REM Sleep

Study shows a drink before bed can cause reductions in REM sleep

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Study shows a drink before bed can cause reductions in REM sleep

A team of neuroscientists and sleep researchers at E.P. Bradley Hospital Sleep Research Laboratory, working with colleagues from Brown University and Providence VA Medical Center, has found that rather than improving sleep, consuming an alcoholic beverage before bed can cause a reduction in REM sleep. The group describes their sleep experiments in the journal Sleep.

Prior research has shown that REM sleep takes up approximately 20% of a typical night’s sleep, but is still important. Though scientists have not yet figured out the purpose of REM sleep, they do know that people who do not get enough can experience emotional problems, mental acuity difficulties and memory issues.

In this new study, the researchers explored whether consumption of alcohol prior to sleep might have a positive or negative impact on sleep quality and REM sleep in particular. To find out, they recruited 30 adult volunteers who spent three consecutive days and nights in a sleep lab on two occasions, where their brains could be monitored as they slept.

To assess the impact of having a nightcap before going to bed, the researchers served only a mixer (non-alcoholic ingredients typically used to make cocktails) on one of their stays, and a mixer with added alcohol on the other. Both times the drink was consumed one hour before the volunteer went to bed.

The research team found that drinking just one alcoholic beverage led to an increase in slow-wave sleep across all three nights. It also decreased the duration of REM sleep. Overall, they found that the volunteers were able to fall asleep faster after consuming alcohol, but their quality of sleep suffered due to shortened REM periods.

They also noted that drinking an alcoholic beverage on consecutive nights did not change the amount of REM sleep impacted—their body did not adapt to overcome the effects of alcohol. The team concludes that drinking even a small amount of alcohol before bed can adversely affect sleep quality.

Treatment Recommendations for People Who Act Out Their Dreams While Asleep

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Summary: REM sleep behavior disorder, or parasomnia, affects more than 80 million people worldwide. The disorder causes sufferers to experience nightmare-like violent dreams. Sufferers act on their dreams while sleeping, often resulting in violent or dangerous sleep behaviors and injuries. Researchers propose new guidelines, including medical and pharmacological recommendations, to help curb symptoms of parasomnia and promote healthier sleep.

Source: American Academy of Sleep Medicine

A new clinical practice guideline developed by the American Academy of Sleep Medicine provides recommendations for the management of REM sleep behavior disorder in adults.  

The guideline, available online as an accepted paper in the Journal of Clinical Sleep Medicine, updates the AASM’s previous guidance published in 2010. Several clinical trials conducted in the last decade have contributed new evidence to the published literature, providing additional support for the recommendations.  

“REM sleep behavior disorder is common, affecting more than 80 million people worldwide,” said lead author Dr. Michael Howell, chair of the AASM task force and a professor and division head of sleep medicine in the department of neurology at the University of Minnesota in Minneapolis.

“This clinical practice guideline provides clinicians with insight on how best to prevent sleep-related injury and how to provide patients with a risk assessment for neurological disease. The task force assembled by the AASM diligently reviewed thousands of clinical studies to provide an up-to-date guideline for clinicians managing REM sleep behavior disorder.” 

REM sleep behavior disorder is classified as a parasomnia, a group of sleep disorders involving undesirable physical events or experiences that happen while falling asleep, sleeping, or waking from sleep. REM sleep is characterized by rapid eye movements and dream activity, and it normally involves skeletal paralysis.

This paralysis — or muscle atonia — is lost in REM sleep behavior disorder, causing individuals to act out their dreams with potentially injurious behaviors. These dreams tend to be unpleasant, action-filled, or violent, with the dreamer being confronted, attacked, or chased by unfamiliar people or animals.

The symptoms of REM sleep behavior disorder are often ignored for years, usually until an injury occurs to the dreamer or the bed partner. REM sleep behavior disorder often occurs due to an underlying neurological disorder, such as dementia with Lewy bodies, Parkinson’s disease, multiple system atrophy, narcolepsy, or stroke. 

The guideline provides recommendations for specific medications, such as clonazepam and immediate-release melatonin, that clinicians should consider when treating REM sleep behavior disorder in adults.

All of the recommendations are conditional, requiring the clinician to use clinical knowledge and experience, and to strongly consider the patient’s values and preferences, to determine the best course of action.

Treatment options also depend on whether the case of REM sleep behavior disorder is isolated, secondary to another medical condition, or drug induced.  

