Chapter 14. Biological Rhythms, Sleep, and Dreaming

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By Eric A. Taub Like clockwork, the sound of the freight train came roaring through our bedroom in the middle of each night. Or at least what sounded like a freight train. In reality, it was me, snoring. And according to my wife, that freight train had gotten considerably louder over the years. Unfortunately, snoring frequency and volume is exacerbated by age, among other factors. While there’s nothing I can do about getting older, there are products and procedures available that can eliminate or significantly reduce the annoyance to one’s bed partner caused by all that nighttime snorting and wheezing. Snoring and sleep apnea are not the same, although severe snoring can be an indication of apnea. If sleep apnea is not present, snoring is simply the benign result of an obstructed airway. As we age, the uvula — that soft, floppy, fingerlike projection in the back of the throat — gets softer and floppier. At the same time, muscles under the tongue get lax. And the condition is exacerbated if we are overweight or drink too much alcohol. “With age, the muscle tone of our airways decreases. That decreased tone allows the tissues to move more readily and become more prone to collapse and to vibrate,” said Dr. Michael D. Olson, an ear, nose and throat doctor and sleep surgeon in the Mayo Clinic’s department of head and neck surgery. In addition, if the size of the airway decreases, air pressure increases, allowing for tissue vibration and snoring. “Combine that with nasal congestion, a big tongue and body fat, and that leads to an excessive collapse of the airways,” Dr. Olson said. Another cause of snoring: teeth extraction, a particular issue for baby boomers who had braces in their youth. With the removal of four bicuspids as a common practice at the time, boomers may now be suffering snoring because of a larger tongue in a smaller mouth. © 2019 The New York Times Company

Keyword: Sleep
Link ID: 26731 - Posted: 10.22.2019

Emma Yasinski Delta waves, patterns of slow, synchronized brain activity that occur during deep sleep, have long been considered “periods of silence,” in which neurons in the cortex stop firing. But these intervals may not be silent after all, researchers reported yesterday in Science. In rats, some cortical neurons remain active during delta waves, and their firing may even be involved in consolidating memories. “The paper is absolutely fascinating and will have a large impact on the field of memory and sleep,” says Björn Rasch, a biopsychologist at the University of Fribourg in Switzerland who was not involved in the study. He suggests it might even help explain surprising results in his own research in humans published earlier this year that indicated participants may better remember words from a foreign language if they are replayed during delta wave sleep than if they are never repeated during sleep. The latest study “challenges our views on the potential function of down states [when cortical neurons seem silent] in memory consolidation processes.” When humans (and rats) are awake, a brain structure called the hippocampus records the ongoing episodes of our lives. When we sleep, the hippocampus replays this activity, which is transmitted to the cortex where it forms long-term memories. Afterward, the cortex seems to go silent. This quiet delta wave period is known to be important for memory consolidation, but researchers have wondered how it helps the process. © 1986–2019 The Scientist.

Keyword: Sleep; Learning & Memory
Link ID: 26730 - Posted: 10.22.2019

By Karen Weintraub We all wish we could get by on less sleep, but one father and son actually can—without suffering any health consequences and while actually performing on memory tests as well as, or better than, most people. To understand this rare ability, researchers at the University of California, San Francisco, first identified a genetic mutation—in both individuals—that they thought might deserve the credit. Then the scientists intentionally made the same small genetic spelling mistake in mice. The mice also needed less sleep, remembered better and suffered no other ill effects, according to a study published today in Science Translational Medicine. Although a medication with the same benefits will not be available anytime soon—and might never materialize—the idea is incredibly appealing: take a pill that replicates whatever the father and son’s body does and sleep less, with no negative repercussions. “I find the concept of a gene product that might potentially provide protection against comorbid disorders of restricted sleep tantalizing,” says Patrick Fuller, an associate professor of neurology at Harvard Medical School and Beth Israel Deaconess Medical Center in Boston, who was not involved with the work. “If true, this would indeed have ‘potential therapeutic implications,’ as well as provide another point of entry for exploring and answering the question ‘Why do we sleep?’ which remains [one] of the greatest mysteries in neuroscience.” © 2019 Scientific American

