Chapter 14. Biological Rhythms, Sleep, and Dreaming
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Chris Samoray People in the postindustrial world don’t always get a sound night sleep. But they appear to spend a similar amount of time sleeping as do people in hunter-gatherer communities in Africa and South America, a new study finds. “It’s absolutely clear that they don’t sleep more than we do,” says Jerome Siegel, a UCLA sleep scientist. In fact, on average, hunter-gatherers may sleep a little less. Recommended nightly sleep for adults is typically seven to nine hours; a 2013 Gallup poll showed that most Americans get around 6.8 hours. On most nights, members of three hunter-gatherer groups — the Hadza of Tanzania, the Ju/’hoansi San of Namibia and the Tsimane of Bolivia — sleep 5.7 to 7.1 hours, Siegel and colleagues report online October 15 in Current Biology. That’s on the lower end of the sleep spectrum in postindustrial societies, the researchers say. Evidence from the new study also suggests that these groups experience less insomnia than sleepers in postindustrial societies. (The three hunter-gatherer languages even lack a word for insomnia.) Hunter-gatherer sleep patterns are closely tied to temperature, a new study shows. Among the Hadza of Tanzania, for instance, people fell asleep about three hours after sunset, on average, as ambient temperatures decreased. People then woke up about an hour before sunrise, when temperatures reached their lowest point. © Society for Science & the Public 2000 - 2015.
Link ID: 21520 - Posted: 10.16.2015
The month of your birth influences your risk of developing dementia. Although the effect is small compared to risk factors such as obesity, it may show how the first few months of life can affect cognitive health for decades to come. Demographers Gabriele Doblhammer and Thomas Fritze from the University of Rostock, Germany, studied data from the Allgemeine Ortskrankenkasse – Germany’s largest public health insurer – for nearly 150,000 people aged 65 and over. After adjusting for age, they found that those born in the three months from December to February had a 7 per cent lower risk of developing dementia than those born in June to August, with the risk for other months falling in between. There’s nothing astrological about the effect, however. Instead, birth month is a marker for environmental conditions such as weather and nutrition, says Gerard van den Berg, an economist at the University of Bristol, UK, who studies the effects of economic circumstances on health. Summer-born babies are younger when they face the respiratory infections of their first winter, for example. And in the past, babies born in spring and summer would have been in late gestation when the supply of fresh fruit and vegetables from the autumn harvest would have largely run out. Pollution from wood fires or coal heating might also have played a role. There’s evidence from other studies that such factors can have lifelong effects on metabolism and the immune system, increasing the risk of conditions such as diabetes, obesity and high blood pressure. Doblhammer and Fritze’s results show this is true for dementia too. © Copyright Reed Business Information Ltd.
by Sarah Schwartz People with multiple sclerosis who got less sun exposure and had higher body mass as young adults developed the disease sooner than those who spent more time in the sun and were a normal weight, a new study finds. In a study of over 1,100 Danish people with MS — a nervous system condition that causes muscle weakness and pain — patients who were overweight at age 20 developed multiple sclerosis an average of 1.5 years sooner than patients of normal weight. And subjects who reported spending time in the sun every summer’s day during adolescence developed the disease 1.8 years later, on average, than patients who got less sun exposure, Danish researchers report online October 7 in Neurology. The results echo earlier work that found a link between adolescent obesity and risk of MS. And sun exposure may increase patients’ levels of vitamin D, which has been shown to protect against the disease, the researchers say. © Society for Science & the Public 2000 - 2015
By Nicholas Bakalar There may be a link between later bedtimes and weight gain, new research suggests. Researchers studied 3,342 adolescents starting in 1996, following them through 2009. At three points over the years, all reported their normal bedtimes, as well as information on fast food consumption, exercise and television time. The scientists calculated body mass index at each interview. After controlling for age, sex, race, ethnicity and socioeconomic status, the researchers found that each hour later bedtime during the school or workweek was associated with about a two-point increase in B.M.I. The effect was apparent even among people who got a full eight hours of sleep, and neither TV time nor exercise contributed to the effect. But fast food consumption did. The study, in the October issue of Sleep, raises questions, said the lead author, Lauren D. Asarnow, a graduate student at the University of California, Berkeley. “First, what is driving this relationship?” she said. “Is it metabolic changes that happen when you stay up late? And second, if we change sleep patterns, can we change eating behavior and the course of weight change?” The scientists acknowledge that their study had limitations. Their sleep data depended on self-reports, and they did not have complete diet information. Also, they had no data on waist circumference, which, unlike B.M.I., can help distinguish between lean muscle and abdominal fat. © 2015 The New York Times Company
