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Investigates the hypothesis that sleep deprivation leads to a short temper, which hinders the ability of young adults in college to properly socially interact with others because sleep plays a significant role in determining our emotional state. Upon research, the essay finds that while sleep deprivation is tied to anger, specifically the REM stage of sleep,  sleepiness, and provocation is what leads to increased anger. Raises an interesting question about  what makes the neural structure in the individuals that claim they can properly function on reduced hours of sleep different? "Although each stage is important for the brain to function at its full capacity, the lack of one particular stage, REM sleep, has proven to be the root of negative social interaction.

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Survey of 50 college students between the ages of 17 and 25 at Diablo Valley College. The survey assesses how widespread the issue of sleep deprivation among college students is. When prompted whether they feel they receive enough sleep at night, 58% of the participants responded “No” due to their heavy school workload. Students were asked, “On average how many hours of sleep do you get each night?” Answers ranging from 3 all the way up to 10.  After averaging out the hours of my sample, the typical college student receives about 6.12 hours of sleep a night. When participants were asked, “Has your lack of sleep ever negatively impacted your social interaction with others?,” an astounding 76% of participants responded “Yes.” Most participants associated this negative social interaction with annoyance and not wanting to be around others.

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Reporters at CBS Philly show how sleep deprivation can lead to anger. Reporters also interview everyday people that agree their lack of sleep has led to negative emotions such as anger or irritation. In addition, they suggest ways to combat this issue. Surprisingly, sleep deprivation goes up between the months of November and January. "Someone whose tired has less of an ability to concentrate, and that can affect mood."

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Lack Of Sleep Intensifies Anger, Researchers Confirm

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Describes the emotional along with the physical impacts that sleep deprivation can have. The example confirms that staying awake will negatively impact our mood. Adults need 7-8 hours of sleep while adolescents need at least 10 to properly function. This source also relates to the concept of sleep and "cleaning" in the brain. This clarified to me that the lack of sleep correlates with a negative emotional state, however raises the question of how this is possible in the first place. "When we lose sleep, learning, memory, mood, and reaction time are affected."

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REM sleep is essential in maintaining proper emotional health. Sleep deprivation can also have various negative effects on our emotions as well as emotional reactivity. I feel this accurately proves how the lack of sleep leads to a negative emotional perception while highlighting that specifically REM deprivation can lead to such a thing. The article addresses emotional reactivity, however can you become an angry person in general with chronic sleep loss? "These studies indicate that the nature of sleep deprivation affects results, with different sleep stages exerting different effects on performance."

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Social Interactions, Emotions and Sleep A Systematic Review and Research Agenda

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The lack of sleep can hinder the brain’s ability to “clean,” which can lead to reduced cognitive function and lead to various illnesses. Sleep is a time for the brain to clear out toxins, or broken down byproducts of cells using energy during the day. From the information presented, it can be extrapolated that the lack of sleep can lead to serious consequences. I think many of us overlook the need for sleep when it comes to getting work done. The article gives a "behind the scenes" look at what is going on in the brain while we sleep. "In one set of studies, ... the Veasey lab found that while our brains can recover quite readily from short-term sleep loss, chronic prolonged wakefulness and sleep disruption stresses the brain’s metabolism."

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Opinion

Credit... Eiko Ojala

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.

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Credit... Eiko Ojala

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.

The lymphatic system serves as the body's custodian: Whenever waste is formed, it sweeps it clean. The brain, however, is outside its reach - despite the fact that your brain uses up about 20 percent of your body's energy. How, then, does its waste - like beta-amyloid, a protein associated with Alzheimer's disease - get cleared? What happens to all the wrappers and leftovers that litter the room after any mental workout?

"Think about a fish tank," says Dr. Nedergaard. "If you have a tank and no filter, the fish will eventually die. So, how do the brain cells get rid of their waste? Where is their filter?"

UNTIL a few years ago, the prevailing model was based on recycling: The brain got rid of its own waste, not only beta-amyloid but other metabolites, by breaking it down and recycling it at an individual cell level. When that process eventually failed, the buildup would result in age-related cognitive decline and diseases like Alzheimer's. That "didn't make sense" to Dr. Nedergaard, who says that "the brain is too busy to recycle" all of its energy. Instead, she proposed a brain equivalent of the lymphatic system, a network of channels that cleared out toxins with watery cerebrospinal fluid. She called it the glymphatic system, a nod to its dependence on glial cells (the supportive cells in the brain that work largely to maintain homeostasis and protect neurons) and its function as a sort of parallel lymphatic system.

