Chapter 8 Wakefulness and Sleep

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Chapter 8Wakefulness and Sleep

• Module 8.1

• Rhythms of Waking and Sleeping

Module 8.2

• Stages of Sleep and Brain Mechanisms

Module 8.3

• Why Sleep? Why REM?
• Why Dreams?

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Why Sleep?

• Functions of sleep include
• Restoration of the brain and body
• Energy conservation
• Memory consolidation/learning

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Why Sleep?Restoration of the Brain and Body

• Moderate sleep deprivation can result in
• impaired concentration
• irritability
• hallucinations
• tremors
• unpleasant mood
• decreased immune system function

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Why Sleep?Restoration of the Brain and Body

• Optimal sleep time 8-10 hrs

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Why Sleep?Restoration of the Brain and Body

• Prolonged sleep deprivation in laboratory animals
  results in
• Increased metabolic rate, appetite and body
  temperature
• Immune system failure
• Decrease in brain activity

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Why Sleep?Energy Conservation

• Evolutionary Theory of Sleep The function of
  sleep is to conserve energy by
• decreasing body temperature 1-2 Celsius degrees
  in mammals
• decreasing muscle activity
• Sleep is analogous to the hibernation of animals

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Why Sleep? Memory and Learning

• Sleep enhances
• learning and memory
• performance on a newly learned task
• Increased brain activity occurs in the area of
  the brain activated by a newly learned task while
  one is asleep

• Link to video, Whats in a Dream?(13m)
• https//www.youtube.com/watch?vGxGLes-0JVg

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Why Dreams?Activation synthesis hypothesis

• Activation-synthesis hypothesis dreams begin
  with spontaneous activity in pons
• Pons activates many parts of cortex
• Cortex synthesizes story from pattern of
  activation
• Normal sensory information cannot compete with
  the self-generated stimulation and hallucinations
  result.

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Why Dreams?The clinico-anatomical hypothesis

• Clinico-anatomical hypothesis Dreams are similar
  to thinking, just under unusual circumstances.
• Dreams begin with arousing stimuli that are
  generated within the brain.
• Stimulation is combined with recent memories and
  current sensory stimulation.
• ?

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Rhythms of Waking and Sleep

• Endogenous generated from within
• Endogenous circannual rhythms internal
  mechanisms that operate on an annual cycle
• Examples
• Birds migratory patterns
• Animals storing food for winter

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Rhythms of Waking and Sleep

• Endogenous circadian rhythms, internal mechanisms
  that operate on an approximate 24 hour cycle
• sleep/ wake cycle
• frequency of eating and drinking
• body temperature
• secretion of hormones
• volume of urination
• sensitivity to drugs

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The Circadian Rhythm(AKA The Biological Clock)

• Free-running rhythm rhythm that occurs when no
  stimuli reset or alter it
• Human circadian clock generates a rhythm slightly
  longer than 24 hours when it has no external cue
  to set it
• Most people can adjust to 23- or 25- hour day
  but not to a 22- or 28- hour day

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Biological cues

• Sunrise Light increasing temperature

• Sunset Dark decreasing temperature

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The Circadian RhythmResetting the Biological
Clock

• Purpose of circadian rhythm to keep our internal
  workings in phase with the outside world
• Light is critical for periodically resetting our
  circadian rhythm.
• Zeitgeber term used to describe any stimulus
  that resets circadian rhythms exercise, noise,
  meals, temperature and more

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The Circadian RhythmResetting the Biological
Clock

• Jet lag disruption of circadian rhythm due to
  crossing time zones
• Characterized by sleepiness during the day,
  sleeplessness at night, and impaired
  concentration.

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Rhythms of Waking and SleepBiological Mechanisms

• Suprachiasmatic Nucleus (SCN)
• Part of the hypothalamus
• Main control center of circadian rhythms for
  sleep and temperature
• Genetically controlled and independently
  generates circadian rhythm

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Rhythms of Waking and SleepBiological Mechanisms

• Light resets the SCN via a small branch of the
  optic nerve known as the retinohypothalamic path.
• Travels directly from the retina to the SCN.

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Rhythms of Waking and SleepBiological Mechanisms

• SCN regulates the pineal gland (endocrine gland
  located posterior to the thalamus)

• Pineal gland secretes melatonin, a hormone that
  increases sleepiness.

