Infradian/Ultradian Rhythms

• Infradian rhythms - A bio rhythm which takes more than a day to complete.
• Examples of infradian rhythms 


  Menstruation, SAD and hibernation
• Ultradian Rhythms - bio rhythms which occurs many times within a 24hr period.
• Examples of Ultradian Rhythms 


  Stages of sleep and meal patterns.
• I - >24hrs

  C - 24hrs

  U - <24hrs
• IR- menstrual cycle lasts around 28 days, or one lunar month, and has been the subject of psych research due to the behavioural changes that are often linked to the cycle, such as increase in accidents, lower academic achievement, suicides and crime pre menstrual sandame (Dalton, 1964). Understanding biological rhythms has changed PMS from being a psychological disorder to a physiological event.
• Monthly changes in hormone levels regulate ovulation. A menstrual cycle is defined as the time between the first day of a woman's period up till the day before her next period. It can take between 24-35 days, but mostly cycles are 28 days long.
• Menstrual cycle - During each cycle, riding levels of oestrogen cause ovary to dev and release an egg (ovulation) after, progrestorone helps womb lining grow thicker in preparation for pregnancy. If pregnancy does not occur, the egg absorbed into body and lining is shed in menstrual flow.
• Menstrual cycle is and endegneous system that may be influenced by exogenous factors.
• Russell et al (1980) found that the menstrual cycle can be synchronized by exogenous cues, which explains the phenomenon that women who live together often have synchronized cycles. To demonstrate this the researchers used volunteer p's who did not live together, and transferred sweat from the upper lips of the P's to each other with the results that their cycles quickly became synchronized. They hypothesized that sweat must contain a pheromone, or chemical messenger, that resets the menstrual cycle.
• What did Stern and McClintock (1998) study?


  The effects of pheromones on women's menstrual cycles
• How many women were studied by Stern and McClintock (1998)?


  29 women
• What was the history of the women studied by Stern and McClintock (1998)?


  They had a history of irregular periods
• How many women provided pheromone samples in the study?


  9 women
• How long were the pheromone pads worn by the participants?


  At least 8 hours
• What treatment was applied to the pheromone pads after collection?


  They were treated with alcohol and frozen
• Where were the pheromones rubbed on the other participants?


  On the upper lip
• What procedure was followed for applying the pheromone pads in the study?


  • Pads from the start of the menstrual cycle were applied to all 20 women.
  • This process was repeated with pads from different points in the cycles.
• What percentage of women experienced changes to their cycle in the study?

  68%
• What was the effect of the pheromones on the women's cycles?


  It brought their cycles closer to that of their 'odour donor'
• What concept is suggested by the interaction of nature and nurture in the study?


  Female pheromones can synchronize menstrual cycles
• What are the key findings of Stern and McClintock (1998) regarding pheromones?


  • Pheromones can influence menstrual cycle synchronization.
  • 68% of women experienced changes in their cycles.
  • The changes brought their cycles closer to their 'odour donor'.
• Seasonal affective disorder (SAD) is an infradian rhythm that lasts about a year. It can also be classed as a circadian rhythm as SAD may be due to the disruption of the sleep/wake cycle which may be attributed to prolonged periods of darkness during winter.
• Features of SAD include depression in winter months that improves to normal mood in summer months. It is described and diagnosed as a mental disorder in DSMV. SAD is believed to be caused by low light levels in winter, especially as an effective treatment for the disorder is to spend time exposed to bright light from a light box during the winter months.
• Psychologists have hypothesised that the hormone melatonin is implicated in the cause of SAD.
• Dusing night, the pineal gland secrets melatonin until dawn, when light increases. As there is lack of light in the morning, during winter the secretion of melatonin continues for longer. Ths may have knock-on effect on production of seretonjn which has been linked to onset of depression.
• Ur - The sleep cycle (sleep stages) is an ultradian rhythm. Five distinct stages of cycle have been identified, which span about 90 minutes, and the cycle com through the night.
• UR - Each stage of sleep is characterised by different brain wave activity.
• UR - Stages 1 and 2 - 'light sleep' where a person may be easily woken. In stage 1, brain waves are high frequency and have a short amplitude, also may experience hypnic jolts and or hypnogenic hallucinations. These are alpha waves. In stage 2, the alpha waves continue but there are occasional random changes in pattern called sleep spindles.
• UR - Stages 3 and 4 - 'deep sleep' or 'slow wave sleep'. The brain waves are delta waves with lower frequency and higher amplitude. It is difficult to wake someone at this point
• UR - Stage 5 (REM sleep) The body is paralysed yet brain activity closely resembles that of the awake brain. During this time, the brain produces theta waves and the eyes occasionally move around, thus rapid eye movement (REM). Dreams are most often experienced during REM sleep, but may also occur in deep sleep. Body is said to be paralysed.
• AO3 - Basic Rest-Activity Cycle (BRAC) is a 90-minute cycle suggested by Kleitman (1969) characterised by periods of alertness followed by physical fatigue, which occurs during the day. often observed in students and workers, that people find it difficult to concentrate for more than 90 minutes without having a break.
• Ericsson et al (1993) found that the best violinists tended to practice for three sessions in a day, with a break between each, and the sessions lasting no more than 90 minutes.
• Whst type of rhythm is BRAC


  Ultradian because it's an under 24 hour cycle 
• S of menstrual cycle - thought to have an evolutionary basis. For ancestors it may have been an advantage to menstruate at same time and therefore fall pregnant at same time so newly born could be cared for collectively increasing chances of survival.
• W of menstrual cycle - Synchronisation studies may be flawed. Studies such as McClintock's may have had confounding variables such as stress, diet changes, exercise. All of which can have an effect on menstrual cycles. Therefore, synchronisation patterns may have occurred by chance. Also, the samples are small and rely on self-reports about cycles
• Evaluation of sleep cycle - Dement and Kleitman (1957) monitored the sleep patterns of 9 P's in a sleep lab. Caffeine and alcohol were controlled. Their brain wave patterns were observed with an EEG. REM activity was highly correlated with dreaming, brain activity varied with how vivid the dreams were, and P's woken during dreaming reported very accurate recall of the dream. Replications have had similar findings. These findings suggest that REM is an important part of the ultradian sleep cycle. (lab... Not represent real sleep patterns)
• S of sleep cycle - Practical application. Phototherapy is a treatment used for SAD where a light box simulates very strong light in the morning and evening, which is thought to reset melatonin levels. Up to 60% of symptoms may be relieved in sufferers (Eastman et al 1998)
• W of sleep cycle - Placebo study found a 30% reduction in symptoms which casts doubt on the chemical influence of light therapy.