of Cambridge. Once a brood climbs out of the ground, the cicadas crawl up trees to mate, and the females lay eggs in tree branches. After hatching, the young insects drop to earth and burrow into the soil. Then, each cicada spends the next 13 or 17 years underground before emerging to mate and repeat the cycle. That means that trillions of insects have to track the passage of time in the soil. It’s possible that they detect annual changes in tree roots. But how can cicadas add up those changes to divine when 13 or 17 years have passed? Scientists cannot say. © 2024 The New York Times Company

Keyword: Biological Rhythms
Link ID: 29272 - Posted: 04.26.2024

Kimberly Rosvall Liz Aguilar The total solar eclipse on April 8, 2024, coincides with an exciting time for wild birds. Local birds are singing for mates and fighting for territories as they gear up for their once-a-year chance to breed. Tens of millions of migrating birds will be passing through the path of totality, and they mostly migrate at night. Because birds use light to match their behaviors to their environment, scientists like us have lots of questions about how they will respond to the eclipse. Will they pause their fighting and wooing and shift toward bedtime-like behaviors? How about a nocturnal animal like an owl or those nighttime migrants – will they start to rustle from their roosts before they realize it’s not night? As behavioral biologists at Indiana University, we research wild breeding birds, with a goal of understanding why animals behave the way that they do in response to environmental challenges and opportunities. For the 2024 eclipse, our team is launching a new project and developing an app. If everything goes as planned, we should end up with a large dataset after the eclipse, collected by community scientist volunteers across the country. On average, a total solar eclipse occurs in the same place only once every 375 years. Most wild animals, like most people, have never seen the sky quickly switch to night in the middle of the day. These rare events are a natural experiment that can help scientists like us understand how animals respond to an unusual sudden change in light. Most past research on animal behavior during total solar eclipses is anecdotal. Observers have reported that zoo animals acted distressed or went into their enclosures. Scientists have spotted spiders starting the nightly deconstruction of their webs in the middle of the day, and farmers have heard their roosters start to crow after totality, as if it’s once again dawn. Other reports suggest more subtle effects on animal behavior. © 2010–2024, The Conversation US, Inc.

Keyword: Biological Rhythms; Vision
Link ID: 29246 - Posted: 04.06.2024

By Erin Blakemore More than three-quarters of sudden infant deaths involved multiple unsafe sleep practices, including co-sleeping, a recent analysis suggests. A study published in the journal Pediatrics looked at 7,595 sudden infant death cases in a Centers for Disease Control and Prevention registry between 2011 and 2020. The majority of deaths occurred in babies less than 3 months old. The statistics revealed that 59.5 percent of the infants who died suddenly were sharing a sleep surface at the time of death, and 75.9 percent were in an adult bed when they died. Though some demographic factors such as sex and length of gestation were not clinically significant, the researchers found that the babies sharing a sleep surface were more likely to be Black and publicly insured than those who didn’t share sleep surfaces. Soft bedding was common among all the infants who died, and 76 percent of the cases involved multiple unsafe practices. The analysis mirrors known risk factors for sudden infant death. Current recommendations direct parents and other caretakers to provide infants with firm, flat, level sleep surfaces that contain nothing but a fitted sheet. Though room sharing reduces the risk of sudden infant death, CDC officials discourage parents from sharing a sleep surface with their child. Exposure to cigarette smoke during pregnancy was more common among infants who shared surfaces when they died. Though most infants were supervised by an adult when they died, the supervisor was more likely to be impaired by drug and alcohol use among those who shared a sleeping surface.

