Pinel basics ch12


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Pinel basics ch12

  1. 1. Chapter 12 Sleep, Dreaming and Circadian Rhythms How Much Do You Need to Sleep? <ul><li>This multimedia product and its contents are protected under copyright law. The following are prohibited by law: </li></ul><ul><li>any public performance or display, including transmission of any image over a network; </li></ul><ul><li>preparation of any derivative work, including the extraction, in whole or in part, of any images; </li></ul><ul><li>any rental, lease, or lending of the program. </li></ul>
  2. 2. How much sleep do we need? <ul><li>The amount of time spent sleeping suggests that sleep has a significant biological function </li></ul><ul><li>What is that function? </li></ul><ul><li>What brain mechanisms control sleep? </li></ul><ul><li>How does sleep deprivation impact functioning? </li></ul>
  3. 3. 3 Physiological Measures of Sleep <ul><li>Electroencephalogram (EEG) </li></ul><ul><ul><li>“ brain waves” </li></ul></ul><ul><li>Electrooculogram (EOG) </li></ul><ul><ul><li>Eye movements seen during rapid eye movement (REM) sleep </li></ul></ul><ul><li>Electromyogram (EMG) </li></ul><ul><ul><li>Loss of activity in neck muscles during some sleep stages </li></ul></ul>
  4. 4. 4 Stages of Sleep EEG <ul><li>Alpha waves – still awake </li></ul><ul><ul><li>Bursts of 8- to 12-Hz EEG waves </li></ul></ul><ul><ul><li>Eyes closed, preparing to sleep </li></ul></ul><ul><li>Stage 1 </li></ul><ul><ul><li>similar to awake EEG, but slower </li></ul></ul><ul><ul><li>low-voltage, high-frequency </li></ul></ul>
  5. 5. Stages of Sleep EEG <ul><li>EEG voltage increases and frequency decreases as one progresses from stage 1 through 2, 3, and 4 </li></ul><ul><li>Stage 2 – characterized by </li></ul><ul><ul><li>K complexes – large negative waves </li></ul></ul><ul><ul><li>Sleep spindles – burst of 12-14 Hz waves </li></ul></ul><ul><li>Stages 3 and 4 – delta waves, large and slow </li></ul>
  6. 7. Stages of Sleep EEG <ul><li>Progress to stage 4 sleep and then retreat to stage 1 </li></ul><ul><li>Emergent stage 1 differs from initial stage 1 </li></ul><ul><ul><li>REMs </li></ul></ul><ul><ul><li>Loss of body core muscle tone </li></ul></ul><ul><li>Progress through sleep stages in 90 minute cycles </li></ul><ul><li>More time spent in emergent stage 1 as night progresses </li></ul>
  7. 9. Stages of EEG Sleep <ul><li>Emergent stage 1 sleep = REM sleep </li></ul><ul><ul><li>Non-REM (NREM) sleep = all other stages </li></ul></ul><ul><li>Stage 3 + 4 = slow-wave sleep (SWS) </li></ul><ul><li>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 </li></ul>
  8. 10. REM Sleep and Dreaming <ul><li>80% of awakenings from REM yield reports of story-like dreams </li></ul><ul><li>External stimuli may be incorporated into dreams </li></ul><ul><li>Dreams run on real time </li></ul><ul><li>Everyone dreams </li></ul><ul><li>Penile erections are not a result of erotic dreams </li></ul><ul><li>Sleepwalking and talking are less likely to occur while dreaming </li></ul>
  9. 11. Interpretation of Dreams <ul><li>Freud thought dreams were triggered by unacceptable repressed wishes </li></ul><ul><li>Manifest dreams – what we experience </li></ul><ul><li>Latent dreams – the underlying meaning </li></ul><ul><li>No evidence for this </li></ul>
  10. 12. Why do we dream? <ul><li>Freudian theory of dreams </li></ul><ul><li>Activation-synthesis theory </li></ul><ul><ul><li>Cortex creates a story in an effort to make sense of the brain’s activity </li></ul></ul><ul><ul><li>Story is synthesized as a consequence of brain activity </li></ul></ul>
