Ultradian rhythms

• What are ultradian rhythms?

  • Biological rhythms with a frequency of more than one in 24 hours
  • E.g. the sleep cycle
• The sleep cycle

  • 5 stages - 90 minutes each
  • Measured using EEG
  • Stages 1 and 2 - light sleep, easy to wake, brain waves high frequency low amplitude, alpha waves, sleep spindles
  • Stages 3 and 4 - Deep sleep/slow wave sleep, delta waves, low frequency high amplitude, difficult to wake
  • Stage 5 (REM) - body is paralysed, brain activity resembles awake, theta waves, eyes move occasionally, dreams most often
• Sleep staircase

  Stages 1, 2, 3, 4 then 3, 2, REM, then 2, 3, 4, 3, 2, REM etc