Sleep

During sleep, even anesthesia–induced sleep, part of the brain appears to continue working to process information and cement memories. That’s according to a study (subscription required) published yesterday in Nature Neuroscience, and the findings, say researchers, could offer new insights into better understanding Alzheimer’s disease.

Health Day reports on the UC Los Angeles research:

For the study, which was performed on mice, the researchers measured the activity of single neurons from three parts of the brain involved in memory formation in order to identify which brain region was activating other areas of the brain and how this activation was spreading.

The investigators discovered that the entorhinal cortex has what is called persistent activity, which is believed to be involved in working memory when people are awake, such as remembering a phone number or following directions.

…

Persistent activity in the entorhinal cortex during sleep may be a way to unclutter memories and delete information that was processed during the day but not needed, which results in important memories becoming prominent and readily accessible, [senior author, Mayank R. Mehta, PhD,] suggested.

The findings are important because people spend one-third of their lives sleeping, and a lack of sleep causes various health problems, including learning and memory problems, Mehta said. The researcher also noted that Alzheimer’s disease starts in the entorhinal cortex and these patients are known to have sleep problems.

Related to this, a previous mouse study done at Stanford showed that fragmented sleep can cause memory impairment.

Previously: Is quietly resting as helpful to your brain as sleeping?, Experts discuss possible link between sleep disorder and dementia and In mice, at least, uninterrupted sleep is critical for memory
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I’m a few days late to this (I was off dipping apples in honey with my family), but I can’t resist pointing to an article on sleep from The Atlantic. Writer Brian Fung tackles a question that has been debated in my house for years: Is lying down and resting just as good for you as sleeping? (My hubby says yes, I say no.) Fung writes:

Part of what makes this question so slippery is that it hinges in large part on the matter of what sleep is actually for. We can all name the benefits of sleep, but saying what sleep accomplishes is a far cry from identifying what sleep is meant to do. The distinction is important. If the point of sleep is that being inactive frees up our energy for other tasks (say, recovering from a cold), we might expect lying in bed with our eyes closed — what some studies call “quiet wakefulness” — to accomplish much the same thing. 

Researchers are growing increasingly confident, though, that sleep evolved specifically to recharge the brain. Dr. Chiara Cirelli, a neuroscientist at the University of Wisconsin, has been studying the difference between sleep and quiet wake in humans. She says that while we’re awake, all of our neurons are constantly firing, but that when we’re asleep, the neurons revert to an “up-and-down” state in which only some are active at a given time. During some stages of sleep, all neuron activity goes silent. And that’s likely when the restful part of sleep takes place.   

Read the rest of Fung’s piece for the full answer. And just for the record: It appears I was correct.

Previously: In mice, at least, uninterrupted sleep is critical for memory and Stanford expert: Quality, not quantity, of sleep is what counts
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Overall, 30 percent of employed U.S. adults get less sleep than the recommended seven to nine hours of sleep a day, according to the latest data from the Centers for Disease Control and Prevention. Now new research from Brigham and Women’s Hospital offers insights into how our poor sleep habits may be influencing our performance at work.

Findings published yesterday in The Journal of Vision show the longer a person is awake, the slower he is in performing complex visual search tasks, which are common in jobs such as air-traffic control and monitoring power plant operations.

Descriptions of the study and researchers’ results are described in a hospital release:

In the first week, all participants were scheduled to sleep 10-12 hours per night to make sure they were well-rested. For the following three weeks, the participants were scheduled to sleep the equivalent of 5.6 hours per night, and also had their sleep times scheduled on a 28-hour cycle, mirroring chronic jet lag. The research team gave the participants computer tests that involved visual search tasks and recorded how quickly the participants could find important information, and also how accurate they were in identifying it. The researchers report that the longer the participants were awake, the more slowly they identified the important information in the test. Additionally, during the biological night time, 12 a.m. -6 a.m., participants (who were unaware of the time throughout the study) also performed the tasks more slowly than they did during the daytime.

While the accuracy of the participants stayed the fairly constant, they were slower to identify the relevant information as the weeks went on. The self-ratings of sleepiness only got slightly worse during the second and third weeks on the study schedule, yet the data show that they were performing the visual search tasks significantly slower than in the first week.

Although additional studies are needed, researchers say these findings suggest that while you may not feel especially tired, your lack of sleep may be notably affecting your performance on the job.

Previously: A look at the most sleep-deprived and well-rested occupations, Study estimates Americans’ insomnia costs nation $63 billion annually and CDC report highlights the dangers of sleep deprivation
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We all know that a good night’s sleep is important in maintaining good health. New research, however, hints that sleep deprivation within six hours after a traumatic event may actually be therapeutic in preventing symptoms of post-traumatic stress disorder (PTSD).

