Why We Sleep: Unlocking the Power of Sleep and Dreams

by Matthew Walker

It turns out that the drug prazosin, which Raskind was prescribing simply to lower blood pressure, also has the fortuitous side effect of suppressing noradrenaline in the brain.

These were hairs-on-the-back-of-your-neck-standing-up conversations, perhaps the most exciting I have ever experienced in my career.

Me too!

when those same participants were deprived of sleep, including the essential influence of REM sleep, they could no longer distinguish one emotion from another with accuracy.

the sleep-deprived participants slipped into a default of fear bias, believing even gentle- or somewhat friendly looking faces were menacing.

Deep NREM sleep strengthens individual memories,

Overall, problem-solving abilities rocketed up, with participants solving 15 to 35 percent more puzzles when emerging from REM sleep compared with awakenings from NREM sleep or during daytime waking performance!

the way in which the participants were solving the problems after exiting REM sleep was different from how they solved the problems both when emerging from NREM sleep and while awake during the day. The solutions simply “popped out” following awakenings from REM sleep, one subject told me, though at the time, they did not know they had been in REM sleep just prior.

Even eighteen-month-old babies have been shown to deduce high-level grammatical structure from novel languages they hear, but only after they have slept following the initial exposure.

REM sleep that plays a critical role in the development of language, we believe.

Things were very different for those participants who had obtained a full night of sleep—one dressed with late-morning, REM-rich slumber. Almost 60 percent returned and had the “ah-ha!” moment of spotting the hidden cheat—which is a threefold difference in creative solution insight afforded by sleep!

Scientists placed lucid dreamers inside an MRI scanner.

The participants were allowed to fall asleep in the MRI scanner, entering REM sleep where they could dream. During REM sleep, however, all voluntary muscles are paralyzed, preventing the dreamer from acting out ongoing mental experience. Yet, the muscles that control the eyes are spared from this paralysis, and give this stage of sleep its frenetic name. Lucid dreamers were able to take advantage of this ocular freedom, communicating with the researchers through eye movements. Pre-defined eye movements would therefore inform the researchers of the nature of the lucid dream (e.g., the participant made three deliberate leftward eye movements when they gained lucid dream control, two rightward eye movements before clenching their right hand, etc.).

most people believe these events happen during REM sleep as an individual is dreaming, and specifically acting out ongoing dreams. However, all these events arise from the deepest stage of non-dreaming (NREM) sleep, and not dream (REM) sleep.

At the moment when a sleepwalking event occurs, the video camera footage and the electrical brainwave readouts stop agreeing. One suggests that the other is lying.

After falling asleep on the couch around 1:30 a.m. while watching television, Parks arose and got in his car, barefoot. Depending on the route, it is estimated that Parks drove approximately fourteen miles to his in-laws’ home. Upon entering the house, Parks made his way upstairs, stabbed his mother-in-law to death with a knife he had taken from their kitchen, and strangled his father-in-law unconscious after similarly attacking him with a cleaver (his father-in-law survived). Parks then got back in his car and, upon regaining full waking consciousness at some point, drove to a police station and said, “I think I have killed some people… my hands.” Only then did he realize the blood flowing down his arms as a result of severing his own flexor tendons with the knife.

a team of defense experts concluded that Ken Parks was asleep when he committed the crime, suffering a severe episode of sleepwalking.

sleep-state misperception, also known as paradoxical insomnia. Here, patients will report having slept poorly throughout the night, or even not sleeping at all. However, when these individuals have their sleep monitored objectively using electrodes or other accurate sleep monitoring devices, there is a mismatch. The sleep recordings indicate that the patient has slept far better than they themselves believe, and sometimes indicate that a completely full and healthy night of sleep occurred.

