8 minute read

Notes from the book

Part 1: This thing called sleep

Chap I + II: Sleep and caffeine

  • Human, animals and plants have their own rhythm of sleep which weakly depends on other environmental factors such as sunlight, the temperature of the day. This rhythm is regarded as circadian rhythm.
  • The circadian rhythm (or sleep/awake circle) is regulated by melatonin.
  • Brain uses a chemical called adenosine to increase the desire for sleep or sleep pressure. Caffeine deactivates “receptors” in brain which is targeted by adenosine but the adenosine still accumulates in your brain.

Chap III: Defining and Generating Sleep

  • A small part in the center of the brain called thalamus which blocks most of the signals from our “sensors” to the brain center during our sleep.
  • Human lose their perception of time in the conscious part, but for the non-conscious part, it sometimes could estimate the time at remarkable precision. (e.g. remember you wake up just right before the alarm when you have an important event to catch up next day).
  • Brain replays what it learns during wake time in the sleep time at a very slow speed.
  • During sleep, we cycle through two types of sleep: rapid eye movement (REM) where the brain wave is active as wake time (dream) and non-rapid eye movement (NREM). Each cycle could last around 90 minutes.
  • The NREM dominates in the first half of the sleep and the REM is more likely in the second half, especially early morning hour –> this explains why dreams are more likely happen in the early morning.

Chap IV: Who sleeps, How do we sleep and How much?

  • Sleep is observed in many species across the animal kingdom from worms to developed mammals. Sleep started with the presence of light during day and night of simple bacterial.
  • Birds and aquatic mammals could allow half of their brain (which corresponds to one of two eyes) to enter sleep while the other half stays awake to spot threats from their environment.
  • Under life pressure (e.g. starvation), desire or need for sleep could be reduced to seek food to survive.
  • Old communities in Greece used to maintain biphasic sleep which was proved to benefit their health but industrial life has changed it forever.
  • NREM sleep (predominates in the first half of the night) helps transfer and organise newly learned information into long-term storage sites while REM sleeps fuels creativity by dreaming based on the obtained information. This explains why we sometimes would come up with radical ideas or solutions after a good sleep.

Chap V: Changes in sleep across the life span

  • Babies have REM sleep when they are in the womb before they are born. Lack of REM sleep in this period could lead to autism.
  • The baby body is not paralysed as after birth so mothers could feel their kicks and punches happen in the final months of the pregnancy.
  • The ratio of NREM/REM sleep keeps increasing from 50/50 of infants to reach 80/20 of the late teen years and remains so through adult time.
  • The adolescents are less rational and poorer in making decisions as adults. The event the number of neural connections decrease but the physical size of the brain cells increases when we turn to adults.
  • The bedtime of adolescents are rather later than their parents and their younger sibling and wake up later also. In the nature view, adolescence is the time that young animals separate themselves from their parents to start their independent life. Mother nature makes this transition more smooth by pushing their circadian ryhthm forward several hours. Thus, teenagers usually could not sleep until late and find it very hard to wake up early. The sleep hours will be back to normal when they enter the adult period.
  • The part of the brain that generates sleep deteriorates in elder adults. This explains why elders adults have worse quality of sleep. This lead to the deduction in the memorization.

Part 2: Why should we sleep

Chap VI: The benefits of sleep for the brain

  • An experiment shows that before sleep, the new information that a person has just learned is stored in the hippocampus - an area of the brain that keeps the short-term information. However, when that person retrieves the same information after sleep, brain signals came from the cortex where long-term information is stored. Thus, sleep allows short-term information from the hippocampus to move to the cortex for long-term storage.
  • A group of researcher experimented with simulating brain waves during NREM sleep by applying electrical pulsations which are similar to the slow brain waves. The result is that the information that participants who are applied this type of simulation could recall are doubled to the normal group. Scientists also use tagged sound to simulate the learning where sounds tagged to images played during NREM sleep. This experiment also obtained the same result.
  • Not only enhancing the ability to remember, NREM sleep also allow people to forget the discard information easier. Remember when teachers tell you what information you should focus on for your exam, you would want to strengthen information to focus while discards the other from your memory. Sleep helps both of those processes happen perfectly.
  • Sleep helps us learn better information that we obtain from practising. The experiment of two groups who have to learn to type as fast as possible a sequence of keystrokes show that, the group who learn at 6 am and being tested at 6 pm (no sleep between the times) shows poorer performance than the group who learn the same thing at 6 pm and tested at 6 am next morning. The same phenomenon was observed in people who learn to play musical instruments.

