Chapter 14. Biological Rhythms, Sleep, and Dreaming
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By James Gallagher Health and science reporter, BBC News Doing the night shift throws the body "into chaos" and could cause long-term damage, warn researchers. Shift work has been linked to higher rates of type 2 diabetes, heart attacks and cancer. Now scientists at the Sleep Research Centre in Surrey have uncovered the disruption shift work causes at the deepest molecular level. Experts said the scale, speed and severity of damage caused by being awake at night was a surprise. The human body has its own natural rhythm or body clock tuned to sleep at night and be active during the day. It has profound effects on the body, altering everything from hormones and body temperature to athletic ability, mood and brain function. The study, published in Proceedings of the National Academy of Sciences, followed 22 people as their body was shifted from a normal pattern to that of a night-shift worker. Blood tests showed that normally 6% of genes - the instructions contained in DNA - were precisely timed to be more or less active at specific times of the day. Once the volunteers were working through the night, that genetic fine-tuning was lost. "Over 97% of rhythmic genes become out of sync with mistimed sleep and this really explains why we feel so bad during jet lag, or if we have to work irregular shifts," said Dr Simon Archer, one of the researchers at the University of Surrey. BBC © 2014
By Megan Wiegand and Slate, Tips for beating the seasonal blues are as numerous as the winter night is long. Light boxes, touted to “uplift people’s spirits” and “improve mood and energy,” offer a New-Agey-seeming solution to propel us into the cold as if it’s the first beautiful day of spring. But can sitting in front of a light for a few minutes a day actually counteract the dreariest months? Yes, in many cases. Light-box therapy has been shown to alleviate symptoms in people who suffer from seasonal affective disorder, or SAD. Symptoms of this form of depression — they can include lost interest in beloved activities, overeating, loss of energy, disrupted sleep cycles and feelings of hopelessness or guilt — typically appear in late fall or early winter and dissipate in spring. Women are twice as likely as men to seek treatment for SAD, and those farther away from the equator are more likely to be diagnosed: About 11 percent of Mainers have a clinical SAD diagnosis, but only 2 percent of Floridians report the illness, according to Kathryn Roecklein, an assistant professor of psychology at the University of Pittsburgh. One tool doctors use to treat SAD is light-box therapy. Light boxes use bright white fluorescent bulbs (or sometimes blue light) that reproduce some wavelengths of the sun’s light. They contain filters to block harmful UV rays and come in various shapes, sizes, light types and price points. © 1996-2014 The Washington Post
By C. CLAIBORNE RAY Q. Why do I wake up at exactly the same time every night, without any stimulus? It has happened all my life, and it doesn’t even matter what time I went to bed. A. What you are experiencing is probably a normal period of relative alertness that happens in the middle of the night, said Dr. Carl W. Bazil, director of the division of epilepsy and sleep at NewYork-Presbyterian/Columbia University Medical Center. “Most people realize that there is a natural drowsiness midday, usually around lunchtime,” Dr. Bazil said. “This is why many fortunate cultures developed the siesta.” But the reverse normally happens at night. The two interludes are both part of the body’s circadian rhythm, which he said is “controlled by an internal clock but of course influenced by lots of external things,” like caffeine, light, exercise and stress. Dr. Bazil said it might also help those who wake up midsleep to know that “before the advent of electrical lighting, it was normal for people to go to bed at sundown, sleep for about four hours and arise during that natural alertness for a few hours before returning for a ‘second sleep.’ ” © 2014 The New York Times Company
