More on this book
Community
Kindle Notes & Highlights
Read between
January 28 - February 15, 2020
melatonin is not a powerful sleeping aid in and of itself, at least not for healthy, non-jet-lagged individuals
For every day you are in a different time zone, your suprachiasmatic nucleus can only readjust by about one hour.
Scientists have studied airplane cabin crews who frequently fly on long-haul routes and have little chance to recover. Two alarming results have emerged. First, parts of their brains—specifically those related to learning and memory—had physically shrunk, suggesting the destruction of brain cells caused by the biological stress of time-zone travel. Second, their short-term memory was significantly impaired. They were considerably more forgetful than individuals of similar age and background who did not frequently travel through time zones. Other studies of pilots, cabin crew members, and shift
...more
At this very moment, a chemical called adenosine is building up in your brain. It will continue to increase in concentration with every waking minute that elapses. The longer you are awake, the more adenosine will accumulate.
when adenosine concentrations peak, an irresistible urge for slumber will take hold.VII It happens to most people after twelve to sixteen hours of being awake.
caffeine is the most widely used (and abused) psychoactive stimulant in the world. It is the second most traded commodity on the planet, after oil.
Caffeine has an average half-life of five to seven hours. Let’s say that you have a cup of coffee after your evening dinner, around 7:30 p.m. This means that by 1:30 a.m., 50 percent of that caffeine may still be active and circulating throughout your brain tissue. In other words, by 1:30 a.m., you’re only halfway to completing the job of cleansing your brain of the caffeine you drank after dinner.
Also be aware that de-caffeinated does not mean non-caffeinated. Depending on the decaffeination method and the bean that is used, one cup of decaf can have between 3 to as high as 10 percent
you may have assumed that the two governing forces that regulate your sleep—the twenty-four-hour circadian rhythm of the suprachiasmatic nucleus and the sleep-pressure signal of adenosine—communicate with each other so as to unite their influences. In actual fact, they don’t. They are two distinct and separate systems that are ignorant of each other. They are not coupled; though, they are usually aligned.
how do you know whether you’re routinely getting enough sleep?
First, after waking up in the morning, could you fall back asleep at ten or eleven a.m.? If the answer is “yes,” you are likely not getting sufficient sleep quantity and/or quality. Second, can you function optimally without caffeine before noon? If the answer is “no,” then you are most likely self-medicating your state of chronic sleep deprivation.
Consider the last time you fell asleep on an airplane. When you woke up, you probably checked a clock to see how long you had been asleep. Why? Because your explicit tracking of time was ostensibly lost while you slept.
I’m sure you have had the experience of needing to wake up the next morning at a specific time. Perhaps you had to catch an early-morning flight. Before bed, you diligently set your alarm for 6:00 a.m. Miraculously, however, you woke up at 5:58 a.m., unassisted, right before the alarm. Your brain, it seems, is still capable of logging time with quite remarkable precision while asleep.
REM sleep, in which brain activity was almost identical to that when we are awake, was intimately connected to the experience we call dreaming, and is often described as dream sleep.
It works both ways. If you wake up at ten a.m., but don’t go to bed until four a.m., then you will lose a significant amount of your normal deep NREM sleep.
Really? Is the stage of sleep really regulated by the time of the night, rather than sequentially starting with more NREM and ending with REM?
What you are actually experiencing during deep NREM sleep is one of the most epic displays of neural collaboration that we know of.
REM sleep brain activity is an almost perfect replica of that seen during attentive, alert wakefulness—the
recent MRI scanning studies have found that there are individual parts of the brain that are up to 30 percent more active during REM sleep than when we are awake!
While awake, even lying in bed and relaxed, there remains a degree of overall tension, or tone, in your muscles. This steady muscular hum is easily detected by the electrodes listening in on your body. As you pass into NREM sleep, some of that muscle tension disappears, but much remains. Gearing up for the leap into REM sleep, however, an impressive change occurs. Mere seconds before the dreaming phase begins, and for as long as that REM-sleep period lasts, you are completely paralyzed. There is no tone in the voluntary muscles of your body. None whatsoever.
The brain paralyzes the body so the mind can dream safely.