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Stages of Sleep And Brain Mechanisms

• Electroencephalography (EEG) allowed researchers
  to discover that there are various stages of
  sleep
• Polysomnography measures EEG, eye-movements, and
  facial twitching

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Stages of Sleep And Brain Mechanisms

• Over the course of about 90 minutes
• a sleeper goes through sleep stages 1, 2, 3, and
  4
• then returns through the stages 3 and 2 to a
  stage called REM.

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Stages of Sleep And Brain Mechanisms

• Alpha waves state of relaxation
• Stage 1 sleep is when sleep has just begun.
• the EEG is dominated by irregular, jagged, low
  voltage waves.
• brain activity begins to decline.

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Stages of Sleep And Brain Mechanisms

• Stage 2 sleep is characterized by the presence
  of
• Sleep spindles - 12- to 14-Hz waves during a
  burst that lasts at least half a second.
• K-complexes - a sharp high-amplitude negative
  wave followed by a smaller, slower positive wave.

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Stages of Sleep And Brain Mechanisms

• Stage 3 and stage 4 together constitute slow wave
  sleep (SWS) and is characterized by
• EEG recording of slow, large amplitude wave.
• Slowing of heart rate, breathing rate, and brain
  activity.
• Highly synchronized neuronal activity.

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Stages of Sleep And Brain Mechanisms

• Rapid eye movement sleep (REM) periods
  characterized by rapid eye movements during sleep
• Also known as paradoxical sleep because it is
  like deep sleep in some ways, but light sleep in
  other ways.
• EEG waves resemble awake state
• Postural muscles of the body are more relaxed
  than other stages

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Stages of Sleep And Brain Mechanisms

• REM is strongly associated with dreaming, but
  people also report dreaming in other stages of
  sleep.
• Stages other than REM are referred to as non-REM
  sleep (NREM).

• Sleep stages change as the night progresses
• Deep sleep (stages 3 4) gets shorter as the
  night progresses
• REM sleep gets longer as the night progresses

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Why Sleep? Why REM? Why Dreams?

• REM deprivation results in
• Increased attempts of the brain/ body for REM
  sleep throughout the night
• Increased time spent in REM when no longer REM
  deprived.
• Subjects deprived of REM for 4 to 7 nights
  increased REM by 50 when no longer REM deprived.

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Why Sleep? Why REM? Why Dreams?

• Possible functions of REM sleep
• Brain may discard useless connections
• Learned motor skills may be consolidated
• Oxygen may be delivered to the corneas

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Sleep Disorders

• Insomnia inability to fall asleep or stay asleep
• Causes noise, stress, pain medication, epilepsy,
  Parkinsons disease, depression, anxiety, other
  psychiatric conditions
• Treatment relaxation techniques, sleeping pills

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Sleep Disorders

• Sleep apnea periodic inability to breathe while
  sleeping
• Causes obesity, growth in windpipe, weak lungs,
  deterioration of brain mechanisms that control
  breathing
• Can result in cognitive impairment if there is a
  loss of neurons due to insufficient oxygen levels
• Treatments include Weight loss, surgery, forced
  air

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Sleep Disorders

• Narcolepsy frequent periods of sleepiness
• 4 main symptoms
• Gradual or sudden attack of sleepiness
• Cataplexy - muscle weakness triggered by strong
  emotions
• Sleep paralysis- inability to move while asleep
  or waking up
• Hypnagogic hallucinations- dreamlike experiences
  the person has difficulty distinguishing from
  reality

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Sleep Disorders

• Narcolepsy frequent periods of sleepiness
• Cause Lack of hypothalamic cells that produce
  neurotransmitter orexin
• Treatments Napping schedules and stimulant drugs

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Sleep Disorders

• Periodic limb movement disorder repeated
  involuntary movement of the legs and arms while
  sleeping
• Legs kick once every 20 to 30 seconds for periods
  of minutes to hours.
• Usually occurs during NREM sleep.
• Treatment tranquilizers

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Sleep Disorders

• REM behavior disorder is associated with vigorous
  movement during REM sleep.
• Usually associated with acting out dreams.
• Occurs mostly in the elderly and in older men
  with brain diseases such as Parkinsons.
• Presumed cause damage to pons (inhibits spinal
  neurons that control large muscle movements).

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Sleep Disorders

• Night terrors experiences of intense anxiety
  from which a person awakens screaming in terror.
• Usually occurs in NREM sleep.
• Sleep talking occurs during both REM and NREM
  sleep.
• Sleepwalking runs in families, mostly occurs in
  young children, and occurs mostly in stage 3 or 4
  sleep.