Why We Sleep

by Matthew Walker

  Almost a hundred research participants explored the maze during the first learning session. Thereafter, half of them took a ninety-minute nap, while the other half remained awake and watched a video, all monitored with electrodes placed on the head and face. Throughout the ninety-minute epoch, Stickgold would occasionally wake the napping individuals and ask them about the content of any dreams they were having, or for the group that remained awake, ask them to report any particular thoughts that were going through their minds at the time. Following the ninety-minute period, and after another hour or so to overcome sleep inertia in those who napped, everyone was dropped back into the virtual maze and tested once more to see if their performance was any better than during initial learning.

  It should come as no surprise by now that those participants who took a nap showed superior memory performance on the maze task. They could locate the navigation clues with ease, finding their way around and out of the maze faster than those who had not slept. The novel result, however, was the difference that dreaming made. Participants who slept and reported dreaming of elements of the maze, and themes around experiences clearly related to it, showed almost ten times more improvement in their task performance upon awakening than those who slept just as much, and also dreamed, but did not dream of maze-related experiences.

  As in his earlier studies, Stickgold found that the dreams of these super-navigators were not a precise replay of the initial learning experience while awake. For example, one participant’s dream report stated: “I was thinking about the maze and kinda having people as checkpoints, I guess, and then that led me to think about when I went on this trip a few years ago and we went to see these bat caves, and they’re kind of like, maze-like.” There were no bats in Stickgold’s virtual maze, nor were there any other people or checkpoints. Clearly, the dreaming brain was not simply recapitulating or re-creating exactly what happened to them in the maze. Rather, the dream algorithm was cherry-picking salient fragments of the prior learning experience, and then attempting to place those new experiences within the back catalog of preexisting knowledge.

  Like an insightful interviewer, dreaming takes the approach of interrogating our recent autobiographical experience and skillfully positioning it within the context of past experiences and accomplishments, building a rich tapestry of meaning. “How can I understand and connect that which I have recently learned with that I already know, and in doing so, discover insightful new links and revelations?” Moreover, “What have I done in the past that might be useful in potentially solving this newly experienced problem in the future?” Different from solidifying memories, which we now realize to be the job of NREM sleep, REM sleep, and the act of dreaming, takes that which we have learned in one experience setting and seeks to apply it to others stored in memory.

  When I have discussed these scientific discoveries in public lectures, some individuals will question their validity on the grounds of historical legends who were acclaimed short-sleepers, yet still demonstrated remarkable creative prowess. One common name that I frequently encounter in such rebuttals is the inventor Thomas Edison. We will never truly know if Edison was the short-sleeper that some, including himself, claim. What we do know, however, is that Edison was a habitual daytime napper. He understood the creative brilliance of dreaming, and used it ruthlessly as a tool, describing it as “the genius gap.”

  Edison would allegedly position a chair with armrests at the side of his study desk, on top of which he would place a pad of paper and a pen. Then he would take a metal saucepan and turn it upside down, carefully positioning it on the floor directly below the right-side armrest of the chair. If that were not strange enough, he would pick up two or three steel ball bearings in his right hand. Finally, Edison would settle himself down into the chair, right hand supported by the armrest, grasping the ball bearings. Only then would Edison ease back and allow sleep to consume him whole. At the moment he began to dream, his muscle tone would relax and he would release the ball bearings, which would crash on the metal saucepan below, waking him up. He would then write down all of the creative ideas that were flooding his dreaming mind. Genius, wouldn’t you agree?

  CONTROLLING YOUR DREAMS—LUCIDITY

  No chapter on dreaming can go unfinished without mention of lucidity. Lucid dreaming occurs at the moment when an individual becomes aware that he or she is dreaming. However, the term is more colloquially used to describe gaining volitional control of what an individual is dreaming, and the ability to manipulate that experience, such as deciding to fly, or perhaps even the functions of it, such as problem solving.

  The concept of lucid dreaming was once considered a sham. Scientists debated its very existence. You can understand the skepticism. First, the assertion of conscious control over a normally non-volitional process injects a heavy dose of ludicrous into the already preposterous experience we call dreaming. Second, how can you objectively prove a subjective claim, especially when the individual is fast asleep during the act?

  Four years ago, an ingenious experiment removed all such doubt. Scientists placed lucid dreamers inside an MRI scanner. While awake, these participants first clenched their left and then right hand, over and over. Researchers took snapshots of brain activity, allowing them to define the precise brain areas controlling each hand of each individual.

