Biological Rhythms: Ultradian rhythms

What are ultradian rhythms?

A type of biological rhythm with a frequency of more than 1 cycle in 24 hours

What is an example of an ultradian rhythm?

The sleep cycle

What is the sleep cycle?

• Stage 1+2 - Light sleep where the person is easily awoken, In stage 1, brain waves are high frequency and short amplitude (aka alpha waves). In stage 2, the alpha waves continue but there are occasional random changes in pattern called sleep spindles

• Stage 3+4 - Deep sleep or slow wave sleep. Brain waves are delta waves with lower frequency and higher amplitude. Difficult to wake someone here.

• Stage 5 - REM sleep, Body is paralysed but brain activity resembles an awake brain, brain produces theta waves and eyes occasionally move around (rapid eye movement), Dreams are experienced during REM sleep.

How can psychologists study the sleep cycle?

Each of these stages is characterised by a different level of brainwave activity which can be monitored using an EEG

What is a strength of research into ultradian rhythms?

It has improved understanding of age-related changes in sleep

Sleep scientists have observed that slow wave sleep reduces with age. Growth hormone is produced during SWS thus this is reduced in older people.

Eve van Cauter et al found that less SWS explains various issues in old age e.g. reduced alertness

To increase SWS, relaxation and medication may be used.

This suggests that knowledge of ultradian rhythms has practical value

What is a limitation of research into ultradian rhythms?

There is significant variation between people

Tucker et al found large differences between participants in the duration of each sleep stage, particularly stages 3+4.

Tucker et al suggests that these differences are likely to be biologically determined.

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

What is another strength of research into ultradian rhythms?

Control of extraneous variables

Conducting studies of sleep in lab settings allows the control of EVs. 

Researcher can exclude temporary variables like noise or temp that may affect sleep

What is another limitation of research into ultradian rhythms?

Lab studies involve being attached to complicated machinery, leading to participants to sleep in a way that does not represent their ordinary sleep patterns.