Biological rhythms: Ultradian rhythms + Evaluation

Ultradian rhythms

Frequency of more than one cycle in 24 hours, such as stages of sleep

Stages of sleep

5 distinct stages, span 90 minutes. Stage 1 to 5 (REM). Brain activity changes. Cycle repeats itself during the night

Stage 1 and 2

Alpha waves and sleep spindles

Stage 3 and 4

Deep sleep, delta waves

Stage 5

REM sleep, theta waves.

Supporting research: Dement and Kleitman 1957

• 9 participants, using EEG in sleep lab, found distinct stages of NEEM and REM sleep, repeating themselves across the night.

• Dreaming more likely to be reported when woken from REM rather than NREM

Metholodical issues

-Sleep lab studies may control extraneous variables (noise) but doesn't represent ordinary sleep patterns.

+Distinct cyclical pattern of brain activity confirmed in replications, high reliability, validity.

+EEG is objective.

Real life applications:

+improved understanding: SWS reduces with age, explains issues in old age. (reduced alertness, daytime naps)

Individual differences

-Differences found in duration of each sleep stage, particularly 3 and 4. Low external validity.