  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.). Non-lucid dreamers find it difficult to believe that such deliberate eye movements are possible while someone is asleep, but watch a lucid dreamer do it a number of times, and it is impossible to deny.

  When participants signaled the beginning of the lucid dream state, the scientists began taking MRI pictures of brain activity. Soon after, the sleeping participants signaled their intent to dream about moving their left hand, then their right hand, alternating over and over again, just as they did when awake. Their hands were not physically moving—they could not, due to the REM-sleep paralysis. But they were moving in the dream.

  At least, that was the subjective claim from the participants upon awakening. The results of the MRI scans objectively proved they were not lying. The same regions of the brain that were active during physical right and left voluntary hand movements observed while the individuals were awake similarly lit up in corresponding ways during times when the lucid participants signaled that they were clenching their hands while dreaming!

  There could be no question. Scientists had gained objective, brain-based proof that lucid dreamers can control when and what they dream while they are dreaming. Other studies using similar eye movement communication designs have further shown that individuals can deliberately bring themselves to timed orgasm during lucid dreaming, an outcome that, especially in males, can be objectively verified using physiological measures by (brave) scientists.

  It remains unclear whether lucid dreaming is beneficial or detrimental, since well over 80 percent of the general populace are not natural lucid dreamers. If gaining voluntary dream control were so useful, surely Mother Nature would have imbued the masses with such a skill.

  However, this argument makes the erroneous assumption that we have stopped evolving. It is possible that lucid dreamers represent the next iteration in Homo sapiens’ evolution. Will these individuals be preferentially selected for in the future, in part on the basis of this unusual dreaming ability—one that may allow them to turn the creativ
e problem-solving spotlight of dreaming on the waking challenges faced by themselves or the human race, and advantageously harness its power more deliberately?

  Part 4

  * * *

  FROM SLEEPING PILLS TO SOCIETY TRANSFORMED

  Chapter 12

  Things That Go Bump in the Night

  Sleep Disorders and Death Caused by No Sleep

  Few other areas of medicine offer a more disturbing or astonishing array of disorders than those concerning sleep. Considering how tragic and remarkable disorders in those other fields can be, this is quite a claim. Yet when you consider that oddities of slumber include daytime sleep attacks and body paralysis, homicidal sleepwalking, dream enactment, and perceived alien abductions, the assertion starts to sound more valid. Most astonishing of all, perhaps, is a rare form of insomnia that will kill you within months, supported by the life-extinguishing upshot of extreme total sleep deprivation in animal studies.

  This chapter is by no means a comprehensive review of all sleep disorders, of which there are now over one hundred known. Nor is it meant to serve as a medical guide to any one disorder, since I am not a board certified doctor of sleep medicine, but rather a sleep scientist. For those seeking advice on sleep disorders, I recommend visiting the National Sleep Foundation website,fn1 and there you will find resources on sleep centers near you.

  Rather than attempting a quick-fire laundry list of the many tens of sleep disorders that exist, I have chosen to focus on a select few—namely somnambulism, insomnia, narcolepsy, and fatal familial insomnia—from the vantage point of science, and what the science of these disorders can meaningfully teach us about the mysteries of sleeping and dreaming.

  SOMNAMBULISM

  The term “somnambulism” refers to sleep (somnus) disorders that involve some form of movement (ambulation). It encompasses conditions such as sleepwalking, sleep talking, sleep eating, sleep texting, sleep sex, and, very rarely, sleep homicide.

  Understandably, 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. If you rouse an individual from a sleepwalking event and ask what was going through their mind, rarely will they report a thing—no dream scenario, no mental experience.

  While we do not yet fully understand the cause of somnambulism episodes, the existing evidence suggests that an unexpected spike in nervous system activity during deep sleep is one trigger. This electrical jolt compels the brain to rocket from the basement of deep NREM sleep all the way to the penthouse of wakefulness, but it gets stuck somewhere in between (the thirteenth floor, if you will). Trapped between the two worlds of deep sleep and wakefulness, the individual is confined to a state of mixed consciousness—neither awake nor asleep. In this confused condition, the brain performs basic but well-rehearsed actions, such as walking over to a closet and opening it, placing a glass of water to the lips, or uttering a few words or sentences.

  A full diagnosis of somnambulism can require the patient to spend a night or two in a clinical sleep laboratory. Electrodes are placed on the head and body to measure the stages of sleep, and an infrared video camera on the ceiling records the nighttime events, like a single night-vision goggle. 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. Watching the video, the patient is clearly “awake” and behaving. They may sit up on the edge of the bed and begin talking. Others may attempt to put on clothes and walk out of the room. But look at the brainwave activity and you realize that the patient, or at least their brain, is sound asleep. There are the clear and unmistakable slow electrical waves of deep NREM sleep, with no sign of fast, frenetic waking brainwave activity.

