However, a strong case can already be made for defending sleep time in our adolescent youth, rather than denigrating sleep as a sign of laziness. We are still learning more about the role of sleep in development.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.Alcohol is one of the most powerful suppressors of REM sleep that we know of.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.Ĭhapter 5 - Changes in Sleep Across the Life Span.

REM sleep exquisitely recalibrates and fine-tunes the emotional circuits of the human brain (discussed in detail in part 3 of the book).It is perhaps unsurprising that in the small enclaves of Greece where siestas still remain intact, such as the island of Ikaria, men are nearly four times as likely to reach the age of ninety as American males. Apparent from this remarkable study is this fact: when we are cleaved from the innate practice of biphasic sleep, our lives are shortened.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. 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. Visit cultures that are untouched by electricity and you often see something rather different.Throughout developed nations, most adults currently sleep in a monophasic pattern-that is, we try to take a long, single bout of slumber at night, the average duration of which is now less than seven hours.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.Why did evolution decide to outlaw muscle activity during REM sleep? Because by eliminating muscle activity you are prevented from acting out your dream experience.Ĭhapter 4 - Ape Beds, Dinosaurs, and Napping with Half a Brain.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).Can you function optimally before noon without caffeine?Ĭhapter 3 - Defining and Generating Sleep.Do you find yourself re-reading things?.If you didn’t set an alarm clock, would you wake up on time?.Some people process caffeine faster than others, and we get less efficient as we age.Caffeine works by blocking the receptors that adenosine affects (after about 30 minutes).Sleep pressure, caused by a buildup of the chemical adenosine in your brain, is the second factor affecting sleepiness.Melatonin helps regulate the timing of when sleep occurs by signalling darkness throughout the organism, but has little influence on the generation of sleep itself. Your circadian rhythm is one of two factors determining wake and sleep.Sleep is the most effective thing we can do to reset our brain and body health each day.Ĭhapter 2 - Caffeine, Jet Lag, and Melatonin.The shorter your sleep, the shorter your life span.Notes Part 1 - This Thing Called Sleep Chapter 1 - To Sleep.

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