Biological Rhythms, Sleep, and Dreaming

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Biological Rhythms, Sleep, and Dreaming

• There is a wide variety of biological
  rhythmsperiodically recurring features of
  biological organisms, which are classified by the
  period of the cycle. In this lecture, we explore
  biological clocks, and the external and internal
  cues of different cycles
• Sleep is the most well-known cycle, and we look
  at studies of sleep deprivation, the theories
  explaining the purpose of sleep, and the theories
  of why we dream

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Biological Rhythms
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Different Kinds of Biological Rhythms

• Circadian rhythm
• About a day
• 24 hours
• Ultradian rhythm
• Less than a day
• 90 minute cycles of lighter and deeper sleep
• Infradian rhythm
• Greater than one day
• Menstrual cycle

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The SleepWaking Cycle A Circadian Rhythm

• Biological clock
• Siffre (1975)
• Wever (1979)
• Folkard (1996)
• Endogenous factors
• Suprachiasmatic nucleus (SCN)
• the amount of light entering the eye
• pineal gland
• melatonin

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• Exogenous factors
• Campbell and Murphy (1998)
• Light as the dominant zeitgeber or timer
  giver
• Miles et al. (1977)
• Luce and Segal (1966)
• Internal and external control
• Shiftwork
• Jet lag
• Indirect effects of circadian rhythms
• Blake (1967)

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The Menstrual Cycle An Infradian Rhythm

• Governed by hormones
• oestrogen
• progesterone
• 28 days
• Reinberg (1967) external cues
• McClintock (1971)
• synchronised cycles through pheromones of other
  women
• synchronised cycles through pheromones of men

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Circannual Rhythms

• Rhythms that last for about 1 year or more
• Hibernation
• Seasonal Affective Disorder (SAD)
• Severe depression during the winter months
• Seasonal variation in the production of melatonin
  (Barlow Durand, 1995)
• More common in northern latitudes where winter
  days are very short (Terman, 1988)
• Phototherapy (Barlow Durand, 1995)

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The Consequences of Disrupting Biological Rhythms

• Jet lag
• Changing time zones
• Klein et al. (1972) westbound flights less
  disruptive to the sleepwaking cycle than
  eastbound flights
• Melatonin and aircrew
• Shiftwork
• Moore-Ede (1993) shiftworker fatigue
• Monk and Folkard (1983)

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Sleep
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Stages of Sleep An Ultradian Rhythm

• Stage 1
• Relaxation with synchronous brain waves
• Stage 2
• EEG becomes slower and larger
• Stage 3
• EEG consists of long, slow delta waves
• Stage 4
• Slow-wave sleep (SWS)
• Stage 5
• Rapid eye movement or REM sleep

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1 2 3
Examples of EEGs from various stages of sleep
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4 5
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Cyclic variations in EEG during sleep and their
relation to eye movements, body motility, and
dreaming
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REM Sleep and Dreaming

• Aserinsky and Kleitman (1955)
• First discovered the association between REM
  sleep and dreaming
• Dement and Kleitman (1957)
• Between 70 and 75 of participants woken in REM
  sleep report dreaming
• Green (1994)
• 30 of sleepers in SWS report dreaming
• REM dreams
• Are vivid and detailed
• Non-REM dreams
• Are vague and less coherent

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Studies of Sleep Deprivation

• Famous cases
• Peter Tripp 8 days (200 hours)
• Randy Gardner 11 days (264 hours) (Horne, 1988)
• Rechtschaffen et al. (1983)
• sleep deprivation in rats
• Lugaressi et al. (1986) 52-year-old man who could
  not sleep due to damage to parts of the brain
  regulating sleep
• REM deprivation
• Dement (1960)
• Jouvet (1967)
• Task performance
• Effects over time
• Partial deprivation

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Theories of Sleep

• Recovery or restoration theories
• Physiological restoration
• Psychological functions

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• Adaptive or evolutionary theories
• Sleep as a protection against predation
• Meddis (1975)
• Hibernation theory
• Webb (1982)
• Recovery or adaptation?
• Horne (1988) sleep probably serves different
  purposes in different species

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Dreaming
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The Nature of Dreams

• Remembering your dreams
• 95 of dreams are forgotten
• An objective method for the study of dreaming
• Dement and Kleitman (1957)
• high correlation between amount of time spent in
  REM and verbal reports of dreaming
• Dreaming and consciousness
• Empson (1989)
• lucid dreams

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Theories of the Functions of Dreaming

• Neurobiological theories
• Activation-synthesis theory
• Hobson and McCarley (1977)
• dreamers try to make sense of random brain
  activation
• Reverse-learning theory
• Crick and Mitchison (1983)
• gets rid of useless information stored in the
  brain
• spiny anteater does not have REM

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• Psychological theories
• Freuds wish-fulfilment theory
• dreamers dream of repressed desires
• manifest content of dream is latent content
  disguised
• Problem-solving theory
• Webb and Cartwright (1978)
• problem-solving after sleepsleep on it
• manifest content is the real content
• Survival strategy theory
• Winson (1997)
• memories of new experiences are placed close
  together with older memories to form a strategy
  for survival

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