Keyword: Sleep
Link ID: 29230 - Posted: 04.02.2024

By Charles Digges My default mode for writing term papers during my student days was the all-night slog, and I recall the giddy, slap-happy feeling that would steal over me as the sun rose. There was a quality of alert focus that came with it, as well as a gregariousness that would fuel bonding sessions with my other all-night companions. After we’d turned in the products of our midnight oil to our professors, we would all head out for pancakes. Then I’d go home and sleep the magic off. For years, I’d wondered if there was any basis for this temporary euphoria that I—though certainly not all my classmates—experienced after those sleepless nights. That I should feel so expansive and goofy after skipping sleep while many of them turned into drowsy grouches seemed to defy logic. Going without sleep isn’t supposed to be a good thing, especially for folks who experience depression, as I have. But it turns out this paradox has been the subject of inquiry for at least two centuries. In 1818, University of Leipzig psychiatrist Johann Christian August Heinroth was reportedly the first to suggest that partial or total sleep deprivation could be temporarily effective against “melancholia,” as depression was called in those days. He found this to be true only in a certain subset of patients—around 60 percent. More than a hundred years later, in the 1970s, evidence emerged that a “resynchronization” of disturbed circadian rhythms could be responsible for the improved moods of depressed patients after a night without sleep. And more recently, researchers have found that a neurotransmitter involved in reward known as dopamine may play a role in this effect, as may neuroplasticity—the nervous system’s ability to rearrange itself in response to stimuli. But the precise neural mechanisms responsible have remained unclear. © 2024 NautilusNext Inc.,

Keyword: Sleep; Depression
Link ID: 29220 - Posted: 03.28.2024

Ian Sample Science editor Two nights of broken sleep are enough to make people feel years older, according to researchers, who said consistent, restful slumber was a key factor in helping to stave off feeling one’s true age. Psychologists in Sweden found that, on average, volunteers felt more than four years older when they were restricted to only four hours of sleep for two consecutive nights, with some claiming the sleepiness made them feel decades older. The opposite was seen when people were allowed to stay in bed for nine hours, though the effect was more modest, with participants in the study claiming to feel on average three months younger than their real age after ample rest. “Sleep has a major impact on how old you feel and it’s not only your long-term sleep patterns,” said Dr Leonie Balter, a psychoneuroimmunologist at the Karolinska Institute in Stockholm and first author on the study. “Even when you only sleep less for two nights that has a real impact on how you feel.” Beyond simply feeling more decrepit, the perception of being many years older may affect people’s health, Balter said, by encouraging unhealthy eating, reducing physical exercise, and making people less willing to socialise and engage in new experiences. The researchers ran two studies. In the first, 429 people aged 18 to 70 answered questions about how old they felt and on how many nights, if any, they had slept badly in the past month. Their sleepiness was also rated according to a standard scale used in psychology research. For each day of poor sleep the volunteers felt on average three months older, the scientists found, while those who reported no bad nights in the preceding month felt on average nearly six years younger than their true age. It was unclear, however, whether bad sleep made people feel older or vice versa. © 2024 Guardian News & Media Limited

Keyword: Sleep
Link ID: 29219 - Posted: 03.28.2024

By Maria Popova I once dreamed a kiss that hadn’t yet happened. I dreamed the angle at which our heads tilted, the fit of my fingers behind her ear, the exact pressure exerted on the lips by this transfer of trust and tenderness. Freud, who catalyzed the study of dreams with his foundational 1899 treatise, would have discounted this as a mere chimera of the wishful unconscious. But what we have since discovered about the mind — particularly about the dream-rich sleep state of rapid-eye movement, or REM, unknown in Freud’s day — suggests another possibility for the adaptive function of these parallel lives in the night. One cold morning not long after the kiss dream, I watched a young night heron sleep on a naked branch over the pond in Brooklyn Bridge Park, head folded into chest, and found myself wondering whether birds dream. The recognition that nonhuman animals dream dates at least as far back as the days of Aristotle, who watched a sleeping dog bark and deemed it unambiguous evidence of mental life. But by the time Descartes catalyzed the Enlightenment in the 17th century, he had reduced other animals to mere automatons, tainting centuries of science with the assumption that anything unlike us is inherently inferior. In the 19th century, when the German naturalist Ludwig Edinger performed the first anatomical studies of the bird brain and discovered the absence of a neocortex — the more evolutionarily nascent outer layer of the brain, responsible for complex cognition and creative problem-solving — he dismissed birds as little more than Cartesian puppets of reflex. This view was reinforced in the 20th century by the deviation, led by B.F. Skinner and his pigeons, into behaviorism — a school of thought that considered behavior a Rube Goldberg machine of stimulus and response governed by reflex, disregarding interior mental states and emotional response. © 2024 The New York Times Company

Keyword: Sleep; Evolution
Link ID: 29216 - Posted: 03.26.2024

By Meghan Bartels No matter how much trouble your pet gets into when they’re awake, few sights are as peaceful as a dog curled up in their bed or a cat stretched out in the sun, snoring away. But their experience of sleep can feel impenetrable. What fills the dreams of a dog or cat? That’s a tricky question to answer. Snowball isn’t keeping a dream journal, and there’s no technology yet that can translate the brain activity of even a sleeping human into a secondhand experience of their dream world, much less a sleeping animal. “No one has done research on the content of animals’ dreams,” says Deirdre Barrett, a dream researcher at Harvard University and author of the book The Committee of Sleep. But Rover’s dreamscape isn’t entirely impenetrable, at least to educated guesses. First of all, Barrett says, only your furrier friends appear to dream. Fish, for example, don’t seem to display rapid eye movement (REM), the phase of sleep during which dreams are most common in humans. “I think it’s a really good guess that they don’t have dreams in the sense of anything like the cognitive activity that we call dreams,” she says. Whether birds experience REM sleep is less clear, Barrett says. And some marine mammals always keep one side of their brain awake even while the other sleeps, with no or very strange REM sleep involved. That means seals and dolphins likely don’t dream in anything like the way humans do. But the mammals we keep as pets are solidly REM sleepers. “I think it’s a very safe, strong guess that they are having some kind of cognitive brain activity that is as much like our dreams as their waking perceptions are like ours,” she says. That doesn’t mean that cats and dogs experience humanlike dreams. “It would be a mistake to assume that other animals dream in the same way that we do, just in their nonhuman minds and bodies,” says David Peña-Guzmán, a philosopher at San Francisco State University and author of the book When Animals Dream. For example, humans rarely report scents when recounting dreams; however, we should expect dogs to dream in smells, he says, given that olfaction is so central to their waking experience of the world. © 2024 SCIENTIFIC AMERICAN

Keyword: Sleep; Consciousness
Link ID: 29176 - Posted: 03.05.2024

By Jackie Rocheleau Every day about 60,000 people have surgery under general anesthesia in the United States. Often casually compared to falling into a deep sleep, going under is in fact wildly different from your everyday nocturnal slumber. Not only does a person lose the ability to feel pain, form memories, or move—they can’t simply be nudged back into conscious awareness. But occasionally, people do wake unexpectedly—in about 1 out of every 1,000 to 2,000 surgeries, patients emerge from the fog of anesthesia into the harsh light of the operating room while still under the knife. One question that has dogged researchers over the past several decades is whether women are more likely to find themselves in these unfortunate circumstances. A number of recent studies, including a 2023 meta-analysis, suggest that the answer is yes. But the findings are controversial: Other studies have found no differences in waking frequency between the sexes and most of the studies were not designed specifically to identify sex differences. It’s also difficult to know whether other factors might have influenced the results: rates of metabolization of drugs by male and female bodies, as well as variation in kinds of surgeries and anesthetic regimens among study participants. No causal link had been established. Now, a new study published in the Proceedings of the National Academy of Sciences helps untangle some of the mystery. In a series of experiments in mice and in humans, the researchers found that females do wake more easily from anesthesia and that testosterone plays an important role in how quickly and deeply we go under, and how easily we wake up. “There seems to be something hardwired into the female brain that biases it more toward a state of wakefulness,” says University of Pennsylvania anesthesiologist Max Kelz, co-author of the study. © 2024 NautilusNext Inc., All rights reserved.

Keyword: Sexual Behavior; Sleep
Link ID: 29156 - Posted: 02.22.2024

By Carolyn Todd Any sleep tracker will show you that slumber is far from a passive affair. And no stage of sleep demonstrates that better than rapid eye movement, or REM, commonly called dream sleep. “It’s also called paradoxical sleep or active sleep, because REM sleep is actually very close to being awake,” said Dr. Rajkumar Dasgupta, a sleep medicine and pulmonary specialist at the Keck School of Medicine of the University of Southern California. Before scientists discovered REM sleep in the 1950s, it wasn’t clear that much of anything was happening in the brain at night. Researchers today, however, understand sleep as a highly active process composed of very different types of rest — including REM, which in some ways doesn’t seem like rest at all. While the body typically remains “off” during REM sleep, the brain is very much “on.” It’s generating vivid dreams, as well as synthesizing memories and knowledge. Scientists are still working to unravel exactly how this strange state of consciousness works. “It is fair to say that there is a lot left to learn about REM sleep,” Dr. Dasgupta said. But from what researchers do understand, REM is critical to our emotional health and brain function — and potentially even our longevity. Where does REM sleep fall in the sleep cycle? Throughout the night, “We’re going in and out of this rhythmic, symphonic pattern of the various stages of sleep: non-REM 1, 2, 3 and REM,” said Rebecca Robbins, an instructor in medicine at Harvard Medical School and an associate scientist in the division of sleep and circadian disorders at Brigham and Women’s Hospital. © 2024 The New York Times Company

