W9 Sleep dreaming and circadian rhythms Flashcards
Recuperatin theories
Sleep is needed to restore homeostasis
Wakefulness cause a deviation from homeostasis
Adaptation theories
Sleep is the result of internal timing mechanism
Sleep evolve to protect s from the dangers of the night.
Circadian rhythms
are endogenous and persist without environmental cue, however they are modulated by environmental cues (light/external cues), external timing cues: zeitgebers. These adapt the rhythm to the environment.
Suprachiasmatic nucleus (SCN)
A major internal clock is the suprachiasmatic nucleus (SCN) of the medial hypothalamus. Lesioning of the suprachiasmatic tract dampens down the circadian rhythm of sleep. Suprachiasmatic nucleus regulates timing of sleep itself.
Sleep define behaiorally as:
Reduce motor activity, stereotypic posture (closed eyes), reduce muscle movement, relatively easy reversibility.
EGG during the stages of sleep: alert awake
Beta Activity: alert, the EEG high frequency (15-30 Hz), low amplitude electrical activity.
EGG during the stages of sleep: restful awake
Alpha Activity: relaxed, the EEG shows medium frequency (8-12 Hz), medium amplitude activity.
EGG during the stages of sleep: 1 and 2 stage
Theta activity; 1st and 2nd stage of sleep ( transition sleep-wakefulness): EEG activity of 3.5-7.5 Hz;
EGG during the stages of sleep: 3rd and 4th
Delta Activity: 3rd and 4th stages of sleep, high amplitude activity of less than 3.5 Hz; slow-wave sleep. Sleep talking and walking more likely.
EGG during the stages of sleep: REM sleep
REM sleep: EEG that is typical of a person who is awake and active (theta, alpha and beta activity).
Stage 1
a transition wakefulness-sleep; muscles are still active; the eyes show slow, gentle, rolling movements; some theta activity.
Stage 2/3
sleep gets deeper and deeper; the EEG gets progressively lower in frequency and higher in amplitude.
Stage 4
the deepest stage of sleep; reached in less than an hour and continues for up to half an hour; relatively high amplitude (delta) EEG activity.
REM Sleep
the EEG looks like that of a person who is awake and active although EMG is generally quiet.
Little effect of sleep deprivation
logical deduction, critical thinking. Physical strength and motor performance
Larger effeect of sleep deprivation
executive function (prefrontal cortex): assimilating hanging information, updating plans and strategies, innovative lateral insightful thinking, reference memory.
Sleep deprivation increases sleep efficiency
After sleep deprivation, most of lost stage 4 is regained and SWS is increased. Short sleepers get as much SWS as long sleepers
Naps without SWS do not decrease the night’s sleep. Gradual reductions in sleep time lead to decreases in stages 1 and 2. Little sleepiness produced with repeated REM awakenings, unlike SWS.
Default thoery
it is difficult to remain in NREM sleep
Nycamp and others (1998) awoke sleepers in REM for 15 minutes. They were awake for a bit rather than REM Result: no sleepiness or REM rebound the next day
REM-blocking drugs cause periods of wakefulness
Brain development and REM
70% REM new born
30% REM 6 months
22% REM adulthood
15% REM late adulthood
REM sleep and dreaming
80% of awakenings from REM yield reports of story-like dreams
External stimuli may be incorporated into dreams. Dreams run on real time
Everyone dreams. Sleepwalking and talking are less likely to occur while dreaming. NREM dreams are isolated experiences such as falling
Freud’s explanation dreams
are triggered by unacceptable repressed wishes.
Manifest dreams what we experience
Latent dreams the underlying meaning
No evidence for this
Activation synthesis
Modern alternative to Freuds explanation of dreams: dreams due to cortex attempt to make sense of random brain activity.
depression and sleep
Depression is association with both insomnia and hypersomnia
Total sleep deprivation (TSD) for one whole night improves depressive symptoms in 40–60% of treatments. It is still unknown how sleep deprivation works.
Bipolar depression – level 3 extended essay!
