sleep and circadian rhythms

NREM Sleep

restful inactivity, brain on idle, slow/deep breathing

REM Sleep

enter about 90 minutes after sleep onset, rapid eye movements, brain activated irregular 

NREM vs. REM

progressive decreases in spinal reflexes/reduction in heart and breathing rates vs. irregular breathing and heart rate with desynchronised cortical activity

sleep is an altered state of consciousness

brain processes external information and internal messages, sleep is alteration from normal consciousness

awake

alpha rhythm brain waves/alert

stage 1 of sleep

less regular low amplitude waves; brief bizarre hypnagogic dreams

stage 2 of sleep

sleep spindles, claim not asleep

stage 3 of sleep

delta-waves, k-complexes, deep sleep, very little content reported

sleep spindles

play an essential role in sensory processing, long-term memory consolidation, the density of spindles increase after extensive learning of declarative memory tasks

k-complexes

help you transition from stage 2 to 3, help you stay asleep

delta sleep

a stage when you are hard to awaken but are still aware of stimuli around you

paradoxical sleep

REM, heart rate increases, breathing becomes more rapid, eyes dart behind closed lids

50:50

Infancy REM:NREM ratio

20:80

Adulthood REM:NREM ratio

body restoration theory

an increase in time devoted to NREM after periods of intense exercise, as demonstrated in several species, growth hormone important for RNA and protein synthesis

evolutionary theory

carnivores sleep more than omnivores, function of sleep to increase animal’s efficiency and minimize risk

polysomnography

gold standard of sleep study; empirical measurement and not estimation

EMG

measures muscle tension

EEG

measures brain waves

EOG

measures eye movements

BEARS

bedtime, excessive daytime sleepiness, awakenings at night and early morning, regularity/duration, snoring

multiple sleep latency test (MSLT)

standard for quantifying physiological sleepiness, 2-hr intervals throughout the day, individuals are permitted to fall asleep lying in quiet, dark bedroom

Maintenance of Wakefulness test (MWT)

participant tries to stay awake while sitting, eyes open, on a comfortable chair in a quiet, controlled room

actigraphy

valid and reliable method of assessing sleep-wake patterns in children, adolescents and adults

actigraphy vs. diaries/logs

actigraphy more objective compared to diaries bc of human judgement errors

wearables vs. actigraphy

wearables not nearly as accurate bc they only measure heart rate and activity

salivary melatonin

key marker of sleep circadian rhythm, levels rise at night and fall in morning, non-invasive measurement, every 30 minutes

sleep onset 

time fell asleep

sleep offset

time awakened

bedtime

time got into bed

risetime

time got out of bed

TST (total sleep time)

sleep onset to sleep offset

TIB (time in bed)

bedtime to risetime

sleep onset latency

length of time to fall asleep (in minutes)

sleep efficiency

ratio of tst to tib (percentage)

sleep debt

hours of sleep you need vs hours you get

midsleep time

middle time point between bedtime and wakeup time

endogenous rhythm

biological clock that does not rely on external cues

mammoth cave

28 hr sleep/wake schedule, rhythm not synchronized with sleep/wake

bunker studies

no time cues or social interaction, participants selected own light/dark schedule

SCN

master biological clock

process S

sleep propensity increases as waking accumulates and dissipates during sleep

process C

sleep propensity oscillates with a circadian rhythm

role of light vs. dark

light limits melatonin secretion by suppressing an enzyme, thus light limits melatonin secretion

circadian

about a day

oscillator

something that produces repeated, regular fluctuations

pacemaker

oscillator that sets pace for other oscillators (conductor of a symphony)

phase

an instantaneous state of rhythm within a period, serves as a reference point

period

time interval between recurrences of a defined phase of the rhythm

free run

repetitive cycles of rhythm in the absence of a synchronising signal

zeitgeber

forced environmental oscillation that entrains a biological self-sustaining rhythm (having to wake up for school)

entrainment

synchronization of endogenous rhythms by repetitive signal of zeitgeber

illuminance

amount of light on a surface, measured in lux levels

melatonin

secretion peaks at night and increases when it is time to wake up

daylight savings time

light too late in the evenings delays brain’s release of melatonin and makes it harder to sleep at night

circadian misalignment

shiftwork, jet lag, on-call schedules, social jet lag, adolescents school schedules

flying west

less jet lag than flying east

minoritized communities

more likely to get insufficient, poor-quality sleep

gender sleep differences

sleep latency longer in women vs men, women get less n1 sleep

monophasic

one burst of sleep