Researchers at Ben-Gurion University and Tel Aviv University led the animal study, which was published in the the latest issue of Neuropsychopharmacology. Medical Daily reports:

Researchers found that rats that were not allowed to sleep after the stress  exposure did not exhibit behavior indicating memory of the stressful event, while the control group of rats that were allowed to sleep after the stressful  event appeared to remember past trauma and exhibited post trauma-like behavior  in elevated plus-maze and acoustic startle response tests.

“Post-exposure SD effectively ameliorated long-term, stress-induced, PTSD-like behavioral disruptions, reduced trauma reminder freezing responses, and decreased hippocampal expression of GR compared with exposed-untreated controls,” researchers wrote in the study.

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Researchers said that that intentionally preventing sleep in the early aftermath of stress exposure may be effective in reducing traumatic stress because sleep deprivation may play a role in disrupting the consolidation of stressful fear-inducing memories by decreasing activity in the hippocampus, an essential area of the brain responsible for memory.

The investigators are already planning a similar study on humans to further understand the relationship between sleep deprivation and PTSD.

Previously: Using a mobile-based app to help manage PTSD and In mice, at least, uninterrupted sleep is critical for memory
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A Stanford study published last month found that 3.6 percent of U.S. adults sleepwalk. That means that more than 8.4 million Americans could be wandering in the night unconscious of their actions. Some, like my brother who once woke up in the kitchen after chewing through a PowerBar wrapper, exhibit harmless behavior. But others may attempt to drive a car or engage in far more dangerous activities.

As reported in a recent Observations post, a subset of sleepwalkers, comprising about 2 percent of the general population in North America and Europe, may be at risk for one of three disorders associated with sleep violence, and related incidents have ranged from running and kicking to assault and even murder. Daisy Yuhas writes:

Because various disorders can underlie sleep violence, investigating incidents is understandably challenging. Michel Cramer Bornemann, [MD,] a sleep specialist at the Minnesota Regional Sleep Disorders Center, and his colleagues at the center’s Sleep Forensics Associates have handled more than 200 forensic cases related to sleep disorders, often at the request of law enforcement. Of these, only arousal disorders have been associated with criminal behavior during sleepwalking. He estimates that about a third of cases the forensics associates encounter involve sleep drugs, such as Ambien, which may increase the risk of experiencing an arousal disorder.

Ongoing research to better understand the brain states of those afflicted by such disorders is highlighted in a feature (subscription required) in the latest issue of Scientific American. The article also discusses symptoms of arousal disorders, wherein a person “operates in a mental state between wakefulness and sleep, carrying out complex behaviors with no evident conscious awareness.” Other disorders associated with sleep violence include nocturnal frontal lobe epilepsy and rapid eye movement (REM) sleep behavior disorder.

Previously: Stanford study shows millions of Americans are prone to sleepwalking and Video: Patient does art while sleepwalking
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Have you ever sleepwalked? If so, you’re not alone: According to new research out of Stanford’s medical school, about 3.6 percent of U.S. adults - or around 8.4 million – are prone to wandering around in the night. The study is the first to use a large, representative sample of the U.S. general population to demonstrate the number of sleepwalkers (19,136 adults in 15 states were surveyed), and the researchers say the findings underscore “the fact that sleepwalking is much more prevalent in adults than previously appreciated.”

The work of Maurice Ohayon, MD, DSc, PhD, and his colleagues also shed light on the theory that medication use and certain psychological and psychiatric conditions act as sleepwalking triggers:

The study also showed that people with depression were 3.5 times more likely to sleepwalk than those without, and people with alcohol abuse/dependence or obsessive-compulsive disorder were also significantly more likely to have sleepwalking episodes. In addition, individuals taking SSRI antidepressants were three times more likely to sleepwalk twice a month or more than those who didn’t.

“There is no doubt an association between nocturnal wanderings and certain conditions, but we don’t know the direction of the causality,” said Ohayon. “Are the medical conditions provoking sleepwalking, or is it vice versa? Or perhaps it’s the treatment that is responsible.”

The study appears online today in Neurology, the medical journal of the American Academy of Neurology.

Previously: Video: Patient does art while sleepwalking and Stanford expert: Quality, not quantity, of sleep is what counts
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An estimated 15 percent of adults and seven percent of teens get fewer than six hours of sleep on weeknights. Besides suffering from daytime sleepiness and fatigue, these individuals may also have an increased risk of obesity, according to findings recently published in the American Journal of Human Biology.

Past research, including a 2004 Stanford study, has suggested that sleep duration is an important regulator of body weight and metabolism. The new study took a closer look at accumulated evidence from experimental and observational studies of sleep. According to a journal release, the review showed:

…cross-sectional associations between getting fewer than six hours sleep and increased body mass index (BMI) or obesity.

The studies [also] revealed how signals from the brain, which control appetite regulation, are impacted by experimental sleep restriction. Inadequate sleep impacts secretion of the signal hormones ghrelin, which increases appetite, and leptin, which indicates when the body is satiated. This can lead to increased food intake without the compensating energy expenditure.

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The evidence suggests the association between inadequate sleep and higher BMI is stronger in children and adolescents. It also shows that sleep deficiency in lower socioeconomic groups may result in greater associated obesity risks.

