infradian and ultradian rhythms

• Infradian Rhythm = One of 3 types of biological rhythms, with a frequency of one complete cycle occurring less than once every 24 hours. Such rhythms are entrained by endogenous pacemakers and exogenous zeitgebers. Notable examples of infradian rhythms include the menstrual cycle and SAD (seasonal affective disorder).
• McClintock et al (1998) demonstrated menstrual cycle synchronisation amongst 29 women who all had irregular periods. The pheromones from 9 of the women were collected through the use of a pad under the armpit, and then rubbed onto the upper lip of the remaining 20 women, corresponding to the specific days of their cycle. The researchers found that “recipients had shorter cycles when receiving axillary compounds producing by donors in the follicular phase of the menstrual cycle (+ 1.7 +/- 0.9 days) and longer cycles when receiving ovulatory compounds (+ 1.4 +/— 0.5 days).
• Seasonal affective disorder is an example of the influence of endogenous pacemakers on the circadian sleep-wake cycle. SAD is an infradian disorder caused by disruption to the sleep-wake cycle, and commonly occurs in the winter. Longer nights means that more melatonin is secreted from the pituitary gland, via the endocrine system, which changes the production of melatonin, leading to feelings of loneliness and depression
• Ultradian Rhythm = One of 3 types of biological rhythms, with a frequency of one complete cycle occurring more than once every 24 hours. A notable example are the stages of sleep, where a full sleep cycle takes 90 minutes to complete.
• Stages 1 and 2 represent the ‘sleep escalator’ where the participant can easily be awoken, stages 3 and 4 coincide with deeper and slower delta waves (compared to theta waves during the sleep escalator), whilst stage 5 represents REM sleep. REM sleep is closely associated with dreaming and characterised by movement inhibition and a sensory blockade. The stages of sleep have been demonstrated by Dement and Kleitman.
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  The stages of sleep have clearly been demonstrated = Dement and Kleitman (1957) studied 33 adults, Using EEG scans, the researchers found that “discrete periods of rapid eye movement potentials were recorded without 15 exception during each of 126 nights of undisturbed sleep”. Since participants were able to accurately recall their dreams when awoken during REM sleep, the assumption was made that dreaming is associated with REM sleep. Therefore, there is clear evidence supporting the idea of a distinct set of sleep stages.
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  Trevathan et al (1993) noted that he had found no evidence of menstrual synchronisation in the all-female participants used, which suggests that there are external (extraneous) variables which may affect the timing and duration of their menstrual cycles. McClintock et al. did not control for such extraneous factors e.g. smoking, physical activity and alcohol consumption. Therefore, this raises doubts about the strength of the influence of pheromones, as an exogenous zeitgeber which can entrain infradian rhythms.
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  Gloth et al (1999) found that, when treating sufferers of SAD with either Vitamin D supplements or broad-spectrum phototherapy, “all subjects receiving vitamin D improved in all outcome measures. The phototherapy group showed no significant change in depression scale measures”. Therefore, suggests phototherapy is ineffective in treating SAD. = phototherapy involves exposure to bright light in order to increase the rate the pineal gland secretes melatonin, this implies that melatonin and serotonin levels have little parts to play in SAD
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  The link between the pheromone release and animal behaviour has been extensively supported. For example, Luo et al (2003) studied the effects of pheromonal signals in the olfactory bulb of mice and concluded that “mammals encode social and 16 reproductive information by integrating vomeronasal sensory activity specific to sex and genetic makeup”. Therefore, this suggests that endogenous pacemakers have a critical role in the entraining of biological rhythms in animals, whose findings can then be generalised to humans.