Some people with a certain type of insomnia are not able to accurately gauge whether they have been asleep or awake at night. As a consequence of this “sleep misperception,” they underestimate how much slumber they have successfully obtained—a condition that we will return to later in the book.
regardless of the amount of recovery opportunity, the brain never comes close to getting back all the sleep it has lost.
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,
almost impossible to believe. 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! One half of the brain must always stay awake to maintain life-necessary movement in the aquatic environment.
When birds are alone, one half of the brain and its corresponding (opposite-side) eye must stay awake, maintaining vigilance to environmental threats.
Things get even more interesting when birds group together. In some species, many of the birds in a flock will sleep with both halves of the brain at the same time. How do they remain safe from threat? The answer is truly ingenious.
if you bring that person into a sleep laboratory, or take them to a hotel—both of which are unfamiliar sleep environments—one half of the brain sleeps a little lighter than the other, as if it’s standing guard with just a tad more vigilance due to the potentially less safe context that the conscious brain has registered while awake.
It is perhaps one reason why so many of us sleep so poorly the first night in a hotel room.
Place an organism under conditions of severe famine, and foraging for food will supersede sleep.
In-flight, migrating birds will grab remarkably brief periods of sleep lasting only seconds in duration.
If you sleep-deprive this sparrow in the laboratory during the migratory period of the year (when it would otherwise be in flight), it suffers virtually no ill effects whatsoever. However, depriving the same sparrow of the same amount of sleep outside this migratory time window inflicts a maelstrom of brain and body dysfunction.
Hunter-gatherer tribes, such as the Gabra in northern Kenya or the San people in the Kalahari Desert, whose way of life has changed little over the past thousands of years, sleep in a biphasic pattern. Both these groups take a similarly longer sleep period at night (seven to eight hours of time in bed, achieving about seven hours of sleep), followed by a thirty- to sixty-minute nap in the afternoon.
The separation from biphasic sleep occurred at, or even before, our shift from an agrarian existence to an industrial one.
The total amount of time we spend asleep is markedly shorter than all other primates (eight hours, relative to the ten to fifteen hours of sleep observed in all other primates), yet we have a disproportionate amount of REM sleep, the stage in which we dream. Between 20 and 25 percent of our sleep time is dedicated to REM sleep dreaming, compared to an average of only 9 percent across all other primates!
It is only when the fetus enters the final trimester that the glimmers of real wakefulness emerge. Far less than you would probably imagine, though—just two to three hours of each day are spent awake in the womb.
In the last week before birth, REM-sleep amount hits a lifetime high of twelve hours a day.
What does that mean for premature birth consequences?
Our current understanding of what causes autism is incomplete, but central to the condition appears to be an inappropriate wiring up of the brain during early developmental life, specifically in the formation and number of synapses—that is, abnormal synaptogenesis. Imbalances in synaptic connections are common in autistic individuals: excess amounts of connectivity in some parts of the brain, deficiencies in others.
Infants and young children who show signs of autism, or who are diagnosed with autism, do not have normal sleep patterns or amounts.
Autistic individuals show a 30 to 50 percent deficit in the amount of REM sleep they obtain, relative to children without autism.
Just because autism and REM-sleep abnormalities go hand in hand does not mean that one causes the other.
rats deprived of REM sleep during infancy go on to become socially withdrawn and isolated as adolescents and adults.
Alcohol is one of the most powerful suppressors of REM sleep that we know of.
Newborns of heavy-drinking mothers did not have the same electrical quality of REM sleep.
unborn infants suffered a depression in breathing during REM sleep, with breath rates dropping from a rate of 381 per hour during natural sleep to just 4 per hour when the fetus was exposed to alcohol.
When babies consume alcohol-laced milk, their sleep is more fragmented, they spend more time awake, and they suffer a 20 to 30 percent suppression of REM sleep after.
blocking or reducing REM sleep in newborn animals hinders and distorts brain development, leading to an adult that is socially abnormal.
As deep NREM sleep performs its final overhaul and refinement of the brain during adolescence, cognitive skills, reasoning, and critical thinking start to improve, and do so in a proportional manner with that NREM sleep change.
deep sleep may be a driving force of brain maturation, not the other way around.
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.
we have also observed that in young individuals who are at high risk of developing schizophrenia, and in teenagers and young adults with schizophrenia, there is a two- to threefold reduction in deep NREM sleep.