Keyword: Sleep; Neuroimmunology
Link ID: 29128 - Posted: 02.03.2024

Ashley Montgomery In December 1963, a military family named the Gardners had just moved to San Diego, Calif. The oldest son, 17-year-old Randy Gardner, was a self-proclaimed "science nerd." His family had moved every two years, and in every town they lived in, Gardner made sure to enter the science fair. He was determined to make a splash in the 10th Annual Greater San Diego Science Fair. When researching potential topics, Gardner heard about a radio deejay in Honolulu, Hawaii, who avoided sleep for 260 hours. So Gardner and his two friends, Bruce McAllister and Joe Marciano, set out to beat this record. Randy Gardner spoke to NPR's Hidden Brain host Shankar Vedantam in 2017. When asked about his interest in breaking a sleep deprivation record, Gardner said, "I'm a very determined person, and when I get things under my craw, I can't let it go until there's some kind of a solution." Of his scientific trio, Randy lost the coin toss: He would be the test subject who would deprive himself of sleep. His two friends would take turns monitoring his mental and physical reaction times as well as making sure Gardner didn't fall asleep. The experiment began during their school's winter break on Dec. 28, 1963. Three days into sleeplessness, Gardner said, he experienced nausea and had trouble remembering things. Speaking to NPR in 2017, Gardner said: "I was really nauseous. And this went on for just about the entire rest of the experiment. And it just kept going downhill. I mean, it was crazy where you couldn't remember things. It was almost like an early Alzheimer's thing brought on by lack of sleep." But Gardner stayed awake. The experiment gained the attention of local reporters, which, in Gardner's opinion, was good for the experiment "because that kept me awake," he said. "You know, you're dealing with these people and their cameras and their questions." The news made its way to Stanford, Calif., where a young Stanford sleep researcher named William C. Dement was so intrigued that he drove to San Diego to meet Gardner. © 2024 npr

Keyword: Sleep
Link ID: 29120 - Posted: 01.31.2024

By Christian Guay & Emery Brown What does it mean to be conscious? People have been thinking and writing about this question for millennia. Yet many things about the conscious mind remain a mystery, including how to measure and assess it. What is a unit of consciousness? Are there different levels of consciousness? What happens to consciousness during sleep, coma and general anesthesia? As anesthesiologists, we think about these questions often. We make a promise to patients every day that they will be disconnected from the outside world and their inner thoughts during surgery, retain no memories of the experience and feel no pain. In this way, general anesthesia has enabled tremendous medical advances, from microscopic vascular repairs to solid organ transplants. In addition to their tremendous impact on clinical care, anesthetics have emerged as powerful scientific tools to probe questions about consciousness. They allow us to induce profound and reversible changes in conscious states—and study brain responses during these transitions. But one of the challenges that anesthesiologists face is measuring the transition from one state to another. That’s because many of the approaches that exist interrupt or disrupt what we are trying to study. Essentially, assessing the system affects the system. In studies of human consciousness, determining whether someone is conscious can arouse the person being studied—confounding that very assessment. To address this challenge, we adapted a simple approach we call the breathe-squeeze method. It offers us a way to study changes in conscious state without interrupting those shifts. To understand this approach, it helps to consider some insights from studies of consciousness that have used anesthetics. For decades researchers have used electroencephalography (EEG) to observe electrical activity in the brains of people receiving various anesthetics. They can then analyze that activity with EEG readings to characterize patterns that are specific to various anesthetics, so-called anesthetic signatures. © 2024 SCIENTIFIC AMERICAN

