Infradian and Ultradian Rhythms Flashcards
What is an Infradian Rhythm
A type of biological rhythm which takes longer than 24 hours to complete
Includes Menstruation and Seasonal Affective Disorder
Infradian Rhythm - Menstrual Cycle
A typical cycle takes approximately 28 days to complete
During each cycle, rising levels of the hormone, oestrogen caused the ovary to develop an egg and release it
After ovulation, the hormone progesterone helps the womb lining to grow thicker, breathing the body for pregnancy
If pregnancy does not occur, the egg is absorbed into the body, the womb lining comes away and it leaves the body
Menstrual Cycle - Stern and McClintock (1998)
Demonstrated how menstrual cycles may synchronise as a result of the influence of female pheromones
Involved 29 women with a history of a regular periods
Samples of pheromones were gathered from nine of the women at different stages of their menstrual cycles via a cotton pad placed in their armpit
The pads were worn for at least eight hours to ensure the pheromones were picked up
The pads were treated with alcohol and frozen to be rubbed on the upper lip of the other participants
On day, one pads from the start of the menstrual cycle were applied to all women
On day two, they were all given a pad from the second day of the menstrual cycle and so on
Found that 68% of women experience changes to the cycle which brought them closer to the cycle of their odour donor
Infradian Rhythm - Seasonal Affective Disorder (SAD)
A depressive disorder with a seasonal pattern of onset
Main symptoms are a persistent low mood with a general lack of activity and interest in life
Symptoms are triggered during the winter months when the number of daylight hours becomes shorter
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)
Psychologist have hypothesise that the hormone melatonin is implicated in the cause of SAD
During the night, the pineal gland secretes melatonin until dawn when there is an increase in light
During winter, the lack of light in the morning means this secretion process continues for longer
This is thought to have a knock on effect on the production of serotonin in the brain, a chemical that has been linked to the onset of depressive symptoms
What is an Ultradian Rhythm
A type of biological rhythm which takes less than 24 hours to complete
Includes the stages of sleep
Describe the stages of sleep
Stage 1 + 2 -
Light sleep
Person can be easily woken
Brainwave patterns start to become slower and more rhythmic (alpha waves)
Brainwave patterns become even slower as sleep becomes deeper (theta waves)
Stages 3 + 4 -
Deep sleep
Person is difficult to rouse
Brainwave patterns are even slower (delta waves) and have a greater amplitude than earlier patterns
Stage 5 -
REM sleep
Body is paralysed
Brain act activity speeds up in a manner that resembles the awake brain
Fast, jerky activity of the eyes under the eyelids
Research has suggested that REM activity is highly correlated with the experience of dreaming
Evaluation (STRENGTH/WEAKNESS) - Menstrual Cycle
Menstrual synchrony is thought to have an evolutionary value
For our ancestors, it may have been advantageous for females to menstruate together and therefore be pregnant around the same time meaning newborns could be cared for collectively in increasing the chance of survival
Schank (2004)
Questioned the validity of the evolutionary perspective
Argued if there were too many females cycling together, this would produce competition for the highest quality males lowering the fitness of potential offspring
The avoidance of synchrony would appear to be the most adaptive evolutionary strategy and therefore, naturally selected
Evaluation (WEAKNESS) - Methodological Limitations in Synchronisation Studies
Criticisms have been made of early synchronisation studies and the methods employed
Argued there are confounding variables that may affect a woman’s menstrual cycle including stress, changes in diet or exercise
research involves small samples of women and relies on participants self reporting the onset of their own cycle
Evaluation (WEAKNESS) - Animal Studies on Pheromones
Evidence for the effect in human behaviour remains speculative and inconclusive
Evaluation (STRENGTH) - Practical Application for SAD
One of the most effective treatments for SAD is phototherapy
This is a light box that simulates very strong light in the morning and evening
It is thought to reset melatonin levels in people with SAD
This relief symptoms in up to 60% of sufferers - Eastman et al (1998)
A placebo effect of 30% was recorded in the same study
This cast doubt on the chemical influence of phototherapy
Evaluation (STRENGTH) - Evidence supporting Stages of Sleep
Dement and Kleitman (1957)
Monitored the sleep patterns of nine adult participants in a sleep lab
Brainwave activity was recorded on an EEG and the researcher controlled for the effects of caffeine and alcohol
REM activity during sleep was highly correlated with the experience of dreaming brain act activity varied according to how vivid dreams were and participants woken during dreaming reported very accurate recall of their dreams
Replications of this investigation have noted similar findings, though the small size of the original sample has been criticised
Suggest REM sleep is an important component of the sleep cycle
