Which Bird Are You?

Early Bird Or Night Owl?

Sunday, February 12, 2017

The Purpose of Sleep? To Forget, Scientists Say

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Carl Zimmer
MATTER
A PET scan of a brain during normal sleep. Two scientists say sleep may help the brain prune back unneeded synapses. Hank Morgan/Science Source
Over the years, scientists have come up with a lot of ideas about why we sleep.
Some have argued that it’s a way to save energy. Others have suggested that slumber provides an opportunity to clear away the brain’s cellular waste. Still others have proposed that sleep simply forces animals to lie still, letting them hide from predators.
A pair of papers published on Thursday in the journal Science offer evidence for another notion: We sleep to forget some of the things we learn each day.
In order to learn, we have to grow connections, or synapses, between the neurons in our brains. These connections enable neurons to send signals to one another quickly and efficiently. We store new memories in these networks.
In 2003, Giulio Tononi and Chiara Cirelli, biologists at the University of Wisconsin-Madison, proposed that synapses grew so exuberantly during the day that our brain circuits got “noisy.” When we sleep, the scientists argued, our brains pare back the connections to lift the signal over the noise.
In the years since, Dr. Tononi and Dr. Cirelli, along with other researchers, have found a great deal of indirect evidence to support the so-called synaptic homeostasis hypothesis.
It turns out, for example, that neurons can prune their synapses — at least in a dish. In laboratory experiments on clumps of neurons, scientists can give them a drug that spurs them to grow extra synapses. Afterward, the neurons pare back some of the growth.
Other evidence comes from the electric waves released by the brain. During deep sleep, the waves slow down. Dr. Tononi and Dr. Cirelli have argued that shrinking synapses produce this change.
Four years ago, Dr. Tononi and Dr. Cirelli got a chance to test their theory by looking at the synapses themselves. They acquired a kind of deli slicer for brain tissue, which they used to shave ultrathin sheets from a mouse’s brain.

How to Get a Better Night’s Sleep

How do you become a more successful sleeper? Grab a pillow, curl up and keep reading to find out.
Luisa de Vivo, an assistant scientist working in their lab, led a painstaking survey of tissue taken from mice, some awake and others asleep. She and her colleagues determined the size and shape of 6,920 synapses in total.
The synapses in the brains of sleeping mice, they found, were 18 percent smaller than in awake ones. “That there’s such a big change over all is surprising,” Dr. Tononi said.
The second study was led by Graham H. Diering, a postdoctoral researcher at Johns Hopkins University. Dr. Diering and his colleagues set out to explore the synaptic homeostasis hypothesis by studying the proteins in mouse brains. “I’m really coming at it from this nuts-and-bolts place,” Dr. Diering said.
In one experiment, Dr. Diering and his colleagues created a tiny window through which they could peer into mouse brains. Then he and his colleagues added a chemical that lit up a surface protein on brain synapses.
Looking through the window, they found that the number of surface proteins dropped during sleep. That decline is what you would expect if the synapses were shrinking.
Dr. Diering and his colleagues then searched for the molecular trigger for this change. They found that hundreds of proteins increase or decrease inside of synapses during the night. But one protein in particular, called Homer1A, stood out.
In earlier experiments on neurons in a dish, Homer1A proved to be important for paring back synapses. Dr. Diering wondered if it was important in sleep, too.
To find out, he and his colleagues studied mice genetically engineered so that they couldn’t make Homer1A proteins. These mice slept like ordinary mice, but their synapses didn’t change their proteins like the ones in ordinary mice.
Dr. Diering’s research suggests that sleepiness triggers neurons to make Homer1A and ship it into their synapses. When sleep arrives, Homer1A turns on the pruning machinery.
To see how this pruning machinery affects learning, the scientists gave regular mice a memory test. They put the animals in a room where they got a mild electric shock if they walked over one section of the floor.
That night, the scientists injected a chemical into the brains of some of the mice. The chemical had been shown to block neurons in dishes from pruning their synapses.
The next day, the scientists put all the mice back in the chamber they had been in before. Both groups of mice spent much of the time frozen, fearfully recalling the shock.
But when the researchers put the mice in a different chamber, they saw a big difference. The ordinary mice sniffed around curiously. The mice that had been prevented from pruning their brain synapses during sleep, on the other hand, froze once again.
Dr. Diering thinks that the injected mice couldn’t narrow their memories down to the particular chamber where they had gotten the shock. Without nighttime pruning, their memories ended up fuzzy.
In their own experiment, Dr. Tononi and his colleagues found that the pruning didn’t strike every neuron. A fifth of the synapses were unchanged. It’s possible that these synapses encode well-established memories that shouldn’t be tampered with.
“You can forget in a smart way,” Dr. Tononi said.
Other researchers cautioned that the new findings weren’t definitive proof of the synaptic homeostasis hypothesis.
Marcos G. Frank, a sleep researcher at Washington State University in Spokane, said that it could be hard to tell whether changes to the brain at night were caused by sleep or by the biological clock. “It’s a general problem in the field,” he said.
Markus H. Schmidt, of the Ohio Sleep Medicine Institute, said that while the brain might prune synapses during sleep, he questioned whether this was the main explanation for why sleep exists.
“The work is great,” he said of the new studies, “but the question is, is this a function of sleep or is it the function?”
Many organs, not just the brain, seem to function differently during sleep, Dr. Schmidt pointed out. The gut appears to make many new cells, for example.
Dr. Tononi said that the new findings should prompt a look at what current sleeping drugs do in the brain. While they may be good at making people sleepy, it’s also possible that they may interfere with the pruning required for forming memories.
“You may actually work against yourself,” Dr. Tononi said.
In the future, sleep medicines might precisely target the molecules involved in sleep, ensuring that synapses get properly pruned.
“Once you know a little bit of what happens at the ground-truth level, you can get a better idea of what to do for therapy,” Dr. Tononi said.
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Wednesday, February 8, 2017