Archy de Berker and Sven Bestmann A great deal of excitement has been generated in recent weeks by a review paper examining the literature on the drug modafinil, which concluded that “modafinil may well deserve the title of the first well-validated pharmaceutical ‘nootropic’ [cognitive enhancing] agent”. Coverage in the Guardian, Telegraph, British Medical Journal, and the Independent all called attention to the work, with a press release from Oxford University trumpeting “Review of ‘smart drug’ shows modafinil does enhance cognition”. The paper in question is a well-written summary of the recent literature (although though it probably underestimates side effects, as pointed out in the British Medical Journal). A deeper problem is that reviews do not “show” anything. Reviews can be educational and informative, but that’s not the same as using all of the available data to test whether something works or not. Two different scientists can write reviews on the same topic and come to completely different conclusions. You can think of reviews as a watercolour painting of current knowledge. We sometimes forget that this is a far cry from a technical drawing, each element measured, quantified, and bearing a strict resemblance to reality. Scientists, and the public, trying to figure out what works face a tricky problem: there will often be many papers on a given topic, offering a variety of sometimes conflicting conclusions. Fortunately, we have a well-developed toolkit for assessing the state of the current literature and drawing conclusions from it. This procedure is called meta-analysis; it combines the available sources of data (e.g., published studies), and is extensively used to assess the efficacy of medical interventions. Initiatives such as the Cochrane Collaboration use meta-analyses to synthesize available evidence into a consensus on what works and what doesn’t. © 2015 Guardian News and Media Limited
Joe Palca Mothers have been warned for years that sleeping with their newborn infant is a bad idea because it increases the risk the baby might die unexpectedly during the night. But now Israeli researchers are reporting that even sleeping in the same room can have negative consequences: not for the child, but for the mother. Researchers at Ben-Gurion University of the Negev wanted to see whether sleeping in the same room as their newborn affected mothers' or babies' sleep. The short answer: It did, and the effect wasn't good for moms. The researchers recruited 153 married couples expecting their first child to participate in the study. The new parents weren't told where or how to sleep. They were simply asked to record whether they slept in the same room as their newborn, the same bed and same room, or if the child slept in another room. To measure sleep patterns, both mom and baby wore wristbands designed to measure movement during the night, a measurement that gives a pretty accurate indication of sleep patterns for both mother and child. The researchers measured sleep patterns before the babies were born, at 3 months and at 6 months. Mothers who slept in the same room as their infants, whether in the same bed or just the same room, had poorer sleep than mothers whose babies slept elsewhere in the house: They woke up more frequently (approximately three times per night versus two), were awake approximately 20 minutes longer per night, and had shorter periods of uninterrupted sleep (approximately 136 minutes versus 166 minutes). These results held true even taking into account that many of the women in the study were breast-feeding their babies. © 2015 NPR
Link ID: 21468 - Posted: 10.03.2015
Dark puffy eyes, a feeling of deep exhaustion, and a foul mood to match – we’ve all experienced the side effects of a lack of sleep. It’s no wonder that sleep-deprivation has been used as a method of torture. Our brains seem to lose the ability to distinguish between the innocuous and emotional in such circumstances, turning us into overreacting, exhausted wrecks. We all know that a good night’s sleep is vital for a day of clear thinking, but exactly why sleep is so important remains a mystery. Talma Hendler of Tel Aviv University in Israel is particularly interested in how lack of sleep leaves us with a short emotional fuse. “We know that sleep affects our emotional behaviour, but we don’t know how,” she says. To investigate further, Hendler and her colleagues kept 18 adults awake all night. “It took a great effort,” she says. “During the night, we repeatedly measured their sleepiness, and unsurprisingly they got more and more tired.” The volunteers were put through two rounds of tests while their brains were scanned, both the day after a good night’s sleep and after being awake for 24 hours. In one test, volunteers were asked to give the direction in which yellow dots moved on a screen. In each case, the dots were laid over a potentially distracting picture that was either positively emotional (of a kitten or a couple in love, for example), negatively emotional (such as a mutilated body or a snake) or neutral (such as a cow or spoon). © Copyright Reed Business Information Ltd.