On a related note, a separate study published last week showed that poor sleep and shift work can impair glucose regulation and metabolism, which could result in obesity or diabetes over time.

Previously: How lack of sleep affects the brain and may increase appetite, weight gain, Study shows link between lack of sleep and obesity in teen boys and Study: Staying up late tied to poor eating habits, weight gain
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Students everywhere, rejoice. Scientific research seems to support the nap you just got in trouble for taking during English class.

A new study from the University of Notre Dame tested sleep’s effect on 207 students’ success in remembering declarative information – facts and events – in semantically related or unrelated word pairs. Students learned at either 9 a.m. or 9 p.m., and underwent recall testing 30 minutes, 12 hours, or 24 hours later. While the time of day during which students learned showed no effect on memory initially, testing results after 12 hours were better in those who slept overnight versus those who spent the day awake. And in tests done 24 hours after learning, students who had slept immediately after learning demonstrated significantly greater recall of the unrelated word pairs.

A Notre Dame article quotes psychologist Jessica Payne, PhD, first author of the study, on its significance:

Since we found that sleeping soon after learning benefited both types of memory, this means that it would be a good thing to rehearse any information you need to remember just prior to going to bed. In some sense, you may be ‘telling’ the sleeping brain what to consolidate.

Previously: Discussing sleep and work performance among health-care professionals, In mice, at least, uninterrupted sleep is critical for memory and Do siestas make you smarter?
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I sleep like a champ – or at least, I’d like to think I do. But frequent bouts of temporary restlessness and insomnia have left me questioning whether I’m doing something wrong.

In a recent interview with 7 Live Online, Clete Kushida, MD, PhD, director of sleep medicine at Stanford, provides sleeping tips for people like me. As you’ll see in the video above, he discusses the recent time change as well as ways to establish a healthy pattern of behavior for better sleep.

Previously: Ask Stanford Med: Rafael Pelayo answers questions on sleep research and offers tips for ‘springing forward’, Stanford sleep expert Rafael Pelayo featured on KGO, Stanford expert: Quality, not quantity, of sleep is what counts and Tips for not losing sleep over daylight-saving time

Changes to our sleep schedules like the upcoming change to daylight saving time can make it hard to fall or stay asleep. In an effort to help you spring forward and stay on track, Stanford’s Rafael Pelayo, MD, recently took questions on sleep research and offered techniques for making sure disruptions like daylight saving time don’t cut into your sleep.

Below are Pelayo’s responses to a selection of questions submitted using the hashtag #AskSUMed, @replies to the @SUMedicine feed or the comments section here on Scope.

Erin asks: I’m the mom of a toddler and would love your suggestions for how to help him deal with the time change. In addition, my husband is a real night owl and tends to suffer every year when we “spring forward.” How can people whose bodies don’t like early mornings adjust to the time change?

Unless your toddler needs to wake up at a set time, for example to go to childcare, your child will most likely self-correct. If your toddler does need to wake up at a set time, these tips may be useful in making the transition smoother for him when the clocks change Sunday.

But your night owl husband is a different situation. It is very difficult to go to bed early and much easier to stay up later. I would suggest he, and others with a similar problem, use the following tips to minimize the impact of the time shift. Go to bed 15 minutes earlier for a few nights preceding the time change. Make sure to avoid light as much as possible within an hour or two of going to sleep in order to adjust to an earlier bedtime. If possible, refrain from sleeping late during the weekend and rise within a few minutes of your usual wake-up time on workdays. Keeping the same wake time will help maintain the body’s internal circadian rhythm. Upon awakening, immediately maximize your exposure to sunlight. If you’re fatigued during the day take a short afternoon nap.

@ChilunjeZ asks: I can’t seem to ever get an early night no matter what I try. I always tend to go to sleep after midnight. How can I develop healthy habits to help me get to bed at an earlier time and wake up earlier the next morning?

It is important to remember that you did not always go to sleep after midnight so this is a behavior that you are capable of changing. Past studies have shown that your biological clock is located in an area of the brain called the “suprachiasmatic nucleus.” This clock sets your sleep schedule tendency based on a series of time givers called “zeitgebers.” Zeitgebers can be manipulated to adjust your sleep time.

To change your sleep-wake behavior, I recommend that you focus more on the specific time you want to wake up in the morning rather than the time you want to go to sleep at night. It is easier to force yourself to wake up, than it is to fall asleep. Generally speaking, humans have peak alertness about two hours before falling asleep. So it is extremely difficult to make large, abrupt shifts our bedtime. Instead, try locking in a wake-up time of about 30 minutes earlier than usual for one week. The following week, move the wake-up time back another 30 minutes. Continue making these gradual adjustments over a period of time. Eventually, your wake-up time will predict the time you fall asleep. As you’re making these adjustments to your sleep schedule, keep in mind that it is very important to lock in the same wake-up time on weekends and weekdays.

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