Infradian and Ultradian

• Infradian rhythms of over 24 hours - weeks, months, or years (leaf cycle of a tree)
• Weekly rhythms

  • Male testosterone levels peak at weekends
  • Lower frequency of births on weekends
  • Harlberg et al (2002) found 7 day rhythms of blood pressure and heart rate
• Monthly rhythms

  • Menstrual cycle - 23-36 days and is regulated by hormones, either promoting ovulation or stimulate uterus for fertilisation
  • Dictated by the SCN
  • Ovulation occurs roughly halfway through, when oestrogen peaks. After this phase, progesterone levels start to rise in preparation of a possible implantation of embryo in the uterus
• Infradian rhythm strength - exogenous cues and menstrual cycle

  • Russel et al (1980) - sample of sweat from a donor were taken and rubbed onto the upper lips of women in the second group. The women were kept separate but their menstrual cycles synced with the donor
• Ultradian rhythms are cycles that last less than 24 hours (sleep cycle)

  The sleep cycle has 5 distinct stages:

  1. Drowsy (first 5-10 minutes)
  2. Light sleep (20 minutes)
  3. Moderate sleep (10-20 minutes)
  4. Deep sleep (30 minutes)
  5. REM- rapid eye movement

  Deeper sleep slows down breathing and heart rate
• Ultradian rhythm - Kleitman 1969

  • Described 90 minute cycles as basic rest activity cycle (BRAC)
  • Also suggested that this cycle continues during the day, even when awake
  • Alertness followed by fatigue / loss of control and hunger
  • Everyday observations have provided evidence
• Ultradian rhythms - Peter Tripp

  • Radio DJ stayed awake for 8.5 days for charity
  • Suffered mood swings, body temperature drop, hallucinations, REM like brain waves and paranoia
• Ultradian rhythms - Randy Gardener

  • Teen stayed awake for 11 days
  • Some nausea and forgetfulness but no symptoms
  • Later developed extreme insomnia
• Ultradian rhythms strength - research support

  • Ericsson et al 2006 - group of elite violinists had practice sessions of around 90 minutes, distributed across the day. They napped frequently - the more able the violinist, the more naps
• Ultradian rhythm weakness - validity and reliability of sleep patterns research

  • Ability to sleep can be affected by multiple things - individual differences, lab environment, biological and non biological factors