How to Reset Your Sleep Routine

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For their mental and physical health, adults need between seven and nine hours of sleep, and it’s important that they get this sleep night after night.

One of the best ways to promote consistent sleep is having a healthy sleep routine. By following a standard schedule and healthy sleep habits, the mind and body become accustomed to a routine that includes plenty of high-quality sleep.

Unfortunately, many factors can throw a sleep routine out of whack. When that happens, bedtimes and wake-up times can fluctuate wildly, and a person may bounce back and forth between nights of too much and too little sleep.
Knowing how to reset your sleep routine offers a way of resolving this type of sleep inconsistency. It also provides a blueprint for people who are looking to optimize their sleep and be in a position to get the best sleep possible every night.

Why Does a Sleep Routine Matter?

Humans are often described as creatures of habit1 because we become conditioned to distinct patterns of behavior2 through repetition of certain cues and responses. Routines can make actions nearly automatic in numerous aspects of daily life, including sleep.

Actively cultivating a healthy sleep routine makes it easier to get the sleep you need on a consistent basis. By creating habits and cues that promote sleep, the norm becomes falling asleep quickly and staying asleep through the night. With more repetition, the routine gets reinforced, facilitating increasingly stable sleep patterns over time.

What Is Circadian Rhythm?

Circadian rhythm is a principal driver of your sleep routine. It is a 24-hour cycle that is part of the body’s internal clock. Circadian rhythm is crucial to managing the delicate balance between sleep and wakefulness3, helping us be alert or drowsy at the appropriate time.

Light exposure is an essential influence on circadian rhythm4, which is closely aligned with the day-night cycle. When the eyes are exposed to light, the brain sends signals associated with wakefulness. When light exposure decreases at night, the signals switch to promote relaxation and sleep.

In this way, circadian rhythm helps to synchronize our internal clock with our external environment5. Research demonstrates that a well-synchronized circadian rhythm can contribute not only to healthy sleep but also to numerous other aspects of health6.

How Does a Sleep Routine Get Thrown Off?

There are multiple ways for sleep routines and circadian rhythms to get thrown off-kilter:

  • Jet lag: Associated with rapid traveling across multiple time zones, jet lag occurs when the body’s internal clock is at odds with the day-night cycle at the travel destination.
  • Shift work: People who work night shifts have to be awake when it’s dark and sleep when the sun’s out, disrupting normal circadian synchronization.
  • Advanced or delayed sleep timing: Some people are extreme “early birds” or “night owls,” meaning that their sleep timing, also known as their sleep phase, is shifted forward or back by several hours.
  • Artificial light exposure: Biologically, the circadian rhythm developed to correspond to sunlight long before electricity was invented. However, the brain responds to artificial light as well, which means that constant exposure to indoor lighting as well as electronic devices like cell phones, tablets, televisions, and computers can interfere with typical signals that convey whether it’s day or night.
  • Fluctuating sleep hours: Many people have no set bedtime or wake-up time. Their sleep schedule can swing wildly back and forth from one day to the next or between weekdays and weekends, which prevents establishing a steady sleep pattern.
  • Behavior choices: Deciding to stay up late or wake up early to study, play sports, or take part in social activities can throw off normal sleep routines.
  • Caffeine and energy drinks: Stimulants may help you feel alert, but they can upset the body’s ability to naturally balance sleep and wakefulness, making it more difficult to sleep when you need to.
  • Stress and emotional difficulties: Many sleeping problems are tied to stress, anxiety, depression, and other emotional or mental health problems. These conditions can cause the mind to race when it’s time for sleep or cause sleepiness during the day when you should be awake, foiling hopes of a consistent and healthy sleep routine.

How Can You Adjust Your Sleep Routine?

Adjusting your sleep routine starts by making consistency a priority. Habits and routines are powerful precisely because they are repeated over and over again in order to create a pattern.

A key first step is to reset your sleep schedule. Pick a bedtime and wake-up time that you can stick with and that offer ample time for the sleep you need. Follow this schedule every day, even on weekends.

At first, you may find it hard to adjust to this new sleep schedule, and that’s normal. A new routine won’t feel normal immediately; it takes time to get used to.

In order to gradually adjust to a new sleep schedule, you can make adjustments in 15 or 30 minute increments over a series of days. You can also focus first on the wake-up time, creating one fixed part of your schedule, and then use the tips described below to modify your sleep habits so that you can incrementally get used to falling asleep at your scheduled bedtime.

