1. Prepared by Jeffrey W. Grimm Western Washington University
PowerPoint Presentation for Biopsychology, 8th Edition by John P.J. Pinel
Prepared by Jeffrey W. Grimm
Western Washington University
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2. How Much Do You Need to Sleep?
Chapter 14
Sleep, Dreaming, and Circadian Rhythms
How Much Do You Need to Sleep?
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3. How Much Sleep Do We Need?
The vast amount of time spent sleeping suggests that sleep has a significant biological function
Most people sleep over 175,000 hours in their lifetime
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4. Three Standard Physiological Measures of Sleep
Electroencephalogram (EEG)
Reveals “brainwaves”
Electrooculogram (EOG)
Records eye movements seen during rapid eye movement (REM) sleep
Electromyogram (EMG)
Detects loss of activity in neck muscles during some sleep stages
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5. Four Stages of Sleep EEG
Alpha waves
Bursts of 8- to 12-Hz EEG waves
Eyes closed, preparing to sleep
EEG voltage increases and frequency decreases as one progresses from stage 1 through 2, 3, and 4
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6. Four Stages of Sleep EEG Continued
Similar to awake EEG, but slower
Low-voltage, high-frequency
Stage 2
K complexes – one large negative (upward deflection) wave followed by one large positive wave
Sleep spindles – bursts of Hz waves
Stages 3 and 4 – delta waves, large and slow
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FIGURE 14.2 The EEG of alert
wakefulness, the EEG that precedes
sleep onset, and the four stages
of sleep EEG. Each trace is about
10 seconds long.
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8. Four Stages of Sleep EEG Continued
Progress to stage 4 sleep and then back to stages 3, 2, and (emergent) 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
Durations of emergent stage 1 periods lengthen as night progresses
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FIGURE 14.3 The course of
EEG stages during a typical
night’s sleep and the relation of
emergent stage 1 EEG to REMs
and lack of tone in core muscles.
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10. Four Stages of Sleep EEG Continued
Emergent stage 1 sleep = REM sleep
All other stages = Non-REM (NREM) sleep
Stages = slow-wave sleep (SWS)
During REM sleep: REMs, loss of core muscle tone, low-amplitude/high-frequency EEG, increased cerebral and autonomic activity, muscles may twitch, penile erection
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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
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12. Interpretation of Dreams
Freud’s explanation: dreams are triggered by unacceptable repressed wishes
Manifest dreams – what we experience
Latent dreams – the underlying meaning
No evidence for this
Activation-Synthesis
Modern alternative to Freud’s explanation of dreams
Dreams due to cortex’s attempt to make sense of random brain activity (Hobson, 1989)
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13. Why Do We Sleep, and Why Do We Sleep When We Do?
Recuperation theories
Sleep is needed to restore homeostasis
Wakefulness causes a deviation from homeostasis
Adaptation theories
Sleep is the result of an internal timing mechanism
Sleep evolved to protect us from the dangers of the night
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14. Comparative Analysis of Sleep
All mammals and birds sleep – 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
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15. Effects of Sleep Deprivation
It is difficult, if not impossible, to separate the effects of stressors used to prevent sleep from the effects of lost sleep
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16. Effects of Sleep Deprivation Continued
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
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17. Two Classic Sleep-Deprivation Case Studies
Sleep-deprived students
By the third night, subject found desire for sleep overpowering
Randy Gardner
Stayed awake for 11 days
Only slept 14 hours the first night after the study
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18. Experimental Studies of Sleep Deprivation in Humans
Little effect of sleep deprivation:
Logical deduction, critical thinking
Physical strength and motor performance
Larger effect of sleep deprivation: executive function (prefrontal cortex)
Assimilating changing information
Updating plans and strategies
Innovative, lateral, insightful thinking
Reference memory
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19. Experimental Studies of Sleep Deprivation in Humans Continued
3-4 hours of deprivation in one night
Increased sleepiness
Disturbances displayed on written tests of mood
Poor performance on tests of vigilance
2-3 days of continuous deprivation
Experience microsleeps, naps of 2-3 seconds
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20. Sleep-Deprivation Studies with Laboratory 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
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FIGURE 14.5 The carousel apparatus used to deprive an experimental
rat of sleep while a yoked control rat is exposed to the same number and pattern of disk rotations. The disk on
which both rats rest rotates every time the experimental rat has a sleep EEG. If the sleeping rat does not awaken immediately, it is deposited in the water. (Based on Rechtschaffen et al., 1983.)
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22. REM-Sleep Deprivation
Two 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
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Purpose of REM
Processing of explicit memories?
