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Pinel basics ch12



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  • 1. Chapter 12 Sleep, Dreaming and Circadian Rhythms How Much Do You Need to Sleep?
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  • 2. How much sleep do we need?
    • The amount of time spent sleeping suggests that sleep has a significant biological function
    • What is that function?
    • What brain mechanisms control sleep?
    • How does sleep deprivation impact functioning?
  • 3. 3 Physiological Measures of Sleep
    • Electroencephalogram (EEG)
      • “ brain waves”
    • Electrooculogram (EOG)
      • Eye movements seen during rapid eye movement (REM) sleep
    • Electromyogram (EMG)
      • Loss of activity in neck muscles during some sleep stages
  • 4. 4 Stages of Sleep EEG
    • Alpha waves – still awake
      • Bursts of 8- to 12-Hz EEG waves
      • Eyes closed, preparing to sleep
    • Stage 1
      • similar to awake EEG, but slower
      • low-voltage, high-frequency
  • 5. Stages of Sleep EEG
    • EEG voltage increases and frequency decreases as one progresses from stage 1 through 2, 3, and 4
    • Stage 2 – characterized by
      • K complexes – large negative waves
      • Sleep spindles – burst of 12-14 Hz waves
    • Stages 3 and 4 – delta waves, large and slow
  • 6.  
  • 7. Stages of Sleep EEG
    • Progress to stage 4 sleep and then retreat to stage 1
    • Emergent stage 1 differs from initial stage 1
      • REMs
      • Loss of body core muscle tone
    • Progress through sleep stages in 90 minute cycles
    • More time spent in emergent stage 1 as night progresses
  • 8.  
  • 9. Stages of EEG Sleep
    • Emergent stage 1 sleep = REM sleep
      • Non-REM (NREM) sleep = all other stages
    • Stage 3 + 4 = slow-wave sleep (SWS)
    • During REM: REMs, loss of core muscle tone, low-amplitude/high-frequency EEG, increased cerebral and autonomic activity, muscles may twitch, clitoral or penile erection
  • 10. 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
    • Penile erections are not a result of erotic dreams
    • Sleepwalking and talking are less likely to occur while dreaming
  • 11. Interpretation of Dreams
    • Freud thought dreams were triggered by unacceptable repressed wishes
    • Manifest dreams – what we experience
    • Latent dreams – the underlying meaning
    • No evidence for this
  • 12. Why do we dream?
    • Freudian theory of dreams
    • Activation-synthesis theory
      • Cortex creates a story in an effort to make sense of the brain’s activity
      • Story is synthesized as a consequence of brain activity
  • 13. Why do we sleep?
    • Recuperation theories
      • Sleep is needed to restore homeostasis
      • Wakefulness causes a deviation from homeostasis
    • Circadian theories
      • Sleep is the result of an internal timing mechanism
      • Sleep evolved to protect us from the dangers of the night
  • 14. Comparative Analysis of Sleep
    • All mammals and birds do it – must have an important function
    • Not a special higher-order human function
    • Not necessarily needed in large quantities
    • No clear relationship between species’ sleep time and activity level
  • 15. Circadian Sleep Cycles
    • Circadian rhythms – about a day
    • Virtually all physiological, biochemical, and behavioral processes show some circadian rhythmicity
    • Zeitgebers – environmental cues that entrain circadian cycles
  • 16. Free-Running Cycles
    • Remove zeitgebers – still see circadian sleep-wake cycles?
    • Free-running periods vary, but are usually constant within a subject
    • Most are longer than 24 hours - ~ 25
    • What happens on days when you don’t need to get up?
  • 17. Jet Lag and Shift Work
    • Jet lag – zeitgebers are accelerated or decelerated
    • Shift work – zeitgebers unchanged, but sleep-wake cycle must be altered
    • Both produce a variety of deficits
    • Can the effects be prevented or minimized?
  • 18. Reducing Jet Lag
    • Gradually shift sleep-wake cycle prior to travel
    • Administer post-flight treatments to promote the needed shift
      • Phase advance following east-bound travel with intense light early in the morning
      • Hamster studies suggest a good early morning workout may also help
  • 19. Reducing the Effect of Shift Changes
    • Schedule phase delays, rather than phase advances
      • Move from current schedule to one that starts later
      • It is easier to stay up later and get up later than to retire and arise earlier
    • Phase advances are harder, explaining why east-bound travel tends to be more problematic
  • 20. Effects of Sleep Deprivation
    • Recuperation theories predict:
      • Long periods of wakefulness will result in disturbances
      • Disturbances will get worse as deprivation continues
      • After deprivation, much of the missed sleep will be regained
    • What does the research indicate?
  • 21. Effects of Sleep Deprivation
    • How do you separate the effects of stressors used to prevent sleep from the effects of lost sleep?
    • Does sleep loss affect your performance?
    • We tend to be poor judges of the effects of sleep deprivation on our performance
  • 22. Studies of Sleep Deprivation in Humans
    • 3-4 hours of deprivation in one night
      • Increased sleepiness
      • Disturbances displayed on written tests of mood
      • Perform poorly on tests of vigilance
    • 2-3 days of continuous deprivation
      • Experience microsleeps, naps of 2-3 seconds
    • Effects on complex cognitive function, motor performance, and physiological function are less consistent
  • 23. Sleep-Deprivation Studies with Lab Animals
    • Carousel apparatus used to deprive rats of sleep
      • When the experimental rat’s EEG indicates sleep, the chamber floor moves – if the rat does not awaken, it falls into water
      • Yoked controls – subjected to the same floor rotations
    • Experimental rats typically die after several days
    • Postmortem studies reveal the extreme stress experienced by the experimental rats
  • 24. REM-Sleep Deprivation
    • 2 consistent effects
      • Proceed more rapidly into REM as REM deprivation increases
      • REM rebound – more time spent in REM when deprivation is over
    • REM rebound suggests that REM sleep serves a special function
  • 25. Purpose of REM?
