Biopsych: Ultradian and Infradian rhythms Flashcards
What are ultradian rhythms?
take less than 24 hours e.g., the sleep-wake cycle. Psychologists have identified 5 stages of the sleep cycle which span for approx 90 mins. The cycle continues throughout the course of the night, each stage is characterised by a different level of brainwave activity which can be monitored using an EEG.
What are the 5 stages of the SWC?
Stages 1 and 2 – referred to as the sleep escalators, brain waves become slower as sleep becomes deeper alpha and theta waves.
Stages 3 and 4 – characterised as deep sleep, delta waves are slow and have a great amplitude.
Stage 5 – REM- dreaming, the body is paralysed but brain activity resembles an awake brain.
What’s the basic rest-activity cycle (BRAC)?
is a psychological arousal mechanism in humans proposed by Kleitman, hypothesised to occur during both sleep and wakefulness. Empirically, it’s an ultradian rhythm of approx 90 mins (80-120 mins) characterised by different levels of excitement and rest.
What are Infradian rhythms?
has a duration of over 24 hours – may occur weekly, monthly or annually e.g., the menstrual cycle and seasonal affective disorder (SAD).
Example of Infradian rhythms
Menstrual cycles
What’s an Menstrual cycle?
a monthly infradian rhythm which is regulated by hormones that either promote ovulation it stimulate the uterus for fertilisation. Ovulation occurs roughly halfway through the sleep wake cycle when oestrogen levels are at their highest, and usually last for 13-62 hours. After the ovulating phase, progesterone levels increase in preparation for the possible implant of an embryo in the uterus. It’s also important to note that although the usual menstrual cycle is 28 days there’s considerable variation with some women experiencing a short cycle of 23 days and others up to 36 days.
What’s the role of exogenous zeitgebers?
Stern and McClintock (1988) studied 29 women with irregular periods. Pheromones were taken from some at different stages in their cycles via a cotton pad under their armpits. Fuses pads were cleaned with alcohol and later rubbed on the upper lips of the other ppts. 68% of women experienced changes to their cycle which brought them close to the cycle of their ‘odour donor.’ This suggests that the menstrual cycle can be influenced by exogenous factors, such as the cycles of other women.
What’s Seasonal Affective Disorder (SAD)
a mood disorder which results in feelings of depression normally brought upon by changes in the seasons. The majority of individuals that experience SAD show symptoms in the winter months making them feel lower in mood and lacking in energy. In rare cases, SAD can occur in the spring and summer months, which can result in irritability and difficulty sleeping. SAD is an infradian rhythm called circannual as the cycles lasts longer than 24 hours to complete. Melatonin located in the pineal gland is predicted to be linked to SAD. During night melatonin is secreted when daylight increases. Dying the winter, the lack of light in the mornings means melatonin is secreted for longer.
4 AO3 points for Ultradian and Infradian rhythms?
+Strength of research into infradian rhythms
+Research evidence for stages of sleep
-Limitation of theories of sleep cycles
-Methodological limitations of research into menstrual cycles
(+AO3) What’s a strength of research into infradian rhythms?
Developments of treatments for SAD. Phototherapy: light box stimulates strong light in the morning and evening resets melatonin levels. Relieves symptoms in 60% of sufferers (placebo effect applies here).
(+AO3) What’s the research evidence for stages of sleep?
Dement and Kleitman – sleep patterns of 9 adults using EEGs. Found distinct wave patterns, especially in REM. REM activity highly correlated with experiences of dreaming.
(-AO3) What’s the limitation of theories of sleep cycles?
Big individual differences in sleep patterns. Environmental influences such as room temp impacts patterns. But when measured in controlled lab, time taken to fall asleep and time of each stage varied between ppts suggests patterns are flexible and maybe influenced by biological/ genetic factors.
(-AO3) What are the methodological limitations of research into menstrual cycles?
Many factors impact menstrual cycles – stress, patterns, exercise etc. Extraneous variables – changed in patterns msg be due to chance. Small sample provides issues with generalisability. Research also relies on self-report and so, the study lacks validity.
