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Copyright © 2007 by Allyn a nd 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
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Pinel basics ch12

May 07, 2015

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Page 1: Pinel basics ch12

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.

Page 2: Pinel basics ch12

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?

Page 3: Pinel basics ch12

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

Page 4: Pinel basics ch12

Copyright © 2007 by Allyn and Bacon

4 Stages of Sleep EEG

Alpha waves – still awakeBursts of 8- to 12-Hz EEG wavesEyes closed, preparing to sleep

Stage 1similar to awake EEG, but slowerlow-voltage, high-frequency

Page 5: Pinel basics ch12

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 byK complexes – large negative wavesSleep spindles – burst of 12-14 Hz waves

Stages 3 and 4 – delta waves, large and slow

Page 6: Pinel basics ch12

Copyright © 2007 by Allyn and Bacon

Page 7: Pinel basics ch12

Copyright © 2007 by Allyn and Bacon

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

Page 8: Pinel basics ch12

Copyright © 2007 by Allyn and Bacon

Page 9: Pinel basics ch12

Copyright © 2007 by Allyn and Bacon

Stages of EEG Sleep

Emergent stage 1 sleep = REM sleepNon-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

Page 10: Pinel basics ch12

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

Page 11: Pinel basics ch12

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

Page 12: Pinel basics ch12

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

Page 13: Pinel basics ch12

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

Page 14: Pinel basics ch12

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

Page 15: Pinel basics ch12

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

Page 16: Pinel basics ch12

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?

Page 17: Pinel basics ch12

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?

Page 18: Pinel basics ch12

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 shiftPhase advance following east-bound travel

with intense light early in the morningHamster studies suggest a good early

morning workout may also help

Page 19: Pinel basics ch12

Copyright © 2007 by Allyn and Bacon

Reducing the Effect of Shift Changes Schedule phase delays, rather than phase

advancesMove 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

Page 20: Pinel basics ch12

Copyright © 2007 by Allyn and Bacon

Effects of Sleep Deprivation

Recuperation theories predict:Long periods of wakefulness will result in

disturbancesDisturbances will get worse as deprivation

continuesAfter deprivation, much of the missed sleep

will be regained What does the research indicate?

Page 21: Pinel basics ch12

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

Page 22: Pinel basics ch12

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

Page 23: Pinel basics ch12

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

Page 24: Pinel basics ch12

Copyright © 2007 by Allyn and Bacon

REM-Sleep Deprivation

2 consistent effectsProceed more rapidly into REM as REM

deprivation increasesREM rebound – more time spent in

REM when deprivation is over REM rebound suggests that REM

sleep serves a special function

Page 25: Pinel basics ch12

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

Page 26: Pinel basics ch12

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

Page 27: Pinel basics ch12

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

Page 28: Pinel basics ch12

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

Page 29: Pinel basics ch12

Copyright © 2007 by Allyn and Bacon

Page 30: Pinel basics ch12

Copyright © 2007 by Allyn and Bacon

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

Page 31: Pinel basics ch12
Page 32: Pinel basics ch12

Copyright © 2007 by Allyn and Bacon

Reticular Formation

Something between the cuts producing the cerveau and encpehale isole preparations maintains wakefulness – the reticular formationLeave intact, little effect on cortical EEGStimulation leads to wakefulness

Page 33: Pinel basics ch12

Copyright © 2007 by Allyn and Bacon

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

Page 34: Pinel basics ch12
Page 35: Pinel basics ch12

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

Page 36: Pinel basics ch12

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

Page 37: Pinel basics ch12

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

Page 38: Pinel basics ch12

Copyright © 2007 by Allyn and Bacon

Antihypnotic Drugs

Decrease sleep Stimulants and tricyclic

antidepressantsBoth increase activity of catecholamines

Act preferentially on REM – may totally suppress REM with little effect on total sleep time

Page 39: Pinel basics ch12

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

Page 40: Pinel basics ch12

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

Page 41: Pinel basics ch12

Copyright © 2007 by Allyn and Bacon

Insomnia

Iatrogenic – physician createdConsequence of sleeping pill use, for example

Sleep apnea – stop breathing during the night leads to repeated wakenings – 2 typesCaused by muscle spasms or atoniaFailure of the CNS to stimulate breathingMost commonly seen in males, the

overweight, and in the elderly

Page 42: Pinel basics ch12

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

Page 43: Pinel basics ch12

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

Page 44: Pinel basics ch12

Copyright © 2007 by Allyn and Bacon

Hypersomnia - Narcolepsy

Appears to be an abnormality in the mechanisms that triggers REMNarcoleptics enter directly into REMDreaming and loss of muscle tone while

awake – suggest REM intruding into wakefulness

Page 45: Pinel basics ch12

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

Page 46: Pinel basics ch12

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 daysSlight 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

Page 47: Pinel basics ch12

Copyright © 2007 by Allyn and Bacon

How much sleep do you need?

Can this question be answered? Why or why not?