Keyword: Sleep; Genes & Behavior
Link ID: 26710 - Posted: 10.17.2019

By Emily Willingham Most of us could use more sleep. We feel it in our urge for an extra cup of coffee and in a slipping cognitive grasp as a busy day grinds on. And sleep has been strongly tied to our thinking, sharpening it when we get enough and blunting it when we get too little. What produces these effects are familiar to neuroscientists: external light and dark signals that help set our daily, or circadian, rhythms, “clock” genes that act as internal timekeepers, and neurons that signal to one another through connections called synapses. But how these factors interact to freshen a brain once we do sleep has remained enigmatic. Findings published on October 10 in two papers in Science place synapses at center stage. These nodes of neuronal communication, researchers show, are where internal preparations for sleep and the effects of our sleep-related behaviors converge. Cellular timekeepers rhythmically prep areas around the synapses in anticipation of building synaptic proteins during slumber. But the new findings indicate neurons don’t end up building these critical proteins in the absence of sleep. Advertisement The results suggest the brain is “getting prepared for an event, but it doesn’t mean you actually follow through on doing it,” says Robert Greene, a neuroscientist at the University of Texas Southwestern Medical Center, who was not involved in the study. Greene calls the studies “fascinating,” saying they confirm a “long suspected” connection between internal timekeeping and sleep behaviors. © 2019 Scientific American

Keyword: Sleep
Link ID: 26695 - Posted: 10.11.2019

By Elizabeth Preston Heidi the octopus is sleeping. Her body is still, eight arms tucked neatly away. But her skin is restless. She turns from ghostly white to yellow, flashes deep red, then goes mottled green and bumpy like plant life. Her muscles clench and relax, sending a tendril of arm loose. From the outside, the cephalopod looks like a person twitching and muttering during a dream, or like a napping dog chasing dream-squirrels. “If she is dreaming, this is a dramatic moment,” David Scheel, an octopus researcher at Alaska Pacific University, said in the documentary. Heidi was living in a tank in his living room when her snooze was captured by the film crew, and he speculates that she is imagining catching and eating a crab. But an octopus is almost nothing like a person. So how much can anyone really say with accuracy about what Heidi was doing? When our two branches of the animal family tree diverged, backbones hadn’t been invented. Yet octopuses, cuttlefish and squid, on their own evolutionary path, developed impressive intelligence. They came up with their own way to build big brains. Much of an octopus’s brain is spread throughout its body, especially its arms. It makes sense to be cautious when we guess what’s going on in these animals’ minds. Looking at a behavior like Heidi’s is “a bit like going to a crime scene,” said Nicola Clayton, a psychologist at the University of Cambridge who studies comparative cognition. “You’ve got some evidence in front of you, but you’d need to know so much more to understand better what’s causing the behavior.” It’s only conjecture to say the octopus is dreaming without more data, she said. Does the sequence of Heidi’s color changes match an experience she had while awake? Dreaming in humans mostly happens during rapid-eye movement, or R.E.M., sleep. Could we observe something similar in octopuses? Dr. Clayton points out that a human sleeper might flush red because she’s overheated. © 2019 The New York Times Company

Keyword: Sleep; Evolution
Link ID: 26686 - Posted: 10.09.2019

By Nicholas Bakalar During pregnancy, sleeping on your back may be a bad idea. Previous studies have found that sleeping in a supine position causes compression of veins and arteries that can lead to a reduction in blood flow to the placenta severe enough to double the risk for stillbirth after 28 weeks of gestation. Now a new study, in JAMA Network Open, concludes that supine sleeping is also associated with low birth weight in full-term babies. Of 1,760 pregnant women in the analysis, 57 went to sleep lying on their backs. (The initial sleep position is the one maintained for the longest time during the night.) After controlling for age, body mass index, previous pregnancies, hypertension, diabetes and other factors, they found that compared with those sleeping in other positions, women who slept on their backs had babies who were three times as likely to be in the lowest 10th percentile for birth weight. “It’s a small number of pregnant women who go to sleep on their backs — only about 3 percent,” said the lead author, Dr. Ngaire H. Anderson, a senior lecturer in obstetrics and gynecology at the University of Auckland. “But we are keen to encourage the message that sleeping on one’s side is a way to optimize the baby’s health, both in reducing stillbirth and optimizing the baby’s growth.” © 2019 The New York Times Company