  11. 13. Why do we sleep? <ul><li>Recuperation theories </li></ul><ul><ul><li>Sleep is needed to restore homeostasis </li></ul></ul><ul><ul><li>Wakefulness causes a deviation from homeostasis </li></ul></ul><ul><li>Circadian theories </li></ul><ul><ul><li>Sleep is the result of an internal timing mechanism </li></ul></ul><ul><ul><li>Sleep evolved to protect us from the dangers of the night </li></ul></ul>
  12. 14. Comparative Analysis of Sleep <ul><li>All mammals and birds do it – must have an important function </li></ul><ul><li>Not a special higher-order human function </li></ul><ul><li>Not necessarily needed in large quantities </li></ul><ul><li>No clear relationship between species’ sleep time and activity level </li></ul>
  13. 15. Circadian Sleep Cycles <ul><li>Circadian rhythms – about a day </li></ul><ul><li>Virtually all physiological, biochemical, and behavioral processes show some circadian rhythmicity </li></ul><ul><li>Zeitgebers – environmental cues that entrain circadian cycles </li></ul>
  14. 16. Free-Running Cycles <ul><li>Remove zeitgebers – still see circadian sleep-wake cycles? </li></ul><ul><li>Free-running periods vary, but are usually constant within a subject </li></ul><ul><li>Most are longer than 24 hours - ~ 25 </li></ul><ul><li>What happens on days when you don’t need to get up? </li></ul>
  15. 17. Jet Lag and Shift Work <ul><li>Jet lag – zeitgebers are accelerated or decelerated </li></ul><ul><li>Shift work – zeitgebers unchanged, but sleep-wake cycle must be altered </li></ul><ul><li>Both produce a variety of deficits </li></ul><ul><li>Can the effects be prevented or minimized? </li></ul>
  16. 18. Reducing Jet Lag <ul><li>Gradually shift sleep-wake cycle prior to travel </li></ul><ul><li>Administer post-flight treatments to promote the needed shift </li></ul><ul><ul><li>Phase advance following east-bound travel with intense light early in the morning </li></ul></ul><ul><ul><li>Hamster studies suggest a good early morning workout may also help </li></ul></ul>
  17. 19. Reducing the Effect of Shift Changes <ul><li>Schedule phase delays, rather than phase advances </li></ul><ul><ul><li>Move from current schedule to one that starts later </li></ul></ul><ul><ul><li>It is easier to stay up later and get up later than to retire and arise earlier </li></ul></ul><ul><li>Phase advances are harder, explaining why east-bound travel tends to be more problematic </li></ul>
  18. 20. Effects of Sleep Deprivation <ul><li>Recuperation theories predict: </li></ul><ul><ul><li>Long periods of wakefulness will result in disturbances </li></ul></ul><ul><ul><li>Disturbances will get worse as deprivation continues </li></ul></ul><ul><ul><li>After deprivation, much of the missed sleep will be regained </li></ul></ul><ul><li>What does the research indicate? </li></ul>
  19. 21. Effects of Sleep Deprivation <ul><li>How do you separate the effects of stressors used to prevent sleep from the effects of lost sleep? </li></ul><ul><li>Does sleep loss affect your performance? </li></ul><ul><li>We tend to be poor judges of the effects of sleep deprivation on our performance </li></ul>
  20. 22. Studies of Sleep Deprivation in Humans <ul><li>3-4 hours of deprivation in one night </li></ul><ul><ul><li>Increased sleepiness </li></ul></ul><ul><ul><li>Disturbances displayed on written tests of mood </li></ul></ul><ul><ul><li>Perform poorly on tests of vigilance </li></ul></ul><ul><li>2-3 days of continuous deprivation </li></ul><ul><ul><li>Experience microsleeps, naps of 2-3 seconds </li></ul></ul><ul><li>Effects on complex cognitive function, motor performance, and physiological function are less consistent </li></ul>