What Is the Ideal Time To Go To Bed and Wake-Up?

There is no single ideal time for going to bed and waking up that is best for everyone. In general, in order to synchronize your circadian rhythm, you should try to wake up around the start of daylight hours and wind down and get ready for bed when it gets dark in the evening.

That said, daylight hours can vary significantly based on your geographic location, and for many people, it’s impractical to follow a sleep schedule that strictly follows the day-night cycle. For that reason, the general principles to follow are that your bedtime and wake-up time should:

  • Stay consistent from day-to-day
  • Provide for seven to nine hours of sleep
  • Align as closely with day and night as possible in your personal circumstances

What Are the Best Tips for Resetting Your Sleep Routine?

There are multiple elements to a healthy sleep routine. Setting a consistent sleep schedule is a start, but other steps can help you achieve the sleep you need.

Sleep hygiene plays an essential role in making your sleep routine effective. One fundamental part of sleep hygiene is ensuring that your daily habits and sleep environment are conducive to sleep and work in your favor:

  • Get a daily dose of natural light: Because daylight is a vital influence on your circadian rhythm, exposure to natural light can promote better synchronization7 of your internal clock.
  • Reduce artificial lighting at night: Keeping your lights on long into the evening can prevent your body from properly transitioning toward sleep. Try using a dimmer or low-wattage lamp to minimize the brightness of indoor lighting.
  • Cut down on evening screen time: Cell phones and other devices are sources of excess mental stimulation and emit blue light that can affect circadian timing. To avoid the negative effects of screen time on sleep, try not to use your phone, tablet, or laptop for at least an hour before bed.
  • Commit to physical activity: Regular exercise is good not only for your cardiovascular health but also for your sleep. You don’t have to be a triathlete to get these benefits; even mild physical activity like going for a walk can be beneficial, and it’s a great opportunity to get daylight exposure. If you are going to do intense exercise, try to finish your workout at least an hour before bed.
  • Have a bedtime routine: Consistent cues can play a powerful psychological role in routines. For this reason, try to follow the same steps each night before going to bed such as dimming the lights, quietly reading or stretching, putting on pajamas, and brushing your teeth. Over time, those actions become cues that tell you that it’s time for sleep.
  • Develop a personal relaxation plan: Being able to relax both mentally and physically is a major contributor to falling asleep easily. Regardless of whether it’s meditation, yoga, listening to soothing music, reading, or another activity, make time in your bedtime routine for whatever relaxation method that allows you to wind down.
  • Be careful with naps: There are times during the day when your energy level dips and you may be tempted to nap. While naps can be restorative in some cases, they can disrupt your sleep routine if you’re not careful. As a general rule, try to keep naps under 30 minutes and only early in the afternoon so that they don’t make it harder to get to sleep at night.
  • Limit alcohol and caffeine: Both alcohol and caffeine can be detrimental to a healthy sleep routine. Alcohol makes you sleepy but affects your sleep cycle, making you prone to awakenings and lower-quality sleep as the night goes on. Caffeine makes you wired and alert and can linger in your system, frustrating attempts to fall asleep at bedtime. As a result, it’s best to eliminate or reduce consumption of alcohol and caffeine, especially in the late afternoon and evening.
  • Cultivate an inviting sleep environment: You want your bedroom to be quiet and dark to avoid disruptions. A cool yet comfortable temperature and soothing smells, like lavender, may promote relaxation and provide cues for sleep. Finding the best mattress, best pillow, and bedding can make your bedroom a haven for comfort and rest.

If you have significant sleeping problems, talk with your doctor about the best way to reset your sleep routine. Depending on the causes of your sleep difficulties, a doctor may recommend therapies to adjust your sleep routine such as:

  • Melatonin: This hormone is made naturally by the body when darkness falls, and it helps stabilize circadian rhythm and promote sleep. For some sleep conditions, melatonin supplements can help kickstart a new sleep pattern.
  • Light Therapy: This treatment involves sitting in front of a high-powered lamp for a short period of time, usually in the morning. The high dose of light is designed to help correct for a misaligned circadian rhythm.
  • Cognitive behavioral therapy for insomnia (CBT-I): This type of therapy works to identify and reorient negative thoughts and behaviors about sleep, while structuring a plan for a healthier sleep routine.

Does Pulling an All-Nighter Help Rest Your Sleep Routine?

