Chapter 14. Biological Rhythms, Sleep, and Dreaming
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Ed Yong As the H1N1 swine flu pandemic swept the world in 2009, China saw a spike in cases of narcolepsy — a mysterious disorder that involves sudden, uncontrollable sleepiness. Meanwhile, in Europe, around 1 in 15,000 children who were given Pandemrix — a now-defunct flu vaccine that contained fragments of the pandemic virus — also developed narcolepsy, a chronic disease. Immunologist Elizabeth Mellins and narcolepsy researcher Emmanuel Mignot at Stanford University School of Medicine in California and their collaborators have now partly solved the mystery behind these events, while also confirming a longstanding hypothesis that narcolepsy is an autoimmune disease, in which the immune system attacks healthy cells. Narcolepsy is mostly caused by the gradual loss of neurons that produce hypocretin, a hormone that keeps us awake. Many scientists had suspected that the immune system was responsible, but the Stanford team has found the first direct evidence: a special group of CD4+ T cells (a type of immune cell) that targets hypocretin and is found only in people with narcolepsy. “Up till now, the idea that narcolepsy was an autoimmune disorder was a very compelling hypothesis, but this is the first direct evidence of autoimmunity,” says Mellins. “I think these cells are a smoking gun.” The study is published today in Science Translational Medicine1. Thomas Scammell, a neurologist at Harvard Medical School in Boston, Massachusetts, says that the results are welcome after “years of modest disappointment”, marked by many failures to find antibodies made by a person's body against their own hypocretin. “It’s one of the biggest things to happen in the narcolepsy field for some time.” It is not clear why some people make these T cells and others do not, but genetics may play a part. In earlier work2, Mignot showed that 98% of people with narcolepsy have a variant of the gene HLA that is found in only 25% of the general population. © 2013 Nature Publishing Group
By Sanaz Majd MD Scientific American presents House Call Doctor by Quick & Dirty Tips. Scientific American and Quick & Dirty Tips are both Macmillan companies. Have you been told by your spouse that you “fidget” in the middle of the night? Or have you noticed your legs or feet may have a mind of their own when you’re trying to fall asleep? Do you have an urge to move your legs a lot at bedtime? You may very well be one of the many people who remain undiagnosed with the condition called Restless Legs Syndrome, or RLS. For those who have never experienced RLS, it may seem like a very odd and peculiar phenomenon. But if you’ve ever had these symptoms, you may be surprised to learn that this is an actual medical condition. Maybe you’ve already mentioned it to your doctor, or maybe you never realized it was real until now. Either way, let’s find out more about Restless Legs Syndrome and how it’s treated. What Is RLS? I’ve actually discussed RLS in a previous episode on insomnia, and you may want to revisit that episode before moving on to this one. But in a nutshell, here are the symptoms that up to 10% of the American population are estimated to be suffering from: © 2013 Scientific American
Link ID: 19026 - Posted: 12.12.2013
By MAGGIE KOERTH-BAKER More than a decade ago, a 43-year-old woman went to a surgeon for a hysterectomy. She was put under, and everything seemed to be going according to plan, until, for a horrible interval, her anesthesia stopped working. She couldn’t open her eyes or move her fingers. She tried to breathe, but even that most basic reflex didn’t seem to work; a tube was lodged in her throat. She was awake and aware on the operating table, but frozen and unable to tell anyone what was happening. Studies of anesthesia awareness are full of such horror stories, because administering anesthesia is a tightrope walk. Too much can kill. But too little can leave a patient aware of the procedure and unable to communicate that awareness. For every 1,000 people who undergo general anesthesia, there will be one or two who are not as unconscious as they seem — people who remember their doctors talking, and who are aware of the surgeon’s knife, even while their bodies remain catatonic and passive. For the unlucky 0.13 percent for whom anesthesia goes awry, there’s not really a good preventive. That’s because successful anesthetization requires complete unconsciousness, and consciousness isn’t something we can measure. There are tools that anesthesiologists use to get a pretty good idea of how well their drugs are working, but these systems are imperfect. For most patients receiving inhaled anesthesia, they’re no better at spotting awareness than dosing metrics developed half a century ago, says George Mashour, a professor of anesthesiology at the University of Michigan Medical School. There are two intertwined mysteries at work, Mashour told me: First, we don’t totally understand how anesthetics work, at least not on a neurological basis. Second, we really don’t understand consciousness — how the brain creates it, or even what, exactly, it is. © 2013 The New York Times Company
