Posts Tagged ‘sleep’

By Chris Mercer

Eating cheese before you go to bed will not give you nightmares but different varieties could help you choose the dreams you do want to have, says a study by the British Cheese Board.

Not one of the 200 volunteers who took part in the British Cheese Board’s ‘cheese & dreams’ study reported having nightmares after eating 20g of cheese 30 minutes before bed.

The industry body said 72 per cent of participants slept very well and 67 per cent remembered their dreams.

The study, believed to be the first of its kind, serves to dispel the old wives’ tale that eating cheese before bed means a restless night in-store. It was endorsed by Neil Stanley of the Sleep Research HPRU Medical Research Centre at the University of Surrey.

Dr. Judith Bryans, a nutrition scientist at Britain’s Dairy Council, added the science bit: “One of the amino acids in cheese – tryptophan – has been shown to reduce stress and induce sleep.”

The research, in an intriguing twist, also found that different cheeses appeared to give participants different kinds of dreams.

Cheddar, officially Britain’s most popular cheese with 55 per cent of the market, enhanced dreams about celebrities. One girl said she dreamt of helping to form a human pyramid under the supervision of film star Johnny Depp.

Stilton was the wild card, especially for women. Around 85 per cent of women experienced bizarre dreams after eating Britain’s iconic blue cheese, including talking soft toys, dinner party guests being traded for camels and a vegetarian crocodile upset because it could not eat children.

Of the others, Red Leicester is likely to have you dwelling on the past and Lancashire will get you focused on the future.

The boring award goes to crumbly Cheshire, which gave more than half its consumers dreamless nights. Cheshire and Red Leicester, however, gave the best nights’ sleep.

So there it is, although with more than 700 varieties of British cheese it seems there is much left to discover.

The British Cheese Board said it hoped to use the results to encourage more cheese eating before bed. Britons currently eat 30g of cheese every day on average, yet continental Europeans eat twice as much.

The Cheese Board says 30g of cheddar contains around 30 per cent of the recommended daily calcium intake for adults.


by Philip Perry

According to the National Institutes of Health, we spend about 26 years of our life asleep, one-third of the total. The latest research states that between 6.4 and 7.5 hours of sleep per night is ideal for most people. But some need more and others less. A contingent out there, mostly women, who do surprisingly well on just six hours.

There is even some data to suggest that a slim minority, around three percent of the population, thrive on just three hours sleep per night, with no ill effects. Of course, most people need much more. Even though in general, Americans are getting far less sleep today than in the past.

Cutting out needful rest could damage your health, long-term. A recent study showed that sleep is essential to clearing the brain of toxins that build up over the course of the day. It also helps in memory formation and allows other organs to repair themselves. Our professional lives and our natural cycles don’t always mesh. Often, they are at odds.

What if you are insanely busy, like ten times the norm? Say you are going to medical school, earning your PhD, or are trying to get a business off the ground. There may not be enough hours in the day for what you have to do.

One thing you can do is rearrange your sleep cycle to give yourself more time. Paleoanthropologists espouse that our ancestors probably didn’t sleep for seven hours at a clip, as it would make them easy prey. Instead, they probably slept at different periods throughout the day and night, and you can too.

What we consider a “normal” sleep cycle is called monophasic. This is sleeping for one long period throughout the night. In some Southern European and Latin American countries, the style is biphasic. They sleep five to six hours per night, with a 60-90 minute siesta during midday. There is a historical precedent too. Before the advent of artificial light, most people slept in two chunks each night of four hours each, with an hour of wakefulness in-between. That’s also a biphasic system. Then there is polyphasic sleep. This is sleeping for different periods and amounts of time throughout the day.

Certain paragons of history slept this way including Leonardo Da Vinci, Nikola Tesla, Franz Kafka, Winston Churchill, and Thomas Edison, among others. The idea gained popularity in the 1970’s and 80’s among the scientific community. Buckminster Fuller, a famous American inventor, architect, and philosopher of the 1900’s, championed this kind of slumber. He branded his version Dymaxion sleep.

