Infradian rhythms and Ultradian rhythms Flashcards
Infradian rhythms (IR) - Menstrual Cycle
Governed by monthly changes in hormone levels which regulate ovulation.
During each cycle, rising levels of the hormone oestrogen cause the ovary to develop an egg and release it - ovulation.
After ovulation, the hormone progesterone helps the womb lining to grow thicker, readying the body for pregnancy.
If pregnancy doesn’t occur, the egg is absorbed into the body, the womb lining comes away and leaves the body - menstrual flow.
(IR) Although the menstrual cycle is an…
Endogenous system, evidence suggests that it may be influenced by exogenous factors, such as the cycles of other women.
(IR) A study by Kathleen Stern and Martha McClintock (1998) demonstrates…
How menstrual cycles may synchronise as a result of the influence of female pheromones.
(IR) McClintock’s pps
29 women with a history of irregular periods.
(IR) How were samples of pheromones were gathered?
From 9 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 8 hours to ensure that pheromones were picked up. The pads were treated with alcohol and frozen, to be rubbed on the upper lip of the other pps.
On day 1, pads from the start of the menstrual cycle were applied to all 20 women, on day 2 they were all given a pad from the 2nd day of the cycle, and so on.
(IR) McClintock’s results
Found that 68% of women experienced changes to their cycle which brought them closer to the cycle of their ‘odour donor’.
(IR) Seasonal affective disorder - SAD
A depressive disorder has a seasonal pattern of onset and is described and diagnosed as a mental disorder in DSM-5.
(IR) SAD’s symptoms
Persistent low mood with a general lack of activity and interest in life.
Referred to winter blues as symptoms are triggered during winter months when the number of daylight hours becomes shorter.
A particular type of infradian rhythm - circannual rhythm; subject to a yearly cycle.
Experience of SAD may be due to the disruption of the sleep/wake cycle and can be attributed to prolonged periods of daily darkness during winter.
(IR) Psychologists have hypothesised that the hormone melatonin is…
Implicated in the cause of SAD.
During the night, the pineal gland secretes melatonin until sawn when there’s 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.
Ultradian rhythms (UR) - stages of sleep.
5 stages with approximately a span of 90 minutes - cycle continuing throughout the course of the night.
(UR) Each of the stages is…
characterised by a different level of brainwave activity which can be monitored using an EEG.
(UR) Stages 1 and 2
‘Sleep escalator’ - light sleep where the person may be easily woken.
Beginning of sleep, brainwave patterns start to become slower and more rhythmic (alpha waves), becoming even slower as sleep becomes deeper (theta waves).
(UR) Stages 3 and 4
Delta waves - slower still and have a greater amplitude than earlier wave patterns; deep sleep or slow-wave sleep and difficult to rouse someone at this point.
(UR) Stage 5 - REM sleep
The body’s paralysed yet brain activity speeds up significantly in a manner that resembles the awake brain.
REM = rapid eye movement to denote the fast, jerky activity of the eyes under the eyelids at the point.
Research has suggested that REM activity during sleep is highly correlated with the experience of dreaming.
Weakness - methodological limitations of synchronisation studies
Criticisms have been made of early synchronisation studies and the methods employed.
Commentators argue that there are many factors that may affect change in a women’s menstrual cycle, including stress, changes in diet, exercise, etc., that might act as confounding variables. This means that any supposed pattern of synchronisation, as seen in s studies by McClintock and others, is no more than would have been expected to occur by chance.
In addition, research typically involves small samples of women and relies on pps self-reporting the onset of their own cycle.
Other studies failed to find any evidence of menstrual synchrony in all-female samples.