ULTRADIAN RHYTHMS

~The Sleep Cycle~

• 5 stages of sleep

• Sleep cycle spans 90 minutes, and repeats

~Non-Rapid Eye Movement (NREM) Sleep~

Stage 1 (NREM-1) & Stage 2 (NREM-2)

• ‘Light sleep’ stages

• Individual can be easily woken

• At the beginning of sleep, brainwave patterns become slower (alpha waves)

• As sleep becomes deeper, brainwave patterns become even slower (theta waves)

Stage 3 (NREM-3) & Stage 4 (NREM-4)

• ‘Deep sleep’ or ‘Slow wave sleep’

• Individual is difficult to wake

• Brainwave patterns are very slow (delta waves)

~Rapid Eye Movement (REM) Sleep~

Stage 5 (REM)

• Brainwave patterns speed up significantly and resemble the awake brain

• The body is paralysed

• The eyes move in a fast and jerky action under the eyelids

• Dreaming occurs

EVALUATION

Research Support:

→ IMPROVED UNDERSTANDING

• One strength of research into ultradian rhythms is that it has improved understanding of age-related changes in sleep.

• Sleep scientists have observed that slow-wave sleep (SWS) reduces with age. Growth hormone is mostly produced during SWS; therefore this is reduced in older people.

• According to Eve van Cauter et al (2000), the resulting sleep deficit may explain various issues in old age, such as reduced alertness. In order to increase SWS, relaxation and medication may be used.

• This suggests that knowledge of ultradian rhythms has practical value.

Conflicting Evidence:

→ INDIVIDUAL DIFFERENCES

• One limitation of ultradian rhythms is there is significant variation between people.

• Tucker et al (2007) found large differences between participants in terms of the duration of each sleep stage, particularly stages 3 and 4.

• Tucker et al suggest that these differences are likely to biologically determined.

• This makes it difficult to describe ‘normal sleep’ in any meaningful way.