by Laura Sanders If you own a television, a computer or a smartphone, you may have seen ads for Lumosity, the brain-training regimen that promises to sharpen your wits and improve your life. Take the bait, and you’ll first create a profile that includes your age, how much sleep you get, the time of day you’re most productive and other minutiae about your life and habits. After this digital debriefing, you can settle in and start playing games designed to train simple cognitive skills like arithmetic, concentration and short-term recall. The 50 million people signed up for Lumosity presumably have done so because they want to improve their brains, and these games promise an easy, fun way to do that. The program also offers metrics, allowing users to chart their progress over weeks, months and years. Written in these personal digital ledgers are clues that might help people optimize their performance. With careful recordkeeping, for example, you might discover that you hit peak brainpower after precisely one-and-a-half cups of medium roast coffee at 10:34 a.m. on Tuesdays. But you’re not the only one who has access to this information. With each click, your performance data will fly by Internet into the eager hands of scientists at Lumos Labs, the San Francisco company that created Lumosity. Giant datasets like this one, created as a by-product of people paying money to learn about and improve themselves, will revolutionize research in human health and behavior, some scientists believe. Lumos Labs researchers hope that their brain-training data in particular could reveal deep truths about how the human mind works. They believe that they have a nimble, customizable and cheap way to discover things about the brain that would otherwise take huge amounts of money and many years to unearth with standard lab-based studies. Other researchers have also taken note, and some have gotten permission to use Lumosity data in their own research. Some of these researchers are hunting for subtle signatures of Alzheimer’s in the data. Others are investigating more fundamental mysteries with cross-cultural studies of how the brain builds emotions and how memory works. © Society for Science & the Public 2000 - 2013.
By Emilie Reas Did you make it to work on time this morning? Go ahead and thank the traffic gods, but also take a moment to thank your brain. The brain’s impressively accurate internal clock allows us to detect the passage of time, a skill essential for many critical daily functions. Without the ability to track elapsed time, our morning shower could continue indefinitely. Without that nagging feeling to remind us we’ve been driving too long, we might easily miss our exit. But how does the brain generate this finely tuned mental clock? Neuroscientists believe that we have distinct neural systems for processing different types of time, for example, to maintain a circadian rhythm, to control the timing of fine body movements, and for conscious awareness of time passage. Until recently, most neuroscientists believed that this latter type of temporal processing – the kind that alerts you when you’ve lingered over breakfast for too long – is supported by a single brain system. However, emerging research indicates that the model of a single neural clock might be too simplistic. A new study, recently published in the Journal of Neuroscience by neuroscientists at the University of California, Irvine, reveals that the brain may in fact have a second method for sensing elapsed time. What’s more, the authors propose that this second internal clock not only works in parallel with our primary neural clock, but may even compete with it. Past research suggested that a brain region called the striatum lies at the heart of our central inner clock, working with the brain’s surrounding cortex to integrate temporal information. For example, the striatum becomes active when people pay attention to how much time has passed, and individuals with Parkinson’s Disease, a neurodegenerative disorder that disrupts input to the striatum, have trouble telling time. © 2013 Scientific American