Sleep Problems Tied to Diabetes in Men




Men who do not get enough sleep — or get too much — may have an increased risk for Type 2 diabetes, a new study suggests.

Researchers studied 788 healthy men and women participating in a larger health study, measuring their sleep duration using electronic monitors and testing them for markers of diabetes — how well pancreatic cells take up glucose and how sensitive the body’s tissues are to insulin. The study is in the Journal of Clinical Endocrinology & Metabolism.

The average sleep time for both men and women was about seven hours. As the men diverged from the average, in either direction, their glucose tolerance and insulin sensitivity decreased, gradually increasing the deleterious health effects. There was no such association in women.

The researchers weren’t sure why men but not women showed this association but caution that this was a cross-sectional study, a snapshot of one moment in time, and that they draw no conclusions about cause and effect.

The lead author, Femke Rutters, an assistant professor at the VU Medical Center in Amsterdam, said that it is easy to advise men to get regular and sufficient sleep, but because so many lifestyle and health factors may contribute to poor sleep, acting on that advice is much harder.

“There has been a lot of observational work on sleep, but trying to change it is difficult,” she said. “Ideally, men should try for regular sleep.”





 Source: https://well.blogs.nytimes.com/2016/07/05/sleep-problems-tied-to-diabetes-in-men/


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Getting Older, Sleeping Less


Paul Rogers

Getting Older, Sleeping Less

Personal Health
By JANE E. BRODY  


Insomnia, Dr. Alon Y. Avidan says, “is a symptom, not a diagnosis” that can be a clue to an underlying and often treatable health problem and, when it persists, should be taken seriously. Dr. Avidan is director of the sleep clinic at the University of California, Los Angeles, David Geffen School of Medicine.
So-called transient insomnia that lasts less than a month may result from a temporary problem at work or an acute illness; short-term insomnia lasting one to six months may stem from a personal financial crisis or loss of a loved one. Several months of insomnia are distressing enough, but when insomnia becomes chronic, lasting six months or longer, it can wreak serious physical, emotional and social havoc. 