Ian Sample Science editor Government lawyers are seeking to block compensation payments to people who developed the devastating sleep disorder, narcolepsy, as a result of a faulty swine flu vaccine. The Pandemrix vaccine made by GlaxoSmithKline (GSK) was given to 6 million people in Britain and millions more across Europe during the 2009-10 swine flu pandemic, but was withdrawn when doctors noticed a rise in narcolepsy cases among those who received the jab. In June, a 12-year-old boy was awarded £120,000 by a court that ruled he had been left severely disabled by narcolepsy caused by Pandemrix. The win ended a three-year battle with the government that argued his illness was not serious enough to warrant compensation. Narcolepsy is a permanent condition that can cause people to fall asleep dozens of times a day, even when they are in mid-conversation. Some suffer from night terrors and a problem with muscular control called cataplexy that can lead them to collapse on the spot. The boy, who remains anonymous, has become disruptive at school because he is so tired and finds it almost impossible to socialise. He needs to take several naps in the school day and cannot shower unattended or take a bus alone. He may never be able to drive as an adult. © 2015 Guardian News and Media Limited
By Diana Kwon Multiple sclerosis (MS) relapses are known to swing with the seasons. Scientists have attributed these fluctuations to the rise and fall of vitamin D production, which is triggered by exposure to seasonal sunlight. Now a new study suggests that melatonin, a hormone that regulates your internal body clock and sleep cycles, could also play a protective role. MS is a disease of the central nervous system in which an abnormal immune response attacks the myelin sheath, or fatty protective layer, around neurons. The resulting degradation slows signaling between the brain and the rest of the body, potentially leading to a wide variety of symptoms that include weakness, vision problems and cognitive changes. The condition may affect as many as 2.3 million people worldwide. The cause of the disease remains unknown, although researchers have started to identify genetic risks and environmental factors, including smoking, viral infections and vitamin D levels in the bloodstream. The latest environmental influence, observed by Mauricio Farez, a neuroscientist at the Raúl Carrea Institute for Neurological Research, and colleagues could involve peak melatonin levels in the body, which occur during the darker months. The researchers assessed a group of 139 multiple sclerosis patients in Buenos Aires and found a 32 percent reduction in the number of relapses in the fall and winter, when people living in the Southern Hemisphere produce more of the hormone, compared with summer and spring. The results are published on the September 10 Cell. © 2015 Scientific American
By C. CLAIBORNE RAY A. Wild canines that rely on strenuous hunting to survive may sleep or rest as much as, or even more than, indolent human-created breeds that rely on a can or a bag of kibble. Domestic dogs, with their great range of body types and personalities, show a tremendous variety of sleep patterns, often including relatively brief periods of deep sleep spread out over several hours. A half-century-long study of wolves and their interaction with their prey on Isle Royale, a wilderness island in Lake Superior, found that in winter the wolves would feed for hours on a fresh kill, then sprawl out or curl up in the snow and rest or sleep about 30 percent of the time. “Wolves have plenty of reason to rest,” the study’s researchers wrote. “When wolves are active, they are really active. On a daily basis, wolves burn about 70 percent more calories compared to typical animals of similar size.” The researchers note that while hunting, wolves may burn calories at 10 to 20 times the rate they do while resting. “When food is plentiful, wolves spend a substantial amount of time simply resting, because they can,” the study said. “When food is scarce, wolves spend much time resting because they need to.” Wolves may eat only once every five to 10 days, the researchers said, losing as much as 8 to 10 percent of body weight, but regaining all the lost weight in just two days of eating and resting. © 2015 The New York Times Company
Link ID: 21419 - Posted: 09.20.2015
By Barbara S. Moffet It’s 1 in the morning and I’ve been in bed for a few hours now. Maybe it’s the few drops of caffeine I mistakenly drank earlier in the day. Or perhaps it’s the 26 wires that are attached to my scalp, face, finger and legs and the strap pulled taut around my waist. All I know is I’m not doing what you’re supposed to do in a sleep lab, and if I don’t fall asleep soon, it’ll be time to take off my pajamas and go home. I’m here because my doctor thought it was time to find out what was causing a cluster of possibly sleep-related health issues: snoring, frequent middle-of-the-night waking and some problems with concentrating that I’ve had most of my 63 years. I also have a genetic condition, Ehler-Danlos syndrome, that can cause airways to partially close during sleep. I’ve landed at Sleep Centers of Northern Virginia in Alexandria, one of at least two dozen sleep labs in the area. According to the National Institutes of Health, some 70 million Americans are “poor sleepers,” and the ramifications of inadequate shut-eye can range from grumpiness and lack of focus to heart disease, diabetes, high blood pressure and even a diminished life expectancy. Research published this year in the journal Neurology concluded that people with sleep apnea — a disorder that causes a person to repeatedly stop breathing during the night, rousing them from sleep — developed problems with cognition about 10 years earlier than other people.