Keyword: Consciousness; Sleep
Link ID: 29116 - Posted: 01.27.2024

By Sara Reardon Lustful male marsupials sacrifice their sleep for weeks to make more time for mating1. The antechinus, an Australian marsupial roughly the size of a gerbil, is a rare example of a mammal that mates during a certain season and never again. Roughly every August, male antechinus enter a three-week breeding frenzy in which they mate with every female they can and then die en masse. “It’s very short, very intense,” says zoologist Erika Zaid at La Trobe University in Melbourne, Australia. Males generally live for only one year; females can live for at least a year longer and produce more than one litter. To find out how males make enough time for sex in their short lives, Zaid and her colleagues trapped ten male and five female dusky antechinus (Antechinus swainsonii) and kept them in separate enclosures so they couldn’t mate. They attached activity monitors to the animals’ collars and collected blood samples to measure biomarkers. The researchers found that captive males, but not females, moved around much more and slept less during breeding season than they did the rest of the year. On average, the males’ sleep time per day was around 20% lower during the breeding season than during the non-breeding season ― and one male’s sleep time per day was more than 50% lower. At the end of breeding season, two of the males died within a few hours of one another. The other eight became sterile. To determine whether sleep loss occurs in the wild, Zaid and her colleagues trapped 38 animals from a related species called agile antechinus (A. agilis) before and during breeding season and measured the animals’ oxalic acid, a chemical in the blood whose levels drop when an animal is short on sleep. Males’ oxalic acid levels fell sharply during the breeding season. Unlike the captive females, wild females showed drops as well, suggesting that males were waking them up for shenanigans. Mysterious death © 2024 Springer Nature Limited

Keyword: Sleep; Sexual Behavior
Link ID: 29113 - Posted: 01.27.2024

By Lauren Peace Tampa Bay Times Nina Shand couldn’t stay awake. She had taken afternoon naps since she was a teenager to accommodate her “work hard, play hard” attitude, but when she was in her mid-20s the sleepiness became more severe. Menial computer tasks put her to sleep, and a 20-minute drive across her city, St. Petersburg, Florida, brought on a drowsiness so intense that her eyelids would flutter, forcing her to pull over. She knew something was really wrong when she no longer felt safe behind the wheel. In 2021, she received a diagnosis: narcolepsy, a rare disorder that causes excessive daytime sleepiness. Her doctor prescribed her Adderall, the brand-name version of the amphetamine-powered medication commonly known for treating attention-deficit/hyperactivity disorder. It worked. For the first time in years, Shand, now 28, felt energized. She was no longer struggling at work, sneaking naps, or downing coffees to trick her body into staying awake. She felt hope. But by 2022, a national Adderall shortage meant pharmacies were no longer able to fill her prescription. Shand and countless others across the country were being turned away, left to piece together a new — and often less effective — treatment plan with doctors scrambling to meet their needs. More than a year later, the shortage continues. In October, Democrats in the U.S. House of Representatives implored the FDA and Drug Enforcement Administration to work with drug manufacturers to ensure better supply. “We cannot allow this to be the continuing reality for Americans,” read their letter, led by Rep. Abigail Spanberger (D-Va.). But for now, it is.

Keyword: Sleep; Drug Abuse
Link ID: 29102 - Posted: 01.16.2024

By Laura Sanders In this busy holiday season, many of us multitask. Arctic reindeer are no exception. Reindeer can eat and sleep at the same time, a new study suggests. This timesaving strategy, described December 22 in Current Biology, adds to the number of ingenious ways animals can catch some z’s under tough conditions (SN: 11/30/23). Arctic reindeer are quite busy in the summer — eating when the sun shines around the clock and the food is abundant. Like other ruminants, reindeer spend a considerable amount of time chewing on regurgitated food, making it smaller and easier to digest. Finding time to sleep amid all this cud chewing might be tough. But not if the reindeer could sleep while they chewed. To find out if the reindeer could actually sleep-eat, neuroscientist Melanie Furrer and chronobiologist Sara Meier, along with their colleagues, trained four female Eurasian tundra reindeer (Rangifer tarandus tarandus) to tolerate a pen and electrodes on shaved patches of skin. The process involved some kicks and lots of lichen treats, “which is like candy to them,” says Meier, of the University of Zurich. The researchers were looking for the brain waves that appear during non-REM sleep, a deep, restorative sleep phase. These waves appeared when the reindeer were chewing cud, though the chewing motion itself made it hard to say whether the signal was identical to that of a regular sleep session. “We couldn’t go into detail by looking only at the brain waves, because we have this chewing in there that disturbs it a bit,” says Furrer, also of the University of Zurich. Still, other signs also pointed to sleep while chewing. The reindeer were calm while chewing, often with their eyes closed. “They were in a very relaxed state that resembles the body position of non-REM sleep,” Furrer says. Ruminating reindeer were also harder to disturb; rustling from neighboring reindeer was less likely to get a look from a ruminating reindeer. When reindeer are kept awake, they need catch-up recovery sleep. But time spent chewing decreased this time spent in recovery sleep, the researchers found. © Society for Science & the Public 2000–2023.