  21. 23. Sleep-Deprivation Studies with Lab Animals <ul><li>Carousel apparatus used to deprive rats of sleep </li></ul><ul><ul><li>When the experimental rat’s EEG indicates sleep, the chamber floor moves – if the rat does not awaken, it falls into water </li></ul></ul><ul><ul><li>Yoked controls – subjected to the same floor rotations </li></ul></ul><ul><li>Experimental rats typically die after several days </li></ul><ul><li>Postmortem studies reveal the extreme stress experienced by the experimental rats </li></ul>
  22. 24. REM-Sleep Deprivation <ul><li>2 consistent effects </li></ul><ul><ul><li>Proceed more rapidly into REM as REM deprivation increases </li></ul></ul><ul><ul><li>REM rebound – more time spent in REM when deprivation is over </li></ul></ul><ul><li>REM rebound suggests that REM sleep serves a special function </li></ul>
  23. 25. Purpose of REM? <ul><li>Necessary for mental health </li></ul><ul><ul><li>Inconsistent with the effects of tricyclic antidepressants – block REM </li></ul></ul><ul><li>Necessary for maintenance of normal levels of motivation </li></ul><ul><li>Necessary for processing of memories </li></ul><ul><li>No clear purpose </li></ul>
  24. 26. Default Theory of REM <ul><li>REM serves no critical function </li></ul><ul><li>One can’t stay continuously in non-REM sleep, so we switch between REM and wakefulness </li></ul><ul><li>When bodily needs exist – wake up </li></ul><ul><li>No immediate needs – REM </li></ul><ul><li>No REM rebound seen when lost REM periods replaced with 15-mins awake </li></ul>
  25. 27. Sleep Deprivation Increases Sleep Efficiency <ul><li>After sleep deprivation, most of lost stage 4 is regained and SWS is increased </li></ul><ul><li>Short sleepers get as much SWS as long sleepers </li></ul><ul><li>Naps without SWS do not decrease the night’s sleep </li></ul><ul><li>Gradual reductions in sleep time lead to decreases in stages 1 and 2 </li></ul><ul><li>Little sleepiness produced with repeated REM wakenings </li></ul>
  26. 28. Hypothalamus and Sleep <ul><li>During WWI – victims of encephalitis lethargica caused some to sleep continuously and others to sleep little </li></ul><ul><li>Damage in posterior hypothalamus and adjacent midbrain > excessive sleep </li></ul><ul><li>Damage in preoptic area and adjacent forebrain > wakefulness </li></ul>
  27. 30. Cerveau Isole Preparation <ul><li>“ isolated forebrain” produced by severing cat brain stems between the inferior and superior colliculi </li></ul><ul><li>Cortical EEG indicated continuous SWS </li></ul><ul><li>A cut caudal to this produced the encephale isole preparation – normal sleep cycle </li></ul>
  28. 32. Reticular Formation <ul><li>Something between the cuts producing the cerveau and encpehale isole preparations maintains wakefulness – the reticular formation </li></ul><ul><ul><li>Leave intact, little effect on cortical EEG </li></ul></ul><ul><ul><li>Stimulation leads to wakefulness </li></ul></ul>
  29. 33. Reticular REM-sleep Nuclei <ul><li>Similarities between REM and wakefulness suggest that the same brain area might be involved in both </li></ul><ul><li>REM sleep is controlled by nuclei in the caudal reticular formation, each controlling a different aspect of REM </li></ul>
  30. 35. Suprachiasmatic Nucleus (SCN) of the Medial Hypothalamus <ul><li>Location of the major circadian clocks </li></ul><ul><li>Lesions do not reduce sleep time, but they abolish its circadian periodicity </li></ul><ul><li>Exhibit activity that can be entrained by the light-dark cycle </li></ul><ul><li>Transplant SCN, transplant sleep-wake cycle </li></ul><ul><li>Other circadian timing mechanisms exist </li></ul>
