Lesson 12- Infradian and Ultradian rhythms Flashcards
ultradian rhythms
last fewer than 24 hours, found in human sleep patterns, cycle alternates between REM and NREM and consists of 5 stages
starts at light sleep, progresses to deep sleep, then REM sleep where brain waves speed up and dreaming occurs, repeats itself every 90 mins throughout the night
research using eeg has highlighted distinct brain wave patterns during different stages of sleep
1 and 2- light sleep stages, brainwave patterns become slower and more rhythmic, starting with alpha waves progressing to theta waves
3 and 4- deep sleep, slow wave sleep stages, difficult to wake, slower delta waves
5- rem, dream sleep, body is paralysed, brain activity resembles that of an awake person
BRAC
basic rest activity cycle
-kleitman 1969, 90 minute cycle found during sleep
during the day rather than moving through sleep stages we move progressively from a state of alertness into psychological fatigue
-research suggests humam mind can focus for about 90 mins and towards the end the body begins to run out of resources, results in loss of concentration, fatigue, hunger
ultradian research
-dement and kleitman 1957
brain activity of 7 males and 2 females recorded with EEG in sleep lab, 5 in detail
effects of alcohol and caffeine controlled
reported distinct patterns in EEG patterns during each sleep phase and than rem sleep was highly correlated with dreaming, also found by waking pps using doorbell during rem period that brain activity varied depending on how vivid the dreams were (asked to describe)
-has small sample size
-findings have been repliated since, reliable link
ultradian evaluation
-research support from dement and kleitman for stages of sleep, supports ultradian rhythms
-Ericsson et al 2006, studied a group of elite violinists and found that among this group practice sessions were limited to 90 mins at a time, frequently napped to recover from practice, best ones napped more, same pattern found among musicians, athletes, chess players and writers, study shows that ultradian rhythms can help explain for max performance 90 mins is best, supports brac and has practical applications
-individual differences in sleep patterns, cant generalise
Tucker et al 2007, suggests many individual differences in sleep patterns which are biologically determined and may even be genetic in origin, pps were studied over 11 consecutive days and nights in lav experiment, researchers assessed sleep duration, time to fall asleep, amount of time in each sleep stage, found differences in all characteristics, study shows need caution when generalising how ultradian rhythms work with regards to stages of sleep, people who dont go through stages the same are not abnormal
infradian rhythms
span a period longer than 24 hours, may last weeks, months, or even a year, menstrual cycle and SAD
menstrual cycle
monthly, regulated by hormines that either promote ovulation or stimulate the uterus for fertilisation
ovulation occurs roughly half way through the cycle, when oestrogen levels are at their highest, usually last for 16-32 hours
after ovulatory phase progesterone levels increase in preparation for the possible implantation of an embryo in the uterus
usual menstrual cycle is around 28 days, considerable variation, some women experience short cycle of 32 days, others experiencing longer cycles up to 36 days
endogenous system but can be influenced by exogenous factors
SAD
seasonal variation in mood, some people become depressed in winter, governed by yearly cycle, psychologists claim that melatonin which is secreted in pineal gland during night is partly responsible, lack of light during winter months results in longer period of melatonin secretion, linked to depressive symptoms
menstrual evaluation
-research suggests to some extent menstrual cycle governed by exogenous zeitgebers, Reinberg 1967 examined a woman who spent three months in a cave with only a small lamp to provide light, noticed her menstual cycle shortened from the usual 28 days to 25.7 days, suggests lack of light affected cycle, effect of external factors
-Russell et al 1980 found that menstrual cycles became synchronised with other females through odour exposure, in one study sweat samples from one group were rubbed onto the upper lip of another group, despite two groups being separate, menstrual cycles synchronised, suggests cycle can be affected by pheromones, need to take into account external factors, holistic approach opposed to reductionist only looking at endogenous
-evolutionary psychologists claim synchronised menstrual cycle provides evolutionary advantage for groups of women, synchronisation of pregnancies means childcare can be shared among multiple mothers
-important regulators of behaviour, Penton-Volk 1999 found women expressed a preferenced for femenised faces at the least fertile stage of their menstrual cycle and more masculine face at the most fertile point, indicates womans sexual behaviour is motivated by their cycle/rhythm, relates to human behaviour
-methodological limitations, many factors may effect/change menstrual cycle-stress, changes to diet, exercise, act as confounding variables, any patterns would have occurred by chance, could explain failure to replicate findings
SAD evaluation
-support for role of melatonin, Terman 1988 found rate of sad is more common in northern countries where the winter nights are longer, affects roughly 10% of people living new hampshire and only 2% in southern Florida, suggests sad affected by light
-practical applications, most effective treatment is phototherapy-lightbox that stimulates very strong light in the morning and evening, thought to reset melatonin levels which in turn regulates serotonin levels and improves symptoms in upto 60% of sufferers (Eastman. et al 1998), supports cuase specifically being reduction in light leading to biochemical reactions
-same study found 30% participants showed improvement when treated with a placebo, suggests effectiveness of phototherapy could be partly due to placebo effect
-increased understaning undoubtedly leads to development of more effective treatments
