Biological Rhythms, Sleep and Dreaming

Biological Rhythms, Sleep and Dreaming: Introduction

• There is a wide variety of biological rhythms — periodically 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 differenct 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

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

The Sleep—Waking Cycle: A Circadian Rhythm

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

The visual pathway in the brain

Endogenous mechanisms involved in regulating bodily rhythms

The Sleep—Waking Cycle: A Circadian Rhythm (continued)

• 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)

The Menstrual Cycle: An Infradian Rythym

• 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

Circannual Rhythms

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

The Consequences of Disrupting Biological Rhythms

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

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

EEGs from various stages of sleep

Examples of EEGs from various stages of sleep (continued)

Cyclic variations in EEG during sleep

Cyclic variations in EEG during sleep and their relation to eye movements, body motility, and dreaming

Reprinted from W.C. Dement and N. Kleitman (1957), Cyclic variations in EEG during sleep and their relation to eye movements, body motility, and dreaming. Clinical Neurophysiology, 9, 673–690. Copyright © 1957 Elsevier, reprinted with permission.

REM Sleep and Dreaming

• Aserinsky and Kleitman (1955)
  • First discovered the asociation 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

Studies of Sleep Deprivation

• Famous cases
  • Peter Tripp: 8 days (200 hours)
  • Randy Gardner: 11 days (264) (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)

Studies of Sleep Deprivation (continued)

• Task Performance
• Effects over time
• Partial deprivation

Theories of Sleep

• Recovery or restoration theories

  • Physiological restoration (Oswald, 1980)

    
  • Psychological functions

Theories of Sleep (continued)

• 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

The Nature of Dreams

• Rembering 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 conciousness
  • Empson (1989)
    • lucid dreams

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

Theories of the Functions of Dreaming (continued)

Psychological theories

• Freud's 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 sleep— "sleep on it"
  • manifest content is the real content
• Survival strategy theory
  • Winson (1977)
  • memories of new experiences are placed close together with older memories to form a strategy for survival

Biological Rhythms, Sleep and Dreaming

End of Presentation

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