Infraradian And Ultraradian Rhythm

• •Infradian rhythm = A type of biological rhythm with a duration of over 24 hours.
• •Ultradian rhythm = A type of biological rhythm that lasts less than 24 hours (more than one cycle in 24 hours)
• –Menstrual cycle – infradian–Seasonal affective disorder (SAD) – infradian–Stages of sleep – ultradian–The basic rest activity cycle - ultradian
• Stages Of Sleep

  •One of the most extensively researched ultradian rhythms is the stages of sleep – the sleep cycle. Psychologists have identified five distinct stages of sleep (REM and four non-REM) that altogether span approximately 90-100 minutes.•Each stage of sleep has a different duration. A complete cycle consists of a progression through the four stages of non-REM sleep (stages 1-4) before entering a final stage of REM sleep, then the whole cycle stars again.•This is a cycle that repeats throughout the course of the night and therefore occurs more than once in every 24 hours.•
• Stages of Sleep

  • Stage 1 (4-5%)
  • Stage 2 (45-55%)
  • Stage 3 (4-6%)
  • Stage 4 (12-15%)
  • Stage 5 (REM sleep – 20-25%)
• Stage 1

  • Light sleep
  • Muscle activity slows down
  • Occasional muscle twitching
  • Person is easily woken
• Stage 2

  • Breathing pattern and heart rate slows
  • Slight decrease in body temperature
• Stage 3

  • Deep sleep begins
  • Brain begins to generate slow delta waves
  • Greater amplitude than earlier wave patterns
• Stage 4

  • Very deep sleep
  • Difficult to rouse someone
  • Rhythmic breathing
  • Limited muscle activity
  • Brain produces delta waves
• Stage 5 (REM sleep)

  • Rapid eye movement
  • Brainwaves speed up
  • Dreaming occurs
  • Muscles relax
  • Heart rate increases
  • Breathing is rapid and shallow
  • Body is paralysed
  • Brain activity speeds up significantly in a manner that resembles the awake brain
• Basic rest-activity cycle (BRAC)

  Ultradian rhythm
• Basic rest-activity cycle

  • Characterized by a period of alertness followed by a spell of physiological fatigue
  • Occurs across a 90-minute cycle which then recurs during the course of the day
• The human mind can focus for about 90 minutes, and towards the end of these 90 minutes, the body begins to run out of resources, resulting in a loss of concentration, fatigue and hunger
• Best performers in a study of violinists

  • Tended to practise for three sessions during the course of the day
  • Each session lasted no more than 90 minutes
  • There was a break between each in order to 'recharge'
• Kleitman (1969): 'Suggested that a similar 90-minute rhythm cycle continues during waking hours. He called this the Basic rest-activity cycle.'
• Menstruation cycle

  An example of an infradian rhythm which is governed by monthly changes in hormone levels that regulate ovulation
• Menstrual cycle

  1. Time between the first day of a woman's period, when the womb lining is shed, to the day before her next period

  2. Typically takes approximately 28 days to complete
• Ovulation

  1. Rising levels of the hormone oestrogen cause the ovary to develop an egg and release it

  2. Occurs roughly halfway through the menstrual cycle when oestrogen levels are highest

  3. Lasts for 16-32 hours
• After ovulation

  1. Levels of the hormone progesterone increase

  2. Helps the womb lining to grow thicker, readying the body for pregnancy

  3. If pregnancy does not occur, the egg is absorbed into the body and the womb lining comes away and leaves the body (the menstrual flow)
• Seasonal Affective Disorder (SAD)

  A depressive disorder which has a seasonal pattern of onset and is described and diagnosed in the DSM-5
• Symptoms of SAD

  • Persistent low mood
  • General lack of activity and interest in life
• Winter blues

  The symptoms of SAD are triggered during the winter months when the number of daylight hours becomes shorter
• Infradian rhythm

  A biological rhythm that occurs less frequently than 24 hours
• Lack of light in the morning

  Melatonin secretion process continues for longer
• Melatonin secretion process continuing for longer

  Knock-on effect on the production of serotonin in the brain
• Serotonin

  A chemical that has been linked to the onset of depressive symptoms
• Menstrual synchrony as found in Stern and McClintock's study

  Thought to have an evolutionary value
• Evolutionary value of menstrual synchrony

  • For our ancestors, it may have been advantageous for females to menstruate together and therefore fall pregnant at around the same time
  • This would mean that new-borns could be cared for collectively within a social group increasing the chances of the offspring's survival
• The validity of the evolutionary perspective on menstrual synchrony has been questioned
• If there were too many females cycling together within a social group

  This would produce competition for the highest quality males
• methodological issues with stern & mcclintock

  •For example, there may be other factors that change a woman’s menstrual cycle that act as confounding variables e.g. stress, changes in diet and exercise. Furthermore, the research typically involves small samples of women and relies on participants self-reporting the onset of their own cycle. Additionally, other studies have failed to find any evidence of menstrual synchrony in all-female samples.••we cannot strongly support the internal validity of this idea from the research as we cannot determine cause and effect.
• Research Support

  •Derment and Kleitman (1957) monitored the sleep patterns of nine adult participants in a sleep lab. Brainwave activity was recorded on an EEG and the researchers controlled for the effects of caffeine and alcohol. REM activity during sleep was highly correlated with the experience of dreaming, brain activity varied according to how vivid dreams were, and participants woken during dreaming reported very accurate recall of their dreams.••Replications of this investigation have noted similar findings, although the size of the original sample has been criticised.
• Real World Application

  •One of the most effective treatments for SAD is phototherapy. This is a lightbox that simulates very strong light in the morning and evening. It is thought to reset melatonin levels in people with SAD. This relieves the symptoms in up to 60% of sufferers.••This supports the importance of knowing about infradian rhythms and therefore the external validity of this theory#