    • Necessary for mental health
      • Inconsistent with the effects of tricyclic antidepressants – block REM
    • Necessary for maintenance of normal levels of motivation
    • Necessary for processing of memories
    • No clear purpose
  • 26. Default Theory of REM
    • REM serves no critical function
    • One can’t stay continuously in non-REM sleep, so we switch between REM and wakefulness
    • When bodily needs exist – wake up
    • No immediate needs – REM
    • No REM rebound seen when lost REM periods replaced with 15-mins awake
  • 27. 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 wakenings
  • 28. Hypothalamus and Sleep
    • During WWI – victims of encephalitis lethargica caused some to sleep continuously and others to sleep little
    • Damage in posterior hypothalamus and adjacent midbrain > excessive sleep
    • Damage in preoptic area and adjacent forebrain > wakefulness
  • 29.  
  • 30. Cerveau Isole Preparation
    • “ isolated forebrain” produced by severing cat brain stems between the inferior and superior colliculi
    • Cortical EEG indicated continuous SWS
    • A cut caudal to this produced the encephale isole preparation – normal sleep cycle
  • 31.  
  • 32. Reticular Formation
    • Something between the cuts producing the cerveau and encpehale isole preparations maintains wakefulness – the reticular formation
      • Leave intact, little effect on cortical EEG
      • Stimulation leads to wakefulness
  • 33. Reticular REM-sleep Nuclei
    • Similarities between REM and wakefulness suggest that the same brain area might be involved in both
    • REM sleep is controlled by nuclei in the caudal reticular formation, each controlling a different aspect of REM
  • 34.  
  • 35. Suprachiasmatic Nucleus (SCN) of the Medial Hypothalamus
    • Location of the major circadian clocks
    • Lesions do not reduce sleep time, but they abolish its circadian periodicity
    • Exhibit activity that can be entrained by the light-dark cycle
    • Transplant SCN, transplant sleep-wake cycle
    • Other circadian timing mechanisms exist
  • 36. Evidence of Other Clocks
    • Some circadian rhythms intact after SCN lesion
    • SCN lesions do not eliminate the ability of all environmental stimuli (such as food or water availability) to entrain circadian rhythms
    • Cells in other parts of the body exhibit free-running circadian rhythms
  • 37. Hypnotic Drugs
    • Increase sleep
    • Benzodiazepines – Valium, Librium
    • Most commonly prescribed hypnotic
    • Effective in the short-term
    • Complications – tolerance, cessation leads to insomnia, “addictive”, increase stage 2 while decreasing 4 and REM
  • 38. Antihypnotic Drugs
    • Decrease sleep
    • Stimulants and tricyclic antidepressants
      • Both increase activity of catecholamines
    • Act preferentially on REM – may totally suppress REM with little effect on total sleep time
  • 39. Melatonin
    • A hormone synthesized from serotonin in the pineal gland
    • Melatonin levels display circadian rhythms controlled by the SCN
    • Pineal involved in timing of sexual maturity – function after this is not clear
    • Melatonin is not a sleep aid, but may be used to shift circadian rhythms
  • 40. Sleep Disorders
    • Insomnia – disorders of sleep initiation and maintenance
    • Hypersomnia – disorders of excessive sleep or sleepiness
    • REM-sleep dysfunctions
    • ~30% of respondents report sleep-related problems - far fewer truly have a problem
  • 41. Insomnia
    • Iatrogenic – physician created
      • Consequence of sleeping pill use, for example
    • Sleep apnea – stop breathing during the night leads to repeated wakenings – 2 types
      • Caused by muscle spasms or atonia
      • Failure of the CNS to stimulate breathing
      • Most commonly seen in males, the overweight, and in the elderly
  • 42. Insomnia
    • Nocturnal myoclonus – twitching of the body, usually the legs, during sleep – most are not aware of why they don’t feel rested
    • Restless legs – sufferers complain of uneasiness in legs that prevents sleep
    • Both are often treated with benzodiazepines
  • 43. Hypersomnia - Narcolepsy
    • Severe daytime sleepiness and repeated brief daytime sleeping - “sleep attacks”
    • Cataplexy – loss of muscle tone while awake
    • Sleep paralysis – paralyzed while falling asleep or upon waking
    • Hypnagogic hallucinations – dreaming while awake
  • 44. Hypersomnia - Narcolepsy
    • Appears to be an abnormality in the mechanisms that triggers REM
      • Narcoleptics enter directly into REM
      • Dreaming and loss of muscle tone while awake – suggest REM intruding into wakefulness
  • 45. REM-Sleep-Related Disorders
    • Narcolepsy (also a form of hypersomnia)
    • REM without atonia – able to act out dreams – possibly caused by damage to the nucleus magnocellularis or its output
  • 46. Effects of Long-Term Sleep Reduction
    • The brain is adaptable – may be able to function well with very little sleep
    • One deficit seen with subjects sleeping only 5.5 hours for 60 days
      • Slight deficit in a test of auditory vigilance
    • Other study – no ill effects seen at I year with subjects sleeping 7-18 hours less per week than before study
  • 47. How much sleep do you need?
    • Can this question be answered?
    • Why or why not?