She was hardly the first to think in those terms. "It had been proposed about one hundred years ago, but they didn't have the tools to study it properly," she says. Now, however, with advanced microscopes and dyeing techniques, her team discovered that the brain's interstitial space - the fluid-filled area between tissue cells that takes up about 20 percent of the brain's total volume - was mainly dedicated to physically removing the cells' daily waste.

When members of Dr. Nedergaard's team injected small fluorescent tracers into the cerebrospinal fluid of anesthetized mice, they found that the tracers quickly entered the brain - and, eventually, exited it - via specific, predictable routes.

The next step was to see how and when, exactly, the glymphatic system did its work. "We thought this cleaning process would require tremendous energy," Dr. Nedergaard says. "And so we asked, maybe this is something we do when we're sleeping, when the brain is really not processing information."

In a series of new studies on mice, her team discovered exactly that: When the mouse brain is sleeping or under anesthesia, it's busy cleaning out the waste that accumulated while it was awake.

In a mouse brain, the interstitial space takes up less room than it does in ours, approximately 14 percent of the total volume. Dr. Nedergaard found that when the mice slept, it swelled to over 20 percent. As a result, the cerebrospinal fluid could not only flow more freely but it could also reach further into the brain. In an awake brain, it would flow only along the brain's surface. Indeed, the awake flow was a mere 5 percent of the sleep flow. In a sleeping brain, waste was being cleared two times faster. "We saw almost no inflow of cerebrospinal fluid into the brain when the mice were awake, but then when we anesthetized them, it started flowing. It's such a big difference I kept being afraid something was wrong," says Dr. Nedergaard.

Similar work in humans is still in the future. Dr. Nedergaard is currently awaiting board approval to begin the equivalent study in adult brains in collaboration with the anesthesiologist Helene Benveniste at Stony Brook University.

So far the glymphatic system has been identified as the neural housekeeper in baboons, dogs and goats. "If anything," Dr. Nedergaard says, "it's more needed in a bigger brain."

MODERN society is increasingly ill equipped to provide our brains with the requisite cleaning time. The figures are stark. Some 80 percent of working adults suffer to some extent from sleep deprivation. According to the National Sleep Foundation, adults should sleep seven to nine hours. On average, we're getting one to two hours less sleep a night than we did 50 to 100 years ago and 38 minutes less on weeknights than we did as little as 10 years ago. Between 50 and 70 million people in the United States suffer from some form of chronic sleep disorder. When our sleep is disturbed, whatever the cause, our cleaning system breaks down. At the University of Pennsylvania's Center for Sleep and Circadian Neurobiology, Sigrid Veasey has been focusing on precisely how restless nights disturb the brain's normal metabolism. What happens to our cognitive function when the trash piles up?

At the extreme end, the result could be the acceleration of neurodegenerative diseases like Alzheimer's and Parkinson's. While we don't know whether sleep loss causes the disease, or the disease itself leads to sleep loss - what Dr. Veasey calls a "classic chicken-and-egg" problem - we do know that the two are closely connected. Along with the sleep disturbances that characterize neurodegenerative diseases, there is a buildup of the types of proteins that the glymphatic system normally clears out during regular sleep, like beta-amyloids and tau, both associated with Alzheimer's and other types of dementia.

"To me," says Dr. Veasey, "that's the most compelling part of the Nedergaard research. That the clearance for these is dramatically reduced from prolonged wakefulness." If we don't sleep well, we may be allowing the very things that cause neural degeneration to pile up unchecked.

Even at the relatively more benign end - the all-nighter or the extra-stressful week when you caught only a few hours a night - sleep deprivation, as everyone who has experienced it knows, impedes our ability to concentrate, to pay attention to our environment and to analyze information creatively. "When we're sleep-deprived, we can't integrate or put together facts," as Dr. Veasey puts it.

But there is a difference between the kind of fleeting sleep loss we sometimes experience and the chronic deprivation that comes from shift work, insomnia and the like. In one set of studies, soon to be published in The Journal of Neuroscience, the Veasey lab found that while our brains can recover quite readily from short-term sleep loss, chronic prolonged wakefulness and sleep disruption stresses the brain's metabolism. The result is the degeneration of key neurons involved in alertness and proper cortical function and a buildup of proteins associated with aging and neural degeneration.