Keyword: Sleep; Development of the Brain
Link ID: 26677 - Posted: 10.08.2019

By Eva Frederick Yellow is usually the color of happy, joyful emotions. But according to a new study, not all people associate the sunshiney shade with good vibes. To find out what factors might play a role, researchers tested a new hypothesis: What if people’s physical surroundings affect their feelings about certain colors? For instance, if someone lived in cold and rainy Finland, would they feel differently about the color yellow from someone who lived near the Sahara Desert? The researchers looked at color-emotion data from an ongoing international survey of 6625 people in 55 countries. The survey asks participants to rate 12 colors on how closely they are associated with feelings including joy, pride, fear, and shame. Yellow is not so fun in the sun The darker the shade in the below map, the higher the likelihood of people associating the color yellow with joyful emotions. Overall, people were more likely to associate yellow with joy when they lived in rainier countries that lay farther from the equator, researchers report in the Journal of Environmental Psychology. © 2019 American Association for the Advancement of Science

Keyword: Emotions; Biological Rhythms
Link ID: 26675 - Posted: 10.07.2019

By Laura Sanders A sleeping rat may look peaceful. But inside its furry, still head, a war is raging. Two types of brain waves battle over whether the rat will remember new information, or forget it, researchers report October 3 in Cell. Details of this previously hidden clash may ultimately help explain how some memories get etched into the sleeping brain, while others are scrubbed clean. By distinguishing between these dueling brain waves, the new study helps reconcile some seemingly contradictory ideas, including how memories can be strengthened (SN: 6/5/14) and weakened during the same stage of sleep (SN: 6/23/11). “It will help unite the field of sleep and learning, because everyone gets to be right,” says neuroscientist Gina Poe of the University of California, Los Angeles, who wasn’t involved in the study. Researchers led by neuroscientist and neurologist Karunesh Ganguly of the University of California, San Francisco, have been teaching rats to control a mechanical water spout with nothing but their neural activity. The team soon realized that the rats’ success with these brain-computer interfaces depended heavily on something that came after the training: sleep. To study how the new learning was strengthened during snoozing, Ganguly and his team monitored the brains of sleeping rats after they practiced moving the spout. The scientists focused on brain waves that wash over the motor cortex, the part of the brain that was controlling the external water spout, during non-REM sleep. That stage of sleep usually makes up more than half of an adult human’s night. © Society for Science & the Public 2000–2019.

Keyword: Sleep; Learning & Memory
Link ID: 26672 - Posted: 10.04.2019

By Lisa Sanders, M.D. “I don’t know what’s going on,” the 19-year-old exclaimed in a panicked voice as his parents entered the nearly deserted emergency room of a hospital in Eau Claire, Wis. He was a freshman at the university there. A high school friend, now at the university with him, had called them with a strange story. She told them that their son had been uncharacteristically quiet for a couple of days — he had a terrible headache. But that morning, he felt well enough to go with her to pick apples. He had been a little out of it all morning, but suddenly he was totally gone — just standing in the orchard staring into space. He wouldn’t even respond to his name. That’s when she called his mother. Take him to the emergency room, the mother instructed. She and her husband drove 90 minutes from their home near Minneapolis to meet them. The doctors there had ordered tests but gotten no answers. A head CT scan was normal; so were the basic blood tests looking for signs of an electrolyte abnormality or infection. There was no evidence that drugs were involved. The young man had been there for a couple of hours, and he seemed a little more engaged. Though the doctors weren’t sure what was going on, they felt that he wasn’t in danger and said he could go home. But he is not O.K., the mother protested; he had no history of mental illness or drug use. The doctors replied that she should take him to his primary-care doctor in the next couple of days. The young man was quiet on the drive home. He couldn’t articulate how he felt. At home, he continued to act strange. He didn’t even recognize the family dog. © 2019 The New York Times Company