Pulling an all-nighter doesn’t help develop a better sleep routine. Without sleeping, you’re likely to suffer from impaired thinking and concentration the next day, putting you at risk of accidents, including potentially life-threatening auto accidents.

In addition, your sleep isn’t normal after a period of sleep deprivation. For example, your sleep stages may be off-kilter because of a REM sleep rebound8, which means you spend an abnormal amount of time in the rapid eye movement sleep stage. Because staying up all night is contrary to healthy sleep practices, it isn’t normally advised for resetting your sleep routine.

While there is a method, known as chronotherapy, that adjusts your sleep schedule by staying up later and later at night to reach your desired bedtime, it’s far different than just pulling an all-nighter. Even in the circumstances where it may be beneficial, chronotherapy requires careful planning and should only be conducted under the guidance of a trained health professional.

The Science of Sleep: Dreaming, Depression, and How REM Sleep Regulates Negative Emotions

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“Memory is never a precise duplicate of the original… it is a continuing act of creation. Dream images are the product of that creation.”

For the past half-century, sleep researcherRosalind D. Cartwright has produced some of the most compelling and influential work in the field, enlisting modern science in revising and expanding the theories of Jung and Freud about the role of sleep and dreams in our lives. In The Twenty-four Hour Mind: The Role of Sleep and Dreaming in Our Emotional Lives (public library), Cartwright offers an absorbing history of sleep research, at once revealing how far we’ve come in understanding this vital third of our lives and how much still remains outside our grasp.

One particularly fascinating aspect of her research deals with dreaming as a mechanism for regulating negative emotion and the relationship between REM sleep and depression:

The more severe the depression, the earlier the first REM begins. Sometimes it starts as early as 45 minutes into sleep. That means these sleepers’ first cycle of NREM sleep amounts to about half the usual length of time. This early REM displaces the initial deep sleep, which is not fully recovered later in the night. This displacement of the first deep sleep is accompanied by an absence of the usual large outflow of growth hormone. The timing of the greatest release of human growth hormone (HGH) is in the first deep sleep cycle. The depressed have very little SWS [slow-wave sleep, Stages 3 and 4 of the sleep cycle] and no big pulse of HGH; and in addition to growth, HGH is related to physical repair. If we do not get enough deep sleep, our bodies take longer to heal and grow. The absence of the large spurt of HGH during the first deep sleep continues in many depressed patients even when they are no longer depressed (in remission).

The first REM sleep period not only begins too early in the night in people who are clinically depressed, it is also often abnormally long. Instead of the usual 10 minutes or so, this REM may last twice that. The eye movements too are abnormal — either too sparse or too dense. In fact, they are sometimes so frequent that they are called eye movement storms.

But what has perplexed researchers is that when these depressed patients are awakened 5 minutes into the first REM sleep episode, they’re unable to explain what they are experiencing. This complete lack of dream recall in depression has showed up in study after study, but it’s been unclear whether it’s due to patients’ reluctance to talk with researchers or to truly not forming and experiencing any dreams. That’s where recent technology has helped shed light:

Brain imaging technology has helped to shed light on this mystery. Scanning depressed patients while they sleep has shown that the emotion areas of the brain, the limbic and paralimbic systems, are activated at a higher level in REM than when these patients are awake. High activity in these areas is also common in REM sleep in nondepressed sleepers, but the depressed have even higher activity in these areas than do healthy control subjects. This might be expected — after all, while in REM these individuals also show higher activity in the executive cortex areas, those associated with rational thought and decision making. Nondepressed controls do not exhibit this activity in their REM brain imaging studies. This finding has been tentatively interpreted… as perhaps a response to the excessive activity in the areas responsible for emotions.

Cartwright spent nearly three decades investigating “how a mood disorder that affects cognition, motivation, and most of all the emotional state during waking shows itself in dreams.” What proved particularly difficult was understanding the basis for this poor dream recall during REM sleep, since anti-depressants suppress that stage of the sleep cycle, but early research suggested that this very suppression of REM might be the mechanism responsible for reinvigorating the depressed.