In addition to excessive daytime sleepiness, which can be dangerous in and of itself, Dr. Avidan reports that chronic insomnia “may result in disturbed intellect, impaired cognition, confusion, psychomotor retardation, or increased risk for injury.” 

Understandably, it is often accompanied by depression either as a cause or result of persistent insomnia. 

Untreated insomnia also increases the risk of falls and fractures, a study of nursing home residents showed.
There are two types of insomnia. One, called primary insomnia, results from a problem that occurs only or mainly during sleep, like obstructive sleep apnea, restless leg syndrome (which afflicts 15 to 20 percent of older adults), periodic limb movements or a tendency to act out one’s dreams physically, which can be an early warning sign of Parkinson’s disease.
Unless noted by their bed partners, people with primary sleep disorders may not know why their sleep is disrupted. An accurate diagnosis often requires a professional sleep study: spending a night or two in a sleep lab hooked up to instruments that record respiration, heart rate, blood pressure, bodily movements and time spent in the various stages of sleep.
The other, more common type of insomnia is secondary to an underlying medical or psychiatric problem; the side effects of medications; behavioral factors like ill-timed exposure to caffeine, alcohol or nicotine or daytime naps; or environmental disturbances like jet lag or excessive noise or light — especially the blue light from an electronic device — in the bedroom.
Among the many medical conditions that can cause insomnia are heart failure, gastroesophageal reflux (GERD), lung disease, arthritis, Alzheimer’s disease and incontinence. Treating the underlying condition, if possible, often relieves the insomnia.
Regardless of the reason for insomnia, it can become a learned response when people anticipate having difficulty falling asleep or returning to sleep after middle-of-the-night awakenings. They may spend hours lying awake in bed worrying about being unable to sleep, and the anxiety itself impairs their ability to sleep.

The more one frets about a sleep problem, the worse it can get. When on occasion I awaken in the wee hours of the morning and can’t get back to sleep, I usually get up and do something useful, which takes the curse off my insomnia. 

If I’m worried about forgetting something important, I write it on a pad kept next to the bed, taking care not to turn on a light. 

(Bright light in the middle of the night can reset your biological clock; if you get up to use the bathroom, use a night light near the floor.)
Nonmedical causes of insomnia are often successfully treated by practicing “good sleep hygiene,” a concept developed by the late Peter J. Hauri, a sleep specialist at the Mayo Clinic.

Good sleep hygiene means:
-limiting naps to less than 30 minutes a day, preferably early in the afternoon;
-avoiding stimulants and sedatives; 
-avoiding heavy meals and minimizing liquids within two to three hours of bedtime; 
-getting moderate exercise daily, preferably in the morning or early afternoon; 
-maximizing exposure to bright light during the day and minimizing it at night; 
-creating comfortable sleep conditions; and going to bed only when you feel sleepy.

If you still can’t fall asleep within about 20 minutes in bed, experts recommend leaving the bedroom and doing something relaxing, like reading a book (one printed on paper, not on a brightly lit screen), and returning to bed when you feel sleepy.

Many people mistakenly resort to alcohol as a sleep aid. While it may help people fall asleep initially, it produces fragmented sleep and interferes with REM sleep, Dr. Avidan and others report.
For those who still need help with insomnia, cognitive behavioral therapy has proved most effective in clinical trials, though finding a specialist may be challenging in some parts of the country.

Sleeping pills can be problematic, especially for older people who are more sensitive to their side effects, including daytime hangover. Even short-acting drugs like zaleplon (Sonata), zolpidem (Ambien) or ramelteon (Rozerem) can have side effects.

Alternatives include over-the-counter remedies like melatonin or valerian, which have more anecdotal evidence than research to attest to their efficacy. The brain makes melatonin, the body’s natural sleepiness hormone, in response to darkness.

There may also be some useful dietary aids, like bananas, cherries, kiwis, oatmeal, milk and chamomile tea, though evidence for these is also primarily anecdotal. One friend told me she solved a longstanding sleep problem by eating a banana two hours before bedtime.

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