test 2 Flashcards
careful study of circadian rhythms in people requires…
isolate from zeitgebers
constant environments for studying sleeo?
deep underground caves
laboratories
- constant temps and total darkness
who spent time in kentuckys mammoth cave and for how long
nathaniel kleitman and bruce richardson, 32 days
who spent a lot of time in underground caves
michel siffre spent time in caves and underground glaciers in multiple experiments — he was alone in the original studies and calling up to a research team to report
who used a WWII bunker
aschoff and Wever used an underground bunker from WWII modified into a well-equipped and isolated lab for studying individuals living in time-free environments
did lots of people ask to end time in the sleep cave early?
ery few participants found the isolation to be disturbing or asked to be released early
what did aschoff and wever find - interesting finding
Aschoff and Wever reported that some participants developed a strong interest in guessing the time in the external world
- Guessing research assistant’s schedules relative to external time (day crew or night crew)
- Studies in hospitals or universities, participants could feel vibrations from elevator shafts, thus able to guess when the workday started and ended
- Experiments had to work on irregularly staggering schedules to conceal information about the time of day
Without cues, meal patterns, body temperature, and sleep-wake cycles free-run with periods…
different than 24 hours
Spontaneous desynchronization?
different rhythms with different periods
Spontaneous desynchronization examples
Eg. Some participants showed sleep-wake cycles much shorter or longer than 24 hours, while body temperature rhythms free-ran with periods close to 24 hours
spontaneous desynch example siffre
Michel Siffre reported sleep-wake cycle of 50 hours in some cases, but body temperature stayed in circadian range
- This is a bit extreme, his probably ran a little long naturally
- Did cognitive testing: took him a long time to count to three for example, his personal perception of time was longer
those with very long sleep wake cycles
- Average hourly activity levels were lower
- Ate meals at longer intervals
- Estimated an hour as being longer
- Had lower average body temperature
those with very short sleep-wake cycles
- Average hourly activity levels were higher
- Ate meals at shorter intervals
- Estimated an hour as being shorter
- Had higher average body temperature
people with very long and short sleep wake cycles found to…
be active for the same total time at the end
in controlled environments with no external time cues what can still be an issue?
some variables can still affect measurement of rhythms
the circadian rhythm of body temperature responds to a number of masking effects
Large meals increase sleepiness
Exercise increases body temperature
Body temperature decreases during sleep
Even if researchers attempt to limit external variables (eg. Alarm clock), there are still…
many effects that can occur even through participants self-selected patterns
what things can researchers not control in measuring sleep
Body temperature, some hormones, change depending on whether a person is laying down, standing or sitting
Campbell and Broughton study
Purpose:
clarify the temporal relationship between the nightly decline in body temperature and the timing of the onset of nocturnal sleep
Campbell and Broughton whole study
???
Campbell and Broughton correlation
Significant positive correlation between the amount of wakefulness within the first hour after initial sleep onset and MROD relative to both bedtime and sleep onset
- That is, the closer MROD occurred to either bedtime or sleep onset, the less wakefulness there was within the first hour after sleep onset
Campbell and Broughton findings
- Findings indicate that the process of sleep initiation is most likely to occur when the body temperature is declining at its maximum rate and is most successfully accomplished at this phase of the temperature cycle
- If you were too warm when trying to go to bed (artificially raising body temp), it can be hard to fall asleep
- Feet should be warm
internal masking
changes in the value of a target measure (Eg. Body temperature) that result from the participant’s own behaviour rather than from either an external disturbance or the dictates of the circadian clock
internal masking examples
Doing exercise, eating a big meal, etc. could change one of their cycles
how do researchers get around internal masking in lab studies
constant routine
forcred desynchronization
constant routine
participants maintain an unchanging posture (eg. Semi-recumbent), remains awake, consumes identical, isocaloric mini-meals at frequent internals for 36-48 hours. These extreme measures may affect circadian rhythms measures!
forced desynchonrization
create unusual sleep-wake patterns so that sleep occurs at many different phase of a participant’s circadian cycles. Allows researchers to measure the impact of circadian systems on many features of sleep. Eg. How do the different phases of the body temperature rhythm affect REM sleep?