Link ID: 21409 - Posted: 09.15.2015
John Peever, and Brian J. Murray, The function of sleep has mystified scientists for thousands of years, but modern research is providing new clues about what it does for both the mind and body. Sleep serves to reenergize the body's cells, clear waste from the brain, and support learning and memory. It even plays vital roles in regulating mood, appetite and libido. Sleeping is an integral part of our life, and as research shows, it is incredibly complex. The brain generates two distinct types of sleep—slow-wave sleep (SWS), known as deep sleep, and rapid eye movement (REM), also called dreaming sleep. Most of the sleeping we do is of the SWS variety, characterized by large, slow brain waves, relaxed muscles and slow, deep breathing, which may help the brain and body to recuperate after a long day. When we fall asleep, the brain does not merely go offline, as implied by the common phrase “out like a light.” Instead a series of highly orchestrated events puts the brain to sleep in stages. Technically sleep starts in the brain areas that produce SWS. Scientists now have concrete evidence that two groups of cells—the ventrolateral preoptic nucleus in the hypothalamus and the parafacial zone in the brain stem—are involved in prompting SWS. When these cells switch on, it triggers a loss of consciousness. After SWS, REM sleep begins. This mode is bizarre: a dreamer's brain becomes highly active while the body's muscles are paralyzed, and breathing and heart rate become erratic. The purpose of REM sleep remains a biological mystery, despite our growing understanding of its biochemistry and neurobiology. © 2015 Scientific American
Link ID: 21408 - Posted: 09.15.2015
Patricia Neighmond Are you getting enough sleep, or not enough? If your answer to either of these questions is "yes," you may be at risk of heart disease. Just the right amount of good-quality sleep is key to good heart health, according to researchers at the Center for Cohort Studies at Kangbuk Samsung Hospital and Sungkyunkwan University School of Medicine in Seoul, South Korea. Poor sleep habits may put you at higher risk for early signs of heart disease, even at a relatively young age. The researchers studied more than 47,000 young and middle-aged men and women, average age around 41, who answered questions about how long and how well they slept. Then they had tests to measure their cardiovascular health. Early coronary lesions were detected by measuring the amount of calcium in the arteries of the heart. Stiffness of arteries was measured by the speed of blood coursing through the arteries in the upper arm and ankle. Calcium buildup and arterial stiffness are two important warning signs of oncoming heart disease. Findings showed that adults who slept less than five hours a night had 50 percent more calcium in their coronary arteries than those who slept seven hours. Those who slept nine hours or more a night had even worse outcomes, with 70 percent more coronary calcium compared to those who slept seven hours. © 2015 NPR
Link ID: 21406 - Posted: 09.14.2015
By Sarah Schwartz Darkness and light may help prevent multiple sclerosis or fend off its symptoms. People who genetically produce less vitamin D, a compound normally boosted by sun exposure, have a greater risk of multiple sclerosis, researchers find. But the hormone melatonin, which the body produces in response to darkness, may reduce flare-ups for people who have the disease, another team of scientists reports. The studies may help researchers better understand and treat multiple sclerosis, a disease of the nervous system. It causes symptoms including muscle weakness, pain and vision loss in over 2 million people worldwide. Previous studies linked lower vitamin D levels to higher multiple sclerosis risk, but it was unclear whether this relationship was a coincidence. In work appearing August 25 in PLOS Medicine, scientists examined genetic data from thousands of Europeans and found that three genetic changes known to reduce vitamin D levels were associated with increased multiple sclerosis risk. These findings suggest that individuals with a higher risk of developing the disease, such as immediate family members of multiple sclerosis patients, should take steps to ensure they have sufficient levels of vitamin D, says study coauthor Brent Richards, a genetic epidemiologist at McGill University in Montreal. People can raise vitamin D levels to normal by taking an oral supplement. © Society for Science & the Public 2000 - 2015.
