11. Ultradian + Infradian Rhythms

• 1. Ultradian + Infradian Rhythms

  Circadian - 24hr cycle e.g. s/w cycle.

  • Ultradian Rhythm - type of BR w/ frequency of more than one cycle in 24hrs e.g. sleeping stages.
  • Infradian Rhythm - type of BR w/ frequency of less than one cycle in 24hrs e.g. menstruation or seasonal affective disorder (SAD).
• 2. Ultradian + =Infradian Rhythms


  Menstrual Cycle - Infradian Rhythm:

  • average lasts 1 month (28 days); varies between 24-35 days.
  • controlled by endogenous pacemakers that promote ovulation or stimulate uterus for fertilisation.
• 2a. Ultradian + =Infradian Rhythms

  Menstrual Cycle - Infradian Rhythm:

  • FSH causes maturation of egg in ovary.
  • LH stimulates release of egg.
  • Oestrogen involved in repairing/thickening uterus lining.
  • Progesterone maintains lining of uterus in cycle.
  • Oxytocin stimulates contraction of womb = lining being shed (i.e. period).
• 2b. Ultradian + =Infradian Rhythms


  Menstrual Cycle + Exogenous Zeitgebers:

  • McClintock (1998); menstrual synchronicity, longitudinal study of 29 women - irregular cycles.
  • sweat collected, frozen + sterilised, leaving behind pure hormones.
  • 68% experienced change to cycle = closer in line w/ ‘odour donor’.
  • shows infradian rhythms can be controlled by external factors.
  • evolutionary advantage to synchronisation of men. cycle — in past, benefit women fall preg at same time; increased survival.
• 3. Ultradian + =Infradian Rhythms


  Seasonal Affective Disorder (SAD):

  • depressive disorder w/ seasonal pattern; persistent low mood + pleasure.
  • ‘winter blues’ (Sep-Feb).
  • more common away from equator.
• 3a. Ultradian + =Infradian Rhythms


  SAD:

  • effective treatment = phototherapy, involves light box that stimulates v strong light in morning/evening.
  • reset melatonin levels in people w/ SAD.
  • phototherapy relives symptoms in up to 605 sufferers (Eastman 1998).
• 4. Ultradian + =Infradian Rhythms

  Ultradian Rhythms - S/W Cycle:

  • development of cog neuroscience (EEGs) crucial to understanding of sleep stages.
  • technology = analyse sleep patterns = sleep in 4 stages (repeat in 90-100 min cycles through night).
• 4a. Ultradian + =Infradian Rhythms

  Sleep Stages:

  1-2:

  • light sleep, easily woken; brainwave patterns slower + more rhythmic (alpha waves); even slower as sleep becomes deeper (theta waves).
  • S1 = 4-5%, light sleep, slow muscle activity.
  • S2 = 45-55%, breathing/heart slows, lower temp.
• 4b. Ultradian + =Infradian Rhythms

  Sleep Stages:

  2-3:

  • delta waves (slower, greater amplitude); deep sleep.
  • 3 = deep sleep begins, brain generates slow delta w.
  • 4 = very deep sleep, rhythmic breathing/limited muscle activity = produces delta waves.
• 4c. Ultradian + =Infradian Rhythms

  Sleep Stages:

  5:

  • REM sleep, body paralysed, brain activity speeds up; rapid eye movement.
  • dreaming, muscles relax, heart increase, rapid/shallow breathing.
• 4d. Ultradian + =Infradian Rhythms


  Sleep Stages - Dement + Kleitman:

  • monitored sleep pattern of 9 adults in sleeping lab.
  • EEG.
  • controlled effects on caffeine/alcohol.
  • REM activity in sleep correlated w/ experience of dreaming; participants woken in dreaming reported accurate recall.
• 5. Ultradian + =Infradian Rhythms


  Basic Reset Activity Cycle (BRAC):

  • EEG recordings suggest existence of 90min cycle in sleep.
  • Kleitman (1969); similar 90min rhythm continues in waking hrs = BRAC = period of alertness then fatigue.
  • evidence supports BRAC existence e.g. students difficult to concentrate longer than 90 min.
  • Ericsson (1993) found best violin performers practiced for 3 sessions during day (no longer than 90min, break between each).
  • BRAC another e.g. of ultradian rhythm.
• Ultradian + =Infradian Rhythms (Evaluation)

  Limitation:

  P - phototherapy effective treatment for SAD.

  E - light box stimulates strong light in morning/evening; resets melatonin levels in SAD; relieve symptoms in 60%.

  E - placebo effect = 30%.

  L - casts doubt on effectiveness of study.
• Ultradian + =Infradian Rhythms (Evaluation)


  Limitation:

  P - menstrual synchrony evolutionary value; advantageous for ancestors to menstruate together/fall preg same time.

  E - babies cared for collectively = increase survival.

  E - validity of evolutionary perspective questioned; Schank (2004) argued if too many women cycled together, produce compition for highest quality males.

  L - gender debates.
• Ultradian + =Infradian Rhythms (Evaluation)

  Limitation:

  P - criticism of early synchronisation studies; too many factors affect menstrual cycle (e.g. stress, diet).

  E - cofounding variables; McClintock study, patterns of synchronisation may just be down to chance.

  E - small samples + relies on self-reporting (demand c/social desirability).

  L - low gen, lack ecological validity, low internal v, low reliability.