Keyword: Sleep
Link ID: 26668 - Posted: 10.03.2019

By Eva Frederick As the weather cools, one species of squirrel in the U.S. Midwest is gearing up for one of the most intense naps in the animal kingdom. For up to 8 months, the tiny mammals won’t eat or drink anything at all—and now scientists know how they do it. Most squirrels don’t hibernate—instead, they stash food for the cold season and spend the winter snug in their nests. Not the 13-lined ground squirrel (Ictidomys tridecemlineatus), whose heart rate, metabolism, and body temperature dramatically plummet during their long rest—similar to bears, woodchucks, and other hibernating animals. To find out how the squirrels suppress their thirst—a powerful force that could potentially wake them up—researchers measured the blood fluid, or serum, of dozens of squirrels, divided into three groups: those that were still active, those that were in a sleep-of-the-dead hibernation state called torpor, and those that were still hibernating, but in a drowsy in-between state. Generally, a high serum concentration makes animals, including humans, feel thirsty. The sleeping squirrels’ serum concentration was low, preventing them from waking up for a drink. Even when researchers roused the torpid squirrels, they wouldn’t drink a drop—until the team artificially increased the concentration of their blood serum. Next, the researchers wanted to know how the squirrels’ blood concentration dropped so low. Perhaps the squirrels drank a lot of water prehibernation to dilute their blood, the researchers thought. But when they filmed squirrels preparing for their winter snooze, they found the animals actually drank less water than they normally did. © 2019 American Association for the Advancement of Science

Keyword: Sleep
Link ID: 26661 - Posted: 10.02.2019

Patti Neighmond Many American teenagers try to put in a full day of school, homework, after-school activities, sports and college prep on too little sleep. As evidence grows that chronic sleep deprivation puts teens at risk for physical and mental health problems, there is increasing pressure on school districts around the country to consider a later start time. In Seattle, school and city officials recently made the shift. Beginning with the 2016-2017 school year, the district moved the official start times for middle and high schools nearly an hour later, from 7:50 a.m. to 8:45 a.m. This was no easy feat; it meant rescheduling extracurricular activities and bus routes. But the bottom line goal was met: Teenagers used the extra time to sleep in. Researchers at the University of Washington studied the high school students both before and after the start-time change. Their findings appear in a study published Wednesday in the journal Science Advances. They found students got 34 minutes more sleep on average with the later school start time. This boosted their total nightly sleep from 6 hours and 50 minutes to 7 hours and 24 minutes. "This study shows a significant improvement in the sleep duration of students, all by delaying school start times so they're more in line with the natural wake-up times of adolescents," says senior author Horacio de la Iglesia, a University of Washington researcher and professor of biology. The study also found an improvement in grades and a reduction in tardiness and absences.

Keyword: Biological Rhythms; Development of the Brain
Link ID: 26660 - Posted: 10.01.2019

By Natasha Singer CVS Health wants to help millions of American workers improve their sleep. So for the first time, the big pharmacy benefits manager is offering a purely digital therapy as a possible employee benefit. The company is encouraging employers to cover the costs for their workers to use Sleepio, an insomnia app featuring a cartoon therapist that delivers behavior modification lessons. CVS Health’s push could help mainstream the nascent business of digital therapeutics, which markets apps to help treat conditions like schizophrenia and multiple sclerosis. The company recently introduced, along with Sleepio, a way for employers to cover downloads as easily as they do prescription drugs. The company said it had already evaluated about a dozen apps. Some industry executives and researchers say the digital services should make therapy more accessible and affordable than in-person sessions with mental health professionals. Big Health, the start-up behind Sleepio, is one of more than a dozen companies that are digitizing well-established health treatments like cognitive behavioral therapy, or devising new therapies — like video-game-based treatments for children with attention deficit hyperactivity disorder — that can be delivered online. Since last year, a few pharmaceutical companies, including Novartis, announced partnerships with start-ups to develop digital treatments for mental health and other conditions. So far, the use of treatment apps has been limited. But with the backing of CVS Health, which administers prescription drug plans for nearly one-third of Americans, those therapies could quickly reach tens of millions of people. A few employers have started offering Sleepio, and more are expected to sign on this fall, CVS Health said. Like in-person therapy, the insomnia app does not require a prescription. © 2019 The New York Times Company