By MARIA KONNIKOVA SLEEP seems like a perfectly fine waste of time. Why would our bodies evolve to spend close to one-third of our lives completely out of it, when we could instead be doing something useful or exciting? Something that would, as an added bonus, be less likely to get us killed back when we were sleeping on the savanna? “Sleep is such a dangerous thing to do, when you’re out in the wild,” Maiken Nedergaard, a Danish biologist who has been leading research into sleep function at the University of Rochester’s medical school, told me. “It has to have a basic evolutional function. Otherwise it would have been eliminated.” We’ve known for some time that sleep is essential for forming and consolidating memories and that it plays a central role in the formation of new neuronal connections and the pruning of old ones. But that hardly seems enough to risk death-by-leopard-in-the-night. “If sleep was just to remember what you did yesterday, that wouldn’t be important enough,” Dr. Nedergaard explains. In a series of new studies, published this fall in the journal Science, the Nedergaard lab may at last be shedding light on just what it is that would be important enough. Sleep, it turns out, may play a crucial role in our brain’s physiological maintenance. As your body sleeps, your brain is quite actively playing the part of mental janitor: It’s clearing out all of the junk that has accumulated as a result of your daily thinking. Recall what happens to your body during exercise. You start off full of energy, but soon enough your breathing turns uneven, your muscles tire, and your stamina runs its course. What’s happening internally is that your body isn’t able to deliver oxygen quickly enough to each muscle that needs it and instead creates needed energy anaerobically. And while that process allows you to keep on going, a side effect is the accumulation of toxic byproducts in your muscle cells. Those byproducts are cleared out by the body’s lymphatic system, allowing you to resume normal function without any permanent damage. © 2014 The New York Times Company
Link ID: 19123 - Posted: 01.13.2014
By CATHERINE SAINT LOUIS The standard treatment for people with moderate to severe obstructive sleep apnea is a mask worn at night that helps them breathe without interruption. The mask is unwieldy and uncomfortable, however; one study found that46 percent to 83 percent of patients with obstructive sleep apnea do not wear it diligently. Now scientists may have found an alternative, at least for some patients: a pacemaker-like device implanted in the chest that stimulates a nerve in the jaw, helping to keep part of the upper airway open. The device, called a neurostimulator, helped reduce breathing interruptions and raise blood oxygen levels in about two-thirds of sleep apnea patients participating in a trial, researchers reported on Wednesday in The New England Journal of Medicine. “This is a new paradigm of surgical treatment that seems to effectively control obstructive sleep apnea in selected patients,” said Dr. Sean M. Caples, a sleep specialist in the division of pulmonary and critical care medicine at Mayo Clinic in Rochester, Minn. “It’s very exciting.” Still, Dr. Caples, who was not involved in the new study, noted that “a third of patients were not improved when all was said and done,” even though they were chosen because they were seen as likely to benefit. The new trial was funded by the maker of the device, Inspire Medical Systems. At 22 sites internationally, in 126 patients, doctors surgically implanted a remote-controlled neurostimulator that, activated at night, sends regular electric impulses to a nerve inside the jaw. The impulses cause the tongue to move forward during inhalation, opening the airway. Copyright 2014 The New York Times Company
Link ID: 19120 - Posted: 01.11.2014
The maker of a type of sleeping pill is lowering the dose to minimize the risk of next-day drowsiness. The drug, Sublinox, has been associated in the past with abnormal sleep behaviours. In late 2011, Meda Valeant Pharma Canada warned that some people taking the drug had reported getting out of bed while not fully awake and performing activities they were unaware of doing. Those activities including driving a car, eating and making phone calls The drug company has lowered the recommended initial dose to five milligrams for women and either five or 10 milligrams for men. The drug company says Sublinox should be taken immediately before bedtime, when the user will have the opportunity to get at least seven or eight hours of sleep. People aged 65 and older should use the five-milligram dose, regardless of gender, the company says. Meda Valeant Pharma Canada issued the new advice in conjunction with Health Canada. Long-term use not recommended The advisory says women metabolize the drug more slowly than men, and therefore have a higher chance of experiencing next-day drowsiness. Sublinox — the brand name for the drug zolpidem — is a hypnotic. As with all drugs of this class, long-term use is not recommended. It should not be taken in the middle of the night or at any time other than bedtime, the statement says. © CBC 2014
