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• Electroencephalogram (EEG)


  One of the three standard psychophysiological bases for defining sleep
• Electrooculogram (EOG)


  One of the three standard psychophysiological bases for defining sleep
• Electromyogram (EMG)


  One of the three standard psychophysiological bases for defining sleep
• Rapid eye movements (REMs) were discovered when under the eyelids of sleepers during periods of low-voltage, fast EEG activity
• In 1962, Berger and Oswald discovered that there is also electromyographic activity in the neck muscle during these same sleep periods
• Three stages of sleep EEG

  • Stage 1
  • Stage 2
  • Stage 3
• What happens during sleep

  1. Alpha waves begin to punctuate the low voltage, high-frequency waves of alert wakefulness

  2. Sudden transition to period stage 1 sleep EEG

  3. EEG has a slightly higher amplitude and a lower frequency than the stage 1 EEG, punctuated by K complexes and sleep spindles

  4. EEG is defined by a predominance of delta waves

  5. Retreat through stages of sleep to stage 1

  
• Initial Stage 1 EEG

  The first period of stage 1 EEG during night sleep, marked by any striking electromyographic or electrooculographic changes
• Emergent stage I EEG


  The subsequent periods of stage I sleep EEG, accompanied by REMs and by a loss of tone in the muscle of the body core
• Types of sleep


  • REM sleep (rapid eye movement sleep)
  • NREM sleep (non-rapid eye movement sleep)

  
• NREM 3


  Slow-wave sleep (SWS), after the delta waves that characterized it
• 80 percent of awakening from REM sleep, but only 7 percent of awakening from NREM sleep, led to dream recall

  
• Dreams recalled from NREM sleep tended to be isolated experiences, while those associated with REM sleep tended to take the form of stories or narratives

  
• Common beliefs about dreaming tested

  • External stimuli can become incorporated into dreams
  • Dreams last only an instant
  • Some people do not dream
  • Penile erections are indicative of dreams with sexual content
  • Sleeptalking and sleepwalking occur during REM sleep
• Freud's theory of dreams

  Dreams represent unacceptable repressed wishes, often sexual, that are disguised by unconscious censors
• Hobson's activation-synthesis hypothesis


  The information supplied to the cortex during REM sleep is largely random, and the resulting dream is the cortex's effort to make sense of these random signals

  
• Two kinds of theories of sleep

  • Recuperation theories
  • Adaptation theories

  
• Recuperation theories of sleep

  • Sleep restores levels that decline during wakefulness
  • Sleep clears toxins from the brain and other tissues that accumulate during wakefulness

  
• Adaptation theories of sleep

  • Sleep is the result of an internal 24-hour timing mechanism, and early humans had enough time to get their essential activities done during the day, so they evolved to sleep at night to conserve energy and avoid mishaps
• In Western cultures, people who sleep little or irregularly do so because they are under stress, which could have adverse effects independent of any sleep loss
• Predictions of recuperation theories about sleep deprivation

  • Long periods of wakefulness will produce physiological and behavioral disturbances
  • These disturbances will grow worse as the sleep deprivation continues
  • After a period of deprivation has ended, much of the missed sleep will be regained

  
• Moderate amounts of sleep deprivation, 3 or 4 hours less than normal for one night, have three consistent effects: increased sleepiness, negative effects on mood, and poor performance on tests of sustained attention

  
• The effects of sleep deprivation on complex cognitive functions have been less consistent, and may be clarified by the discovery that only some cognitive functions appear to be susceptible

  
• Sleep deprivation


  Experimental studies that assess the effects of sleep schedules on measures of sleepiness, mood, cognition, motor performance, physiological function, and molecular function

  
• Moderate sleep deprivation (3-4 hours less than normal for one night)


  • Increases sleepiness
  • Negative effects on mood tests
  • Poor performance on sustained attention tests

  
• Effects of sleep deprivation on complex cognitive functions have been less consistent

  
• Executive function


  Cognitive abilities that depend on the prefrontal cortex, including innovative thinking, lateral thinking, insightful thinking, and assimilating new information to update plans and strategies
• Effects of sleep deprivation on physical performance have been surprisingly inconsistent

  
• Physiological consequences of sleep deprivation

  • Reduced body temperature increases blood pressure
  • Increases in blood pressure
  • Decrease in some aspects of immune function
  • Hormonal changes
  • Metabolic changes
• There is little evidence that the physiological changes from sleep deprivation have consequences for health or performance

  
• REM sleep deprivation


  • Participants display a REM rebound (more than usual REM sleep) for the first 2-3 nights
  • With each successive night of deprivation, participants have to be awakened more frequently to prevent accumulation of REM sleep
• Some studies have not observed any relationship between memory and sleep, even in depressed patients who get much less slow-wave sleep

  
• Default theory of REM sleep

  REM sleep is more adaptive than wakefulness when there are no immediate bodily needs, and functions to prepare organisms for wakefulness in natural environments where immediate effective activity may be required
• Sleep deprivation increases the efficiency of sleep

  • Deprived individuals regain most of their slow-wave sleep
  • Slow-wave sleep EEG shows an even higher proportion of slow waves
  • People who sleep 0 hours or less per night get as much slow-wave sleep as those who sleep more
• Repeatedly waking individuals during REM sleep produces little increase in sleepiness, whereas waking during slow-wave sleep has major effects

  
• People who have less sleep are more efficient sleepers
• Circadian rhythms


  Biological cycles that vary with different environments, e.g. humans are awake during the day and sleep at night, while nocturnal animals are the opposite

  
• Zeitgebers


  Environmental cues that can entrain (control the timing of) circadian rhythms, such as the light-dark cycle

  
• Free-running circadian rhythms


  Circadian rhythms in constant environments, with a duration usually longer than 24 hours

  
• Free-running sleep-wake cycles provide support for the dominance of circadian factors over recuperative factors in regulating sleep