Infradian and Ultradian cycles

• Ultradian rhythms

  • a type of biological rhythm that lasts less than 24 hours (more than one cycle in 24 hours)
• Infradian rhythms

  • a type of biological rhythm with a duration of over 24 hours
• Sleep Stages

  • ultradian rhythm
  • stage 1 - N1, moving from awake to sleep, can move suddenly (hyponic jerk), waves begin to slow down
  • stage 2 - N2, deeper sleep, harder to wake, body is relaxed, heart rate and body temperature are lowered, eyes are still, waves slow down even further
  • stage 3 - N£3, deepest sleep, very difficult to wake, body is at its most relaxed with heart rate at its lowest, slowest waves
  • stage 4 - REM, brain returns to active state passing back through N2 and N1, similar to wakefulness, characterised by rapid eye movement, associated with dreaming
• How long does each sleep cycle last?

  90 minutes
• What happens after one cycle has been accomplished?

  the cycle returns to N1
• How many cycles of the sleep stages to we go through per night?

  4-5
• The basic rest-activity cycle (BRAC) - Kleitman (1969)

  • conducted two studies, one with 33 participants and one with 9
  • used EEGs to record brain waves in sleep
  • suggested that 90 minute rhythm cycles continue during waking hours
  • suggested that humans can only concentrate for 90 minute cycles, followed by a spell of psychological fatigue
  • towards the end of the day the body begins to run out of resources - loss of concentration, fatigue and hunger
  • Ericsson et al (1993) found that the best performers in a study of violinists where those who practised for three sessions during the day, lasting no more that 90 minutes each and a break in between
• The menstrual cycle - infradian rhythms

  • FSH and LH are hormones which are released from the pituitary glland which causes follicles to release oestrogen
  • FSH helps to manage the menstrual cycle and will stimulate the ovaries to release eggs
  • LH stimulates testorone release and is released during ovulation stage
• Stern and McClintock (1998)

  • they studied 29 women with irregular periods
  • sample of pheromones were gathered from 9 of the women at different stages of their menstrual cycle via a cotton pad placed in their armpit
  • the pads were treated with alcohol and frozen, to be rubbed onto the upper lip of other 20 participants
  • on day one, pads from the start of the menstrual cycle were applied to all 20 women, on day two they were given a pad from the second day of the cycle
  • they found that 68% of women experienced changes to their menstrual cycle which brought them closer to the cycle of their odour donor
• Seasonal Affective Disorder

  • in most animals, annual rhythms are related to seasons, for example, migration in response to lower temperatures and decreased food sources in the winter
  • Magnusson found that some people, especially women, become severely depressed during the winter months
  • heart attacks are associated in winter
• Evaluation of Biological Rhythms

  • Tucker et al (2007) conducted a study and found there was significant differences between participants in terms of duration of each stage particularly in stage 3 and 4
  • study was controlled in a lab setting - good internal validity
  • individual differences - low external validity
  • undermines sleep cycles, ultradian cycles
  • Ericsson et al (2006) - supports ultradian, BRAC cycle
  • Stern and McClintock - supports infradian rhythms, menstrual cycle