ultradian and infradian rhythms

• What is an Ultradian rhythm?

  A cycle that lasts less than 24hours

  • follows pattern of REM and NREM, repeated every 90-100 mins, each stage shows distinct EEG patterns
• What are the Stages of REM sleep in Ultradian rhythms?

  Stage 1 (4-5%) - light sleep, muscle activity, occasional muscle twitching

  Stage 2 (45-55%) - breathing pattern and heart rate slows, slight decrease in body temp

  Stage 3 (4-6%) - deep sleep begins, brain generates slow delta waves

  Stage 4 (12-15%) - very deep sleep, rhythmic breathing, limited muscle activity

  Stage 5 (20-25%) - REM, brain waves speed up, dreaming occurs
• What is a Basic Rest Activity Cycle (BRAC)?

  Kleitman - 90 min cycle continues throughout the day

  • progressively moves from alert state to psychological fatigue
• A03: Individual differences

  Tucker - differences are biologically determined

  • studied ppts over 11 days in strict controlled environment
  • assessed sleep duration, found large individual differences
• A03: Research support for BRAC

  Eriksson -

  • studied group of elite violinists, practice sessions limited to maximum 90 mins
  • distributed throughout the day in a 90 minute cycle
• What is an Infradian rhythm?

  A cycle that lasts over than 24 hours.
• What is a Weekly Rhythm?

  There are obvious and less obvious differences in human behaviour that conforms to this weekly

  • Halberg - 7 day of rhythms of blood pressure and heart rate humans
• What is a Monthly Rhythm?

  Womens reproductive cycle

  • considerable variations in the lengths, 23-36 days
  • average is 28 days, regulated by hormones which promote ovulation
• What is an Annual Rhythm?

  Magnusson - seasonal variations in mood of humans, Season Affective Disorder

  • winter associated with increase in heart attacks
• A03: Menstrual cycle and exogenous cues

  Several women of childbearing age live together and don’t take contraceptives, cycles sync

  • Russell - daily samples of sweat collected from one group of women, placed on upper lip of other women
  • groups kept separate but cycles synced