Here, you take a half hour nap every six hours and sleep a total of just two hours per night. Swiss artist Francesco Jost practiced it for 49 days straight once, while observed by Italian neurologist Claudio Stampi. At first, Jost had trouble adjusting. But soon after, he was able to make it work with few side effects. He did have trouble waking at times, however. But the artist gained five more hours each day.

Do a quick search of polyphasic sleep and you find that many people around the world are experimenting with it. There are different ways of doing it. Some try the Uberman schedule. Here, one takes six 30 minute naps throughout the day at 2 P.M., 6 P.M., 2 A.M., and 10 A.M. That’s three hours of sleep total. Another way to do it is the Everyman Schedule. Here, a three hour chunk of sleep takes place between 1 A.M. and 4 A.M. Then, three 20 minute naps occur throughout the day at 9 A.M., 2 P.M., and 9 P.M. That’s around 4.5 hours of sleep daily.

So what’s the science behind this radical system? Unfortunately, no long-term research has been conducted, yet. One 2007 study, published in the Journal of Sleep Research, found that most animals sleep on a polyphasic schedule, rather getting their sleep all at once. This also begs the question, how much sleep does the human brain need to function properly? The answer is unknown.

Sleep is broken into three cycles. There is light sleep, deep sleep, and rapid eye movement (REM) sleep. The last one is considered the most important and restful of phases. We don’t stay in any one phase for long. Instead, we cycle through these constantly throughout the night. So with polyphasic sleep, the idea is to experience these three phases in shorter amounts of time, and wake up rested.

We don’t know the exact purpose of these phases. Sleep is still something of a mystery. Without a good understanding, it’s difficult to quantify the impact a polyphasic schedule has. One question is whether such a schedule allows for enough REM sleep. Polyphasic practitioners say they are able to enter the REM phase quickly, more so than with a monophasic style. Jost for example, claimed he could enter REM sleep immediately. This quick entry into the REM state is known as “repartitioning.” The deprivation of sleep may help the body enter REM quickly, as an adaptation.

So what are the downsides of this altered sleep cycle? Boredom and a limited social life. For those who want to go out drinking with friends, stay up late watching movies, or spend time with the kids, the drastic schedule change can cause problems. It has to be rigidly kept to work. Another concern, some studies have shown that those who sleep under five or six hours per night may have a higher risk of cardiovascular disease and lower immune system functioning.

Some argue that sleep theories just don’t account for human diversity in needs. For instance, some insomniacs have praised a polyphasic style for helping them regain the ability to sleep. At issue is the lack of data. But of course, anyone who is considering seriously taking part in such a style should consult a physician and keep in touch with him or her regularly, throughout the process.

How people sleep and how much they need varies widely. This may or may not have a genetic component. More research on sleep may help us to determine what our brain and body needs, and how we can adjust our sleep patterns to get the most out of our day, without sacrificing our health.


Sleep deprivation majorly impacts the brain’s connectivity and function, according to a recent study published in NeuroImage. As well as affecting many important networks, sleep deprivation prevented normal changes to brain function between the morning and evening.

Sleep is an essential human state which is necessary for maintaining healthy function throughout the body. Therefore, lack of sleep has severe health-related consequences, with the brain being the most affected organ.

Lack of sleep can negatively affect memory, emotional processing and attentional capacities. For example, sleep deprivation has been shown to disrupt functional connectivity in hippocampal circuits (important for memory), and between the amygdala (important for emotion regulation) and executive control regions (involved in processes such as attention, planning, reasoning and cognitive flexibility). The emotional effects of sleep deprivation can be to both alter response patterns to negative things but also enhance reactivity toward positive things.

The study, led by Tobias Kaufmann of University of Oslo, involved 60 young men who completed three resting state functional magnetic resonance imaging (fMRI) scans – this is used to evaluate connectivity between brain regions when a person is not performing a task.

They were scanned in the morning and evening of the same day – this was to account for changes from morning to evening in normal brain function (diurnal variability). 41 men then underwent total sleep deprivation, whereas the remainder had another night of regular sleep, before they were scanned again the following morning. Finally, behavioural assessments of vigilance and visual attention were assessed.

The findings revealed that sleep deprivation strongly altered the connectivity of many resting-state networks; most clearly affected were networks important for memory (hippocampal networks) and attention (dorsal attention networks), as well as the default mode network (an interconnected set of brain regions active when a person is daydreaming or their mind is wandering).

In fact, they identified a set of 17 brain network connections showing altered brain connectivity. Furthermore, correlation analysis suggested that morning-to-evening connectivity changes returned the next day in the group that had slept the night, but not in the sleep-deprivation group.

The study emphasizes the major impact of sleep deprivation on the brain’s connectivity and function, as well as providing evidence that normal morning-to-evening connectivity changes do not occur after a night without sleep.

By Helen Thomson

What would you do if you had 60 days of extra free time a year? Ask Abby Ross, a retired psychologist from Miami, Florida, a “short-sleeper”. She needs only four hours sleep a night, so has a lot of spare time to fill while the rest of the world is in the land of nod.

“It’s wonderful to have so many hours in my day – I feel like I can live two lives,” she says.

Short-sleepers like Ross never feel lethargic, nor do they ever sleep in. They wake early – normally around four or five o’clock – raring to get on with their day. Margaret Thatcher may have been one – she famously said she needed just four hours a night, whereas Mariah Carey claims she needs 15.

What makes some people fantastically efficient sleepers, while others spend half their day snoozing? And can we change our sleeping pattern to make it more efficient?

In 2009, a woman came into Ying-Hui Fu’s lab at the University of California, San Francisco, complaining that she always woke up too early. At first, Fu thought the woman was an extreme morning lark – a person who goes to bed early and wakes early. However, the woman explained that she actually went to bed around midnight and woke at 4am feeling completely alert. It was the same for several members of her family, she said.

Fu and her colleagues compared the genome of different family members. They discovered a tiny mutation in a gene called DEC2 that was present in those who were short-sleepers, but not in members of the family who had normal length sleep, nor in 250 unrelated volunteers.

When the team bred mice to express this same mutation, the rodents also slept less but performed just as well as regular mice when given physical and cognitive tasks.

Getting too little sleep normally has a significant impact on health, quality of life and life expectancy. It can cause depression, weight gain and put you at greater risk of stroke and diabetes. “Sleep is so important, if you sleep well you can avoid many diseases, even dementia,” says Fu. “If you deprive someone of just two hours sleep a day, their cognitive functions become significantly impaired almost immediately.”

But why sleep is so important is still a bit of a mystery. The general consensus is that the brain needs sleep to do some housekeeping and general maintenance, since it doesn’t get much downtime during the day. While we sleep, the brain can repair cellular damage, remove toxins that accumulate during the day, boost flagging energy supplies and lay down memories.

“Clearly people with the DEC2 mutation can do the same cleaning up process in a shorter period of time – they are just more efficient than the rest of us at sleeping,” says Fu. “But how are they doing that? That’s the key question.”

Since discovering the DEC2 mutation, a lot of people have come forward claiming to only sleep a few hours a day, says Fu. Most of these had insomnia, she says. “We’re not focusing on those people who have sleeping issues that make them sleep less, we wanted to focus on people who sleep for a few hours and feel great.”

A positive outlook is common among all of the short-sleepers that Fu has studied. “Anecdotally,” she says, “they are all very energetic, very optimistic. It’s very common for them to feel like they want to cram as much into life as they can, but we’re not sure how or whether this is related to their mutations.”

Ross would seem to fit that mould. “I always feel great when I wake up,” she says. She has been living on four to five hours sleep every day for as long as she can remember.

