Ultradium and infradian rhythms

• Define ultradian rhythm

  A cycle that happens within the body more than once every 24 hours
• What are the examples of ultradian rhythms

  • Sleep stages
  • basic rest activity cycle (BRAC)
• Explain sleep stages - ultradian rhythms

  • The cycle alternates between REM and NREM sleep
  • the cycle starts at light sleep, progressing to deep sleep and the REM sleep
  • this repeats about every 90 minutes
• Explain the stages of sleep - ultradian rhythms

  • Stages one and two - ‘light sleep’ where brainwave patterns are becoming slower and more rhythmic
  • stages three and four - ‘deep sleep’ where it is difficult to wake someone up
  • stage five - REM sleep when the body is paralysed (to stop the person acting out their dream) and brain activity resembles that of an awake person
• Explain basic rest activity cycle - ultradian rhythm

  • It is suggested that the 90 minute sleep stages continue whilst we are awake during the day
  • the difference is that rather than moving through sleep stages we progress from a state of alertness to fatigue
• Define infradian rhythm

  A cycle in the body that lasts more than 24 hours
• What are the examples of infradian rhythms

  • Menstrual cycle
  • seasonal affective disorder
• Explain the menstrual cycle - infradian rhythm

  • lasts around a month, averaging at 28 days
  • it is regulated by hormones that either promote ovulation or stimulate the uterus for fertilisation
  • oestrogen levels are at their highest halfway through the cycle when ovulation occurs
  • after the ovulation phase, progesterone levels increase in preparation for possible implantation of an embryo
• Explain seasonal affective disorder - infradian rhythm

  • This is a mood disorder linked to the seasons
  • it involves feeling sadness and depression during winter months when there is significantly less exposure to natural light
  • it is thought to be due to a surge of melatonin in the brain
  • melatonin is a hormone that is inhibited by light but in the dark will produce an abundance which leads to sleepiness during the day
• What are the two key studies for ultradian rhythms

  • Dement and Kleitman
  • Ericsson
• Explain Dement and Kleitman - ultradian rhythms

  • EEG monitors were placed on sleeping participants
  • participants seemed to follow predictable patterns of brain activity which were monitored and noted
  • Participants woken up during REM sleep were mostly dreaming
  • however it was also found that dreams were recorded outside of REM sleep and sleepers woken up during REM sleep weren’t always dreaming
• Explain Ericsson - ultradian rhythms

  • A group of elite violinists were studied
  • their practice sessions were limited to a duration of no more than 90 minutes
  • BRAC claims that the end of the cycle causes fatigue which reflects why the violinists frequently napped to recover from their practice sessions
  • the same pattern was found in athletes, other musicians and writers
• What are the two key studies for infradian rhythms

  • McClintock
  • Miller
• Explain McClintock - infradian rhythms

  • McClintock claimed that the menstrual cycle is an infradian rhythm that runs entirely off an endogenous pacemaker (internal body clock)
  • sweat from one woman was presented onto the upper lip of other women who they were not living with
  • this was due to the theory that the synchronisation occured due to pheromones in sweat
  • it was found that these women’s cycles them tended to synchronise with the donor
• Explain Miller - infradian rhythm

  • Light therapy involves sitting close to a special light box for 30 minutes a day, usually as soon as waking up as possible
  • the boxes provided 10,000 lux (a measure of light intensity)
• Evaluate Millers study - infradian rhythms

  • Light therapy is found to be at least effective as antidepressant medications for treating seasonal affective disorder
  • however it isn’t appropriate for everyone due to either the brightness of light needed or possible disorders
  • e.g people with bipolar disorder risk triggering hypomania/mania