ultradian rhythms

• • ultradian rhythms have a frequency of more than 1 cycle in 24 hours, in sleep stages there are 4 or 5 cycles per night
  • the 5 stages of sleep, together they span 90 minutes and each stage is characterised by a different level of brainwave activity, that can be measured using an EEG
  • Stages 1 and 2: light sleep, high frequency + low amplitude = alpha waves, occasional sleep spindles and k-complex in stage 2
  • stages 3 and 4: slow wave sleep, delta waves, flushes out debris of neuronal activity, physically restorative -> releases growth hormones + replenishes, only occurs in first 2 cycles of sleep
• • stage 5: REM sleep (rapid eye movement) theta waves, brain activity resembles awake brain, body is paralysed due to firing in pons to stop acting out dreams
  • demant and kleitman were the pioneers for sleep stages, they intensively studied 5 pps in a sleep lab using EOG (tracks eye movement) and EEG
  • they were the first psychologists to validate the existence of stages of sleep
• • there is lots of practical value to understanding the stages of sleep
  • e.g. there are lots of sleep apps, Fitbits which track your heartbeat
  • these monitor sleep quality to tell you when to go to sleep, or wake you up at the best time so you feel energised even if you wake up earlier than you wanted
  • we know to have naps for 20 minutes or 90 minutes to wake up feeling alert instead of feeling tired
  • we can identify sleep disorders by using a sleep lab and comparing to a typical 90 minute rhythm to identify abnormalities