By Jill U. Adams, Every morning I am greeted by Facebook friends complaining of sleepless nights or awakenings. I know the feeling — as do many other Americans. In a 2005 survey of 1,506 Americans by the National Sleep Foundation, 54 percent reported at least one symptom of insomnia — difficulty falling asleep, waking a lot during the night, waking up too early or waking up feeling unrefreshed — at least a few nights a week over the previous year. Thirty-three percent said they had experienced symptoms almost every night. If insomnia visited me that often, I’d be tempted to pick up something at the pharmacy — something easy, something safe, something that didn’t involve making a doctor’s appointment. Indeed, 10 to 20 percent of Americans take over-the-counter sleep aids each year, according to the American Academy of Sleep Medicine. The way they’re marketed, over-the-counter sleep aids sound very appealing: The new product ZzzQuil (yes, from the maker of NyQuil) promises “a beautiful night’s sleep;” an ad says you’ll “fall asleep faster and stay asleep longer” after using Unisom. Companies marketing the herb valerian root and the hormone melatonin as over-the-counter sleep aids make similar claims. But what’s the evidence that supports these claims? “It’s quite lean,” says Andrew Krystal, who directs the sleep research program at Duke University. Over-the-counter sleep aids work differently from prescription drugs for insomnia. Most are simply antihistamines in sheep’s clothing. (Yes, that’s a joke.) The majority of them — ZzzQuil, TylenolPM and Unisom SleepGels — contain diphenhydramine as the active ingredient, the same compound in Benadryl. (Unisom SleepTabs use doxylamine, another antihistamine.) © 1996-2013 The Washington Post
Link ID: 18973 - Posted: 11.26.2013
By BENEDICT CAREY Curing insomnia in people with depression could double their chance of a full recovery, scientists are reporting. The findings, based on an insomnia treatment that uses talk therapy rather than drugs, are the first to emerge from a series of closely watched studies of sleep and depression to be released in the coming year. A student demonstrating equipment at Colleen Carney’s sleep lab at Ryerson University. Dr. Carney is the lead author of a new report about the effects of insomnia treatment on depression. The new report affirms the results of a smaller pilot study, giving scientists confidence that the effects of the insomnia treatment are real. If the figures continue to hold up, the advance will be the most significant in the treatment of depression since the introduction of Prozac in 1987. Depression is the most common mental disorder, affecting some 18 million Americans in any given year, according to government figures, and more than half of them also have insomnia. Experts familiar with the new report said that the results were plausible and that if supported by other studies, they should lead to major changes in treatment. “It would be an absolute boon to the field,” said Dr. Nada L. Stotland, professor of psychiatry at Rush Medical College in Chicago, who was not connected with the latest research. “It makes good common sense clinically,” she continued. “If you have a depression, you’re often awake all night, it’s extremely lonely, it’s dark, you’re aware every moment that the world around you is sleeping, every concern you have is magnified.” The study is the first of four on sleep and depression nearing completion, all financed by the National Institute of Mental Health. They are evaluating a type of talk therapy for insomnia that is cheap, relatively brief and usually effective, but not currently a part of standard treatment. © 2013 The New York Times Company
By NICHOLAS BAKALAR Children who do not sleep enough may be increasing their risk for obesity, according to a new study. Researchers randomly divided 37 children aged 8 to 11 into two groups. Each group increased their habitual time in bed by an hour and a half per night for one week, then decreased their time by the same amount the next week. They wore electronic devices to measure sleep time, were assessed for daily food intake three times a week, and had blood tests to measure leptin, a hormone that affects hunger, and high levels of which correlate with fat tissue accumulations. Children consumed 134 calories fewer each day during the increased sleep week than the during the week with less sleep. Fasting leptin levels were lower when the children slept more and, over all, the children’s weight averaged about a half pound less at the end of long sleep weeks than short ones. The study was published online in Pediatrics. The lead author, Chantelle N. Hart, an associate professor of public health at Temple University who was at Brown University when she did the study, cautioned that it was small, and looked only at acute changes in sleep and their effect on eating behaviors. Still, she said, “I think these findings suggest that getting a good night’s sleep in childhood could have important benefits for weight regulation through decreased food intake.” Copyright 2013 The New York Times Company