Inconsistent findings
Antidepressant REM-blocking drugs do not interfere with memory
Default theory: it is difficult to remain in NREM sleep
Nycamp and others (1998) awoke sleepers in REM for 15 minutes. Result: no sleepiness or REM rebound the next day
REM-blocking drugs cause periods of wakefulness
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24. 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 awakenings, unlike SWS
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25. 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
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26. Free-Running Circadian Sleep-Wake 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?
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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?
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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
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29. A Circadian Clock in the Suprachiasmatic Nucleus (SCN)
Lesions do not reduce sleep time, but they abolish its circadian periodicity
Exhibits electrical, metabolic, and biochemical activity that can be entrained by the light-dark cycle
Transplant SCN, transplant sleep-wake cycle
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30. Neural Mechanisms of Entrainment
Cutting the optic nerves before the optic chiasm eliminated the ability of the light-dark cycle to entrain circadian rhythms
However, cutting after the chiasm did not have this effect
Later the retinohypothalamic tracts were identified
Leave the optic chiasm and project to the adjacent suprachiasmatic nuclei
Mechanisms of entrainment of SCN cells to light-dark cycle
Rare retinal ganglion cells with no rods or cones
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31. Genetics of Circadian Rhythms
Several mammalian circadian genes have been identified
Some of these have also been identified in other species of other evolutionary ages
Expression of these genes follows a circadian pattern
Most of the gene expression appears to be entrained by activity of the SCN
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32. 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
Like SCN cells, cells in other parts of the body exhibit free-running circadian rhythms in tissue cultures
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33. Four Areas of the Brain Involved in Sleep
Two areas of the hypothalamus:
Economo found that the posterior hypothalamus and the anterior hypothalamus were related to excessive sleep or inability to sleep, respectively
Findings were in patients that had encephalitis lethargica
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34. Four Areas of the Brain Involved in Sleep
Two areas of the brainstem:
Cerveau isolé (“isolated forebrain”) preparation – produced by severing cat brainstem between the superior and inferior colliculi, resulting in continuous SWS
Encéphale isolé (“isolated brain”) preparation – produced by transsection caudal to the colliculi, resulting in normal sleep cycle
Therefore, wakefulness depends on the function of the reticular formation, or “reticular activating system”
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FIGURE Four pieces of evidence that the reticular formation is involved in sleep.
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36. 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
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37. Drugs That Affect Sleep
Drugs that increase sleep (hypnotic drugs): benzodiazepines – Valium, Librium
Most commonly prescribed hypnotic drugs
Effective in the short term
Complications
Tolerance
Cessation leads to insomnia
Addiction
Use leads to next day drowsiness
Increase of stage 2 sleep while decrease of stage 4 and REM
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38. Drugs That Affect Sleep Continued
Drugs that decrease sleep (antihypnotic drugs): stimulants and tricyclic antidepressants
Both increase activity of catecholamines
Act preferentially on REM – may totally suppress REM with little effect on total sleep time
Side effects
Loss of appetite
Addiction
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Melatonin
Synthesized from serotonin in the pineal gland
Melatonin levels follow circadian rhythms controlled by the SCN
Pineal gland triggers seasonal reproductive changes in fish, birds, reptiles, and amphibians – human function is unclear
Melatonin is not a sleep aid, but may be used to shift circadian rhythms
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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
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41. Sleep Disorders: Insomnia
Iatrogenic – physician-created
Consequence of sleeping pill use, for example
Alternative treatment: sleep restriction
Sleep apnea – stop breathing during the night leads to repeated awakenings. Two types:
Obstructive – obstruction of respiratory passages by muscle spasms or atonia
Central – CNS fails to initiate breaths
Most commonly seen in males, the overweight, and the elderly
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42. Sleep Disorders: Insomnia Continued
Periodic limb movement disorder – twitching of the body, usually the legs, during sleep. Most sufferers are not aware of why they don’t feel rested
Restless legs – uneasiness in legs that prevents sleep
Both are often treated with benzodiaze-pines
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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
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44. Hypersomnia – Narcolepsy Continued
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
May be due to genetic orexin deficiency and environmental factors
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45. REM-Sleep-Related Disorders
Narcolepsy
REM without atonia – able to act out dreams – possibly caused by damage to the nucleus magnocellularis or its output
Case history: man with assumed damage to caudal reticular formation had no REM sleep and no ill effects
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46. Effects of Long-Term Sleep Reduction
Differences between short and long sleepers?
No consistent differences
Long-term reduction of nightly sleep?
When reduced to 6h/night subjects often reported daytime sleepiness
Otherwise no ill effects
Overall sleep was more efficient
Effects of napping?
Some evidence that polyphasic sleep is more efficient
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47. Effects of Shorter Sleep Times on Health
Some evidence suggests that 5-7 hours/night of sleep is correlated with greater longevity
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