Why we sleep - Dr Matthew Walker Flashcards
Chapter 1: Caffeine, Jetlag and Melatonin
our internal circadian rhythm is set to 24hrs 15mins, but the daily exposure to sunlight sets it back to 24hrs Food, exercise, temperature, and social interaction can reset internal body clock to 24hrs Night owls that have to wake up early - prefrontal cortex takes a while to “warm-up”
Melatonin - sleep hormone - secreted by pineal gland when initiated by suprachiasmic nucleus when it gets dark
affects timing of sleep - melatonin levels rise from sunset to around 2 am, then decrease until sunrise
Adenosine accumulates throughout the day
Caffeine blocks receptor uptake of adenosine, adenosine accumulates and then when the body removes caffeine you get a “caffeine crash”
Chapter 2: Defining and generating sleep
Rat experiment -rats taught to memorise track they walked - and brain activity recorded- while asleep, durinf REM (rapid eye movement) cycle - same areas of the brain where lighting up - at 1/4 -> 1/2 the speed
Sleep cycles made up of NREM and REM sleep
Chapter 4: Ape beds, dinosaurs, and napping with half a brain
fasting leads to decrease sleep time - evolutionary - when we didn’t eat, we required more time awake to find food
humans are biologically programmed for biphasic sleep, some cultures still have afternoon naps and 7hrs sleep at night
- dip in alertness ingrained in us - post lunch meeting dips in attention
Chapter 5: Changes in sleep across the life span
Babies polyphasic sleep pattern
Young children circadian rhythm set earlier than adults - they go to bed earlier and wake up earlier
Adolescents circadian rhythm is set later than adults - their 11pm is equivilant to adult’s 7pm etc, they go to bed a lot later and wake up a lot later
Older adults - sleep quality and efficiency decline around the same time as cognitive and memory declines - link between the two as MRI shows degeneration in area of the brain that controls sleep - leads to decline in memory of material before bed tested upon waking compared to younger adults
- Afternoon naps rob sleep from the night in older adults resetting adenosine
Chapter 6: Your mother and shakespeare knew
Sleep the night before learning
- refreshes our ability to make new memories
- limited storage capacity of the hippocampus
- long term storage in cortex
- 90 minute naps were shown to increase memory retention of textbook materials
- Stage 2 NREM sleep main contributor to enhancing memories - spindles
- older adults have 40% deficit in spindles
Sleep the night after learning
- Early night NREM sleep leads to better memory results compared to later REM sleep
- Lack of sleep leads to increase risk of injury and decrease performance in elite sportspeople
- Sleep helps with creativity - diffuse mode thinking
Chapter 7: Too extreme for the Guinness Book of World Records
- Guinness World Records deems it too risky to try sleep deprivation records
- microsleep occurs mainly due to chronic sleep deprivation - where eyelids either close or are partially closed for a matter of seconds
- The link between the prefrontal cortex (brake) and amygdala (gas) is lost with sleep deprivation
Ipads, factories whistles, and nightcaps
Alcohol is a sedative, so while people think it helps them sleep better, sedation is not natural sleep and therefore doesn’t have the same benefits
Study on undergrads - 3 groups given content to learn, one had no alcohol, one had 3 shots of vodka and orange juice after learning, one had 3 alcohol three days later. The group w/o alcohol remembered 100% of content 7 days later (with appropriate sleep), group with alcohol first night remembered only 50%, group three recalled 60%. This is due to the sedative effects and the poor quality of sleep that follows
Recommendations- drink in the morning so the effects of alcohol wear off prior to bed, or abstain from alcohol
Sleep and Society