  31. 36. Evidence of Other Clocks <ul><li>Some circadian rhythms intact after SCN lesion </li></ul><ul><li>SCN lesions do not eliminate the ability of all environmental stimuli (such as food or water availability) to entrain circadian rhythms </li></ul><ul><li>Cells in other parts of the body exhibit free-running circadian rhythms </li></ul>
  32. 37. Hypnotic Drugs <ul><li>Increase sleep </li></ul><ul><li>Benzodiazepines – Valium, Librium </li></ul><ul><li>Most commonly prescribed hypnotic </li></ul><ul><li>Effective in the short-term </li></ul><ul><li>Complications – tolerance, cessation leads to insomnia, “addictive”, increase stage 2 while decreasing 4 and REM </li></ul>
  33. 38. Antihypnotic Drugs <ul><li>Decrease sleep </li></ul><ul><li>Stimulants and tricyclic antidepressants </li></ul><ul><ul><li>Both increase activity of catecholamines </li></ul></ul><ul><li>Act preferentially on REM – may totally suppress REM with little effect on total sleep time </li></ul>
  34. 39. Melatonin <ul><li>A hormone synthesized from serotonin in the pineal gland </li></ul><ul><li>Melatonin levels display circadian rhythms controlled by the SCN </li></ul><ul><li>Pineal involved in timing of sexual maturity – function after this is not clear </li></ul><ul><li>Melatonin is not a sleep aid, but may be used to shift circadian rhythms </li></ul>
  35. 40. Sleep Disorders <ul><li>Insomnia – disorders of sleep initiation and maintenance </li></ul><ul><li>Hypersomnia – disorders of excessive sleep or sleepiness </li></ul><ul><li>REM-sleep dysfunctions </li></ul><ul><li>~30% of respondents report sleep-related problems - far fewer truly have a problem </li></ul>
  36. 41. Insomnia <ul><li>Iatrogenic – physician created </li></ul><ul><ul><li>Consequence of sleeping pill use, for example </li></ul></ul><ul><li>Sleep apnea – stop breathing during the night leads to repeated wakenings – 2 types </li></ul><ul><ul><li>Caused by muscle spasms or atonia </li></ul></ul><ul><ul><li>Failure of the CNS to stimulate breathing </li></ul></ul><ul><ul><li>Most commonly seen in males, the overweight, and in the elderly </li></ul></ul>
  37. 42. Insomnia <ul><li>Nocturnal myoclonus – twitching of the body, usually the legs, during sleep – most are not aware of why they don’t feel rested </li></ul><ul><li>Restless legs – sufferers complain of uneasiness in legs that prevents sleep </li></ul><ul><li>Both are often treated with benzodiazepines </li></ul>
  38. 43. Hypersomnia - Narcolepsy <ul><li>Severe daytime sleepiness and repeated brief daytime sleeping - “sleep attacks” </li></ul><ul><li>Cataplexy – loss of muscle tone while awake </li></ul><ul><li>Sleep paralysis – paralyzed while falling asleep or upon waking </li></ul><ul><li>Hypnagogic hallucinations – dreaming while awake </li></ul>
  39. 44. Hypersomnia - Narcolepsy <ul><li>Appears to be an abnormality in the mechanisms that triggers REM </li></ul><ul><ul><li>Narcoleptics enter directly into REM </li></ul></ul><ul><ul><li>Dreaming and loss of muscle tone while awake – suggest REM intruding into wakefulness </li></ul></ul>
  40. 45. REM-Sleep-Related Disorders <ul><li>Narcolepsy (also a form of hypersomnia) </li></ul><ul><li>REM without atonia – able to act out dreams – possibly caused by damage to the nucleus magnocellularis or its output </li></ul>
  41. 46. Effects of Long-Term Sleep Reduction <ul><li>The brain is adaptable – may be able to function well with very little sleep </li></ul><ul><li>One deficit seen with subjects sleeping only 5.5 hours for 60 days </li></ul><ul><ul><li>Slight deficit in a test of auditory vigilance </li></ul></ul><ul><li>Other study – no ill effects seen at I year with subjects sleeping 7-18 hours less per week than before study </li></ul>
  42. 47. How much sleep do you need? <ul><li>Can this question be answered? </li></ul><ul><li>Why or why not? </li></ul>