Ultradian

• A cycle that occurs more than once every 24 hours.

  Ultradian Rhythms
• An example of ultradian rhythms is the stages of sleep whichwe go through in cycles - each lasting around 90 minutes.

  • Each of these stages is characterised by a different level of brainwave activity which can be monitored using an EEG.
• • Stages 1 and 2 are sometimes known as light sleep where the person may be easily woken.
  • At the beginning of sleep, brain wave patterns start to become slower and more rhythmic (alpha waves), becoming slower as sleep gets deeper (theta waves).

  Stages of sleep.
• • Stage 3 and 4 involve delta waves which are slower still.
  • This is known as deep sleep or Slow Wave Sleep (SWS) and it is difficult to rouse someone at this point.


  Stages of sleep.
• • Stage 5, REM sleep, the body is paralysed yet brain activity speeds up significantly in a manner that resembles being awake.
  • REM stands for Rapid Eye Movement
  • Research has suggested that REM activity during sleep is highly correlated with the experience of dreaming.


  Stages of sleep.
• The fact that all humans display similar trends in the stages of sleep suggests that the rhythm is controlled by an endogenous pacemaker.