Keyword: Sleep
Link ID: 26655 - Posted: 09.28.2019

By Tina Hesman Saey Mice (and maybe people) may metabolize food according to daily, circadian rhythms set by gut bacteria. Microbes in the small intestine of mice rhythmically dictate when fat is taken up by cells that line the organ, researchers report. The study, described in the Sept. 27 Science, details how gut microbes influence a host’s metabolism. If the findings carry over to people, the research may give clues to why jet lag and night-shift work, which can throw off circadian rhythms, often lead to obesity, diabetes and other health problems. Researchers knew that human cells have molecular clocks that time 24-hour circadian cycles of metabolism (SN: 11/8/18), and that gut microbes in the colon follow their hosts’ biological beat (SN: 10/16/14). But the new study finds that, at least in the small intestine, microbes can set rhythms for host cells to follow. That work was done in mice, but the process may work similarly in people. The new research “is helping us appreciate just how intertwined are the metabolisms of the microbiota and their mammalian hosts,” says microbiologist and immunologist Andrew Gewirtz of Georgia State University in Atlanta who was not involved in the work. “It’s a very intimate interaction, regulating things as basic as circadian rhythms, which was quite a surprise.” © Society for Science & the Public 2000–2019.

Keyword: Biological Rhythms
Link ID: 26651 - Posted: 09.27.2019

By Rahma Ibrahim University researchers have discovered a new subset of cells — “metronome cells” — that may act as timekeepers in the brain, a finding that contributes new information to one of the biggest debates in neuroscience. While scientists have long known about the existence of cells in the brain that tend to be more reactive to stimuli — called fast spiking cells — they have long debated the function of a specific frequency of rhythm produced by those cells, called gamma oscillations. Some neuroscientists believe that gamma oscillations are at the root of how the brain functions. Other equally qualified scientists believe that these rhythms are merely a byproduct of brain activity. “Scientists’ faces will either light up or grow very overcast when someone mentions gamma oscillation,” explained Christopher Moore, professor of neuroscience and supervisor of the study. These gamma oscillations produce structured ripples in the brain at an interval of 40 Hertz, or 40 cycles per second. This regular pattern has led scientists to believe that perhaps the gamma oscillations act as an organizing clock, helping to align and connect information coming from different areas of the brain. Moore compared this theory to an orchestra; just as a conductor of an orchestra connects the various parts, the gamma oscillations have been thought to have similar function. If the conductor stops, then the whole orchestra cannot make good music. But for years, scientists have acknowledged limitations with this theory. Fast spiking cells and gamma rhythms have been found to respond to stimulus from outside the body of the cell. This raises concern if researchers assume that these oscillations act as a timekeeper; if the conductor is distracted every time they hear a trumpet, then the orchestra cannot be conducted.

Keyword: Sleep
Link ID: 26649 - Posted: 09.27.2019

By Veronique Greenwood When the land-dwelling ancestors of today’s whales and dolphins slipped into the seas long ago, they gained many things, including flippers, the ability to hold their breath for long periods of time and thick, tough skin. Along the way they also discarded many traits that were no longer relevant or useful. In fact, as scientists reported in a study published Wednesday in Science Advances, the loss of some genes in the common ancestor of whales and dolphins allowed them to shed features that would have been liabilities beneath the waves, which may have contributed to the survival of future generations. As more species’ genomes are sequenced, researchers can begin to pick out which genes are shared among groups of organisms. Presumably, these genes were also found in the group’s last common ancestor. A team led by Michael Hiller, a geneticist at the Max Planck Institute of Molecular Cell Biology and Genetics and an author of the new paper, used this technique with modern cetaceans, the group that includes whales, dolphins and porpoises. Then they compared that set of genes to those of the cetaceans’ nearest relatives, the hippo family, and pinpointed 85 genes that were switched off or inactivated in the cetaceans’ ancestor during its move to the aquatic life. These genes were involved in a wide variety of processes, such as blood clotting, sleep and hair growth. Although some of the genes had been flagged before, others had not been identified. (Dr. Hiller and colleagues had previously found that genes necessary for the development of hair had been lost in cetaceans, which perhaps reduced drag as the animals swam through the water.) “Many of the things we found were at least for me quite unexpected,” said Dr. Hiller. For instance, one of the lost genes produces an enzyme involved in DNA repair. © 2019 The New York Times Company