Keyword: Sleep; Attention
Link ID: 29072 - Posted: 12.31.2023

By Elise Cutts On a summer night in the Bay of Naples, hordes of worms swam upward from the seagrass toward the water’s surface under the light of a waning moon. Not long before, the creatures began a gruesome sexual metamorphosis: Their digestive systems withered, and their swimming muscles grew, while their bodies filled with eggs or sperm. The finger-length creatures, now little more than muscular bags of sex cells, fluttered to the surface in unison and, over a few hours, circled each other in a frantic nuptial dance. They released countless eggs and sperm into the bay — and then the moonlit waltz ended in the worms’ deaths. The marine bristle worm Platynereis dumerilii gets only one chance to mate, so its final dance had better not be a solo. To ensure that many worms congregate at the same time, the species synchronizes its reproductive timing with the cycles of the moon. How can an undersea worm tell when the moon is at its brightest? Evolution’s answer is a precise celestial clock wound by a molecule that can sense moonbeams and sync the worms’ reproductive lives to lunar phases. No one had ever seen how one of these moonlight molecules worked. Recently, however, in a study published in Nature Communications, researchers in Germany determined the different structures that one such protein in bristle worms takes in darkness and in sunlight. They also uncovered biochemical details that help explain how the protein distinguishes between brighter sunbeams and softer moonglow. It’s the first time that scientists have determined the molecular structure of any protein responsible for syncing a biological clock to the phases of the moon. “I’m not aware of another system that has been looked at with this degree of sophistication,” said the biochemist Brian Crane of Cornell University, who was not involved in the new study. © 2023 An editorially independent publication supported by the Simons Foundation.

Keyword: Biological Rhythms; Evolution
Link ID: 29062 - Posted: 12.22.2023

By Carl Zimmer Neanderthals were morning people, a new study suggests. And some humans today who like getting up early might credit genes they inherited from their Neanderthal ancestors. The new study compared DNA in living humans with genetic material retrieved from Neanderthal fossils. It turns out that Neanderthals carried some of the same clock-related genetic variants as do people who report being early risers. Since the 1990s, studies of Neanderthal DNA have exposed our species’ intertwined history. About 700,000 years ago, our lineages split apart, most likely in Africa. While the ancestors of modern humans largely stayed in Africa, the Neanderthal lineage migrated into Eurasia. About 400,000 years ago, the population split in two. The hominins who spread west became Neanderthals. Their cousins to the east evolved into a group known as Denisovans. The two groups lived for hundreds of thousands of years, hunting game and gathering plants, before disappearing from the fossil record about 40,000 years ago. By then, modern humans had expanded out of Africa, sometimes interbreeding with Neanderthals and Denisovans. And today, fragments of their DNA can be found in most living humans. Research carried out over the past few years by John Capra, a geneticist at the University of California, San Francisco, and other scientists suggested that some of those genes passed on a survival advantage. Immune genes inherited from Neanderthals and Denisovans, for example, might have protected them from new pathogens they had not encountered in Africa. Dr. Capra and his colleagues were intrigued to find that some of the genes from Neanderthals and Denisovans that became more common over generations were related to sleep. For their new study, published in the journal Genome Biology and Evolution, they investigated how these genes might have influenced the daily rhythms of the extinct hominins. © 2023 The New York Times Company