By Rafael Pelayo, M.D. Perhaps nowhere else does modern neuroscience and psychiatry merge as naturally as in a discussion of sleep disorders. Sleep and dreams are at the core of the mystery (and wonderment) of the relationship between the brain and the mind. Seeking an understanding of sleep has been influential in the development of our culture. As we trace its history, we can also look forward to the advances in the field of sleep medicine that are yet to come. In prehistoric societies, attempts to understand the imagery of nighttime dreams and nightmares might have given rise to concepts of the spiritual world and religion. In medieval times, the phenomena of sleep paralysis, night terrors, and sleepwalking may have been interpreted as supernatural events. Three hundred years ago the recurring nighttime afflictions of restless leg syndrome were thought to be a curse until Dr. Thomas Willis (famed for recognizing the blood supply to the brain, now called the Circle of Willis) accurately described it as a neurological disease. In the late 19th century sleep was viewed as a passive state which occurred in the absence of brain stimulation. Thomas Edison even thought that the invention of the light bulb would allow us to avoid sleeping. The interest of a young neurologist named Sigmund Freud in sleep and dreams opened a new chapter in psychiatry. Years later, a medical student named William Dement was interested in finding a neurological basis to understand Freud's dream theories. In 1952, Dement helped discover the relationship between rapid eye movements in sleep as measured by an electroencephalogram (EEG) and dream recall. © 2014 TheHuffingtonPost.com, Inc.
Link ID: 19093 - Posted: 01.04.2014
One night of sleep deprivation can increase the levels of molecules that are biomarkers for brain damage, according to a new study out of Sweden. The study, conducted by researchers from Uppsala University's Department of Neuroscience and published in the journal Sleep, looked at levels of two types of brain molecules. These molecules typically rise in the blood under conditions resulting in brain damage or distress. An increase in levels of the molecules can be measured after everything from sports injuries to the head and carbon monoxide poisoning, to sleep apnea and fetal distress after childbirth. Researchers measured the levels of NSE and S-100B in the blood of 15 healthy young men who were sleep-deprived for one night, and found morning serum levels of the molecules increased by about 20 per cent compared with values obtained after a night of sleep. "The blood concentration of both biomarkers was elevated after sleep loss. This makes it unlikely that our results were caused by chance," lead researcher Christian Benedict said. He said the results indicate a lack of sleep may promote "neurodegenerative processes. "In conclusion, the findings of our trial indicate that a good night's sleep may be critical for maintaining brain health," he said. © CBC 2014
Link ID: 19085 - Posted: 01.02.2014
By Gary Stix Is sleep good for everything? Scientists hate giving unqualified answers. But the more sleep researchers look, the more the answer seems to be tending toward a resounding affirmative. The slumbering brain plays an essential role in learning and memory, one of the findings that sleep researchers have reinforced repeatedly in recent years. But that’s not all. There’s a growing recognition that sleep appears to be involved in regulating basic metabolic processes and even in mental health. Robert Stickgold, a leading sleep researcher based at Harvard Medical School, gives a précis here of the current state of sommeil as it relates to memory, schizophrenia, depression, diabetes—and he even explains what naps are good for. How far have we come in understanding sleep? Although we understood the function of every other basic drive 2,000 years ago, we are still struggling to figure out what the biological functions of sleep are. One of the clearest messages now is that for every two hours humans spend awake during the day, the brain needs an hour offline to process the information it takes in and figure out what to save and what to dump and how to file and what it all means. So what is sleep for? Memories are processed during sleep. But sleep doesn’t have just one function. It’s a little bit like listening to tongue researchers arguing about whether the function of the tongue has to do with taste or speech. And you want to say: ‘Guys, c’mon, it’s both.’ There’s very good evidence now that sleep, besides helping memory, has a role in immune and endocrine functions. There’s a lot of talk about to what extent the obesity epidemic is actually a consequence of too little sleep. © 2013 Scientific American
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.