  For the most part, there is nothing pathological about sleepwalking or sleep talking. They are common in the adult population, and even more common in children. It is not clear why children experience somnambulism more than adults, nor is it clear why some children grow out of having these nighttime events, while others will continue to do so throughout their lives. One explanation of the former is simply the fact that we have greater amounts of deep NREM sleep when we are young, and therefore the statistical likelihood of sleepwalking and sleep talking episodes occurring is higher.

  Most episodes of the condition are harmless. Occasionally, however, adult somnambulism can result in a much more extreme set of behaviors, such as those performed by Kenneth Parks in 1987. Parks, who was twenty-three years old at the time, lived with his wife and five-month-old daughter in Toronto. He had been suffering from severe insomnia caused by the stress of joblessness and gambling debts. By all accounts, Parks was a nonviolent man. His mother-in-law—with whom he had a good relationship—called him a “gentle giant” on the basis of his placid nature yet considerable height and broad-shouldered form (he stood six foot four, and weighed 225 pounds). Then came May 23.

  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.

  Since he could remember only vague fragments of the murder (e.g., flashes of his mother-in-law’s face with a “help me” look on it), had no motive, and had a long history of sleepwalking (as did other members of his family), a team of defense experts concluded that Ken Parks was asleep when he committed the crime, suffering a severe episode of sleepwalking. They argued that he was unaware of his actions, and thus not culpable. On May 25, 1988, a jury rendered a verdict of not guilty. This defense has been attempted in a number of subsequent cases, most of which have been unsuccessful.

  The story of Ken Parks is of the most tragic kind, and to this day Parks struggles with a guilt one suspects may never leave him. I offer the account not to scare the reader, nor to try to sensationalize the dire events of that late May night in 1987. Rather, I offer it to illustrate how non-volitional acts arising from sleep and its disorders can have very real legal, personal, and societal consequences, and demand the contribution of scientists and doctors in arriving at the appropriate legal justice.

  I also want to note, for the concerned sleepwalkers reading this chapter, that most somnambulism episodes (e.g., sleep walking, talking) are considered benign and do not require intervention. Medicine will usually step in with treatment solutions only if the afflicted patient or his caretaker, partner, or parent (in the case of children) feels that the condition is compromising health or poses a risk. There are effective treatments, and it is a shame one never arrived in time for Ken Parks prior to that ill-fated evening in May.

  INSOMNIA

  For many individuals these days, shudder quotes have come home to roost around the phrase “a good night’s sleep,” as the writer Will Self has lamented. Insomnia, to which his grumblings owe their origin, is the most common sleep disorder. Many individuals suffer from insomnia, yet some believe they have the disorder when they do not. Before describing the features and causes of insomnia (and in the next chapter, potential treatment options), let me first describe what insomnia is not—and in doing so, reveal what it is.

  Being sleep deprived is not insomnia. In the field of medicine, sleep deprivation is considered as (i) having the adequate ability to sleep; yet (ii) giving oneself an inadequate opportunity to sleep—that is, sleep-deprived individuals can sl
eep, if only they would take the appropriate time to do so. Insomnia is the opposite: (i) suffering from an inadequate ability to generate sleep, despite (ii) allowing oneself the adequate opportunity to get sleep. People suffering from insomnia therefore cannot produce sufficient sleep quantity/quality, even though they give themselves enough time to do so (seven to nine hours).

  Before moving on, it is worth noting the condition of 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. Patients suffering from paradoxical insomnia therefore have an illusion, or misperception, of poor sleep that is not actually poor. As a result, such patients are treated as hypochondriacal. Though the term may seem dismissive or condescending, it is taken very seriously by sleep medicine doctors, and there are psychological interventions that help after the diagnosis is made.

  Returning to the condition of true insomnia, there are several different sub-types, in the same way that there are numerous different forms of cancer, for example. One distinction separates insomnia into two kinds. The first is sleep onset insomnia, which is difficulty falling asleep. The second is sleep maintenance insomnia, or difficulty staying asleep. As the actor and comedian Billy Crystal has said when describing his own battles with insomnia, “I sleep like a baby—I wake up every hour.” Sleep onset and sleep maintenance insomnia are not mutually exclusive: you can have one or the other, or both. No matter which of these kinds of sleep problems is occurring, sleep medicine has very specific clinical boxes that must be checked for a patient to receive a diagnosis of insomnia. For now, these are: