Why We Sleep#
Originally started in Oct; Re-started in 2021-11-16
Chapter 1 To Sleep#
To add
Chapter 2 Caffeine, Jet Lag, and Melatonin#
To add
Chapter 3 Defining and Generating Sleep: Time Dilation#
P39, bottom, The thalamus is the sensory gate of the brain. It decides which sensory signals are allowed through its gate, and which are not.
P39-40, Two universal indicators that offer a convincing conclusion of sleep:
First is the loss of external awareness - you stop perceiving the outside world.
The second feature that instructs your own, self-determined judgement of sleep is a sense of time distortion experienced in two contradictory ways.
P41, bottom, the gold-standard scientific verification of sleep requires the recording of signals, using electrodes, arising from three different regions: (1) brainwave activity, (2) eye movement activity, and (3) muscle activities. –> polysomnography (PSG)
P49, middle, sleep spindle—a punchy burst of brainwave activity that often festoons the tail end of each individual slow wave. Sleep spindles occur during both the deep and the lighter stages of NREM sleep, even before the slow, powerful brainwaves of deep sleep start to rise up and dominate. One of their many functions is to operate like nocturnal soldiers who protect sleep by shielding the brain from external noises. The more powerful and frequent an individual’s sleep spindles, the more resilient they are to external noises that would otherwise awaken the sleeper.
P51, top, in deep NREM sleep, we fall into its default model of functioning, That default model is called deep slow-wave sleep. It is an active, deliberate, but highly synchronous state of brain activity. It is a near state of nocturnal cerebral meditation, though I should note that it is very different from the brainwave activity of waking meditative states.
P52, top, We therefore consider waking brainwave activity as that principally concerned with the reception of the outside sensory world, while the state of deep NREM slow-wave sleep donates a state of inward reflection—one that fosters information transfer and the distillation of memories.
P52, bottom, REM sleep has also been called paradoxical sleep: a brain that appears awake, yet a body that is clearly asleep.
P53, middle, When it comes to information processing, think of the wake state principally as reception (experiencing and constantly learning the world around you), NREM sleep as reflection (storing and strengthening those raw ingredients of new facts and skills), and REM sleep as integration (interconnecting these raw ingredients with each other, with all past experiences, and, in doing so, building an ever more accurate model of how the world works, including innovative insights and problem-solving abilities).
2021-11-24
Chapter 4 Ape Beds, Dinosaurs, and Napping with Half a Brain#
P58, top, there are truly remarkable differences in sleep from one species to another. Four such differences
Total amount of time.
the relationship b/t the size of the nervous system, the complexity of the nervous system, and total body mass appears to be a somewhat meaningful predictor. increasing brain complexity relative to body size resulting in greater sleeping amounts
(P59, bottom) For now, our most accurate estimate of why different species need different sleep amounts involves a complex hybrid of factors, such as dietary type (omnivore, herbivore, carnivore), predator/prey balance within a habitat, the presence and nature of a social network, metabolic rate, and nervous system complexity.
Composition (P60, middle).
P63, middle, Sleep rebound after sleep deprivation; NREM and REM rebound at different times
P64, top, That humans (and all other species) can never “sleep back” that which we have previously lost is one of the most important take-homes of this book, the saddening consequences of which I will describe in chapters 7 and 8.
The way in which we all do it. (P64, top)
P64, top, Take cetaceans, such as dolphins and whales, for example. Their sleep, of which there is only NREM, can be unihemispheric, meaning they will sleep with half a brain at a time!
P65, 2nd, The gift of split-brain deep NREM sleep is not entirely unique to aquatic mammals. Birds can do it, too. However, there is a somewhat different, though equally life-preserving, reason: it allows them to keep an eye on things, quite literally.
P65, bottom, Two recently published reports suggest humans have a very mild version of unihemispheric sleep—one that is drawn out for similar reasons.
P66, middle, REM sleep is strangely immune to being split across sides of the brain, no matter who you are.
Sleep pattern. (P66, bottom)
P66, bottom, The infrequent situation happens only in response to extreme environmental pressures or challenges. Starvation is one example.
P69, m, The practice of biphasic sleep is not cultural in origin, however. It is deeply biological. All humans, irrespective of culture or geographical location, have a genetically hardwired dip in alertness that occurs in the midafternoon hours.
P69, b, post-prandial alertness dip (from the Latin prandium, “meal”).
P70, b, the true pattern of biphasic sleep—for which there is anthropological, biological, and genetic evidence, and which remains measurable in all human beings to date—is one consisting of a longer bout of continuous sleep at night, followed by a shorter midafternoon nap.
P72, 2nd, As it turns out, we humans are special when it comes to sleep. Compared to Old- and New- World monkeys, as well as apes, such as chimpanzees, orangutans, and gorillas, human sleep sticks out like the proverbial sore thumb.
P73, 2nd, Homo erectus, the predecessor of Homo sapiens, was the first obligate biped, walking freely upright on two legs. We believe that Homo erectus was also the first dedicated ground sleeper.
P74, 2nd, I offer a theorem: the tree-to-ground reengineering of sleep was a key trigger that rocketed Homo sapiens to the top of evolution’s lofty pyramid. At least two features define human beings relative to other primates.
our degree of sociocultural complexity
our cognitive intelligence.
To the first of these points, we have discovered that REM sleep exquisitely recalibrates and fine-tunes the emotional circuits of the human brain (discussed in detail in part 3 of the book).
Related, the REM-sleep gift of facilitating accurate recognition and comprehension allows us to make more intelligent decisions and actions as a consequence.
Second, and more critical, if you multiply these individual benefits within and across groups and tribes, all of which are experiencing an ever-increasing intensity and richness of REM sleep over millennia, we can start to see how this nightly REM-sleep recalibration of our emotional brains could have scaled rapidly and exponentially.
I will go a step further and suggest that this is the most influential function of REM sleep in mammals, perhaps the most influential function of all types of sleep in all mammals, and even the most eminent advantage ever gifted by sleep in the annals of all planetary life.
The second evolutionary contribution that the REM-sleep dreaming state fuels is creativity.
2021-11-26
Chapter 5 Changes in Sleep Across the Life Span#
Sleep before birth#
P79, b, Detailed creation of the brain and its component parts occurs at a rapid pace during the second and third trimesters of human development—precisely the time window when REM-sleep amounts skyrocket.
REM sleep acts as an electrical fertilizer during this critical phase of early life. Dazzling bursts of electrical activity during REM sleep stimulate the lush growth of neural pathways all over the developing brain, and then furnish each with a healthy bouquet of connecting ends, or synaptic terminals.
P80, top, This phase of development, which infuses the brain with masses of neural connections, is called synaptogenesis, as it involves the creation of millions of wiring links, or synapses, between neurons.
ASD: autism spectrum disorder; ADHD: attention deficit hyper-activity disorder
P81, b, sleep of individuals with autism is atypical.
Infants and young children who show signs of autism, or who are diagnosed with autism, do not have normal sleep patterns or amounts. The circadian rhythms of autistic children are also weaker than their non-autistic counterparts, showing a flatter profile of melatonin across the twenty-four-hour period rather than a powerful rise in concentration at night and rapid fall throughout the day
Most notable, however, is the significant shortage of REM sleep. Autistic individuals show a 30 to 50 percent deficit in the amount of REM sleep they obtain, relative to children without autism.
P82, m, Alcohol is one of the most powerful suppressors of REM sleep that we know of.
P83, t, Newborns of heavy-drinking mothers did not have the same electrical quality of REM sleep.
P83, t, the infants of heavy-drinking mothers showed a 200 percent reduction in this measure of vibrant electrical activity relative to the infants born of non-alcohol-consuming mothers.
Childhood Sleep#
P87, t, During the fourteen hours of total shut-eye per day that a six-month-old infant obtains, there is a 50/50 timeshare between NREM and REM sleep. A five-year-old, however, will have a 70/30 split between NREM and REM sleep across the eleven hours of total daily slumber. In other words, the proportion of REM sleep decreases in early childhood while the proportion of NREM sleep actually increases, even though total sleep time decreases.
The downgrading of the REM-sleep portion, and the upswing in NREM-sleep dominance, continues, throughout early and midchildhood. That balance will finally stabilize to an 80/20 NREM/REM sleep split by the late teen years, and remain so throughout early and midadulthood.
Sleep and adolescence#
P88, 3rd, The human brain undergoes a similar, use-determined transformation during late childhood and adolescence. Much of the original structure laid down early in life will persist, since Mother Nature has, by now, learned to create a quite accurate first-pass wiring of a brain after billions of attempts over many thousands of years of evolution.
The unique experiences of a child during their formative years translate to a set of personal usage statistics. Those experiences, or those statistics, provide the bespoke blueprint for a last round of brain refinement, capitalizing on the opportunity left open by nature. A (somewhat) generic brain becomes ever more individualized, based on the personalized use of the owner.
P89, t, To help with the job of refinement and downscaling of connectivity, the brain employs the services of deep NREM sleep. Of the many functions carried out by deep NREM sleep—the full roster of which we will discuss in the next chapter—it is that of synaptic pruning that features prominently during adolescence.
P90, 2nd, The changes in deep NREM sleep always precede the cognitive and developmental milestones within the brain by several weeks or months, implying a direction of influence: deep sleep may be a driving force of brain maturation, not the other way around.
Feinberg’s second seminal discovery.
the rise- and-fall pattern of maturation always began at the back of the brain, which performs the functions of visual and spatial perception, and then progressed steadily forward as adolescence progressed. Most striking, the very last stop on the maturational journey was the tip of the frontal lobe, which enables rational thinking and critical decision-making. Therefore, the back of the brain of an adolescent was more adult-like, while the front of the brain remained more child-like at any one moment during this developmental window of time.
Adolescents face two other harmful challenges in their struggle to obtain sufficient sleep as their brains continue to develop.
The first is a change in their circadian rhythm. -Adolescent teenagers have a different circadian rhythm from their young siblings. By the time an individual has reached sixteen years of age, their circadian rhythm has undergone a dramatic shift forward in its cycling phase. The rising tide of melatonin, and the instruction of darkness and sleep, is many hours away (to a much later time in the night).
The second is early school start times.
Sleep in midlife and old age#
P95, b, That older adults simply need less sleep is a myth. Older adults appear to need just as much sleep as they do in midlife, but are simply less able to generate that (still necessary) sleep.
P95, b, core impairments of sleep that occur with aging are due to three key changes: (1) reduced quantity/quality, (2) reduced sleep efficiency, and (3) disrupted timing of sleep.
As you enter your fourth decade of life, there is a palpable reduction in the electrical quantity and quality of that deep NREM sleep. You obtain fewer hours of deep sleep, and those deep NREM brainwaves become smaller, less powerful, and fewer in number. Passing into your mid- and late forties, age will have stripped you of 60 to 70 percent of the deep sleep you were enjoying as a young teenager. By the time you reach seventy years old, you will have lost 80 to 90 percent of your youthful deep sleep.
The older we get, the more frequently we wake up throughout the night. There are many causes, including interacting medications and diseases, but chief among them is a weakened bladder.
sleep efficiency, defined as the percent of time you were asleep while in bed.
As healthy teenagers, we enjoyed a sleep efficiency of about 95 percent. As a reference anchor, most sleep doctors consider good-quality sleep to involve a sleep efficiency of 90 percent or above. By the time we reach our eighties, sleep efficiency has often dropped below 70 or 80 percent
the lower an older individual’s sleep efficiency score, the higher their mortality risk, the worse their physical health, the more likely they are to suffer from depression, the less energy they report, and the lower their cognitive function, typified by forgetfulness
In sharp contrast to adolescents, seniors commonly experience a regression in sleep timing, leading to earlier and earlier bedtimes.
P100, b, The change in circadian rhythm as we get older, together with more frequent trips to the bathroom, help to explain two of the three key nighttime issues in the elderly: early sleep onset/offset and sleep fragmentation. They do not, however, explain the first key change in sleep with advancing age: the loss of deep-sleep quantity and quality.
First, the areas of the brain that suffer the most dramatic deterioration with aging are, unfortunately, the very same deep-sleep-generating regions—the middle-frontal regions seated above the bridge of the nose
Second, and unsurprisingly, older adults suffered a 70 percent loss of deep sleep, compared with matched young individuals.
Third, and most critical, we discovered that these changes were not independent, but instead significantly connected with one another: the more severe the deterioration that an older adult suffers within this specific mid-frontal region of their brain, the more dramatic their loss of deep NREM sleep.
2021-11-29
Chapter 6 Your Mother and Shakespeare Knew#
P108, b, Of the many advantages conferred by sleep on the brain, that of memory is especially impressive, and particularly well understood. Sleep has proven itself time and again as a memory aid: both before learning, to prepare your brain for initially making new memories, and after learning, to cement those memories and prevent forgetting.
Sleep-the-night-before learning#
P109, 2nd, A long, finger-shaped structure tucked deep on either side of your brain, the hippocampus offers a short-term reservoir, or temporary information store, for accumulating new memories.
Unfortunately, the hippocampus has a limited storage capacity, almost like a USB memory stick.
Exceed its capacity and you run the risk of not being able to add more information or, equally bad, overwriting one memory with another: a mishap called interference forgetting.
P110, 3rd, The memory refreshment was related to lighter, stage 2 NREM sleep, and specifically the short, powerful bursts of electrical activity called sleep spindles.
The more sleep spindles an individual obtained during the nap, the greater the restoration of their learning when they woke up.
Importantly, sleep spindles did not predict someone’s innate learning aptitude. That would be a less interesting result, as it would imply that inherent learning ability and spindles simply go hand in hand. Instead, it was specifically the change in learning from before relative to after sleep, which is to say the replenishment of learning ability, that spindles predicted.
P111, 3rd, We have found that seniors (aged sixty to eighty years old) are unable to generate sleep spindles to the same degree as young, healthy adults, suffering a 40 percent deficit.
We conducted the study, and that is precisely what we found: the fewer the number of spindles an elderly brain produced on a particular night, the lower the learning capacity of that older individual the next day, making it more difficult for them to memorize the list of facts we presented.
P112, t, Of broader societal relevance, the concentration of NREM-sleep spindles is especially rich in the late-morning hours, sandwiched between long periods of REM sleep.
Sleep-the-night-after learning#
P112, 2nd, The second benefit of sleep for memory comes after learning, one that effectively clicks the “save” button on those newly created files. In doing so, sleep protects newly acquired information, affording immunity against forgetting: an operation called consolidation.
P113, b, It was early-night sleep, rich in deep NREM, that won out in terms of providing superior memory retention savings relative to late-night, REM-rich sleep.
P114, 3rd, We had observed a real-estate transaction that takes place each night when we sleep. Fitting the notion of a long-wave radio signal that carries information across large geographical distances, the slow brainwaves of deep NREM had served as a courier service, transporting memory packets from a temporary storage hold (hippocampus) to a more secure, permanent home (the cortex). In doing so, sleep had helped future-proof those memories.
P116, 2nd, Not only does sleep maintain those memories you have successfully learned before bed (“the vision that was planted in my brain / Still remains”), but it will even salvage those that appeared to have been lost soon after learning.
P117, footnote, tDCS: trans cranial direct current brain stimulation
P119, t, You can (via some means) selectively enhanced only those individual memories that you want to keep. It all sounds like the stuff of science fiction, but it is now science fact: the method is called targeted memory reactivation.
Sleep to forget?#
P121, b, Instead, sleep is able to offer a far more discerning hand in memory improvement: one that preferentially picks and chooses what information is, and is not, ultimately strengthened. Sleep accomplishes this by using meaningful tags that have been hung onto those memories during initial learning, or potentially identified during sleep itself.
Sleep for other types of memory#
P127, 2nd, Indeed, it was the number of those wonderful sleep spindles in the last two hours of the late morning—the time of night with the richest spindle bursts of brainwave activity—that were linked with the offline memory boost.
P127, 3rd, When it comes to motor-skill memories, the brainwaves of sleep were acting like a good masseuse—you still get a full body massage, but they will place special focus on areas of the body that need the most help. In the same way, sleep spindles bathe all parts of the brain, but a disproportionate emphasis will be placed on those parts of the brain that have been worked hardest with learning during the day.
Sleep for creativity#
P132, 2nd, If you ponder the type of conscious experience such outlandish memory blending would produce, you may not be surprised to learn that it happens during the dreaming state—REM sleep
2021-12-15
Chapter 7 Too Extreme for the Guinness Book of World Records (Sleep Deprivation and the Brain)#
P134, 3rd, microsleep. These last for just a few seconds, during which time the eyelid will either partially or fully close. They are usually suffered by individuals who are chronically sleep restricted, defined as getting less than seven hours of sleep a night on a routine basis.
Accumulated sleep deprivation leads to some impairment to the brain function as does with complete sleep deprivation.
P135 - P137, Dinges’s 3 findings from his research experiments
although sleep deprivation of all these varied amounts caused a slowing in reaction time, there was something more telling: participants would, for brief moments, stop responding altogether.
Those in the three-night total sleep deprivation group suffered catastrophic impairment; these impairments continued to escalate at the same ballistic rate after a second and third night of total sleep deprivation, as if they would continue to escalate in severity if more nights of sleep were lost, showing no signs of flattening out.
When participants were asked about their subjective sense of how impaired they were, they consistently underestimated their degree of performance disability.
P140, 2nd, The recycle rate of a human being is around sixteen hours. After sixteen hours of being awake, the brain begins to fail.
P146, b, A structure located in the left and right sides of the brain, called the amygdala ([əˈmɪɡdələ], 杏仁核)—a key hot spot for triggering strong emotions such as anger and rage, and linked to the fight-or-flight response
P147, t, It was as though, without sleep, our brain reverts to a primitive pattern of uncontrolled reactivity. We produce unmetered, inappropriate emotional reactions, and are unable to place events into a broader or considered context.
With a full night of plentiful sleep, we have a balanced mix between our emotional gas pedal (amygdala) and brake (prefrontal cortex). Without sleep, however, the strong coupling between these two brain regions is lost. We cannot rein in our atavistic impulses—too much emotional gas pedal (amygdala) and not enough regulatory brake (prefrontal cortex)
P148, 2nd, different deep emotional centers in the brain just above and behind the amygdala, called the striatum (纹状体，终脑的皮层)—associated with impulsivity and reward, and bathed by the chemical dopamine
P148, 3rd, Insufficient sleep does not, therefore, push the brain into a negative mood state and hold it there. Rather, the under-slept brain swings excessively to both extremes of emotional valence, positive and negative.
148, b, extreme swings in positive mood, though the consequences are different. Hypersensitivity to pleasurable experiences can lead to sensationseeking, risk-taking, and addiction.
Sleep disturbance is a recognized hallmark associated with addictive substance use. Insufficient sleep also determines relapse rates in numerous addiction disorders, associated with reward cravings that are unmetered, lacking control from the rational head office of the brain’s prefrontal cortex.
Relevant from a prevention standpoint, insufficient sleep during childhood significantly predicts early onset of drug and alcohol use in that same child during their later adolescent years, even when controlling for other high-risk traits, such as anxiety, attention deficits, and parental history of drug use.
P149, PTSD: post-traumatic stress disorder
P151, last, Depression is not, as you may think, just about the excess presence of negative feelings. Major depression has as much to do with absence of positive emotions, a feature described as anhedonia: the inability to gain pleasure from normally pleasurable experiences, such as food, socializing, or sex.
P152, 3rd, “The best bridge between despair and hope is a good night’s sleep.” - E. Joseph Cossman
P154, 2nd, hippocampus—the information “in-box” of the brain that acquires new facts. There was lots of healthy, learning-related activity in the hippocampus in the participants who had slept the night before. However, when we looked at this same brain structure in the sleep-deprived participants, we could not find any significant learning activity whatsoever. It was as though sleep deprivation had shut down their memory in-box, and any new incoming information was simply being bounced.
P156, t, theories, beliefs, and practices die one generation at a time.
P157, t, if you don’t sleep the very first night after learning, you lose the chance to consolidate those memories, even if you get lots of “catch-up” sleep thereafter. In terms of memory, then, sleep is not like the bank. You cannot accumulate a debt and hope to pay it off at a later point in time.
P158, 2nd, While much remains to be understood, we now recognize that sleep disruption and Alzheimer’s disease interact in a selffulfilling, negative spiral that can initiate and/or accelerate the condition.
P158, b, The more amyloid deposits there were in the middle regions of the frontal lobe, the more impaired the deep-sleep quality was in that older individual.
P160, t, Those individuals with the highest levels of amyloid deposits in the frontal regions of the brain had the most severe loss of deep sleep and, as a knock-on consequence, failed to successfully consolidate those new memories. Overnight forgetting, rather than remembering, had taken place. The disruption of deep NREM sleep was therefore a hidden middleman brokering the bad deal between amyloid and memory impairment in Alzheimer’s disease. A missing link.
P160, 4th, Glial cells are distributed throughout your entire brain, situated side by side with the neurons that generate the electrical impulses of your brain. Just as the lymphatic system drains contaminants from your body, the glymphatic system collects and removes dangerous metabolic contaminants generated by the hard work performed by neurons in your brain, rather like a support team surrounding an elite athlete.
P161, 3rd, More amyloid (淀粉样蛋白), less deep sleep, less deep sleep, more amyloid, and so on and so forth.
2021-12-15
Chapter 8 Cancer, Heart Attacks, and a Shorter Life (Sleep Deprivation and the Body)#
P166, 4th, One cause of a coronary artery blockage is atherosclerosis (动脉粥样硬化), or the furring up of those heart corridors with hardened plaques that contain calcium deposits.
P168, 4th, During deep NREM sleep specifically, the brain communicates a calming signal to the fight-or-flight sympathetic branch of the body’s nervous system, and does so for long durations of the night. As a result, deep sleep prevents an escalation of this physiological stress that is synonymous with increased blood pressure, heart attack, heart failure, and stroke.
P169, 2nd, Should you tabulate millions of daily hospital records, as researchers have done, you discover that this seemingly trivial sleep reduction (due to daylight saving time change) comes with a frightening spike in heart attacks the following day. Impressively, it works both ways. In the autumn within the Northern Hemisphere, when the clocks move forward and we gain an hour of sleep opportunity time, rates of heart attacks plummet the day after. A similar rise-and-fall relationship can be seen with the number of traffic accidents, proving that the brain, by way of attention lapses and microsleeps, is just as sensitive as the heart to very small perturbations of sleep.
P170, b, Early-warning signs of a link between sleep loss and abnormal blood sugar emerged in a series of large epidemiological studies spanning several continents. Independent of one another, the research groups found far higher rates of type 2 diabetes among individuals that reported sleeping less than six hours a night routinely. The association remained significant even when adjusting for other contributing factors, such as body weight, alcohol, smoking, age, gender, race, and caffeine use.
P171, 4th, In this sleep-deprived state, the cells were stubbornly resisting the message from insulin and refusing to open up their surface channels. The cells were repelling rather than absorbing the dangerously high levels of glucose. The roadside drains were effectively closed shut, leading to a rising tide of blood sugar and a pre-diabetic state of hyperglycemia.
P173, 2nd, At fault were the two characters, leptin (瘦蛋白) and ghrelin (胃饥饿素). Inadequate sleep decreased concentrations of the satiety-signaling hormone leptin and increased levels of the hungerinstigating hormone ghrelin.
P175, sleep deprivation -> eat more, what like to eat
P176, 2nd, Comparing the patterns of brain activity between the two conditions within the same individual, we discovered that supervisory regions in the prefrontal cortex required for thoughtful judgments and controlled decisions had been silenced in their activity by a lack of sleep. In contrast, the more primal deep-brain structures that drive motivations and desire were amplified in response to the food images. This shift to a more primitive pattern of brain activity without deliberative control came with a change in the participants’ food choices. High-calorie foods became significantly more desirable in the eyes of the participants when sleep-deprived.
P176, b, South of the brain, we are also discovering that plentiful sleep makes your gut happier. Sleep’s role in redressing the balance of the body’s nervous system, especially its calming of the fight-or-flight sympathetic branch, improves the bacterial community known as your microbiome, which is located in your gut (also known as the enteric nervous system).
P178, 4th, short sleep (of the type that many adults in first-world countries commonly and routinely report) will increase hunger and appetite, compromise impulse control within the brain, increase food consumption (especially of high-calorie foods), decrease feelings of food satisfaction after eating, and prevent effective weight loss when dieting.
P183, 4th, As with the effects of sleep deprivation on memory, once you miss out on the benefit of sleep in the moment—here, regarding an immune response to this season’s flu—you cannot regain the benefit simply by trying to catch up on lost sleep. The damage is done, and some of that harm can still be measured a year later.
P185, 3rd, Cancers are known to use the inflammation response to their advantage. For example, some cancer cells will lure inflammatory factors into the tumor mass to help initiate the growth of blood vessels that feed it with more nutrients and oxygen. Tumors can also use inflammatory factors to help further damage and mutate the DNA of their cancer cells, increasing the tumor’s potency
P186, 3rd, In a number of studies, Gozal has shown that immune cells, called tumor-associated macrophages, are one root cause of the cancerous influence of sleep loss.
He found that sleep deprivation will diminish one form of these macrophages, called M1 cells, that otherwise help combat cancer.
Yet sleep deprivation conversely boosts levels of an alternative form of macrophages, called M2 cells, which promote cancer growth.
P186, 4th, Poor sleep quality therefore increases the risk of cancer development and, if cancer is established, provides a virulent fertilizer for its rapid and more rampant growth. Not getting sufficient sleep when fighting a battle against cancer can be likened to pouring gasoline on an already aggressive fire. That may sound alarmist, but the scientific evidence linking sleep disruption and cancer is now so damning that the World Health Organization has officially classified nighttime shift work as a “probable carcinogen.”
P188, top, Interestingly, the effect went in both directions: about half of those 711 genes had been abnormally revved up in their expression by the loss of sleep, while the other half had been diminished in their expression, or shut down entirely. The genes that were increased included those linked to chronic inflammation, cellular stress, and various factors that cause cardiovascular disease. Among those turned down were genes that help maintain stable metabolism and optimal immune responses.
2021-12-15
Chapter 9 Routinely Psychotic (REM-Sleep Dreaming)#
P195, 3rd, there are four main clusters of the brain that spike in activity when someone starts dreaming in REM sleep:
(1) the visuospatial regions at the back of the brain, which enable complex visual perception;
(2) the motor cortex, which instigates movement;
(3) the hippocampus and surrounding regions that we have spoken about before, which support your autobiographical memory; and
(4) the deep emotional centers of the brain—the amygdala and the cingulate cortex, a ribbon of tissue that sits above the amygdala and lines the inner surface of your brain—both of which help generate and process emotions.
P201, 2nd, The problem with Freud’s theory
The problem, however, was the lack of any clear predictions from Freud’s theory. Scientists could not design an experiment that would test any tenets of his theory in order to help support or falsify it.
P204, 3rd, Of a total of 299 dream reports that Stickgold collected from these individuals across the fourteen days, a clear rerun of prior waking life events—day residue—was found in just 1 to 2 percent. Dreams are not, therefore, a wholesale replay of our waking lives. We do not simply rewind the video of the day’s recorded experience and relive it at night, projected on the big screen of our cortex. If there is such a thing as “day residue,” there are but a few drops of the stuff in our otherwise arid dreams.
2021-12-16
Chapter 10 Dreaming as Overnight Therapy#
P208, 1st, Concentrations of a key stress-related chemical called noradrenaline (去甲肾上腺素) are completely shut off within your brain when you enter this dreaming sleep state. In fact, REM sleep is the only time during the twenty-four-hour period when your brain is completely devoid of this anxiety-triggering molecule. Noradrenaline, also known as norepinephrine, is the brain equivalent to a body chemical you already know and have felt the effects of: adrenaline (epinephrine).
P210, 4th, As the theory predicted, it was the dreaming state of REM sleep—and specific patterns of electrical activity that reflected the drop in stress-related brain chemistry during the dream state—that determined the success of overnight therapy from one individual to the next. It was not, therefore, time per se that healed all wounds, but instead it was time spent in dream sleep that was providing emotional convalescence. To sleep, perchance to heal.