“Those hours in the morning – around five o’clock – are just fabulous. It’s so peaceful and quiet and you can get so much done. I wish more shops were open at that time, but I can shop online, or I can read – oh there’s so much to read in this world! Or I can go out and exercise before anyone else is up, or talk to people in other time zones.”

Her short sleeping patterns allowed her to complete university in two and a half years, as well as affording her time to learn lots of new skills. For example, just three weeks after giving birth to her first son, Ross decided to use one of her early mornings to attempt to run around the block. It took her 10 minutes. The following day she did it again, running a little further. She slowly increased the time she ran, finally completing not one, but 37 marathons – one a month over three years – plus several ultramarathons. “I can get up and do my exercise before anyone else is up and then it’s done, out of the way,” she says.

As a child, Ross remembers spending very early mornings with her dad, another short-sleeper. “Our early mornings gave us such a special time together,” she says. Now, if she ever oversleeps – which she says has only ever happened a handful of times, her husband thinks she’s dead. “I just don’t lay in, I’d feel terrible if I did,” she says.

Fu has subsequently sequenced the genomes of several other families who fit the criteria of short-sleepers. They’re only just beginning to understand the gene mutations that lead to this talent, but in principle, she says, it might one day be possible to enable short sleeping in others.

Until then, are there any shortcuts to a more efficient night’s sleep for the rest of us? Neil Stanley, an independent sleep consultant, says yes: “The most effective way to improve your sleep is to fix your wake-up time in the morning.”

Stanley says that when your body gets used to the time it needs to wake up, it can use the time it has to sleep as efficiently as possible. “Studies show that your body prepares to wake up one and a half hours prior to actually waking up. Your body craves regularity, so if you chop and change your sleep pattern, your body hasn’t got a clue when it should prepare to wake up or not.”

You could also do yourself a favour by ignoring society’s views on sleep, he says. “There’s this social view that short sleeping is a good thing and should be encouraged – we’re always hauling out the example of Margaret Thatcher and top CEOs who don’t need much sleep. In fact, the amount of sleep you need is genetically determined as much as your height or shoe size. Some people need very little sleep, others need 11 or 12 hours to feel their best.”

Stanley says that a lot of people with sleep issues actually don’t have any problem sleeping, instead they have an expectation that they need to sleep for a certain amount of time. “If we could all figure out what kind of sleeper we are, and live our life accordingly, that would make a huge difference to our quality of life,” he says.

By Clare Wilson

It is one of life’s great enigmas: why do we sleep? Now we have the best evidence yet of what sleep is for – allowing housekeeping processes to take place that stop our brains becoming overloaded with new memories.

All animals studied so far have been found to sleep, but the reason for their slumber has eluded us. When lab rats are deprived of sleep, they die within a month, and when people go for a few days without sleeping, they start to hallucinate and may have epileptic seizures.

One idea is that sleep helps us consolidate new memories, as people do better in tests if they get a chance to sleep after learning. We know that, while awake, fresh memories are recorded by reinforcing connections between brain cells, but the memory processes that take place while we sleep have remained unclear.

Support is growing for a theory that sleep evolved so that connections in the brain can be pruned down during slumber, making room for fresh memories to form the next day. “Sleep is the price we pay for learning,” says Giulio Tononi of the University of Wisconsin-Madison, who developed the idea.

Now we have the most direct evidence yet that he’s right. Tononi’s team measured the size of these connections or synapses in brain slices taken from mice. The synapses in samples taken at the end of a period of sleep were 18 per cent smaller than those in samples taken from before sleep, showing that the synapses between neurons are weakened during slumber.

A good night’s sleep

Tononi announced these findings at the Federation of European Neuroscience Societies meeting in Copenhagen, Denmark, last week. “The data was very solid and well documented,” says Maiken Nedergaard of the University of Rochester, who attended the conference.