By Joss Fong Sleep is such a large feature of our lives that it’s easy to forget how utterly weird it is. Every night, if we’re lucky, our brain cells switch into a synchronized pattern, putting our lives and minds on hold for hours. Sleep scientists have yet to fully explain why we spend a third of our lives in this state, let alone why we use some of that time wandering through vivid, nonsensical and sometimes upsetting hallucinations. A recent study in Science suggests that sleep may serve to wash the brain of harmful waste products that build up during the day. Medical researchers observed an increased flow of cerebrospinal fluid in mice that were sleeping or anesthetized. This fluid carries away waste proteins, including one linked to Alzheimer’s disease. The findings join other theories on the function of sleep, some of which I discuss above, in our latest Instant Egghead video. © 2013 Scientific American
Link ID: 18878 - Posted: 11.06.2013
by Simon Makin Sometimes wacky-sounding ideas aren't so crazy after all. If your body clock is all at sea after a long flight or a night shift, the way to reset it may be to scramble your timekeeping neurons even further. The body's master clock resides in a region of the brain called the suprachiasmatic nucleus. Each neuron in the SCN keeps its own time, but the neurons can synchronise their clocks by sending and receiving signals using a hormone called vasoactive intestinal polypeptide (VIP). When Erik Herzog at Washington University in St Louis, Missouri, and colleagues probed the hormone's effects, they discovered that a glut of VIP caused the neurons to lose the ability to synchronise. Herzog's team wondered whether this might have a beneficial effect. "If the cell rhythms are messed up and out of phase, the system may be more sensitive to environmental cues than it would be if all the cells were in sync," he says, allowing the body clock to adjust more readily. The VIP treatment To test the idea, they gave some mice an injection of VIP into the brain before fast-forwarding the light/dark cycle in their cages by 8 hours. The mice that received the hormone adjusted in 4.5 days on average, whereas untreated mice needed nearly eight days – gauging by how active the animals were when the lights were off. © Copyright Reed Business Information Ltd.
Keyword: Biological Rhythms
Link ID: 18855 - Posted: 10.30.2013
by Linda Geddes Anaesthetics usually knock you out like a light. But by slowing the process down so that it takes 45 minutes to become totally unresponsive, researchers have discovered a new signature for unconsciousness. The discovery could lead to more personalised methods for administering anaesthetics and cut the risks associated with being given too high or too low a dose. It also sheds new light on what happens to our brain when we go under the knife. Hundreds of thousands of people are anaesthetised every day, yet researchers still don't fully understand what's going on in the anaesthetised brain. Nor is there a direct way of measuring when someone is truly unresponsive. Instead, anaesthetists rely on indirect measures such as heart and breathing rate, and monitoring reflexes. To investigate further, Irene Tracey and her colleagues at Oxford University slowed the anaesthesia process down. Instead of injecting the anaesthetic propofol in one go, which triggers unconsciousness in seconds, the drug was administered gradually so that it took 45 minutes for 16 volunteers to become fully anaesthetised. Their brain activity was monitored throughout using electroencephalography (EEG). The study was then repeated on 12 of these volunteers using functional magnetic resonance imaging (fMRI). EEG recordings revealed that before the volunteers became completely unresponsive to external stimuli they progressed through a sleep-like state characterised by slow-wave oscillations – a hallmark of normal sleep, in which neurons cycle between activity and inactivity. As the dose of anaesthetic built up, more and more neurons fell into this pattern, until a plateau was reached when no more neurons were recruited, regardless of the dose administered. © Copyright Reed Business Information Ltd.