P211, 4th, Cartwright had shown that it was not enough to have REM sleep, or even generic dreaming, when it comes to resolving our emotional past. Her patients required REM sleep with dreaming, but dreaming of a very specific kind: that which expressly involved dreaming about the emotional themes and sentiments of the waking trauma. It was only that content-specific form of dreaming that was able to accomplish clinical remission and offer emotional closure in these patients, allowing them to move forward into a new emotional future, and not be enslaved by a traumatic past.
P215, 1st, Accurately reading expressions and emotions of faces is a prerequisite of being a functional human being, and indeed, a functional higher primate of most kinds. Facial expressions represent one of the most important signals in our environment. They communicate the emotional state and intent of an individual and, if we interpret them correctly, influence our behavior in return. There are regions of your brain whose job it is to read and decode the value and meaning of emotional signals, especially faces. And it is that very same essential set of brain regions, or network, that REM sleep recalibrates at night.
P217, 3rd, Looking across the life span, we have discovered that this REM-sleep recalibration service comes into its own just prior to the transition into adolescence. Before that, when children are still under close watch from their parents, and many salient assessments and decisions are made by Mom and/or Dad, REM sleep provides less of a re-tuning benefit to a child’s brain. But come the early teenage years and the inflection point of parental independence wherein an adolescent must navigate the socioemotional world for himself, now we see the young brain feasting on this emotional recalibration benefit of REM sleep.
2021-12-16
Chapter 11 Dream Creativity and Dream Control#
P225, 3rd, When you wake the brain from NREM or measure performance during the day, the operating principles of the brain are closely and logically connected, just as pictured in figure 14. However, wake the brain up from REM sleep and the operating algorithm was completely different. Gone is the hierarchy of logical associative connection. The REM-sleep dreaming brain was utterly uninterested in bland, commonsense links—the one-step-to-the-next associations. Instead, the REM-sleep brain was shortcutting the obvious links and favoring very distantly related concepts. The logic guards had left the REM-sleep dreaming brain. Wonderfully eclectic lunatics were now running the associative memory asylum. From the REM-sleep dreaming state, almost anything goes—and the more bizarre the better, the results suggested.
P227, last, It is sleep that builds connections between distantly related informational elements that are not obvious in the light of the waking day. Our participants went to bed with disparate pieces of the jigsaw and woke up with the puzzle complete. It is the difference between knowledge (retention of individual facts) and wisdom (knowing what they all mean when you fit them together). Or, said more simply, learning versus comprehension. REM sleep allows your brain to move beyond the former and truly grasp the latter.
P232, Lucid dream, 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.
2021-12-16
Chapter 12 Things That Go Bump in the Night (Sleep Disorders and Death Caused by No Sleep)#
P239, 2nd, story of Ken Parks
P240, b,
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 sleep, 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.
paradoxical insomnia (i.e. 睡了感觉自己好像没睡过一样): 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.
P241, 3rd, types of insomnia
sleep onset insomnia: difficulty falling asleep
sleep maintenance insomnia: difficulty staying asleep
Sleep onset and sleep maintenance insomnia are not mutually exclusive: you can have one or the other, or both.
P241, b, sleep medicine has very specific clinical boxes that must be checked for a patient to receive a diagnosis of insomnia.
Dissatisfaction with sleep quantity or quality (e.g., difficulty falling asleep, staying sleep, early-morning awakening)
Suffering significant distress or daytime impairment
Has insomnia at least three nights each week for more than three months
Does not have any coexisting mental disorders or medical conditions that could otherwise cause what appears to be insomnia
P242, 3rd, Even with this strict definition, chronic insomnia is disarmingly common. Approximately one out of every nine people you pass on the street will meet the strict clinical criteria for insomnia, which translates to more than 40 million Americans struggling to make it through their waking days due to wide-eyed nights.
P242, b, Race and ethnicity also make a significant difference, with African Americans and Hispanic Americans suffering higher rates of insomnia than Caucasian Americans—findings that have important implications for well-recognized health disparities in these communities, such as diabetes, obesity, and cardiovascular disease, which have known links to a lack of sleep.
P244, t, The two most common triggers of chronic insomnia are psychological:
(1) emotional concerns, or worry, and
(2) emotional distress, or anxiety
P244-245, why overactive fight-or-flight nervous system prevents good sleep
First, the raised metabolic rate triggered by fight-or-flight nervous system activity, which is common in insomnia patients, results in a higher core body temperature.
Second are higher levels of the alertness-promoting hormone cortisol, and sister neuro-chemicals adrenaline and noradrenaline.
Third, and related to these chemicals, are altered patterns of brain activity linked with the body’s sympathetic nervous system.
Simply put, the insomnia patients could not disengage from a pattern of altering, worrisome, ruminative brain activity.
P247, 4th, 3 core symptoms of narcolepsy (嗜睡症)
(1) excessive daytime sleepiness,
(2) sleep paralysis: the frightening loss of ability to talk or move when waking up from sleep.
(3) cataplexy (猝倒): a falling-down seizure.