This brings us to the regulatory purpose of dreaming. Cartwright explains:

Despite differences in terminology, all the contemporary theories of dreaming have a common thread — they all emphasize that dreams are not about prosaic themes, not about reading, writing, and arithmetic, but about emotion, or what psychologists refer to as affect. What is carried forward from waking hours into sleep are recent experiences that have an emotional component, often those that were negative in tone but not noticed at the time or not fully resolved. One proposed purpose of dreaming, of what dreaming accomplishes (known as the mood regulatory function of dreams theory) is that dreaming modulates disturbances in emotion, regulating those that are troublesome. My research, as well as that of other investigators in this country and abroad, supports this theory. Studies show that negative mood is down-regulated overnight. How this is accomplished has had less attention.

I propose that when some disturbing waking experience is reactivated in sleep and carried forward into REM, where it is matched by similarity in feeling to earlier memories, a network of older associations is stimulated and is displayed as a sequence of compound images that we experience as dreams. This melding of new and old memory fragments modifies the network of emotional self-defining memories, and thus updates the organizational picture we hold of ‘who I am and what is good for me and what is not.’ In this way, dreaming diffuses the emotional charge of the event and so prepares the sleeper to wake ready to see things in a more positive light, to make a fresh start. This does not always happen over a single night; sometimes a big reorganization of the emotional perspective of our self-concept must be made — from wife to widow or married to single, say, and this may take many nights. We must look for dream changes within the night and over time across nights to detect whether a productive change is under way. In very broad strokes, this is the definition of the mood-regulatory function of dreaming, one basic to the new model of the twenty-four hour mind I am proposing.

Towards the end of the book, Cartwright explores the role of sleep and dreaming in consolidating what we call “the self,” with another admonition againstmemory’s self-editing capacity:

[In] good sleepers, the mind is continuously active, reviewing experience from yesterday, sorting which new information is relevant and important to save due to its emotional saliency. Dreams are not without sense, nor are they best understood to be expressions of infantile wishes. They are the result of the interconnectedness of new experience with that already stored in memory networks. But memory is never a precise duplicate of the original; instead, it is a continuing act of creation. Dream images are the product of that creation. They are formed by pattern recognition between some current emotionally valued experience matching the condensed representation of similarly toned memories. Networks of these become our familiar style of thinking, which gives our behavior continuity and us a coherent sense of who we are. Thus, dream dimensions are elements of the schemas, and both represent accumulated experience and serve to filter and evaluate the new day’s input.

Sleep is a busy time, interweaving streams of thought with emotional values attached, as they fit or challenge the organizational structure that represents our identity. One function of all this action, I believe, is to regulate disturbing emotion in order to keep it from disrupting our sleep and subsequent waking functioning.

The rest of The Twenty-four Hour Mind goes on to explore, through specific research case studies and sweeping syntheses of decades worth of research, everything from disorders like sleepwalking and insomnia to the role of sleep in knowledge retention, ideation, and problem-solving.

The Science of Sleep: Dreaming, Depression, and How REM Sleep Regulates Negative Emotions .

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“Memory is never a precise duplicate of the original… it is a continuing act of creation. Dream images are the product of that creation.”

For the past half-century, sleep researcherRosalind D. Cartwright has produced some of the most compelling and influential work in the field, enlisting modern science in revising and expanding the theories of Jung and Freud about the role of sleep and dreams in our lives. In The Twenty-four Hour Mind: The Role of Sleep and Dreaming in Our Emotional Lives (public library), Cartwright offers an absorbing history of sleep research, at once revealing how far we’ve come in understanding this vital third of our lives and how much still remains outside our grasp.

One particularly fascinating aspect of her research deals with dreaming as a mechanism for regulating negative emotion and the relationship between REM sleep and depression:

The more severe the depression, the earlier the first REM begins. Sometimes it starts as early as 45 minutes into sleep. That means these sleepers’ first cycle of NREM sleep amounts to about half the usual length of time. This early REM displaces the initial deep sleep, which is not fully recovered later in the night. This displacement of the first deep sleep is accompanied by an absence of the usual large outflow of growth hormone. The timing of the greatest release of human growth hormone (HGH) is in the first deep sleep cycle. The depressed have very little SWS [slow-wave sleep, Stages 3 and 4 of the sleep cycle] and no big pulse of HGH; and in addition to growth, HGH is related to physical repair. If we do not get enough deep sleep, our bodies take longer to heal and grow. The absence of the large spurt of HGH during the first deep sleep continues in many depressed patients even when they are no longer depressed (in remission).

The first REM sleep period not only begins too early in the night in people who are clinically depressed, it is also often abnormally long. Instead of the usual 10 minutes or so, this REM may last twice that. The eye movements too are abnormal — either too sparse or too dense. In fact, they are sometimes so frequent that they are called eye movement storms.