Some GPs are understandably apt to prescribe a sleeping pill, which is rarely the right answer,

While the reasons remain unclear, insomnia is almost twice as common in women than in men,

External factors that cause poor sleep, such as too much bright light at night, the wrong ambient room temperature, caffeine, tobacco, and alcohol consumption—all of which we’ll visit in more detail in the next chapter—can masquerade as insomnia.

one of the few times that we stop our persistent informational consumption and inwardly reflect is when our heads hit the pillow. There is no worse time to consciously do this.

we must drop core body temperature to initiate and maintain sleep,

Simply put, the insomnia patients could not disengage from a pattern of altering, worrisome, ruminative brain activity.

No wonder the blunt instruments of sleeping pills, which can sedate your higher brain, or cortex, are no longer recommended as the first-line treatment approach for insomnia by the American Medical Association.

About one in every 2,000 people suffers from narcolepsy, making it about as common as multiple sclerosis.

Just to give you a sense of what that feeling is, relative to what you may be considering, it would be the sleepiness equivalent of staying awake for three to four days straight.

It is this set of features of sleep paralysis that we now believe explains a large majority of alien abduction claims.

Tell a funny joke to a narcoleptic patient, and they may literally collapse in front of you.

If you saw a patient collapse under the influence of cataplexy, you would be convinced that they had fallen completely unconscious or into a powerful sleep. This is untrue. Patients are awake and continue to perceive the outside world around them.

After eight straight weeks of no sleep, Corke’s mental faculties were quickly fading.

As Corke approached the six-month mark of no sleep, he was bedridden and approaching death.

Several more months of no sleep and Corke’s body and mental faculties shut down completely.

a rare, genetically inherited disorder called fatal familial insomnia (FFI). There are no cures for

What about general anesthesia?

Their experimental question was simple: Is sleep necessary for life? By preventing rats from sleeping for weeks on end in a gruesome ordeal, they came up with an unequivocal answer: rats will die after eighteen days without sleep, on average.

First, death ensued as quickly from total sleep deprivation as it did from total food deprivation.

Second, rats selectively deprived of REM sleep died within twenty-sev...

What, then, was the cause of death? Therein lay the issue: the scientists had no idea.

The fatal final straw turned out to be septicemia—a toxic and systemic (whole organism) bacterial infection that coursed through the rats’ bloodstream and ravaged the entire body until death.

Fatal familial insomnia is part of a family of prion protein disorders that also includes Creutzfeldt-Jakob disease, or so-called mad cow disease, though the latter involves the destruction of different regions of the brain not strongly associated with sleep.

five key factors have changed how much and how well we sleep: (1) constant electric light as well as LED light, (2) regularized temperature, (3) caffeine (discussed in chapter 2), (4) alcohol, and (5) a legacy of punching time cards.

Even a hint of dim light—8 to 10 lux—has been shown to delay the release of nighttime melatonin in humans.

A subtly lit living room, where most people reside in the hours before bed, will hum at around 200 lux. Despite being just 1 to 2 percent of the strength of daylight, this ambient level of incandescent home lighting can have a significant melatonin-suppressing influence within the brain.

evening blue LED light has a more harmful impact on human nighttime melatonin suppression than the warm, yellow light from old incandescent bulbs, even when their lux intensities are matched.

Compared to reading a printed book, reading on an iPad suppressed melatonin release by over 50 percent at night. Indeed, iPad reading delayed the rise of melatonin by up to three hours, relative to the natural rise in these same individuals when reading a printed book.

individuals lost significant amounts of REM sleep following iPad reading.

Third was a lingering aftereffect, with participants suffering a ninety-minute lag in their evening rising melatonin levels for several days after iPad use ceased—almost

A good start is to create lowered, dim light in the rooms where you spend your evening hours. Avoid powerful overhead lights. Mood lighting is the order of the night.

Did you catch this, Andrew!?

The electrical brainwave state you enter via alcohol is not that of natural sleep; rather, it is akin to a light form of anesthesia.

alcohol fragments sleep, littering the night with brief awakenings.