Keyword: Sleep; Evolution
Link ID: 26648 - Posted: 09.27.2019

By Nicholas Bakalar Sleep apnea may increase the risk for mood disorders, researchers have found. Obstructive sleep apnea, or O.S.A., is a sleep-related breathing disorder that has been linked to many other conditions, including cardiovascular disease, asthma exacerbation, glaucoma, erectile dysfunction and neurocognitive problems. For the new study, in JAMA Otolaryngology—Head & Neck Surgery, researchers enrolled 197 Korean men and women diagnosed with O.S.A. and 788 people without the syndrome matched for age, sex, and health and socioeconomic characteristics. None of the 985 participants had been diagnosed with depression, bipolar illness or an anxiety disorder before the start of the study. The researchers followed them for an average of nine years. Over the course of the study, people with O.S.A. were nearly three times as likely to be diagnosed with depression, and almost twice as likely to be diagnosed with anxiety as those in the control group. Women with O.S.A. were more likely than men to develop a mood disorder. The reason for the association is unknown. The researchers had no information about the use of positive airway pressure devices or oral appliances used to treat sleep apnea, so they could not determine whether treatment would reduce the risk. Still, they write, “studies that investigate O.S.A. management and the risk of developing affective disorders may yield strategies for effective prevention and intervention practices.” © 2019 The New York Times Company

Keyword: Sleep; Depression
Link ID: 26645 - Posted: 09.25.2019

Maryse Zeidler Frustration: that's the word Vancouverite Jacqueline Sinclair uses most often to describe her insomnia. There's the frustration of lying in bed, awake in the middle of the night, knowing how crappy she'll feel the next day. The frustration of struggling to relax as she lies awake. And the frustration of failing at what should be a basic life skill. "Knowing that the rest of the world is able to do something as simple as sleep ... it's frustrating," said Sinclair, 50, who works from home doing administration for the family's construction business. Sleep has eluded Sinclair for the past 10 years. As remedies, she has cut out caffeine, sugar and gluten. She has tried herbal teas, homeopathy and vitamins. CBD oil and prescription sleeping pills have been helpful, but they each had worrisome side effects. "I'm not sure what's next," she said. "I hope I go to bed tonight and sleep for six hours straight. Wouldn't that be fantastic?" Jacqueline Sinclair has struggled with insomnia for 10 years. She says she has tried several remedies, but none has worked effectively. (jacqueline sinclair) Dr. Ram Randhawa, a psychiatrist at the University of British Columbia's Sleep Disorders Program, says about 30 per cent of Canadians struggle with getting to or staying sleep at any given time. The prevalence of insomnia does seem to be higher among women, he said. For most people, sleep issues are a temporary problem brought on by stress or worry. For some, they can be a debilitating, life-long problem. ©2019 CBC/Radio-Canada

Keyword: Sleep
Link ID: 26634 - Posted: 09.23.2019

By Linda Searing Don’t feel guilty about sneaking in a nap now and then: It might be good for your heart. People who napped once or twice a week were 48 percent less likely than non-nappers to face serious cardiovascular problems — heart attack, stroke, heart failure — according to new research. The findings, published in the journal Heart, were based on nearly 3,500 adults, ages 35 to 75, who were tracked for about five years. How long people napped each time made no difference, and napping more frequently than a couple times a week did not improve the results. Sleep experts generally agree that a ­20-minute nap is all that most people need to feel refreshed and less stressed. Napping longer means waking from a deeper sleep and that can leave someone feeling groggy or fuzzy-headed. Napping late in the day also is not recommended because it can mar nighttime sleeping. The recommended amount of sleep for most adults is at least seven hours a night, with an hour or two more for people 61 and older. According to the Centers for Disease Control and Prevention, more than a third of Americans regularly get too little sleep. That can lead to chronic health problems, including diabetes, high blood pressure and heart disease, according to experts at Harvard Medical School’s Division of Sleep Medicine.

