Ultradian rhythms

• What is an ultradian rhythm?

  • Biological rhythms with a frequency of less than 24 hours, such as the multiple cycles of the sleep stages
  • These altogether span approximately 90 minutes and the cycle continues throughout the course of the night
  • Each stage is characterised by a different level of brainwave activity
• What are the stages of sleep?

  • Stage 1 and 2 - light sleep, alpha waves are active with high frequency and a short amplitude. These continue into stage 2 but have occasional random changes called sleep spindles
  • Stages 3 and 4 - know as deep sleep or slow wave sleep (SWS), with delta waves that have a lower frequency and higher amplitude
  • Stage 5 - body is paralysed yet brain activity closely resembles an awake brain, producing theta waves and eyes can move around. Dreams are most often experienced during this stage
• What is the basic rest activity cycle?

  • 90 minute cycle during the day moving progressively from a state of alertness to a state of physiological fatigue
  • Body runs out of resources, leading to loss of concentration, fatigue and hunger
  • Ericsson et al. (1993) found that elite violinists' practice sessions were limited to no more than 90 minutes
  • They also frequently napped to recover from practice, same pattern was discovered in chess players, athletes, writers, etc.
• What is one strength of ultradian rhythms?

  • Improved understanding: sleep scientists have observed that slow-wave sleep reduces with age, as the growth hormone produced is reduced in older people
  • Cauter et al. (2000) suggests that the resulting sleep deficit may explain various issues in old age such as reduced alertness
  • To increase SWS relaxation and medication may be used, showing the knowledge of ultradian rhythms has practical value
• What is one limitation of ultradian rhythms?

  • Individual differences: there is significant variation between people's stages
  • Tucker et al. (2007) found large differences between ppts. in terms of the duration of each sleep stage, particularly 3 and 4
  • They suggested the differences were likely to be biologically determined, making it difficult to describe 'normal sleep' in any meaningful way