P258, 2nd, why sleep deprivation causes death
Unlike starvation, where the cause of death is easily identified, the researchers could not determine why the rats had died following sleep’s absence, despite how quickly death had arrived. Some hints emerged from assessments made during the experiment, as well as the later postmortems.
P259, 4th, 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. Far from a vicious infection that came from the outside, however, it was simple bacteria from the rats’ very own gut that inflicted the mortal blow—one that an otherwise healthy immune system would have easily quelled when fortified by sleep.
2021-12-16
Chapter 13 iPads, Factory Whistles, and Nightcaps (What’s Stopping You from Sleeping?)#
P265, 2nd, five key factors have powerfully changed how much and how well we sleep
(1) constant electric light as well as LED light,
(2) regularized temperature,
(3) caffeine
(4) alcohol,
(5) a legacy of punching time cards
P267, b, The degree to which evening electric light winds back your internal twenty-four-hour clock is important: usually two to three hours each evening, on average.
P269, 3rd, One of the earliest studies found that using an iPad—an electronic tablet enriched with blue LED light—for two hours prior to bed blocked the otherwise rising levels of melatonin by a significant 23 percent.
Compared to reading a printed book, reading on an iPad suppressed melatonin release by over 50 percent at night.
P271, 2nd, Alcohol is in a class of drugs called sedatives. It binds to receptors within the brain that prevent neurons from firing their electrical impulses.
P271, last,
alcohol fragments sleep, littering the night with brief awakenings. Alcohol-infused sleep is therefore not continuous and, as a result, not restorative.
alcohol is one of the most powerful suppressors of REM sleep that we know of.
P275, 3rd, To successfully initiate sleep, as described in chapter 2, your core temperature needs to decrease by 2 to 3 degrees Fahrenheit, or about 1 degree Celsius.
For this reason, you will always find it easier to fall asleep in a room that is too cold than too hot, since a room that is too cold is at least dragging your brain and body in the correct (downward) temperature direction for sleep. (飞机起飞后会调低机舱内空调温度的原因)
P276, 1st, Most of the thermic work is performed by three parts of your body in particular: your hands, your feet, and your head.
P277, 3rd, A bedroom temperature of around 65 degrees Fahrenheit (18.3°C) is ideal for the sleep of most people, assuming standard bedding and clothing.
2021-12-16
Chapter 14 Hurting and Helping Your Sleep (Pills vs. Therapy)#
P282, 3rd, Sleeping pills, old and new, target the same system in the brain that alcohol does—the receptors that stop your brain cells from firing—and are thus part of the same general class of drugs: sedatives. Sleeping pills effectively knock out the higher regions of your brain’s cortex.
P283, 3rd, The cause of rebound insomnia is a type of dependency in which the brain alters its balance of receptors as a reaction to the increased drug dose, trying to become somewhat less sensitive as a way of countering the foreign chemical within the brain.
P290, b, CBT-I: cognitive behavioral therapy for insomnia
P293, 3rd, Sleep and physical exertion have a bidirectional relationship.
Many of us know of the deep, sound sleep we often experience after sustained physical activity, such as a daylong hike, an extended bike ride, or even an exhausting day of working in the garden. Scientific studies dating back to the 1970s support some of this subjective wisdom, though perhaps not as strongly as you’d hope.
Unexpected, however, was the lack of a tight relationship between exercise and subsequent sleep from one day to the next. That is, subjects did not consistently sleep better at night on the days they exercised compared with the days when they were not required to exercise, as one would expect.
One brief note of caution regarding physical activity: try not to exercise right before bed.
2021-12-16
Chapter 15 Sleep and Society: What Medicine and Education Are Doing Wrong; What Google and NASA Are Doing Right#
P301, 2nd, Under-slept employees are not only less productive, less motivated, less creative, less happy, and lazier, but they are also more unethical.
P301, 4th, Ethical deviance linked to a lack of sleep also weasels its way onto the work stage in a different guise, called social loafing.
2021-12-16
Chapter 16 A New Vision for Sleep in the Twenty-First Century#
P335, 2nd, The less sleep you have had, or the more fragmented your sleep, the more sensitive you are to pain of all kinds.
2021-12-16
Appendix Twelve Tips for Healthy Sleep#
Stick to a sleep schedule
Exercise is great, but not too late in the day. Try to exercise at least thirty minutes on most days but not later than two to three hours before your bedtime.
Avoid caffeine and nicotine.
Avoid alcoholic drinks before bed.
Avoid large meals and beverages late at night
If possible, avoid medicines that delay or disrupt your sleep.
Don’t take naps after 3 p.m.
Relax before bed. Don’t overschedule your day so that no time is left for unwinding.
Take a hot bath before bed.
Dark bedroom, cool bedroom, gadget-free bedroom.
Have the right sunlight exposure
Don’t lie in bed awake.
Book completed on 2021-12-14
2021-12-24