It's like the difference between a snowstorm's disrupting a single day of trash pickup and a prolonged strike. No longer quite as easy to fix, and even when the strike is over, there's likely to be some stray debris floating around for quite some time yet. "Recovery from sleep loss is slower than we'd thought," Dr. Veasey notes. "We used to think that after a bit of recovery sleep, you should be fine. But this work shows you're not."

If you put her own research together with the findings from the Nedergaard lab, Dr. Veasey says, it "very clearly shows that there's impaired clearance in the awake brain. We're really starting to realize that when we skip sleep, we may be doing irreparable damage to the brain, prematurely aging it or setting it up for heightened vulnerability to other insults."

In a society that is not only chronically sleep-deprived but also rapidly aging, that's bad news. "It's unlikely that poor sleep as a child would actually cause Alzheimer's or Parkinson's," says Dr. Veasey, "but it's more likely that you may shift one of those diseases by a decade or so. That has profound health and economic implications."

It's a pernicious cycle. We work longer hours, become more stressed, sleep less, impair our brain's ability to clean up after all that hard work, and become even less able to sleep soundly. And if we reach for a sleeping pill to help us along? While work on the effects of sleeping aids on the glymphatic system remains to be done, the sleep researchers I spoke with agree that there's no evidence that aided sleep is as effective as natural sleep.

There is, however, reason to hope. If the main function of sleep is to take out our neural trash, that insight could eventually enable a new understanding of both neurodegenerative diseases and regular, age-related cognitive decline. By developing a diagnostic test to measure how well the glymphatic system functions, we could move one step closer to predicting someone's risk of developing conditions like Alzheimer's or other forms of dementia: The faster the fluids clear the decks, the more effectively the brain's metabolism is functioning.

"Such a test could also be used in the emergency room after traumatic brain injury," Dr. Nedergaard says, "to see who is at risk of developing decline in cognitive function."

We can also focus on developing earlier, more effective interventions to prevent cognitive decline. One approach would be to enable individuals who suffer from sleep loss to sleep more soundly - but how? Dr. Nedergaard's mice were able to clear their brain's waste almost as effectively under anesthesia as under normal sleeping conditions. "That's really fascinating," says Dr. Veasey. Though current sleeping aids may not quite do the trick, and anesthetics are too dangerous for daily use, the results suggest that there may be better ways of improving sleep pharmacologically.

Now that we have a better understanding of why sleep is so important, a new generation of drug makers can work to create the best possible environment for the trash pickup to occur in the first place - to make certain that our brain's sleeping metabolism is as efficient as it can possibly be.

A second approach would take the opposite tack, by seeking to mimic the cleanup-promoting actions of sleep in the awake brain, which could make a full night of sound sleep less necessary. To date, the brain's metabolic process hasn't been targeted as such by the pharmaceutical industry. There simply wasn't enough evidence of its importance. In response to the evolving data, however, future drug interventions could focus directly on the glymphatic system, to promote the enhanced cleaning power of the sleeping brain in a brain that is fully awake. One day, scientists might be able to successfully mimic the expansion of the interstitial space that does the mental janitorial work so that we can achieve maximally efficient round-the-clock brain trash pickup.

If that day comes, they would be on their way to discovering that all-time miracle drug: one that, in Dr. Veasey's joking words, "could mean we never have to sleep at all."

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Opinion 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?

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Paints the picture of neural  coordination in a slow wave rhythm while we are in a state of deep sleep. The rhythms of our neural firing at any time defines who we are. The book is explaining a complex topic in way that is easy for all to understand, thus making them easier to apply to our lives. In this case, it suggests that your personality relates to neuronal activity at any given time. It can be concluded that since the activity of your neurons plays such a significant role in our cognitive state, a disruption or chronic hindrance of this activity will lead to negative emotions, such as aggression or anger. "So who you are depends on what your neurons are up to, moment by moment."

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Read 1,725 reviews from the world's largest community for readers. Locked in the silence and darkness of your skull, your brain fashions the rich narrative...

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T article points to how sleep cycles and sleep in general play a key role in anger. It also explains that rather than anger simply gradually increasing, some type of provocation is required. The article elucidates the importance of REM for emotional processioning. I had not realized that we must take provocation into consideration when examining the impacts sleep deprivation. "Although there are many reasons why sleep disruption may be connected to anger and aggression, the present findings clearly point to sleep loss as an important causal factor in anger."

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This source agrees that REM deprivation leads to increased aggression. However, the authors elucidate their point in a unique way. The article proved that REM deprivation also correlates to aggression in rats.  I think this article raises a debatable topic since other sources have found that men and women experience the same effects of sleep deprivation whereas this article claims these effects are different. "Further, REM sleep deprivation was related to aggression and sleep reduction was at the expense of REM and stage 2 sleep."

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Deep investigation of the connection between emotional reactivity and REM deprivation. Brain activity during NREM and REM sleep stages influences mood during daytime hours. Taking a deep look into the brain, the article explains what parts of the brain relate to this issue. The article answers questions that may have arisen as to what parts of the brain relate to emotions and lack of sleep. This shows how certain aspects of the brain influence others. "In summary, sleep deprivation, and in particular REM deprivation, can increase daytime negative emotions and emotional reactivity to stimuli, though increased positive ratings have also been found."

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SPECIAL ISSUE BEHAVIORAL NEUROSCIENCE OF SLEEP

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This demonstrates how the lack of sleep can impact our social life. The stages of sleep, REM sleep in particular, are necessary for proper cognitive function. The article also validates the notion that while sleep plays a significant role in determining our emotional state, the lack of sleep will cause us to negatively think of others. I think when we lack proper sleep hygiene and run on only a few hours of sleep, we tend to become hasty towards others. “After a sleepless night, research participants were less accurate at judging the emotions of happiness or anger in pictures of strangers, compared with their performance on this task after a good night’s rest.”

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I spent most of my graduate- school years in a state of sleep deprivation. There was just so much work to do - tests to study for, papers to read, and a dissertation to complete. At night, I stayed up as late as copious cups of coffee would keep me awake, then set my alarm for 4:00 a.m. to get an early start on the next day. After a few hours of pre-dawn study, I headed to my 8:00 a.m. statistics class. Finding a seat in the back, I promptly fell asleep.

Since then, I've learned the importance of a good night's sleep. Without it, I'm a lousy teacher, I understand little of what I read, and I'm incapable of writing anything coherent. Most people understand they're cognitively impaired when they're not well rested. That groggy, listless, disoriented feeling is something we've all experienced at one time or another as we try to slog through the day after a sleepless night.

What most people fail to realize, however, is that lack of sleep can have a subtle but important impact on their social life as well. In a recent article, psychologist Amie Gordon and her colleagues at the University of California, San Francisco, argue that our sleep life and social life are intertwined. As our sleep suffers, so do our relationships; likewise, negative social experiences can keep us from getting the sleep we need.

Many people think of sleep as a time when you "recharge your batteries." Just as you can still use your smart phone or laptop even if it's not fully charged, they believe, so you can function just fine through the day even if you didn't get a full eight hours of sleep the night before. But this "battery" metaphor completely misses the true nature of sleep. Instead of being a time when you lie passively in the dark as your body replenishes its energy, sleep is in fact a highly dynamic process. You may be unconscious, but your brain is very busy during those hours - sorting through memories and tidying up the clutter of the previous day's experiences. Instead of just recharging your battery, you're actually engaging in mental maintenance.

Not all sleep is the same. As you go through the night, your brain cycles through four stages of sleep. These include the light sleep of stages 1 and 2, as well as the deep sleep of stage 3. But most important of all is rapid eye movement (REM) sleep - the stage when dreaming takes place. Most people need about two hours of REM sleep per night to feel fully rested and cognitively alert the next day, no matter how many total hours of shuteye they got. This is why people differ in how much total sleep they need.

In fact, just considering the time between going to bed and getting up isn't a good measure of how much sleep you actually got, or a good indicator of the quality of that sleep. Some people take longer to fall asleep than others, and all of us wake up several times during the night, whether to go to the bathroom or just to shift position, even though we may not remember these waking episodes the next morning. In the laboratory, researchers can measure a person's sleep efficiency - that is, the amount of actual sleep obtained during a period of time. However, your own subjective perception of how well you slept is a pretty good indicator of your sleep quality, regardless of how many hours you were in bed.

Researchers have found that daily rhythms are important as well. "Morning people" truly are more alert early in the day, while "evening people" are more alert later. You should assess whether you're a morning or evening person and arrange your activities accordingly, if possible.

Although the cognitive effects of sleep deprivation are widely known, few psychologists or laypeople pay much attention to the "social side of sleep," as Gordon and colleagues call it. Her team points to three areas that are known to be impacted by lack of sleep - namely close relationships, person perception, and social stress.

1. Close relationships. In Western culture, people prefer sleeping alone in their own beds, with the main exception being romantic partners, who typically sleep together. However, in other cultures around the world, communal sleeping is common, if not the norm. An entire extended family may snuggle up to conserve heat through the cold night. And even non-family members may sleep together - with none of the sexual connotations that term implies in the West. When I was teaching in Japan, I went on a faculty retreat to a hot spring resort, and we all slept on futon mattresses laid on the straw-mat floor of one large room. (Co-sleeping promotes group bonding, I was told.)

Sleep has a big impact on our social relationships, especially our most intimate ones. When one partner has slept poorly the night before, there's more conflict in the relationship the next day. This is because we have less empathy when we're sleep deprived, and we're less likely to engage in effective conflict resolution. What's more, even the well-rested partner will show a decrease in empathy when dealing with a sleepless spouse, as if sleep deprivation were contagious. Further, couples report having more difficulty sleeping when they've experienced conflict with their spouse, especially late in the day. Thus, couples can easily fall into a vicious cycle of relationship conflict and poor sleep.

2. Person perception. To effectively interact with others, we need to accurately read their emotional facial expressions. Yet people who are sleep deprived have a lot more difficulty doing this. After a sleepless night, research participants were less accurate at judging the emotions of happiness or anger in pictures of strangers, compared with their performance on this task after a good night's rest. In addition, people are more likely to engage in stereotypic and biased thinking when they haven't had enough sleep. The ability to read the emotions of unfamiliar people and to inhibit prejudiced thinking is essential to smooth functioning in most workplace environments, so not getting enough sleep can impact your job performance as well.

3. Social stress. Negative experiences, such as conflict with a spouse or family member, being discriminated against, or feeling rejected, can make a good night's sleep hard to get. Although stressful social situations are inevitable, our ability to cope with these experiences depends on how well rested we are. Emotion regulation is a process in which we reevaluate our feelings and try to put them in proper perspective. But it requires intense effort, which may simply be out of reach if we haven't been sleeping well. Once again, we see the vicious cycle of sleep deprivation and social conflict.

According to Gordon and colleagues, more than two-thirds of American adults don't get as much sleep as they need. Americans are busier at their jobs than ever, but they also pad their time with leisure activities that induce more stress than they relieve, like competitive sports, thrilling action movies, and high-adrenaline online games.

The impact of sleep deprivation on physical and mental health has long been understood. Now we know it can damage our social relations as well, sending us into an even deeper spiral of conflict and sleeplessness. It's time to turn off the TV, shut down the computer, put away the smartphone - and get a good night's rest.

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How Lack of Sleep Affects Your Social Life

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I spent most of my graduate- school years in a state of sleep deprivation. There was just so much work to do - tests to study for, papers to read, and a dissertation to complete. At night, I stayed up as late as copious cups of coffee would keep me awake, then set my alarm for 4:00 a.m.

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Every night we cycle through four stages of sleep, each stage causing a shift in brain activity. The article explores these stages in depth. occurs. In order to understand how sleep relates to our cognitive state, it is essential to understand what is occurring in the brain while we sleep. How do the stages of sleep tie into emotions? I think the brain activity occurring during these stages in regions of the brain related to emotions and cognitive state. "...lack of REM sleep can alleviate clinical depression..."

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Overview

Usually sleepers pass through four stages: 1, 2, 3, and REM (rapid eye movement) sleep. These stages progress cyclically from 1 through REM then begin again with stage 1. A complete sleep cycle takes an average of 90 to 110 minutes, with each stage lasting between 5 to 15 minutes. The first sleep cycles each night have relatively short REM sleeps and long periods of deep sleep but later in the night, REM periods lengthen and deep sleep time decreases.

There are four stages of sleep: Non-REM (NREM) sleep (Stages 1, 2 & 3) and REM sleep. Periods of wakefulness occur before and intermittently throughout the various sleep stages or as one shifts sleeping position.

Wake is the period when brain wave activity is at its highest and muscle tone is active.

is the lightest stage of NREM sleep. Often defined by the presence of slow eye movements, this drowsy sleep stage can be easily disrupted causing awakenings or arousals. Muscle tone throughout the body relaxes and brain wave activity begins to slow from that of wake. Occasionally people may experience Stage 1 hypnic jerks or abrupt muscle spasms and may even experience sensation of falling while drifting in and out of Stage 1.

Stage 2 is the first actual stage of defined NREM sleep. Awakenings or arousals do not occur as easily as in Stage 1 sleep and the slow moving eye rolls discontinue. Brain waves continue to slow with specific bursts of rapid activity known as sleep spindles intermixed with sleep structures known as K complexes. Both sleep spindles and K complexes are thought to serve as protection for the brain from awakening from sleep. Body temperature begins to decrease and heart rate begins to slow.

Stage 3 is known as deep NREM sleep. The most restorative stage of sleep, stage 3 consists of delta waves or slow waves. Awakenings or arousals are rare and often it is difficult to awaken someone in Stage 3 sleep. Parasomnias ( sleepwalking, sleep talking or somniloquy and night terrors) occur during the deepest stage of sleep.

REM sleep, also known as rapid eye movement, is most commonly known as the dreaming stage. Eye movements are rapid, moving from side to side and brain waves are more active than in Stages 2 & 3 of sleep. Awakenings and arousals can occur more easily in REM; being woken during a REM period can leave one feeling groggy or overly sleepy.

Stages of the Sleep Cycle

Description:
Eyes open, responsive to external stimuli, can hold intelligible conversation

Transition between waking and sleep. If awakened, person will claim was never asleep.

Main body of light sleep. Memory consolidation. Synaptic pruning.

Slow waves on EEG readings.

Brain waves similar to waking. Most vivid dreams happen in this stage. Body does not move.

Time Spent In:
16 to 18 hours per day

4 to 7 hours per night

90 to 120 min/night

What Is a Sleep Cycle?

A sleep cycle is the progression through the various stages of NREM sleep to REM sleep before beginning the progression again with NREM sleep. Typically, a person would begin a sleep cycle every 90-120 minutes resulting in four to five cycles per sleep time, or hours spent asleep.

One does not go straight from deep sleep to REM sleep, however. Rather, a sleep cycle progress through the stages of non-REM sleep from light to deep sleep, then reverse back from deep sleep to light sleep, ending with time in REM sleep before starting over in light sleep again.

For a majority of people, a sleep cycle begins with a short period of Stage 1 sleep whereby the body begins to relax and a drowsy state occurs with slow rolling eye movements. Though arousals or awakenings are prevalent, Stage 1 is important as it allows for the body to enter Stage 2; the first quantifiable stage of NREM sleep.

Stage 2 occurs for longer periods than Stage 1. For most, Stage 2 sleep comprises approximately 40-60% of total sleep time.

Moving through the sleep cycle, Stage 3 is most often found next in the progression. This restorative stage does not last as long as Stage 2, lasting between 5-15% of total time asleep for most adults. For children and adolescents Stage 3 is much higher in duration.

REM can occur at at time during the sleep cycle, but on average it begins 90 minutes following sleep onset and is short in duration as it is the first REM period of the night. Following REM, the process resumes starting with periods of Stage 1, 2 & 3 intermixed before returning to REM again for longer periods of time as sleep time continues.

How long is a sleep cycle? The first sleep cycle takes about 90 minutes. After that, they average between 100 to 120 minutes. Typically, an individual will go through four to five sleep cycles a night.

What Is Deep Sleep?

Deep sleep occurs in Stage 3 of NREM sleep. Brain waves during Stage 3 are called delta waves due to the slow speed and large amplitude. Of all of the sleep stages, Stage 3 is the most restorative and the sleep stage least likely to be affected by external stimuli.

Waking a person from deep sleep can be difficult. Following a period of sleep deprivation, a person experiences extensive time in Stage 3 sleep. Parasomnias such as sleep walking, sleep talking, night terrors and bedwetting can occur. (There is muscle activity, that's how people can talk or kick in their sleep!)

Deep sleep reduces your sleep drive, and provides the most restorative sleep of all the sleep stages. This is why if you take a short nap during the day, you're still able to fall asleep at night. But if you take a nap long enough to fall into deep sleep, you have more difficulty falling asleep at night because you reduced your need for sleep.

During deep sleep, human growth hormone is released and restores your body and muscles from the stresses of the day. Your immune system also restores itself. Much less is known about deep sleep than REM sleep. It may be during this stage that the brain also refreshes itself for new learning the following day .

When Does REM Sleep Occur?

A person's sleep time (approximately 6-8 hours for adults) can be thought of as 2 halves. The first half for a majority of people consists mostly of Stages 2 and 3 with sporadic periods of Stage 1 and short REM periods. As the night progresses, Stage 3 begins to diminish in quantity while Stages 1 and 2 remain with lengthening periods of REM occurring.

A person typically experiences three to five REM periods throughout sleep time with the longest REM period right before awakening for the day. If woken prematurely from completing the REM period a person can experience a period of sleep inertia whereby a heightened sensation of sleepiness can occur for several minutes or even several hours.

In the REM period , breathing becomes more rapid, irregular and shallow, eyes jerk rapidly and limb muscles are temporarily paralyzed. Brain waves during this stage increase to levels experienced when a person is awake. Also, heart rate increases, blood pressure rises, males develop erections and the body loses some of the ability to regulate its temperature .

As an active sleep state, REM is the time when the most vivid dreams occur. The rapid eye movements that occur can be seen as sharp, rapid movements. Brain waves during REM sleep are considered to be of low amplitude and mixed frequency consistent with higher activity than that seen in Stages 2 and 3.

A person may dream 4 to 6 times each night. A French found that all people do in fact dream, whether they remember their dreams or not. However, if awoken during REM sleep, a person often can remember their dreams.

Muscle paralysis often accompanies REM sleep. This muscle atonia or muscle paralysis occurs as a protective means to keep one from acting out their dreams. Obstructive Sleep Apnea is often the worst during REM periods due to the lack of muscle tone within the muscles of the airway. Scientists believe this may be to help prevent us from injury while trying to act out our dreams.

During REM respirations are irregular and shallow and irregularities in heart rate and body temperature also occur.

As sleep research is still a relatively young field, scientists did not discover REM sleep until 1953 when new machines were developed to monitor brain activity. Before this discovery it was believed that most brain activity ceased during sleep. Since then, scientists have also disproved the idea that deprivation of REM sleep can lead to insanity and have found that lack of REM sleep can alleviate clinical depression although they do not know why. Recent theories link REM sleep to learning and memory.

Brain Waves During the Sleep Cycle

Sleep changes throughout a person's life. From a newborn, through toddler years, school age, adolescent and adulthood, sleep is changing.

Newborn (0 - approximately 4 months) Do not have distinctive sleep waves. Sleep is categorized as "Active", "Quiet" and "Indeterminate". Active sleep is the equivalent to REM sleep and quiet sleep is equivalent to non-REM sleep. A majority of the time, newborns are in active sleep which allows for frequent arousals or awakenings; this is necessary for regular periods of feeding.

Infants (Approximately 4 months - 1 year) Standard sleep stage distinction is now apparent. Sleep becomes more consolidated and sleeping routines can be developed, sleep is typically 10-13 hours per 24 hour period with 2-3 daytime naps occuring.

Toddlers (1 year - 3 years) With sleeping patterns fully developed, children spend approximately 25% in Stage 3 deep sleep with almost an equal amount of time in REM. Average sleep time is 9.5-10.5 hours per 24 hour period. Typically naps will reduce to 1 per day most likely occurring early in the afternoon to allow for proper nighttime sleep.

Pre-School (3 - 6 years) Sleep time is similar to that of toddlers, approximately 9-10 hours per 24 hour period. The afternoon nap usually subsides around 3-4 years for a majority of children. Stage 3 sleep still remains high in relation to total sleep time.

School Age (6 years - 12 years) Sleep time remains unchanged; 9-10 hours per 24 hour period and Stage 3 remains approximately 20-25% of total sleep time. Restorative sleep is important for growth and development.

Adolescent (12 years and beyond) Sleep time for adolescents is approximately 9-9.5 hours per 24 hour period. There are physiological changes in circadian rhythm that occur causing sleep onset to be later. This internal shift is is the cause for many adolescents to have later lights out and the desire to want to "sleep in" in the morning. As a person ages, the circadian rhythm shifts back and sleep again appears to regulate to approximately 6.5-8 hours of sleep per 24 hour period as adult.

Additional Resources

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Stages of Sleep - Non-REM and REM Sleep Cycles | Tuck Sleep

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Usually sleepers pass through four stages: 1, 2, 3, and REM (rapid eye movement) sleep. These stages progress cyclically from 1 through REM then begin again with stage 1. A complete sleep cycle takes an average of 90 to 110 minutes, with each stage lasting between 5 to 15 minutes.