Ultradian rhythms

• What are ultradian rhythms?

  Biological rhythms that last less than 24 hours and occur more than once in a 24 hour period
• What are examples of the ultradian rhythms?

  The sleep stages and basic rest-activity cycle (BRAC)
• What occurs in the sleep stages?

  REM and NREM sleep
• How many stages are there in the sleep cycle and how long do they last for?

  There are 5 stages and lasts around 90 minutes each.
• How are the different sleep stages measured?

  By the electrical activities of the brain, with each stage showing a distinct EEG pattern.
• The sleep stages:

  • Stages 1 and 2 - light/shallow sleep
  • Stages 3 and 4 - enter a deep sleep, heart and breathing rates decrease
  • Stage 5 - REM sleep occurs, the EEG pattern resembles that of an awake person and dreaming occurs
• Who conducted the research on sleep and dreaming in 1957?

  Dement and Kleitman
• What method did Dement and Kleitman use to study sleep?

  Connected participants to an EEG machine
• What was measured throughout the night in the study?

  Participants' brain activity during sleep
• When did participants report high incidences of dream recall?

  When they woke during REM sleep
• What was the dream recall like when participants woke during other stages of sleep?

  Very few reported dreaming
• How did REM sleep relate to dream type according to the study?

  REM varied according to dream type
• What did the brain activity during REM sleep mirror?

  Brain activity while awake completing similar tasks
• What pattern do the stages of sleep follow throughout the night?

  An atypical pattern
• When do dreams mostly occur?

  During REM sleep
• What are the limitations and strengths of the study by Dement and Kleitman?

  Limitations:

  • Participants studied in a sleep lab
  • Dreaming is difficult to assess

  
  

  Strengths:

  • EEG is an objective method
  • Scientific approach to measuring sleep
• Why might studying participants in a sleep lab be a limitation?

  It could cause an atypical reaction
• Why is dreaming difficult to assess?

  In terms of type and vividness
• Why is EEG considered a scientific method?

  It is an objective method
• The Basic Rest Activity Cycle (BRAC): Kleitman (1969)

  • Referred to the 90 minute cycle of sleep as the BRAC
  • We move progressively from a state of alertness to a state of physiological fatigue, every 90 minutes
  • Research suggest the human mind can focus for a period of ~90 minutes and towards the end the body begins to run out of resources, resulting in loss of concentration, fatigue and hunger