3 - Human Sleep Flashcards
Mostly talking about undergraduates, which comes with some caveats. - Young Adult - Diurnal (not working night shifts) - Relatively healthy
From what stage do you enter REM sleep?
Stage 2
The stage you spend most of the night in and that you transition through to other stages
How long does the first stretch of low wave sleep last?
60-90 minutes
What is the hypnogogic period?
A period in stage 1 sleep where there might be vivid hallucinations while falling asleep (hypnagogic hallucinations)
What is the hypnopompic period?
The period right after waking
What is the REM/nREM cycle?
The cycles of nREM followed by REM throughout sleep
Does REM or nREM sleep dominate a night of sleep?
nREM
Rank the stages of sleep from most in a night to least
- nREM (mostly stage 2 sleep)
- REM
- WASO (wake after sleep onset) (least, about 5%)
What does the amount of slow wave sleep depend on?
How long you’ve been awake, how much sleep debt you have.
What does the amount of REM sleep you get depend on?
The circadian clock (eg. what time of day the body thinks it is)
The probability of having slow wave sleep increases/decreases throughout the night?
Decreases
The probability of REM sleep increases/decreases throughout the night?
Increases
When are you probable to fall into REM sleep?
The late morning to the early afternoon,
Virtually no chance early in the evening
This is controlled by the circadian clock
What happens to the probability of having REM or slow wave sleep when you are sleep deprived?
REM sleep: Chance decreased from normal levels and decreases even though they’ve been away for longer (doesn’t change a huge amount as it’s modulated by circadian clock)
Slow wave sleep: Chance increases highly and increases further as sleep deprivation continues
Slow wave sleep overtakes the probability of REM sleep during the day after a certain level of sleep deprivation
Forced internal synchronization experiments show what about REM sleep during sleep deprivation?
That REM is closely linked to circadian rhythms
Some behaviours do seem to have a cyclic period to them, eg. eating, chewing, smoking (oral behaviours) that seem to oscillate in a roughly 90 minute basis. What does this maybe suggest?
Suggests that REM/nREM 90-110 minutes cycles at night may be continuous with other ‘day cycles.’
Not much evidence for this.
True or false? Infants have REM/nREM cycles.
Sort of, they’re not the same as in adults (different periodicity)
Small animals have _____ REM/nREM cycles and bigger animals (such as humans) have ___ cycles
Small animals have shorter REM/nREM cycles and bigger animals (such as humans) have longer cycles
But there are lots of possible exceptions to this (eg. elephants having a cycle around 70 minutes - though that is guesswork)
- Perhaps these cycles are linked to metabolism, eg. small animal = fast metabolism = fast cycles
Do newborn infants have a circadian rhythm?
No
Hard to say what age a rhythm develops, as this is different from infant to infant
Kleitman had parents record sleep/eat cycle of infants without an imposed schedule on the infant’s behaviour. What were the results?
- At first totally arrhythmic
- A free running rhythm of wakefulness begins
- Circadian clock begins entrainment to day/night
- Infant becomes diurnal
At birth, infants fall directly into ____ sleep
Why
REM
Maybe incomplete circadian system or REM regulation system (ie gating function)
nREM sleep is concentrated ___ in each sleep bout for infants
early
More REM later in sleep
Do fetuses in utero show circadian rhythms?
The developing SCN begins free running but becomes synchronized by mom’s melatonin cycles
What are some rough estimates for babies at 12 months to 5 years?
14 to 16 hours of sleep daily.
Or 11 hours from actigraphy
Nap duration decreases until age 5 when total sleep is down to 9/10 hours
There is huge variability among children
What is the biggest reduction in sleep from 12 to 60 months?
Nap sleep
What amount of sleep do you need?
The amount of sleep that allows you to function the next day and not be sleepy
There are many societies on Earth in which an afternoon siesta is the norm, not just something that disappears at 5 years old. What is the consequence of not doing this?
The post lunch dip
A feeling of drowsiness and reduced energy/efficiency that can be accompanied by a full blown sleep episode (siestas) in cultures that encourage this. Typical way of dealing with this in other cultures is taking caffeine. In non-siesta societies, senior citizens begin re-adopting the nap.
What is evidence for the post lunch dip being regulated by biological mechanisms?
A physiological adaptation. Evidence is temperature dip in both nap takers and non-nap takers.