Chap VII: Sleep deprivation and the brain

  • Sleep deprivation could be as harmful as using alcohol when you are driving. Stop driving when you are drowsy.
  • Sleep deprivation affects the rationality and ability to study.

Chap VIII: Sleep deprivation and the body

  • Sleep loss could increase the chance of cardiovascular system diseases.
  • Sleep loss could affect metabolism, increase diabetes and obesity.
  • Sleep loss affects the reproductive system of human, reduces the testosterone, density of sperm and size of testicles.

Part 3: How and why we dream

Chap IX: REM-sleep dreaming

  • Dreams occur during REM sleep.
  • Explains different theories about dreaming from past to present.
  • Some theories are considered as “the disease of generic-ness” when people produce those theories which is generic enough to seemingly fit everything (like horoscopes).

Chap X: Dreaming as overnight therapy

  • Traumatic experiences could be healed in the dream or REM sleep. During the REM sleep, the traumatic past could be alleviated and we would never feel it as strong as earlier in the next morning.

Chap XI: Dream creativity and dream control

  • Some people come to important inventions in their dreams, mostly musicians. Experiments of waking people up in NREM and REM shows that people in REM show problem better. –> Me: There are only a few examples to support the idea. The experiment is somehow biased since we are more rational and our brain is more active in REM sleep.
  • The way Thomas Edison takes advantage of short REM sleeps to create interesting ideas is interesting and smart. Edison usually lay on an armchair with a couple of steel balls in his hand. Below his hand is an upside-down saucepan, a pen and a paper. When he starts getting into sleep, his hand will release the stell balls which then make a bang to the saucepan that will wake him up. He then immediately write down the idea that just flows in his mind.
  • Small proportion of human are lucid dreamers - people who could control their dream and their action in the dream. Scientists let them participates in experiments in which they could signal the scientists via eye movements that when they enter the dream and doing pre-defined actions in their dreams.

Part 3: From sleeping pills to society transformed

Chap XII: Sleep disorders and death caused by no sleep

  • Discuss somnambulism, insomnia and nacolepsy.

Chap XIII: iPads, factory whistles and nightcaps

  • Blue lights from screens could reduce the sleep quality and quantity. Reading paper books instead of iPad is better for sleep.
  • Alcohol could suppress the REM sleep and affect our ability of learning and memorizing.
  • At the time of sleep, the human body core temperature will decrease 2 to 3 Celcius degrees to stimulate sleep. Washing face and hands help reduce the core temperature and make sleep easier. We will feel hot in bed at night when starting falling asleep. We usually pull our hands and feet out from underneath the bedcovers as we feel hot. A bedroom temperature of 18.3 Celsius degree is the optimal temperature to sleep for most people.
  • Being woken up by an alarm could create a spike in blood pressure and accelerate the heart rate, especially for the elderly. Self-waken up is good for health. Thus, it’s recommended to sleep and wake up at the same time every day no matter it is the week or weekend.

Chap XIV: Pills vs therapy

  • Sleeping pills are harmful to the body. The sleep effect it creates is not healthy as the natural sleep.
  • Physical exertion could aid sleep. However, the human body needs one to two hours to be cooled down after exercise.

Chap XV: What medicine and education are doing wrong; What Google and NASA are doing right

  • Sleep deprivation could cost businesses millions a year in productivity. Employees should be encouraged to take more naps at work.
  • Early school opening time could affect the students’ performance and social behaviours at school.

Chap XVI: A new vision for sleep in twenty-first century

  • Individuals should have a “sleep target” for their new year resolution.
  • More education about sleep should be added to school programs.
  • One interesting idea is that organizations should have their own “sleep credit system” which rewards their employees with vacation or financial bonuses for each night of continuous sleep.

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