“It’s an extremely elegant idea,” says Vladyslav Vyazovskiy of the University of Oxford

If the housekeeping theory is right, it would explain why, when we miss a night’s sleep, the next day we find it harder to concentrate and learn new information – we may have less capacity to encode new experiences. The finding suggests that, as well as it being important to get a good night’s sleep after learning something, we should also try to sleep well the night before.

It could also explain why, if our sleep is interrupted, we feel less refreshed the next day. There is some indirect evidence that deep, slow-wave sleep is best for pruning back synapses, and it takes time for our brains to reach this level of unconsciousness.

Waking refreshed

Previous evidence has also supported the housekeeping theory. For instance, EEG recordings show that the human brain is less electrically responsive at the start of the day – after a good night’s sleep – than at the end, suggesting that the connections may be weaker. And in rats, the levels of a molecule called the AMPA receptor – which is involved in the functioning of synapses – are lower at the start of their wake periods.

The latest brain-slice findings that synapses get smaller is the most direct evidence yet that the housekeeping theory is right, says Vyazovskiy. “Structural evidence is very important,” he says. “That’s much less affected by other confounding factors.”

Protecting what matters

Getting this data was a Herculean task, says Tononi. They collected tiny chunks of brain tissue, sliced it into ultrathin sections and used these to create 3D models of the brain tissue to identify the synapses. As there were nearly 7000 synapses, it took seven researchers four years.

The team did not know which mouse was which until last month, says Tononi, when they broke the identification code, and found their theory stood up.

“People had been working for years to count these things. You start having stress about whether it’s really possible for all these synapses to start getting fatter and then thin again,” says Tononi.

The team also discovered that some synapses seem to be protected – the biggest fifth stayed the same size. It’s as if the brain is preserving its most important memories, says Tononi. “You keep what matters.”

By Brigitte Steger

The Japanese don’t sleep. This is what everyone – the Japanese above all – say. It’s not true, of course. But as a cultural and sociological statement, it is very interesting.

I first encountered these intriguing attitudes to sleep during my first stay in Japan in the late 1980s. At that time Japan was at the peak of what became known as the Bubble Economy, a phase of extraordinary speculative boom. Daily life was correspondingly hectic. People filled their schedules with work and leisure appointments, and had hardly any time to sleep. The lifestyle of this era is aptly summed up by a wildly popular advertising slogan of the time, extolling the benefits of an energy drink. “Can you battle through 24 hours? / Businessman! Businessman! Japanese businessman!”

Many voiced the complaint: “We Japanese are crazy to work so much!” But in these complaints one detected a sense of pride at being more diligent and therefore morally superior to the rest of humanity. Yet, at the same time, I observed countless people dozing on underground trains during my daily commute. Some even slept while standing up, and no one appeared to be at all surprised by this.

I found this attitude contradictory. The positive image of the worker bee, who cuts back on sleep at night and frowns on sleeping late in the morning, seemed to be accompanied by an extensive tolerance of so-called ‘inemuri’ – napping on public transportation and during work meetings, classes and lectures. Women, men and children apparently had little inhibition about falling asleep when and wherever they felt like doing so.

If sleeping in a bed or a futon was considered a sign of laziness, then why wasn’t sleeping during an event or even at work considered an even greater expression of indolence? What sense did it make to allow children to stay up late at night to study if it meant that they would fall asleep during class the next day? These impressions and apparent contradictions led to my more intensive involvement with the theme of sleep for my PhD project several years later.

Initially, I had to fight against prejudice as people were reluctant to consider sleep a serious topic for academic enquiry. Of course, it was precisely such attitudes that had originally caught my attention. Sleep can be loaded with a variety of meanings and ideologies; analysing sleep arrangements and the discourse on it reveals attitudes and values embedded in the contexts in which sleep is organised and discussed. In my experience, it is the everyday and seemingly natural events upon which people generally do not reflect that reveal essential structures and values of a society.

We often assume that our ancestors went to bed ‘naturally’ when darkness fell and rose with the Sun. However, sleep times have never been such a simple matter, whether in Japan or elsewhere. Even before the invention of electric light, the documentary evidence shows that people were scolded for staying up late at night for chatting, drinking and other forms of pleasure. However, scholars – particularly young samurai – were considered highly virtuous if they interrupted their sleep to study, even though this practice may not have been very efficient as it required oil for their lamps and often resulted in them falling asleep during lectures.

Napping is hardly ever discussed in historical sources and seems to have been widely taken for granted. Falling asleep in public tends to be only mentioned when the nap is the source for a funny anecdote, such as when someone joins in with the wrong song at a ceremony, unaware that they have slept through most of it. People also seem to have enjoyed playing tricks on friends who had involuntarily dozed off.

Early rising, on the other hand, has clearly been promoted as a virtue, at least since the introduction of Confucianism and Buddhism. In antiquity, sources show a special concern for the work schedule of civil servants, but from the Middle Ages onwards, early rising was applied to all strata of society, with “going to bed late and rising early” used as a metaphor to describe a virtuous person.

Another interesting issue is co-sleeping. In Britain, parents are often told they should provide even babies with a separate room so that they can learn to be independent sleepers, thus establishing a regular sleep schedule. In Japan, by contrast, parents and doctors are adamant that co-sleeping with children until they are at least at school age will reassure them and help them develop into independent and socially stable adults.

Maybe this cultural norm helps Japanese people to sleep in the presence of others, even when they are adults – many Japanese say they often sleep better in company than alone. Such an effect could be observed in spring 2011 after the huge tsunami disaster destroyed several coastal towns. Survivors had to stay in evacuation shelters, where dozens or even hundreds of people shared the same living and sleeping space. Notwithstanding various conflicts and problems, survivors described how sharing a communal sleeping space provided some comfort and helped them to relax and regain their sleep rhythm.

However, this experience of sleeping in the presence of others as children is not sufficient on its own to explain the widespread tolerance of inemuri, especially at school and in the workplace. After some years of investigating this subject, I finally realised that on a certain level, inemuri is not considered sleep at all. Not only is it seen as being different from night-time sleep in bed, it is also viewed differently from taking an afternoon nap or power nap.

How can we make sense of this? The clue lies in the term itself, which is composed of two Chinese characters. ‘I’ which means ‘to be present’ in a situation that is not sleep and ‘nemuri’ which means ‘sleep’. Erving Goffman’s concept of “involvement within social situations” is useful I think in helping us grasp the social significance of inemuri and the rules surrounding it. Through our body language and verbal expressions we are involved to some extent in every situation in which we are present. We do, however, have the capacity to divide our attention into dominant and subordinate involvement.

In this context, inemuri can be seen as a subordinate involvement which can be indulged in as long as it does not disturb the social situation at hand – similar to daydreaming. Even though the sleeper might be mentally ‘away’, they have to be able to return to the social situation at hand when active contribution is required. They also have to maintain the impression of fitting in with the dominant involvement by means of body posture, body language, dress code and the like.

Inemuri in the workplace is a case in point. In principle, attentiveness and active participation are expected at work, and falling asleep creates the impression of lethargy and that a person is shirking their duties. However, it is also viewed as the result of work-related exhaustion. It may be excused by the fact that meetings are usually long and often involve simply listening to the chair’s reports. The effort made to attend is often valued more than what is actually achieved. As one informant told me: “We Japanese have the Olympic spirit – participating is what counts.”

Diligence, which is expressed by working long hours and giving one’s all, is highly valued as a positive moral trait in Japan. Someone who makes the effort to participate in a meeting despite being exhausted or ill demonstrates diligence, a sense of responsibility and their willingness to make a sacrifice. By overcoming physical weaknesses and needs, a person becomes morally and mentally fortified and is filled with positive energy. Such a person is considered reliable and will be promoted. If, in the end, they succumb to sleep due to exhaustion or a cold or another health problem, they can be excused and an “attack of the sleep demon” can be held responsible.

Moreover, modesty is also a highly valued virtue. Therefore, it is not possible to boast about one’s own diligence – and this creates the need for subtle methods to achieve social recognition. Since tiredness and illness are often viewed as the result of previous work efforts and diligence, inemuri – or even feigning inemuri by closing one’s eyes – can be employed as a sign that a person has been working hard but still has the strength and moral virtue necessary to keep themselves and their feelings under control.

Thus, the Japanese habit of inemuri does not necessarily reveal a tendency towards laziness. Instead, it is an informal feature of Japanese social life intended to ensure the performance of regular duties by offering a way of being temporarily ‘away’ within these duties. And so it is clear: the Japanese don’t sleep. They don’t nap. They do inemuri. It could not be more different.

There’s an old saying in neuroscience: neurons that fire together wire together. This means the more you run a neuro-circuit in your brain, the stronger that circuit becomes. This is why, to quote another old saw, practice makes perfect. The more you practice piano, or speaking a language, or juggling, the stronger those circuits get.

For years this has been the focus for learning new things. But as it turns out, the ability to learn is about more than building and strengthening neural connections. Even more important is our ability to break down the old ones. It’s called “synaptic pruning.” Here’s how it works.

Imagine your brain is a garden, except instead of growing flowers, fruits, and vegetables, you grow synaptic connections between neurons. These are the connections that neurotransmitters like dopamine, seratonin, and others travel across.

“Glial cells” are the gardeners of your brain—they act to speed up signals between certain neurons. But other glial cells are the waste removers, pulling up weeds, killing pests, raking up dead leaves. Your brain’s pruning gardeners are called “microglial cells.” They prune your synaptic connections. The question is, how do they know which ones to prune?

Researchers are just starting to unravel this mystery, but what they do know is the synaptic connections that get used less get marked by a protein, C1q (as well as others). When the microglial cells detect that mark, they bond to the protein and destroy—or prune—the synapse.

This is how your brain makes the physical space for you to build new and stronger connections so you can learn more.

Have you ever felt like your brain is full? Maybe when starting a new job, or deep in a project. You’re not sleeping enough, even though you’re constantly taking in new information. Well, in a way, your brain actually is full

When you learn lots of new things, your brain builds connections, but they’re inefficient, ad hoc connections. Your brain needs to prune a lot of those connections away and build more streamlined, efficient pathways. It does that when we sleep.

Your brain cleans itself out when you sleep—your brain cells shrinking by up to 60% to create space for your glial gardeners to come in take away the waste and prune the synapses.

Have you ever woken up from a good night’s rest and been able to think clearly and quickly? That’s because all the pruning and pathway-efficiency that took place overnight has left you with lots of room to take in and synthesize new information—in other words, to learn.

This is the same reason naps are so beneficial to your cognitive abilities. A 10- or 20-minute nap gives your microglial gardeners the chance to come in, clear away some unused connections, and leave space to grow new ones.

Thinking with a sleep-deprived brain is like hacking your way through a dense jungle with a machete. It’s overgrown, slow-going, exhausting. The paths overlap, and light can’t get through. Thinking on a well-rested brain is like wandering happily through Central Park; the paths are clear and connect to one another at distinct spots, the trees are in place, you can see far ahead of you. It’s invigorating.

And in fact, you actually have some control over what your brain decides to delete while you sleep. It’s the synaptic connections you don’t use that get marked for recycling. The ones you do use are the ones that get watered and oxygenated. So be mindful of what you’re thinking about.

If you spend too much time reading theories about the end of Game of Thrones and very little on your job, guess which synapses are going to get marked for recycling?

If you’re in a fight with someone at work and devote your time to thinking about how to get even with them, and not about that big project, you’re going to wind up a synaptic superstar at revenge plots but a poor innovator.

To take advantage of your brain’s natural gardening system, simply think about the things that are important to you. Your gardeners will strengthen those connections and prune the ones that you care about less. It’s how you help the garden of your brain flower.