PSY2061 Chapter 14: PSY2061 – Readings – Week 13 – Sleep
5 Jun 2018
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PSY2061 – Readings – Week 13 – Sleep, dreaming and circadian rhythms
• sleep fulfils a critical biological function
• stages of sleep
•
o three standard psychophysiological measures of sleep
o
▪ major changes in EEG - electroencephalogram
▪ electrooculogram - EOG
▪ neck electromyograph EMG
o three stage of sleep EEG
o
▪ after the eyes shut and a person prepares to go to sleep -
alpha waves - bursts of 8-12Hz EEG waves begin to
punctuate the low-voltage high frequency waves of alert-
wakefulness
▪ as the person falls a sleep there is a transition to stage 1
▪
▪ low voltage, high frequency signal
▪ initial stage 1 EEG - no striking changes
▪ gradual increase in voltage and decrease in frequency as
the person progresses from stage 1 to stages 2 and 3
▪ stage 2
▪
▪ k complex
▪
▪ single large negative wave followed by a
singular large positive wave
▪ sleep spindles
▪
▪ 3 second burst of 9-15Hz waves
▪ stage 3
▪
▪ predominance of delta waves - the largest and
slowest EEG waves - frequency of 1 to 2 Hz
▪ slow wave sleep SWS
▪ subsequent stages of stage 1 sleep - emergent stage 1 EEG -
are accompanied by REMs and by a loss of tone in the
muscles of the body core
▪
▪ REM sleep
▪
▪ rapid eye movements
▪
▪ after the first cycle of sleep EEG - from initial stage 1 to
stage 3 and back to emergent stage 1 - the rest of the night
is spent going back and forth through the stages
▪ all other stages of sleep called NREM sleep - non-REM
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• Dreaming
•
o REM sleep and dreaming
o
▪ 80% of awakenings from REM led to dream recall
o testing common beliefs about dreaming
o
▪ dreams run on real time
▪ external stimuli can become incorporated into dreams
▪ sleep talking and walking do not occur during REM - can
occur during any stage
o interpretation of dreams
o
▪ freud
▪
▪ dreams represent unacceptable wishes - the dreams
we experience - our manifest dreams - are merely
disguised versions of our real dreams - latent
dreams
▪ no convincing evidence
▪ hobson’s activation synthesis hypothesis
▪
▪ based on the observation that during REM - many
brain stem circuits become active and bombard the
cerebral cortex with neural signals
▪ the information supplied to the cortex during REM is
largely random and the resulting dream is the
cortex’s effort to make sense of these random
signals
• why do we sleep and why do we sleep when we do?
•
o two kinds of theories of sleep
o
▪ recuperation theories
▪
▪ being awake disrupts the homeostasis - internal
physiological stability of the body in some way and
sleep is required to restore it - sleep is terminated by
a return to homeostasis
▪ various theories differ in the particular physiological
disruption they propose as the trigger for sleep
▪ two most common recuperation theories - the
function of sleep is to
▪
▪ restore energy levels that decline during
wakefulness
▪ clear toxins from the brain and other tissues
that accumulate during wakefulness
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find more resources at oneclass.com
▪ adaptation theories
▪
▪ sleep is not a reaction to the disruptive effects of
being aware but the result of an internal 24 hour
timing mechanisms - humans are programmed to
sleep at night regardless of what happens to us
during ht day
▪ focus more on when we sleep rather than on the
function of sleep
▪ strong motivation to sleep at night evolved to
conserve energy resources and decrease
susceptibility to dangers etc in the dark
▪ highly motivated to engage in it but not needed to
stay healthy
o comparative analysis of sleep
o
▪ the fact that most mammals and birds see suggests sleep
serves some important physiological function - also
suggests its not some higher order human function
• effects of sleep deprivation
•
o interpretation of the effects of sleep deprivation - the stress
problem
o
▪ in western cultures - most people who sleep little or
irregularly do so because they are under stress - which
could have adverse effects independent of any sleep loss
o predictions of recuperation theories about sleep deprivation
o
▪ long periods of wakefulness will produce physiological and
behavioural disturbances
▪ these disturbances will grow worse as the sleep deprivation
continues
▪ after a period of sleep deprivation has ended much of the
missed sleep will be regained
o experimental studies of sleep deprivation in humans
o
▪ moderate amounts of sleep deprivation - e.g. sleeping 3 or 4
hours less than normal for one night has been found to have
three consistent effects
▪
▪ sleep deprived individuals display an increase in
sleepiness
▪ display negative affects on various written tests of
mood
▪ they perform poorly on tests of sustained attention
▪ the effects of sleep deprivation on complex cognitive
functions have been less consistent
▪
find more resources at oneclass.com
find more resources at oneclass.com
