ultradian rhythms

• ultradian rhythm

  biological rhythm that occurs more than once in 24 hours

  e.g. sleep cycle
• Sleep cycle

  • 5 stages of sleep that spans approx 90 minutes
  • characterized by different brainwave activity
• stages 1

  • light sleep, can be easily woken
  • brain waves have high frequency and short amplitude
  • alpha waves
• stage 2

  • light sleep, easily woken
  • alpha waves continue
  • occasional random changes in pattern - sleep spindles
• stages 3 and 4

  • deep sleep / slow wave sleep (SWS)
  • brain waves have a lower frequency and higher amplitude
  • delta waves
  • difficult to wake someone up
• stage 5 (REM sleep)

  • body is paralysed but brain activity resembles an awake brain.
  • theta waves
  • eyes occasionally move (rapid eye movement)
  • dreams often experienced
• Strength - research evidence

  • Dement + Kleitman
  • monitored sleep patterns of 9 adult participants in sleep lab using an EEG to record brainwaves
  • caffeine + alcohol effects controlled.
  • REM activity highly correlated with dreaming. activity varied on how vivid the dream was.
• Limitation - Individual differences

  • Tucker et al
  • large differences between participants in terms of duration of each sleep stage
  • suggests differences are biologically determined.
  • difficult to describe 'normal sleep'
• limitations of sleep lab

  • artificial environment -> low eco validity
  • different environment may disrupt sleep