ultradian rhythm

• ultradian rhythm 


  biological process that repeats more frequently than once ever 24 hours (minute/hours)

  example: sleep cycle
• how we measure sleep?


  EEG measures electrical brain activity.

  EOG measures eye movement.

  EMG measures muscle tension.
• stages of sleep 


  These instruments indicate that during a single night’s sleep we experience a cyclical ultradian rhythm of different stages and types of sleep which can be roughly divided into REM (rapid eye movement) and NREM (non-rapid eye movement)
• N1 light sleep


  'falling asleep' sensation

  easy to wake and body may move suddenly. May be a sensation of falling, mild auditory or visual hallucinations

  EEG shows theta waves, slow frequency but high amplitude
• N2 - deeper sleep


  harder to wake, body relaxed, heart rate and temperature lowered, eyes still

  EEG shows Theta but occasional activity - sleep spindles
• N3 - deepest sleep


  difficult to wake, body most relaxed, heart-rate at lowest

  identified on EEG by slow, large amplitude delta waves
• REM


  brain returns to active state passing back through N2 and N1. Similar to being awake on EEG however body is paralysed. Characterised by rapid eye movement and associated with dreaming

  cycle repeats up to 5 times in 1 night
• Shapiro (1981)


  marathon runners showed longer sleep after intense physical activity

  increased proportion of slow wave sleep, suggesting N3 for physical recovery
• Haider (1970)


  EEG of 10 patients recovering from drug overdose showed increased REM, suggesting REM for mental recovery
• (wekaness) individual differences : Tucker 


  Tucker et al. (2007) found significant differences between participants in terms of the duration of each stage, particularly stages 3 and 4 (just before REM sleep). This demonstrates that there may be innate individual differences in ultradian rhythms, which means that it is worth focusing on these differences during investigations into sleep cycles.
• addition to Tucker's study

  • study was carried out in a controlled lab setting, which meant that the differences in the sleep patterns could not be attributed to situational factors, but only to biological differences between participants. While this study provide convincing support for the role of innate biological factors and ultradian rhythms, psychologists should examine other situational factors that may also play a role.