Keyword: Biological Rhythms; Evolution
Link ID: 29052 - Posted: 12.16.2023

Maria Godoy What do you do when you can't get your kids to settle down to go to sleep? For a growing number of parents, the answer is melatonin. Recent research shows nearly one in five school-age children and adolescents are now using the supplement on a regular basis. Pediatricians say that's cause for alarm. "It is terrifying to me that this amount of an unregulated product is being utilized," says Dr. Cora Collette Breuner, a professor of pediatrics at the University of Washington. Melatonin is a hormone produced by your brain that helps regulate sleep-wake cycles. It's also sold as a dietary supplement and is widely used as a sleep aid. Sponsor Message Lauren Hartstein, a postdoctoral researcher who studies sleep in early childhood at the University of Colorado, Boulder, says she first got an inkling of melatonin's growing use in children and adolescents while screening families to participate in research. "All of a sudden last year, we noticed that there was a big uptick in the number of parents who were regularly giving [their kids] melatonin," Hartstein says. Hartstein and her colleagues wanted to learn more about just how widely melatonin is being used in kids. So they surveyed the parents of nearly 1,000 children between the ages of 1 to 14 across the country. She was surprised by just how many kids are taking the supplement. "Nearly 6% of preschoolers, [ages] 1 to 4, had taken it, and that number jumped significantly higher to 18% and 19% for school-age children and pre-teens," she says. As Hartstein and her co-authors recently reported in the journal JAMA Pediatrics, most of the kids that were using melatonin had been on it for a year or longer. And 1 in 4 kids were taking it every single night. © 2023 npr

Keyword: Biological Rhythms; Sleep
Link ID: 29047 - Posted: 12.16.2023

By Roberta McLain Dreams have fascinated people for millennia, yet we struggle to understand their purpose. Some theories suggest dreams help us deal with emotions, solve problems or manage hidden desires. Others postulate that they clean up brain waste, make memories stronger or deduce the meaning of random brain activity. A more recent theory suggests nighttime dreams protect visual areas of the brain from being co-opted during sleep by other sensory functions, such as hearing or touch. David Eagleman, a neuroscientist at Stanford University, has proposed the idea that dreaming is necessary to safeguard the visual cortex—the part of the brain responsible for processing vision. Eagleman’s theory takes into account that the human brain is highly adaptive, with certain areas able to take on new tasks, an ability called neuroplasticity. He argues that neurons compete for survival. The brain, Eagleman explains, distributes its resources by “implementing a do-or-die competition” for brain territory in which sensory areas “gain or lose neural territory when inputs slow, stop or shift.” Experiences over a lifetime reshape the map of the brain. “Just like neighboring nations, neurons stake out their territory and chronically defend them,” he says. Eagleman points to children who have had half their brain removed because of severe health problems and then regain normal function. The remaining brain reorganizes itself and takes over the roles of the missing sections. Similarly, people who lose sight or hearing show heightened sensitivity in the remaining senses because the region of the brain normally used by the lost sense is taken over by other senses. Reorganization can happen fast. Studies published in 2007 and 2008 by Lotfi Merabet of Harvard Medical School and his colleagues showed just how quickly this takeover can happen. The 2008 study, in which subjects were blindfolded, revealed that the seizing of an idle area by other senses begins in as little as 90 minutes. And other studies found that this can occur within 45 minutes. When we sleep, we can smell, hear and feel, but visual information is absent—except during REM sleep. © 2023 SCIENTIFIC AMERICAN,

Keyword: Sleep; Vision
Link ID: 29045 - Posted: 12.13.2023

Perspective by Michael Varnum and Ian Hohm A growing body of research in psychology and related fields suggests that winter brings some profound changes in how people think, feel and behave. The natural and cultural changes that come with winter often occur simultaneously, making it challenging to tease apart the causes underlying these seasonal swings. Live well every day with tips and guidance on food, fitness and mental health, delivered to your inbox every Thursday. We recently conducted an extensive survey of these findings with research colleagues Alexandra Wormley, a social psychologist at Arizona State University, and Mark Schaller, a psychologist at the University of British Columbia. Wintertime blues and a long winter’s nap Do you find yourself feeling down in the winter months? You’re not alone. As the days grow shorter, the American Psychiatric Association estimates that about 5 percent of Americans will experience a form of depression known as seasonal affective disorder, or SAD. People experiencing SAD tend to have feelings of hopelessness, decreased motivation to take part in activities they generally enjoy, and lethargy. Even those who don’t meet the clinical threshold for this disorder may see increases in anxiety and depressive symptoms. Scientists link SAD and more general increases in depression in the winter to decreased exposure to sunlight, which leads to lower levels of the neurotransmitter serotonin. Consistent with the idea that sunlight plays a key role, SAD tends to be more common in more northern regions of the world, such as Scandinavia and Alaska, where the days are shortest and the winters longest. Humans, special as we may be, are not unique in showing some of these seasonally linked changes. For instance, our primate relative the Rhesus macaque shows seasonal declines in mood.

Keyword: Biological Rhythms; Depression
Link ID: 29043 - Posted: 12.13.2023