By Melinda Wenner Moyer A worrisome new study caught my eye last week as I perused the website of the journal Pediatrics. It was titled “Cognition and Brain Structure Following Early Childhood Surgery With Anesthesia.” Considering that my now 4-year-old underwent general anesthesia for a minor procedure when he was 2 and that my 14-month-old may be a candidate for ear tube surgery, my interest was immediately piqued. I clicked through and came face to face with a whole lot of yuck. The first sentence alone made me gasp: “Anesthetics induce widespread cell death, permanent neuronal deletion, and neurocognitive impairment in immature animals, raising substantial concerns about similar effects occurring in young children.” Wait, so anesthesia causes brain damage? Why didn’t anyone tell me? I thought. Obviously, I needed to know more. Considering that 6 million American children—including 1.5 million babies under the age of 1—undergo general anesthesia each year, this seemed like a pretty serious issue to delve into. Twenty studies and several phone calls later, I’m feeling a lot better about my kids’ brains. There are still many things scientists don’t know about how anesthesia affects the nervous system, in part because they can’t ethically do the types of experiments that would provide clear answers, like unnecessarily exposing kids to anesthesia. But based on the research that does exist, there’s really no need for parents to freak out. If “going under” has an effect on the developing brain, it’s likely to be very small. Even Andreas Loepke, the pediatric anesthesiologist at Cincinnati Children’s Hospital Medical Center who co-authored the Pediatrics paper, was reassuring to me over the phone. “These are theoretical concerns,” he said. © 2015 The Slate Group LLC.
Ian Sample Science editor People who get too little sleep are more likely to catch a cold, according to US scientists who suspect that a good night’s sleep is crucial for the body’s immune defences. Those who slept six hours a night or less were four times more likely to catch a cold when they were exposed to the virus than people who spent more than seven hours a night asleep, their study found. The findings, reported in the journal Sleep, build on previous studies that suggest that the sleep-deprived are more susceptible to infectious diseases and recover more slowly when they do fall ill. “It goes beyond feeling groggy or irritable,” said Aric Prather, a health psychologist at the University of California in San Francisco. “Not getting enough sleep affects your physical health.” The scientists recruited 94 men and 70 women, with an average age of 30, for the study and subjected them to two months of health screening, interviews and questionnaires to establish their baseline stress levels, temperament and usage of alcohol and tobacco. The volunteers then spent a week wearing a wrist-mounted sleep sensor that tracked the duration and quality of their sleep each night. To see how well they fought off infections, the participants were taken to a hotel and given nasal drops containing the cold virus. Doctors monitored them closely for a week after, collecting mucus samples to work out if and when the virus took hold. © 2015 Guardian News and Media Limited
By Jessica Schmerler In the modern age of technology it is not uncommon to come home after a long day at work or school and blow off steam by reading an e-book or watching television. Lately, however, scientists have been cautioning against using light-emitting devices before bed. Why? The light from our devices is “short-wavelength-enriched,” meaning it has a higher concentration of blue light than natural light—and blue light affects levels of the sleep-inducing hormone melatonin more than any other wavelength. Changes in sleep patterns can in turn shift the body’s natural clock, known as its circadian rhythm. Recent studies have shown that shifts in this clock can have devastating health effects because it controls not only our wakefulness but also individual clocks that dictate function in the body’s organs. In other words, stressors that affect our circadian clocks, such as blue-light exposure, can have much more serious consequences than originally thought. How did you become interested in the effects of light on sleep? Brainard: I was interested in the effects of light on animals as a teenager. I never planned to be a scientist—I wanted to be a writer! So I learned more about the topic out of pure curiosity. When I began my career as a journalist, I interviewed researchers on the topic who encouraged me to pursue a career in science. So I returned to school to get my doctorate and studied the effects of different wavelengths and intensities of light on rodents. I have exclusively studied the effects of light on humans for the past 30 years. © 2015 Scientific American
