1. Copyright © 2007 by Allyn and Bacon Chapter 12 Sleep, Dreaming and Circadian Rhythms How Much Do You Need to Sleep? This multimedia product and its contents are protected under copyright law. The following are prohibited by law: any public performance or display, including transmission of any image over a network; preparation of any derivative work, including the extraction, in whole or in part, of any images; any rental, lease, or lending of the program.

2. Copyright © 2007 by Allyn and Bacon 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. Copyright © 2007 by Allyn and Bacon 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. Copyright © 2007 by Allyn and Bacon 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. Copyright © 2007 by Allyn and Bacon 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

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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

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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. Copyright © 2007 by Allyn and Bacon 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. Copyright © 2007 by Allyn and Bacon 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. Copyright © 2007 by Allyn and Bacon 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. Copyright © 2007 by Allyn and Bacon 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. Copyright © 2007 by Allyn and Bacon 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. Copyright © 2007 by Allyn and Bacon 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. Copyright © 2007 by Allyn and Bacon 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. Copyright © 2007 by Allyn and Bacon 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. Copyright © 2007 by Allyn and Bacon 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. Copyright © 2007 by Allyn and Bacon 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. Copyright © 2007 by Allyn and Bacon 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. Copyright © 2007 by Allyn and Bacon 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. Copyright © 2007 by Allyn and Bacon 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. Copyright © 2007 by Allyn and Bacon 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. Copyright © 2007 by Allyn and Bacon 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. Copyright © 2007 by Allyn and Bacon 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. Copyright © 2007 by Allyn and Bacon 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. Copyright © 2007 by Allyn and Bacon 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. Copyright © 2007 by Allyn and Bacon 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

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30. 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

32. Copyright © 2007 by Allyn and Bacon 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

33. Copyright © 2007 by Allyn and Bacon 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

34. Copyright © 2007 by Allyn and Bacon 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

35. Copyright © 2007 by Allyn and Bacon 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

36. Copyright © 2007 by Allyn and Bacon 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

37. Copyright © 2007 by Allyn and Bacon 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

38. Copyright © 2007 by Allyn and Bacon 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

39. Copyright © 2007 by Allyn and Bacon 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

40. Copyright © 2007 by Allyn and Bacon 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

41. Copyright © 2007 by Allyn and Bacon 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

42. Copyright © 2007 by Allyn and Bacon 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

43. Copyright © 2007 by Allyn and Bacon 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

44. Copyright © 2007 by Allyn and Bacon How much sleep do you need? Can this question be answered? Why or why not?