A01

• What is one of the most intensively researched ultradian rhythms?

  The stages of sleep
• How many distinct stages of sleep have psychologists identified?

  Five distinct stages
• How long does a complete sleep cycle last?

  Approximately 90 minutes
• What tool is used to monitor brainwave activity during sleep stages?

  An EEG
• What are the characteristics of stages 1 and 2 of sleep?

  • Light sleep
  • Easily woken
  • Stage 1: high frequency, short amplitude brain waves (alpha waves)
  • Stage 2: alpha waves with sleep spindles
• What type of brain waves are present in stage 1 of sleep?

  Alpha waves
• What occurs in stage 2 of sleep besides alpha waves?

  Occasional random changes called sleep spindles
• What are the characteristics of stages 3 and 4 of sleep?

  • Known as deep sleep or slow wave sleep (SWS)
  • Delta waves present
  • Lower frequency and higher amplitude brain waves
  • Difficult to wake someone
• What is the brain wave type during stages 3 and 4 of sleep?

  Delta waves
• What happens during stage 5 (REM sleep)?

  • Body is paralysed
  • Brain activity resembles that of an awake brain
  • Theta waves produced
  • Eyes move (rapid eye movement)
  • Dreams most often occur
• What type of brain waves are produced during REM sleep?

  Theta waves
• When do dreams most often occur during sleep?

  During REM sleep
• What is a key feature of REM sleep regarding body movement?

  The body is paralysed
• What is the significance of rapid eye movement (REM) during sleep?

  It indicates brain activity similar to wakefulness