ultradian rhythms

• sleep cycle:

  5 stages spanning approx 90mins, characterised by different levels of brainwave activity monitored through EEG

  stage 1+2: light sleep, stage 1: brain waves high frequency + short amplitude (alpha waves), stage 2: same + occasional random changes in patterns (sleep spindles)

  stage 3+4: deep sleep/ slow wave sleep (SWS) - brains aves = delta waves with lower frequency + higher amplitude, difficult to wake

  stage 5 (REM sleep): body paralysed, brain activity resembles that of awake brain - theta waves + eyes occasionally move around (REM), dreams most often now (or in deep sleep)
• evaluations

  • S: improved understanding of age-related changes in sleep: sleep scientist observed SWS reduces with age – growth hormone mostly produced during SWS therefore reduced in older people. Cauter et al: resulting sleep deficit may explain various issues in old age (reduced alertness) – relaxation + medication may be used - knowledge has practical value
• evaluations

  • W: significant variation between people: Tucker et al: differences are likely to be biologically determined - difficult to describe ‘normal sleep’ in a meaningful way