impacts of lab environment
- Laboratory studies permit precise analysis of the effects of experimental manipulations, but constrain behaviour in unusual ways
- Many variables not included in lab studies may affect daily rhythms
predation pressure and resource competition
- Two spices of spiny mice with overlapping habitats in Israel — less aggressive species less active at night because they don’t want to interact
- Norway rat groups in semi-natural enclosures — social dominance and competition determined the daily timing of feeding by non-dominant individual
- Two closely related sloth species — sleep timing differed with exposed to different predation pressures in their natural habitat, because of unsafe during sleep
what do field studies help us to understand
help us understand how circadian rhythms respond to complex variables in real-world environments
there is ____ variability in sleep characteristics across individuals of the stage age and same species
large
newborns show ____ circadian modulation of their sleep-wake cycle
little
polyphasic pattern of newborns
multiple sleep-wake cycles throughout the day (relatively brief sleep episodes occurring throughout the day and night)
Patterns of sleep-wake cycle change dramatically in the _____
first 6 months of life
Generally diurnal sleep pattern develops by
12-14 weeks of age (~3-4 months)
by 6 months, over 50% of parents report
infants sleeping regularly between 22:00-6:00 (10pm-6am) roughly 8 hours overnight, then lots of naps during the day
why do infants develop a regular sleeping pattern
Not really clear if this is excuse they become entrained to environmental cues or social cues, very likely a combination
Infant is starting to go to sleep and wake up at the same time everyday (approx. 7pm to 7am) starting at
18-19 weeks.
seeing a slight _____ in sleep time and adoption of a regular sleep cycle as infants age
derease
Results could suggest that the internal circadian clock for sleep-wake cycle matures….
very early in development and is later entrained to the day-night cycle
sex based differences in baby sleep entrainment
In a second study of a male from bright to 6 months, entrainment appeared much earlier: ~ day 30 vs. ~day 112 (for female)
hard to seperate maturation of circadian system from ___ and ____
parental/social cues
exposure to life
two infant sleep stages?
active sleep
quiet sleep
active sleep (as)…
resembles REM sleep
quiet sleep (qs)…
resembles non-REM sleep
full term infant sleep amount
Sleeps ~16-18h daily broken into 2-4h sleep periods
full term infant rem sleep amount
REM sleep is ~50% (8-9h) and alternates with NREM sleep in ~50-60min cycles
- A lot compared to adults, shorter cycles that ours
when does rem ocur for newborns
Newborns fall directly into REM sleep at sleep ones
at 3 months of age
more NREM sleep, and REM sleep occurs later in each sleep episode
at 6 months of age
typical adult patterns established with NREM sleep regularly occurring at sleep onset, REM sleep now ~25% of sleep cycle
altricial
an animal hatched or born helpless and requiring significant parental care
precocial
capable of moving around on its own soon after hatchin
human auditory system
Humans have a relatively developed auditory system in the womb, visual system is relatively well developed. Other apes can hold onto their parents, however, we cannot.
altricial mammals have an…
immature sleep-wake pattern
precocial mammals show…
adult-like EEG sleep patterns by 1-week after birth
- But show higher levels of REM sleep prenatally (when their sleep anatomically more closely resembles altricial mammals)
how could u measure sleep in childhood
- population based surveys asking about average sleep duration
- sleep studies with children
population based surveys asking about average sleep duration issues
- parents are not always good reporters of their Childs sleep (might not be super accurate)
- Average sleep duration may be affected by societal and cultural norms
- Average sleep duration is not necessarily how much sleep children need
sleep studies with children methods
- Polysomnography in the lab or at home
- Parental reports
- Self-report (older children)
- Sleep diaries
- Actigraphy
Physiological measures and parental reports do not always converge — what is more accurate?
physiological measures are typically more accurate
~1 year of age amount of sleep?
~11h daily
> 1 year of age, total number of hours of sleep
declines reaching 9-9.5 h by age 5
what happens w total REM duration during sleep over 1 year of age
Total duration of REM sleep gets a little higher because there is a total decrease in sleep, REM becomes a higher proportion of sleep increases because you begin sleeping less in total
when are total daytime naps lost in north america?
by 5 years
evidence suggests that midday naps may be
Total duration of REM sleep gets a little higher because there is a total decrease in sleep, REM becomes a higher proportion of sleep increases because you begin sleeping less in total
- apes nap a lot
Study of 3 different cohorts in Switzerland (1974, 1979, 1986) results
- Seeing a gradual decrease in the total duration of sleep
- That observed decrease in sleep over time is most pronounced in younger ages (about an hour difference in total — that is a big chunk of sleep)
- Decreased sleep large because of progressively later sleep onset times — these are believed to be cultural differences
recommendations for sleep duration: infants 4-12 months
12-16h per 24h including naps
recommendations for sleep duration: children 1-2 yrs
11-14h per 24h including naps
recommendations for sleep duration: 3-5 yrs
10-13h per 24h including naps
recommendations for sleep duration: children 6-12 yrs
9-12h per 24h
recommendations for sleep duration: teenagers 13-18 yrs
8-10h per 24h
sleep in adolescence findings
Longitudinal study found steep decline in EEG delta power density during NREM sleep from ages 12-14 years — less delta waves, then continues to decreases
when did decline in delta power density occur for adolescents
began 1 year earlier in girls than in boys (drops around 11 in females, 12 in males)
similar sleep decline in ______ as we age
cortical theta power
campbell and feinberg propose cortical theta power decrease might be linked to decline in
Cortical synaptic connectivity
Grey matter volume
what happens during puberty and its effect
decline in cortical synaptic connectivity and grey matter volume occurs during puberty, resulting in reduced local neural synchrony — fewer connections in the same area because there is an overall decrease in connections being made after puberty
what does reduce local neural synchrony result in
more desynchronization
from birth to 5 years old, huge amount of
synpatogenesis — forming a lot of new connections when really young
between 10-15 (puberty), huge amount of
synaptic pruning, use it or lose it concept
the degree of local synchrony in neural activity contributes to…
the amplitude of EEG fluctuations
a decline in local synchrony of neural activity would result in a
educe the amplitude of EEG voltage changes, leading to reduction of cortical EEG power in theta and delta ranges (waking and sleep)
What accounts for the increase in the ratio of white to grey matter seen in adolescent girls?
