Infradian + Ultradian

• Infradian


  biological rhythms with a frequency of LESS than one in a 24hr cycle
• Ultradian


  biological rhythm with a frequency of MORE than one in a 24hr cycle
• Example of Infradian


  Menstrual Cycle - governed by monthly changes in hormone levels with females, which govern ovulation.

  Seasonal Affective Disorder (SAD) - a depressive disorder with a pattern of onset that varies with the seasons -> mental illness according to DSM5.
• Example of Ultradian


  Sleep Cycle - 5 distinct stages of sleep that occurs 90 minutes and cycles throughout the course of the night. Each level is characterised by a different level of brain activity monitored with EEG.
• Menstrual Cycle - Infradian Cycle

  - governed by hormone levels.

  - cycle lasts approx 28 days.

  - during cycle, increased levels of hormone oestrogen causes ovary to develop an egg and release it.

  - after ovulation, progesterone causes the womb lining to grow thicker, readying body for pregnancy.

  - if pregnancy doesn't occur then egg is absorbed back into the body and womb lining leaves the body.
• Stern and McClintock


  AIM: some exogenous factors are believed to play a role when a women has her period, including idea that women's period synchronise when in regular company.

  SAMPLE: studied 29 women who had a history of irregular periods.

  METHOD: samples of women's pheromones (taken under armpit) was taken at various stages of women's cycles.

  samples were frozen with alcohol, then applied to another ppts lip.

  FINDINGS: 68% of women's cycles started to synchronise with the women whom the pheromone belonged to.

  CONCLUSION: exogenous factors play a greater role on biological rhythms (endogenous).
• SAD - Infradian


  - SAD is a depressive disorder where there's a seasonal pattern of onset.

  - similar to other types of depression with symptoms such as low mood, lack of activity etc.

  - sometimes referred to as 'winter blues' as it usually affects people around this season, when daylight hours become shorter.

  - referred as a circannual rhythm - may be due to differences in the sleep/wake cycle.

  - psychologists suggested that melatonin plays a part in onset of SAD during the night the pineal gland releases melatonin until there's light in the morning.

  - during winter, daylight hours reduced, increased melatonin production -> knock-on effect on serotonin (neurotransmitter).

  - serotonin has been linked to depression.
• Ultradian - Sleep Cycle

  - sleep cycle approx spans 90mins and occurs several times throughout the night.

  - each stage -> distinguished by different brain activity.

  - Stage 1 & 2: light sleep, where someone can easily be woken. waves begin to get slower and more rhythmic (alpha waves) and then even slower when sleep gets deeper (theta waves).

  - Stage 3 & 4: waves become higher in amplitude and even slower (delta waves)

  - Stage 5: (REM sleep) body is paralysed but brain activity speeds up in a manner that resembles the awake brain.

  - REM - rapid eye movement - eyes make fast and jerky movements in this stage.

  - lot of research suggests that REM sleep is when you experience dreams.
• Strength - research support

  - Support from the synchronicity of the menstrual cycle comes from McClintock

  - 29 women with a history of irregular periods gave samples of pheromones at different stages of their menstrual cycle. pads were used to collect this from armpits. these were then rubbed onto upper lips of other ppts.

  - 68% of women experienced changes to their cycle, suggesting that the menstrual cycle can be synchronised to that of other women supporting the role of exogenous factors.
• Weakness - McClintock's study subject to Confounding Variables

  - McClintock's study could have been subject to confounding variables.

  - e.g. there could have been many exogenous factors which influenced the women's menstrual cycles. e.g. diet, stress and lifestyle choices

  - similarly the study relied on women accurately reporting the onset and duration of their cycles

  - major disadvantage of research, implying that synchronisation only occurred by chance, rendering the result as not useful and invalid.
• Strength - McClintock's study provides evolutionary support

  - McClintock's study provides support for the evolutionary basis for menstruation.

  - e.g. our ancestors menstruated together it could've been an evolutionary advantage. new babies would have been part of a social group which cared for one another, enhancing survival.

  - supports the synchronicity of the menstrual cycle.
• Weakness - synchronisation is disadvantageous to evolution

  - some argue that synchronised menstruation would have been more of a disadvantage to evolution.

  - e.g. Schank argues that if all females had their cycles together, this would produce competition for best most healthy males.

  - suggests that no synchrony in menstrual cycles would have been more adaptive for survival and for passing on genes to offspring.