Ultradian Rhythms

• (AO1) Define ultradian rhythms

  Occur more than once a day
• (AO1) What does the cycle alternate between? + explain

  REM (rapid eye movement) and NREM (non rapid eye movement)

  Consists of 5 stages

  Complete sleep cycle = 4 stages of NREM and 1 stage of REM. This repeats itself every 90 minutes throughout the night.

  Research using EEG has highlighted distinct brain wave patterns during different stages of sleep.
• (AO1) Explain stages 1 - NREM

  This is the lightest stage of sleep, lasting for a few minutes.

  
  

  It is the transition period between wakefulness and sleep.

  
  

  During this stage, the body begins to relax, and there may be slow eye movement.

  
  

  The brain waves become slower, and people may experience the sensation of "falling" or muscle jerking.
• (AO1) Describe stages 2 - NREM

  
  

  In this stage, the body enters a deeper state of relaxation, and sleep spindles (short bursts of rapid brain activity) appear.

  
  

  The heart rate & breathing rate slow + body temperature drops.

  
  

  This stage typically lasts for about 20 minutes and represents the longest period of sleep.
• (AO1) Explain stage 3 - NREM

  This is a deep sleep stage, characterised by slow delta waves.

  
  

  It is difficult to wake someone from this stage.

  
  

  It is important for physical restoration, as the body focuses on repairing and regenerating tissues, strengthening the immune system, and promoting growth and development.
• (AO1) Explain stage 4 - NREM

  This is the deepest stage of sleep, where delta waves dominate.

  
  

  Waking up from this stage can lead to feelings of disorientation.

  
  

  This stage is crucial for physical recovery & is believed to support cognitive functioning, including memory consolidation.
• (AO3) Explain stage 5 - REM

  After completing the other stages, the cycle moves into REM sleep, where rapid eye movement occurs, and brain activity becomes more similar to wakefulness.

  
  

  During REM sleep, the most vivid dreaming takes place.

  
  

  REM sleep is thought to play an essential role in emotional regulation, memory consolidation and learning.

  
  

  The body is effectively paralysed during this stage to prevent acting out dreams.
• (AO3) L - Methodological issue

  Point: Methodological issues in studying UR is the use of lab settings.

  
  

  Evidence: In sleep clinics using EEGs, self reports of sleep duration can be unreliable, with ppts often reporting less sleep, especially if fatigue or waking from deep sleep. Lab studies also control behaviour, which may alter natural sleep patterns.

  
  

  Evaluate: While lab settings offer precise measurements, they reduce ecological validity, as behaviour may change due to participants' awareness of being observed, limiting the generalisability of the findings.
• (AO3) Individual differences

  Point: Individual differences, such as those found by Tucker, highlight variability in sleep cycles.

  
  

  Evidence: Tucker's research found significant differences in sleep cycle length and the amount of sleep (stage 3 and 4) among healthy 22-40 year olds. Differences in alertness & the time needed to sleep were also observed. As people age, they tend to become more alter in the morning and need less sleep.

  
  

  Evaluate: This highlights that sleep patterns can vary widely, suggesting the importance of considering individual differences when studying UR. The Watcher hypothesis provides an evolutionary explanation for why older people may need less deep sleep, as they have evolved to stay more alert to guard against threats.
• (AO3) CS - Randy Gardner

  Point: Case studies like RG show that humans can control and change their UR.

  
  

  Evidence: Stayed awake for 11 days. Afterwards only slept for 15 hours and recovered 70% of stage 4 sleep, 50% of REM, and little of the other stages. Suggests the body prioritises key stages when sleep is disrupted and shows how quickly rhythms return to normal.

  
  

  Evaluate: However, being a CS, there are issues with generalisability. RG was a student watched by other students, which may have affected his behaviour and sleep recovery. Thus, CS usefulness is limited.