By Consumer Reports, You wake up tired after a full night’s sleep. Maybe you’ve become a bit forgetful, and you struggle to stay awake at work or behind the wheel. The problem might be obstructive sleep apnea, an often overlooked condition that has increased sharply in the past 20 years. In the United States, more than 40 percent of men and 28 percent of women between the ages of 50 and 70 experience obstructed breathing while asleep, according to researchers whose work was published online in April by the American Journal of Epidemiology. About 17 percent of the men and 9 percent of the women have cases serious enough to meet the Medicare criteria for a sleep apnea diagnosis. But even milder cases can affect your health. Obstructive sleep apnea causes the muscles and tissues in the lower throat to collapse, blocking the flow of air to the lungs during sleep. A person with obstructive sleep apnea may stop breathing, typically for 20 to 25 seconds or for as long as two minutes. The amount of carbon dioxide in the blood rises, triggering an alarm in the brain that stirs the sleeper to resume breathing. That cycle can repeat itself dozens of times an hour throughout the night, preventing the sleeper from reaching the restorative stages of deep sleep. Upon awakening, he or she usually has no recollection of those events. Overweight men are the most frequently affected because they tend to have a throat with bulkier soft tissue and fat deposits, but women and people of normal weight also develop sleep apnea. Loud snoring can be a warning sign, especially if you learn from a bed partner or roommate that you gasp for breath or choke while you are asleep. High blood pressure and heart-rhythm abnormalities are also red flags, especially if you take antihypertensive medication and still have trouble keeping blood pressure under control. Waking up with a headache may also signal the condition. © 1996-2013 The Washington Post
Link ID: 18820 - Posted: 10.22.2013
Maggie Fox NBC News Every cell in your body has a little clock ticking away in it, researchers reported on Sunday. And while most of you is aging in a coordinated way, odd anomalies that have the researchers curious: Your heart may be “younger” than the rest of your tissues, and a woman’s breasts are older. Tumors are the oldest of all, a finding reported in the journal Genome Biology that might help scientists better understand cancer, explain why breast cancer is so common and help researchers find better ways to prevent it. Less surprising, but intriguing: embryonic stem cells, the body’s master cells, look just like newborns with a biological age of zero. The new measurements might be useful in the search for drugs or other treatments that can turn back the clock on aging tissue and perhaps treating or preventing diseases of aging, such as heart disease and cancer, says Steve Horvath, a professor of genetics at the David Geffen School of Medicine at UCLA. “The big question is whether the biological clock controls a process that leads to aging,” Horvath said. Horvath looked at a genetic process called methylation. It’s a kind of chemical reaction that turns on or off stretches of DNA. All cells have the entire genetic map inside; methylation helps determine which bits of the map the cells use to perform specific functions.
Keyword: Biological Rhythms
Link ID: 18816 - Posted: 10.21.2013
By GRETCHEN REYNOLDS If you consider yourself to be a born morning person or an inveterate night owl, there is new research that supports your desire to wake up early or stay up late. Each of us has a personal “chronotype,” or unique circadian rhythm, says Till Roenneberg, a professor of chronobiology at Ludwig Maximilian University in Munich and one of the world’s experts on sleep. In broad strokes, these chronotypes are usually characterized as early, intermediate or late, corresponding to people who voluntarily go to bed and wake early, at a moderate hour or vampirishly late. If you are forced to wake up earlier than your body naturally would, you suffer from what Roenneberg calls “social jet lag.” People with an early chronotype may do well with a 7 a.m. workday rising time, but others do not. Sleeping out of sync with your innate preferences can be detrimental to your health, especially for late chronotypes, who tend to be the most at odds with typical work schedules. A study conducted by the National Institutes of Health and published