Keyword: Sleep
Link ID: 26633 - Posted: 09.23.2019

By Knvul Sheikh One afternoon in April 1929, a journalist from a Moscow newspaper turned up in Alexander Luria’s office with an unusual problem: He never forgot things. Dr. Luria, a neuropsychologist, proceeded to test the man, who later became known as subject S., by spouting long strings of numbers and words, foreign poems and scientific formulas, all of which S. recited back without fail. Decades later, S. still remembered the lists of numbers perfectly whenever Dr. Luria retested him. But S.’s ability to remember was also a hindrance in everyday life. He had a hard time understanding abstract concepts or figurative language, and he was terrible at recognizing faces because he had memorized them at an exact point in time, with specific facial expressions and features. The ability to forget, scientists eventually came to realize, was just as vital as the ability to remember. “We’re inundated with so much information every day, and much of that information is turned into memories in the brain,” said Ronald Davis, a neurobiologist at the Scripps Research Institute in Jupiter, Fla. “We simply cannot deal with all of it.” Researchers like Dr. Davis argue that forgetting is an active mechanism that the brain employs to clear out unnecessary pieces of information so we can retain new ones. Others have gone a step further, suggesting that forgetting is required for the mental flexibility inherent in creative thinking and imagination. A new paper, published Thursday in the journal Science, points to a group of neurons in the brain that may be responsible for helping the brain to forget. Akihiro Yamanaka, a neuroscientist at Nagoya University in Japan, and his team stumbled across the cells, known as melanin-concentrating hormone, or M.C.H., neurons, while studying sleep regulation in mice. Unlike most of the brain’s neurons, which are active when animals are awake, M.C.H. neurons in the hypothalamus start firing electrical signals most actively when a sleeping animal is in a stage called R.E.M. sleep. This phase of sleep is characterized by rapid eye movement, an elevated pulse, unique brain waves and, in humans, vivid dreams. When the researchers tracked M.C.H. signals in mice, they found that the cells were suppressing neurons in the hippocampus, a brain region known to play a role in the consolidation of memory. © 2019 The New York Times Company

Keyword: Sleep; Learning & Memory
Link ID: 26628 - Posted: 09.20.2019

Teen girls — but not boys — who prefer to go to bed later are more likely to gain weight, compared to same-age girls who go to bed earlier, suggests a study funded by the National Institutes of Health. The findings by researchers at Kaiser Permanente in Oakland, California, and other institutions appear in JAMA Pediatrics. A total of 804 adolescents (418 girls and 386 boys) ages 11 to 16 took part in the study. The children responded to questionnaires on their sleep habits and wore an actigraph — a wrist device that tracks movement. Researchers measured their waist size and calculated their proportion of body fat using a technique called dual-energy x-ray absorptiometry. They also estimated the children’s social jet lag — the difference between their weeknight and weekend bedtimes. Those who stayed up far later on weekends than weeknights were considered to have high social jet lag. The authors noted that previous studies had found that adults who preferred to stay up late and had high social jet lag were more likely to gain weight than those who went to be earlier and did not have social jet lag. The researchers undertook the current study to determine if the same associations would be seen in young people. For girls, staying up later was associated with an average .58 cm increase in waist size and a .16 kg/m2 increase in body fat. Each hour of social jet lag was associated with a 1.19 cm larger waste size and a 0.45 kg/m2 increase in body fat. These associations were reduced—but still remained—after the researchers statistically adjusted for other factors known to influence weight, such as sleep duration, diet, physical activity and television viewing. Although the researchers found slight associations between these measures and waist size and body fat in boys, they were not statistically significant. The researchers concluded that improving sleep schedules may be helpful in preventing obesity in childhood and adolescence, especially in girls.

Keyword: Obesity; Biological Rhythms
Link ID: 26618 - Posted: 09.17.2019