By JOAN RAYMOND Rita Gunther McGrath, a Columbia Business School professor, is one of those business travelers who do not care about delays, cancellations or navigating a new location. What does concern her is the seeming inability to conquer jet lag, and the accompanying symptoms that leave her groggy, unfocused and feeling, she says, “like a dishrag.” “Jet lag has always been an issue for me,” says Ms. McGrath, who has been a business traveler for more than two decades and has dealt with itineraries that take her from New York to New Zealand to Helsinki to Hong Kong all within a matter of days. She has scoured the Internet for “jet lag cures,” and has tried preventing or dealing with the misery by avoiding alcohol, limiting light exposure or blasting her body with sunlight and “doing just about anything and everything that experts tell you to do,” Ms. McGrath said. “Jet lag is not conducive to the corporate environment,” she said. “There has to be some kind of help that actually works for those of us that travel a lot, but I sure can’t find it.” Although science is closer to understanding the basic biological mechanisms that make many travelers feel so miserable when crossing time zones, research has revealed that, at least for now, there is no one-size fits-all recommendation for preventing or dealing with the angst of jet lag. Recommendations to beat jet lag include adjusting sleep schedules, short-term use of medications to sleep or stay awake, melatonin supplements and light exposure timing, among others, said Col. Ian Wedmore, an emergency medicine specialist for the Army. © 2015 The New York Times Company
Keyword: Biological Rhythms
Link ID: 21333 - Posted: 08.25.2015
Jon Hamilton More than 50 million adults in the U.S. have a disorder such as insomnia, restless leg syndrome or sleep apnea, according to an Institute of Medicine report. And it's now clear that a lack of sleep "not only increases the risk of errors and accidents, it also has adverse effects on the body and brain," according to Charles Czeisler, chief of the division of sleep and circadian disorders at Brigham and Women's hospital in Boston. Research in the past couple of decades has shown that a lack of sleep increases a person's risk for cardiovascular disease, diabetes, infections, and maybe even Alzheimer's disease. Yet most sleep disorders go untreated. Michael Arnott, of Cambridge, Massachusetts, says he used to have terrible trouble staying awake on long drives. Sleep specialists discovered he has obstructive sleep apnea, though not for the most common reasons — he isn't overweight, and doesn't smoke or take sedatives. "I would get groggy and feel like I've got to keep talking, open the window," Arnott says. His wife, Mary White, says being a passenger on those drives could be scary. "All of a sudden there'd be a change in the speed and I'd look over, and his eyes would be starting to close," she remembers. White thought her husband might have sleep apnea, which interferes with breathing. But Arnott was in denial. He figured he was free of most risk factors for apnea. He wasn't overweight, he didn't smoke or take sedatives, and he has always stayed in great shape. So his wife took the initiative. "I asked him to see a doctor and he wouldn't," she says. In 2012, though, White persuaded him to take part in a sleep research study that paid for his participation, and took place at a sleep lab in Boston –not too far from the couple's home in Cambridge. © 2015 NPR
Link ID: 21330 - Posted: 08.24.2015
Mo Costandi The human brain can be compared to something like a big, bustling city. It has workers, the neurons and glial cells which co-operate with each other to process information; it has offices, the clusters of cells that work together to achieve specific tasks; it has highways, the fibre bundles that transfer information across long distances; and it has centralised hubs, the densely interconnected nodes that integrate information from its distributed networks. Like any big city, the brain also produces large amounts of waste products, which have to be cleared away so that they do not clog up its delicate moving parts. Until very recently, though, we knew very little about how this happens. The brain’s waste disposal system has now been identified. We now know that it operates while we sleep at night, just like the waste collectors in most big cities, and the latest research suggests that certain sleeping positions might make it more efficient. Waste from the rest of the body is cleared away by the lymphatic system, which makes and transports a fluid called lymph. The lymphatic system is an important component of the immune system. Lymph contains white blood cells that can kill microbes and mop up their remains and other cellular debris. It is carried in branching vessels to every organ and body part, and passes through them, via the spaces between their cells, picking up waste materials. It is then drained, filtered, and recirculated. The brain was thought to lack lymphatic vessels altogether, and so its waste disposal system proved to be far more elusive. Several years ago, however, Maiken Nedergaard of the University of Rochester Medical Center and colleagues identified a system of hydraulic “pipes” running alongside blood vessels in the mouse brain. Using in vivo two-photon imaging to trace the movements of fluorescent markers, they showed that these vessels carry cerebrospinal fluid around the brain, and that the fluid enters inter-cellular spaces in the brain tissue, picking up waste on its way. © 2015 Guardian News and Media Limited
Link ID: 21327 - Posted: 08.22.2015