in March in PLOS ONE found that obese adults with late chronotypes tended to eat larger meals, develop more sleep apnea and have higher levels of stress hormones and lower levels of HDL, or “good,” cholesterol than obese people with other chronotypes. Their chronotype may also have contributed to weight gain in the first place, Roenneberg says. Research has shown that a single hour of social jet lag, the mismatch between your chronotype and your schedule, increases your risk for obesity by about 33 percent. In a study published in June in Chronobiology International, late-night chronotypes gained more weight during their freshman years at college than other new students did, even though college is one of the best fits for night owls. Copyright 2013 The New York Times Company
by Tina Hesman Saey Sleep hoses garbage out of the brain, a study of mice finds. The trash, including pieces of proteins that cause Alzheimer’s disease, piles up while the rodents are awake. Sleep opens spigots that bathe the brain in fluids and wash away the potentially toxic buildup, researchers report in the Oct. 18 Science. The discovery may finally reveal why sleep seems mandatory for every animal. It may also shed new light on the causes of neurodegenerative disorders such as Alzheimer’s and Parkinson’s diseases. “It’s really an eye-opening and intriguing finding,” says Chiara Cirelli, a sleep researcher at the University of Wisconsin–Madison. The results have already led her and other sleep scientists to rethink some of their own findings. Although sleep requirements vary from individual to individual and across species, a complete lack of it is deadly. But no one knows why. One popular idea is that sleep severs weak connections between brain cells and strengthens more robust connections to solidify memories (SN Online: 4/2/09; SN Online: 6/23/11). But a good memory is not a biological imperative. “You don’t die from forgetting what you learned yesterday,” says Maiken Nedergaard, a neuroscientist at the University of Rochester Medical Center in New York who led the study. Researchers in Nedergaard’s lab stumbled upon sleep’s role in garbage clearance while studying a brain drainage system they described last year (SN: 9/22/12, p. 15). This service, called the glymphatic system, flushes fluid from the brain and spinal cord into the space between brain cells. Ultimately, the fluid and any debris it carries washes into the liver for disposal. © Society for Science & the Public 2000 - 2013
by Laura Sanders After Baby V joined our team, one of the first things people would ask is, “Are you getting any sleep?” (The answer was, and is, no.) The recurring question highlights how sorely lacking sleep is for new parents. Capitalism noticed us tired parents, too: Countless products beckon exhausted families with promises of eight, 10, even 12 hours of blissful, uninterrupted sleep. You can buy special swaddles, white noise machines, swings that sway like a moving car and books upon books that whisper contradictory secrets of how to get your baby to sleep through the night. (If you don’t have time to read them all, mother-of-twins Ava Neyer helpfully breaks down all of the advice for you.) As the owner of a stack of such books, I was intrigued by this recent review: “Behavioral sleep interventions in the first six months of life do not improve outcomes for mothers or infants: A systematic review.” Excuse me? The Sleep Sheep, the Baby Whisperer and the Sleep Lady lied to me? At the behest of the United Kingdom’s National Institute for Health Research, Australians Pamela Douglas and Peter Hill combed through the existing scientific literature on sleep interventions looking for benefits. These interventions included delaying responses to infant cues (also known by its cold-hearted name of “crying it out”), sticking to a feeding or sleeping schedule and other ways that aim to teach a baby how to fall asleep without the need to eat or be held. After analyzing 43 studies on infant sleep interventions, the team concluded that these methods weren’t beneficial for babies younger than six months, or their mothers. The studies didn’t convincingly show that interventions curb infant crying, prevent sleep or behavioral problems later or protect against maternal depression, Douglas and Hill write in the September Journal of Developmental & Behavioral Pediatrics. © Society for Science & the Public 2000 - 2013.
