Biopsychology: Infradian And Ultradian Rhythmns Flashcards
What is an infradian rhythm
A type of biological rhythm with a frequency of less than one cycle in 24 hours, such as menstruation and seasonal affective disorder
What is an ultradian rhythm
- a type of biological rhythm with a Frequency of more than one cycle in 24 hours, such as the states of sleep
Outline the menstrual cycle as an example of an infradian rhythm
- governed by monthly changes in hormone levels which regulate ovulation
- typical cycle takes approx 28 days to complete (anywhere between 24-35 is normal)
- rising levels of the hormone oestrogen cause ovary to develop an egg + release it
- after ovulation, the hormone progesterone helps the womb lining to grow thicker for pregnancy
- if pregnancy does not occur, the egg is absorbed into the body + lining is shed
Outline research into the menstrual cycle
- although it is an endogenous system, evidence suggests it may be influenced by exogenous factors
- Stern + McClintock showed how menstrual cycles can synchronise as a result of female pheromones
- sample = 29 women with a history of irregular periods
- samples of pheromones gathered from 9 ppts at different stages of their cycles via cotton pad in armpit
- pad was worn for 8 hours minimum, then frozen + rubbed on upper lip of other ppts
- 68% women experienced changes to their cycle, brining it closer to that of their ‘odour donors’
Outline seasonal affective disorder (SAD) as an example of an infradian rythmn
- characterised by low mood and lack of activity and interest in life
- it is a particular type of infradian rhythm called a ‘circannual rhythm’ as it is subject to a yearly cycle
- can also be classed as a circadian rhythm as SAD may be a result of disruption to the sleep/wake cycle
- during winter the lack of light in the morning means the secretion process of melatonin continues for longer which is said to have a knock on effect on the production of serotonin in the brain
What is one of the most intensely researched ultradian rhythms
- the stages of sleep (the sleep cycle)
- psychologists have identified 5 distinct stages of sleep that collectively span around 90 mins (this cycle continues throughout the night)
- each stage is character by a different level of brainwave activity, monitored using an EEG
Outline stage one and two of the sleep cycle
- light sleep, where the person can be easily woken
- at the beginning of sleep, brainwave patterns start to become more slower + rhythmic, beckoning even slower as sleep deepens
Outline stages three and four of the sleep cycle
- involves delta waves which are slower still + have a greater amplitude than earlier wave patterns
- this is a deep sleep (or ‘slow wave sleep’) and it is difficult to rouse someone at this point
Outline stage 5 (REM sleep) of the sleep cycle
- body is paralysed yet brain activity speeds up significantly, resembling the awake brain
- REM stands for rapid eye movement, which can occur in this stage
-research suggests REM activity during sleep is correlated with dreaming
What are the three evaluation points for infradian and ultradian rhythms
- menstrual synchrony thought to have evolutionary value
- methodological limitations in synchronisation studies
- evidence supports idea of distinct stages in sleep
Outline ‘menstrual synchrony thought to have evolutionary value’ as an evaluation point for infradian and ultradian rhythms
-for our ancestors, it may have been advantageous for females to menstruate together + fall pregnant around the same time
- so newborns could be cared for collectively within a social group
- however, Schank - argues if too many females in a social group were cycling together it would produce competition for the highest quality male which would lower fitness of potential offspring
Outline ‘methodological limitations in synchronisation studies ’ as an evaluation point for infradian and ultradian rhythms
- critics argue that there are many factors that may effect the change in women’s menstrual cycle (stress,changes in diet etc)
- these may act as confounding variables + so there is no establishment of cause and effect within synchronisation studies
- also ,research involves small samples of women + relies on them self reporting on the onset of their cycle
Outline ‘evidence supports idea of distinct stages in sleep ’ as an evaluation point for infradian and ultradian rhythms
-Dement + kleitman - monitored sleep patterns of 9 ppts in a sleep lab
- brain wave activity was recorded on an EEG and researchers controlled for the effects of caffeine and alcohol
- REM activity during sleep was highly correlated with the experience of dreaming