But what has perplexed researchers is that when these depressed patients are awakened 5 minutes into the first REM sleep episode, they’re unable to explain what they are experiencing. This complete lack of dream recall in depression has showed up in study after study, but it’s been unclear whether it’s due to patients’ reluctance to talk with researchers or to truly not forming and experiencing any dreams. That’s where recent technology has helped shed light:

Brain imaging technology has helped to shed light on this mystery. Scanning depressed patients while they sleep has shown that the emotion areas of the brain, the limbic and paralimbic systems, are activated at a higher level in REM than when these patients are awake. High activity in these areas is also common in REM sleep in nondepressed sleepers, but the depressed have even higher activity in these areas than do healthy control subjects. This might be expected — after all, while in REM these individuals also show higher activity in the executive cortex areas, those associated with rational thought and decision making. Nondepressed controls do not exhibit this activity in their REM brain imaging studies. This finding has been tentatively interpreted… as perhaps a response to the excessive activity in the areas responsible for emotions.

Cartwright spent nearly three decades investigating “how a mood disorder that affects cognition, motivation, and most of all the emotional state during waking shows itself in dreams.” What proved particularly difficult was understanding the basis for this poor dream recall during REM sleep, since anti-depressants suppress that stage of the sleep cycle, but early research suggested that this very suppression of REM might be the mechanism responsible for reinvigorating the depressed.

This brings us to the regulatory purpose of dreaming. Cartwright explains:

Despite differences in terminology, all the contemporary theories of dreaming have a common thread — they all emphasize that dreams are not about prosaic themes, not about reading, writing, and arithmetic, but about emotion, or what psychologists refer to as affect. What is carried forward from waking hours into sleep are recent experiences that have an emotional component, often those that were negative in tone but not noticed at the time or not fully resolved. One proposed purpose of dreaming, of what dreaming accomplishes (known as the mood regulatory function of dreams theory) is that dreaming modulates disturbances in emotion, regulating those that are troublesome. My research, as well as that of other investigators in this country and abroad, supports this theory. Studies show that negative mood is down-regulated overnight. How this is accomplished has had less attention.

I propose that when some disturbing waking experience is reactivated in sleep and carried forward into REM, where it is matched by similarity in feeling to earlier memories, a network of older associations is stimulated and is displayed as a sequence of compound images that we experience as dreams. This melding of new and old memory fragments modifies the network of emotional self-defining memories, and thus updates the organizational picture we hold of ‘who I am and what is good for me and what is not.’ In this way, dreaming diffuses the emotional charge of the event and so prepares the sleeper to wake ready to see things in a more positive light, to make a fresh start. This does not always happen over a single night; sometimes a big reorganization of the emotional perspective of our self-concept must be made — from wife to widow or married to single, say, and this may take many nights. We must look for dream changes within the night and over time across nights to detect whether a productive change is under way. In very broad strokes, this is the definition of the mood-regulatory function of dreaming, one basic to the new model of the twenty-four hour mind I am proposing.

Towards the end of the book, Cartwright explores the role of sleep and dreaming in consolidating what we call “the self,” with another admonition against memory’s self-editing capacity:

[In] good sleepers, the mind is continuously active, reviewing experience from yesterday, sorting which new information is relevant and important to save due to its emotional saliency. Dreams are not without sense, nor are they best understood to be expressions of infantile wishes. They are the result of the interconnectedness of new experience with that already stored in memory networks. But memory is never a precise duplicate of the original; instead, it is a continuing act of creation. Dream images are the product of that creation. They are formed by pattern recognition between some current emotionally valued experience matching the condensed representation of similarly toned memories. Networks of these become our familiar style of thinking, which gives our behavior continuity and us a coherent sense of who we are. Thus, dream dimensions are elements of the schemas, and both represent accumulated experience and serve to filter and evaluate the new day’s input.

Sleep is a busy time, interweaving streams of thought with emotional values attached, as they fit or challenge the organizational structure that represents our identity. One function of all this action, I believe, is to regulate disturbing emotion in order to keep it from disrupting our sleep and subsequent waking functioning.

The rest of The Twenty-four Hour Mind goes on to explore, through specific research case studies and sweeping syntheses of decades worth of research, everything from disorders like sleepwalking and insomnia to the role of sleep in knowledge retention, ideation, and problem-solving.