Infradian & Ultradian rhythms

• An infradian rhythm takes longer than a day to complete. The female menstrual cycle is an example, as changes in hormones that govern ovulation takes about 28 days to complete
• Stern & McClintock method 1-

  -Study on 29 females with history of irregular periods

  -Samples of phermones were gathered from 9 of women different stages in cycle by placing cotton pad in armpit

  -Pads worn for 8 hours, then treated with alcohol and frozen

  -On day 1, pad from start of cycle were rubbed on upper lip of 20 ppts

  -Day 2, they were given a pad from second day of cycle and so on
• Stern & McClintock results-

  -Found that 68% of ppts experienced changes to their cycles, which bought them closer to cycle of pheromone donor.

  -They demonstrated how menstrual cycles may synchronise due to influences of female pheromones
• Strength- Synchronisation can be adaptive

  -In the EEA, females menstruated together, there was greater chance they would fall pregnant and have offspring at similar time

  -Meaning that new borns could be cared for collectively, increasing offspring survival
• Strength- Synchronisation can be adaptive HOWEVER:

  -Been argued that this evolutionary perspective lacks validity

  -Schank suggests that if too many females had synchronised cycles it would increase the competition for highest quality males and potentially lower the fitness of any offspring

  -Suggests avoidance of synchronicity would be most adaptive strategy
• Weakness- Methodological issues

  -Firstly, there are several factors that can affect a women's menstrual cycle, including stress, diet and exercise. These could act as confounding variables

  -Many studies have used small sample of women and relies on self report techniques for the onset of their own cycles
• Seasonal affective disorder (SAD) -

  -A depressive disorder which follows seasonal patterns, described and diagnosed as a mental disorder in DSM-V

  -Similar symptoms to other forms of depression; persistent low moods and general lack of activity and interest in life

  -Often described as winter blues as symptoms are triggered during winter months
• Seasonal affective disorder (SAD)- Hormones

  -Has been hypothesised that hormone melatonin is implicated in cause of SAD

  -During the night, pineal gland secretes hormone melatonin until there is an increase in light

  -During winter, process continues for longer because dawn is later, thought to have knock on effect to production of serotonin
• Strength of SAD- Lead to improvements in treatment

  -One of the most effective treatments for SAD is phototherapy

  -This is light box that stimulates strong light in morning and evening and thought to work by resetting melatonin levels

  -Eastman found it relieves symptoms in 60% of people
• Ultradian rhythms-

  -Occur more than once every 24 hours

  -Example, stages of sleep
• Stages of sleep-

  Stage 1- light sleep, easily awakened

  Stage 2- eye movement, brain waves slowing

  Stage 3- delta waves begin to appear

  Stage 4- deep sleep, difficult to wake up

  REM stage- breathing becomes more rapid & irregular
• Stages of sleep brain waves-

  Stage 1 - small, irregular

  Stage 2- sleep spindle

  Stage 3- delta waves appear

  Stage 4- mostly delta

  REM- rapid, somewhat irregular
• Stage 1-

  -Brain wave patterns start to become slower and more rhythmic (theta waves)
• Stage 2-

  -Light sleep where person is easily woken
• Stages 3 and 4-

  -Delta waves appear, which are slower still and have greater amplitude

  -Deep sleep, and is difficult to wake someone up at this point
• REM sleep-

  -Body is paralysed, but brain activity speeds up

  -Highly correlated with experience of dreaming

  -REM stands for rapid eye movement and eyes move jerkily under eyelids
• Strength of sleep cycle - Studies

  -Several studies that have found that REM sleep is highly correlated with dreaming and that REM is an important component of sleep cycle
• Strength of sleep cycle- Dement and Kleitman study

  -They monitored brain waves on 9 adult ppts in sleep lab

  -Brain wave activity was recorded on EEG and researchers controlled effects of caffeine and alcohol

  -REM activity during sleep was strongly correlated with dreaming, brain activity varied depending how vivid dream were and when ppts were woken during dreaming