ultradian rhythms

• how long do ultradian rhythms last?

  approximately less than 24 hours
• what is an example of an ultradian rhythm?

  Sleep cycles
• what are the two cycles in sleep?

  NREM and REM
• sleep lab studies - ultradian rhythms

  the participants are wired up to a polysomnograph (to detect pulse, body temp, blood pressure). the participants then go to sleep in the lab, and their sleep is recorded. the participants usually spend several nights in the sleep lab. Dement et al studied 9 participants for 61 nights, finding the mean time to be 92 minutes for NREM/REM cycles.
• evaluation of sleep lab studies - ultradian rhythms

  Polysomnographs have been indispensable in studying sleep, they are controlled studies, giving objective and unbiased findings.

  the findings are reliable, having been replicated many times.

  however sleeping in the lab, is somewhat artificial therefore sleep patterns may differ under normal conditions
• animal studies - ultradian rhythms

  Jouvet (1967) lesioned the raphe nucleus in cats and found that this resulted in sleeplessness. lesioning the locus coeruleus resulted in loss of REM sleep. these appear to be the endogenous factors involved in the REM/NREM ultradian rhythm.
• What have animal studies provided evidence for regarding ultradian rhythms?

  They suggest that the raphe nuclei and locus coeruleus control the NREM/REM cycle.
• Why are animal studies considered valuable in the context of ultradian rhythms?

  They provide invaluable evidence for understanding the mechanisms controlling the NREM/REM cycle.
• What is a major criticism of generalizing findings from animal studies to humans?

  Many believe that animal studies cannot be generalized to humans due to differences in brain structure.
• What is a concern regarding the effects of lesioning the raphe nuclei and locus coeruleus in animal studies?

  There is a possibility that observed effects could be due to the trauma of surgery or damage to other brain areas.
• What ethical concerns are associated with animal studies in the context of ultradian rhythms?

  There are ethical concerns regarding the treatment and welfare of the animals used in the studies.
• What are the key factors influencing the evaluation of animal studies on ultradian rhythms?

  • Evidence of raphe nuclei and locus coeruleus in controlling NREM/REM cycle
  • Difficulty in generalising findings to humans
  • Potential trauma effects from surgery
  • Ethical concerns regarding animal welfare