How does REM sleep from age 5 to death?
Pretty stable
How does stage 2 sleep change across the lifespan?
Pretty stable across the lifespan
What two sleep things change the most across the lifetime?
- Slow wave sleep decreases
- Wake after sleep onset increases
How does stage 1 sleep change across the lifespan?
Decreases from 0 to 10, stays stable and then increases from 55 to death
Infants are sleeping more or less over the years?
Less
Eg. between 1974 and 1986, 1 year olds slept 1 hour less. This difference disappeared in the teens however.
In later childhood. children show a delay in sleep onset on weekends. Why?
Evidence for social factors (eg. parents enforcing bedtime), not biology
How do adolescent’s delta power change?
Around 12 years old, delta power declines, more so in girls than boys. Boys still show same delta power at 9 or 10. Boys change lags behind girls and this change in delta power synchrony is similar to puberty but not correlated to markers of puberty.
How do theta and delta waves change from age 10 to 16? Why?
Decline in delta and theta power
This may be due to the dramatic pruning of neural connections in the brain, especially in the cortex, after the massive overgrowth of these synapses during childhood.
If you have fewer synaptic connections, you may have less synaptic synchrony.
The brain is made up of white matter and grey matter, when you see a decline in brain matter, it could be grey or white. Over adolescents, which one declines more?
Decrease in grey matter over adolescence, suggested by increase in white matter ratio
This is a little bit up in the air
True or false? Some people have an early awakening preference that can last throughout the lifetime. How?
True, this may be based in genetics as well. as it can be seen throughout generations
Casein kinase 1 delta gene
What is the casein kinase 1 delta gene?
Binds to circadian clock genes that gives preference for an advanced sleep phase (early riser)
True or false? Humans are diurnal
True for most people, but there are some people who have genetic patterns that lead to nocturnal preference
What is the adolescent shift in sleep patterns (waking up)?
Shift from delayed sleep phase (waking late) to advanced sleep phase (waking early) as you get older
What is sleep onset insomnia?
Inability to fall asleep or go to bed at the appropriate time
What things can keep people awake at night and producing sleep onset insomnia?
- Anxiety (grades, social situations etc.)
- Depression
How can you determine if an individual with delayed sleep phase syndrome has it because of biological/psychological causes, rather than sociological causes? What is a problem with this?
By removing all social factors
A problem is that taking away familiar environment might cause anxiety
What is delayed sleep phase syndrome?
- A circadian rhythm sleep disorder affecting the timing of sleep, peak period of alertness, the core body temperature rhythm, hormonal and other daily rhythms, compared to the general population and relative to societal requirements.
- People with DSPD generally fall asleep some hours after midnight and have difficulty waking up in the morning.
What is chronotherapy for delayed sleep phase syndrome?
Delaying the patient for 2/3 hours a day until they were at a normal sleep time (eg 11 pm).
Advancing sleep time is just non effective for these people. But delaying can work if it is followed very rigidly.
What is the suggested cause for changes in sleep patterns across the lifespan?
Reduce in circadian rhythm oscillation amplitudes
How does hourly percent of REM sleep change between young people (21 yo) and old people (82 yo)? (4)
- Older group have a flat circadian rhythm, REM % doesn’t really increase throughout night
- Young adults have higher percentages of REM as night goes on (strong circadian rhythms)
- Young adults get much more stage 3 sleep
- Young adults get much more stage 4 (SWS) sleep earlier in night, old people have a flatline of stage 4 sleep and not much of it.
What is one explanation for the reduction of EEG voltage in older people? What does this look like in sleep?
- Shrinking of cortex from skull
- Looks like old people don’t get any slow wave sleep
What are survivor effects?
- Studying old people, you lose a fraction of them due to death.
- What allowed one portion of these people to outlive the other?
- There are factors involved in this that could confound a study containing old people
Is age itself a determining factor in reporting good sleep?
Not really,
Usually bad sleep in older people due to things like arthritis, obstructive pulmonary disease etc.
As people age, how do men and women differ in terms of slow wave sleep?
Females: SWS doesn’t decline much
Males: SWS declines as men age
How does stage 1 sleep change for men and women as they get older?
Men: Stage 1 sleep increases as men age
Women: Stage 1 sleep does not decrease/increase as women age, but they get less slow wave sleep than men