increased myelination (not seen in boys they have testosterone-dependent increases in axon diameter)
adolescents show a ______ and gradual ____ in total time slept
delay in timing of sleep onset, redution
what has delay in sleep onset and reduction of total time slept in adolescents been attributed to?
- Change in the underlying period of the circadian clock regulating sleep-wake timing
- A change in sensitivity to the phase-shifting effects of light — eg. If you are exposed to light in the evening you just end up staying up later
- Fixed waking times determined by school schedules — regardless of when you went to bed and wanted to wake up. Leads to quite negative effects
- Regardless of changes in underlying changes in sleep-wake, school doesn’t take that into account
what reflect different preference for sleeping/waking time?
Remember early risers (phase lead) and night owls (phase leg) — different preferences for timing of sleep and waking represent different chronotypes (reflect differences in the phase of entrainment of the circadian clock to the 24h day)
what are early risers
phase lead
what are night owls
phase lag
roenneberg MCQ study participants
~25000 participants from Germany and Switzerland, had a bunch of ages measured on free days
roenneberg results
From a young age people tend to have an early chronotype, as you age until about the point of 20 that slowly gets later. After about 20, we see it starts to shift towards an early chronotype again
what are free days
‘free days’ — days when there was nothing to do, eg. No social obligations in the morning. Trying to get a measure of common chronotypes regardless of social pressure
female findings for free day patterns
Females start to shift earlier in development (19 rather than 20/21) — see that they converge in 40s to 50s
male findings for free day patterns
Males tend to develop a much more extreme late chronotype — prefer to stay up a lot later and wake a lot later
evidence that ____ act on the period of the circadian clock
sex hormones
delaying of circadian clock tendency begins at…
Delaying tendency begins at puberty, with differences parallel to differences in timing of puberty
what is true about age of reversal from delayed to advanced phase preference
differs in young men and women
there is a sex difference difference in ____ throughout ____
phase preference, young adulthood
when is the phase preference sex differene lost
Difference lost around menopause — as hormones kind of even out between sexes, women develop more testosterone. This is where the timing becomes much more similar
evidence that young adult men with higher levels of testosterone were…
positively correlated with more extreme evening chronotype scores
there is some ____ basis for sleep and wakening time preferences
genetic basis
genetic cause: familiar advanced sleep phase syndrome
mutation in CASEIN KINASE I that regulates expression of criciadna clock gene (PER2)
genetic cause: delayed sleep phase syndrome
polymorphisms in the circadian clock genes PER3, CLOCK and CRY1
triggers for typical sleep phase
close to when dark outside
triggers for delayed sleep phase
doesn’t go asleep until its been dark for a while, sleeping into daylight
triggers for advanced sleep phase
might wake up when still dark outside
delayed/advance sleep phase
actual conditions, can really impact peoples lives
lund american uni students: how many get less than 6.5h of sleep
25%
lund american uni students: how many missed an entire night of sleep in the last month
20%
lund american uni students: how many stayed up until 3am once per week
35%
lund american uni students: how many fall asleep in class once per week
15%
school average start times in the US
7:30-8:30am
students with school start times before 8:30 had…
shorter sleep durations than those with later start times
racidalized people and lower SES groups were…
less likely than others to get a least 7h of sleep nightly
school start times and social jet lag
Average duration of sleep is much higher (an hour more) on weekends and vacation (free) compared to school nights
those getting less sleep report ___ grades, same with really high amount of sleep. best grades with ___ amount of sleep
slightly lower, 8/9hr best
people with less sleep duration =
more depressed moods, more risk-taking behaviour, engage in more self-harming behaviour, increased risk of automobile accidents compared to those with later start times
social jetlag
mismatch between external societal demands and internal temporal physiology