by Andy Coghlan Swifts are said to spend most of their lives airborne, but no one has ever proved this. Now, a study suggests there's some truth to it: alpine swifts spend more than six consecutive months aloft, not even resting after migrating to north Africa following their breeding season in Europe. "Up to now, such long-lasting locomotive activity had been reported only for animals living in the sea," says Felix Liechti of the Swiss Ornithological Institute in Sempach. Liechti and his colleagues attached 1.5-gram data loggers to three alpine swifts (Tachymarptis melba) at a Swiss breeding site, and recaptured the birds the following year. The loggers recorded the birds' acceleration and geographic location. The measurements suggest that for 200 days, all three swifts remained airborne while migrating to and wintering in Africa. Liechti says researchers have previously asserted but never proved that newborn common swifts spend three years aloft before landing for breeding. "Amazing, truly amazing," says Carsten Egevang of the Greenland Institute of Natural Resources in Nuuk of Liechti's findings. "We knew that swifts stay on the wing for long periods, but 200 days is very impressive." The birds survive on airborne plankton, and almost certainly sleep on the wing too, Liechti says. "It has been assumed that the birds 'sleep' only for seconds, or use only one half of the brain while the other half is resting," he says. © Copyright Reed Business Information Ltd
Link ID: 18767 - Posted: 10.09.2013
by Ed Yong I’ve just arrived home from 14 hours of flying. The clocks on my phone and laptop have been ticking away the whole time, and it takes a few seconds to reset them to British time. The clocks in my body are more difficult. We run on a daily 24-hour body clock, which controls everything from our blood pressure to our temperature to how hungry we feel. It runs on proteins rather than gears. Once they’re built, these proteins stop their own manufacture after a slight delay, meaning that their levels rise and fall with a regular rhythm. These timers tick away inside almost all of our cells, and they’re synchronised by a tiny collection of 10,000 neurons at the bottom of our brain. It’s called the suprachiasmatic nucleus (SCN). It’s the master clock. It’s the conductor that keeps the orchestra in sync. The SCN is also sensitive to light. It gets signals from our eyes, which allows it to synchronise its ticking with the 24-hour cycle of day and night outside. The SCN is what connects the rhythms of our bodies with those of the planet. But when we travel far and fast, and suddenly land in a new time zone, the SCN becomes misaligned with the environment. It takes time to re-adjust, typically one day for every time zone crossed. In the meantime, our sleep is disrupted and our physiology goes weird. In other words: jet lag. But at Kyoto University, Yoshiaki Yamaguchi and Toru Suzuki have engineered mice that break this rule. They are, with apologies for the awful word, unjetlaggable. If you change the light in their cages to mimic an 8-hour time difference, they readjust almost immediately. Put them on a red-eye flight from San Francisco to London and they’d be fine.
Answer by Paul King, computational neuroscientist: The emerging view in neuroscience is that dreams are related to memory consolidation happening in the brain during sleep. This may include reorganizing and recoding memories in relation to emotional drives as well as transferring memories between brain regions. During the day, episodic memories (memories for events) are stored in the hippocampus, a region of the brain specialized for long-term memory that learns particularly quickly. At night, memories from this region appear to be transferred to the cerebral cortex, the region specialized for information processing, cognition, and knowledge. Studies in animals have found that during sleep, the neural activity of the hippocampus "replays" the events of the day. This replay happens faster than real-time, and sometimes happens in reverse. The activity replay is correlated with neural activity patterns in both the visual cortex (responsible for visual experience) and the prefrontal cortex (responsible for strategy, goals, and planning). The memory replay occurs during REM sleep and dreaming. Philosopher Daniel Dennett proposes the Dream Weaving party game: One person, the Dream Guesser is asked to leave the room, and while away, someone will share a dream with the group. When the Dream Guesser returns, their job will be to ask yes/no questions of random people in the group to attempt to reconstruct the plot of the dream. © 2013 The Slate Group, LLC.
Link ID: 18744 - Posted: 10.05.2013
by Linda Geddes They say the early bird catches the worm, but night owls may be missing far more than just a tasty snack. Researchers have discovered the first physical evidence of structural brain differences that distinguish early risers from people who like to stay up late. The differences might help to explain why night owls seem to be at greater risk of depression. Around 10 per cent of people qualify as morning people or larks, and a further 20 per cent are night owls – with the rest of us falling somewhere in between. Your lark or night owl status is called your chronotype. Previous studies have suggested that night owls experience worse sleep, more tiredness during the day and consume greater amounts of tobacco and alcohol. This has prompted some to suggest that they are suffering from a form of chronic jet lag. To investigate further, Jessica Rosenberg at RWTH Aachen University in Germany and colleagues used diffusion tensor imaging to scan the brains of 16 larks, 23 night owls and 20 intermediate chronotypes. They found a reduction in the integrity of night owls' white matter – brain tissue largely comprised of fatty insulating material that speeds up the transmission of nerve signals – in areas associated with depression. "We think this could be caused by the fact that late chronotypes suffer from this permanent jet lag," says Rosenberg, although she cautions that further studies are needed to confirm cause and effect. © Copyright Reed Business Information Ltd.