Biological rhythms - Ultradian Rhythms

Question 1

what are ultradian rhythms

Answer 1

Biological rhythms that last less than 24 hours
- they occur more than once in a 24 hour period

Question 2

There are two examples of ultradian rhythms:

Answer 2

Sleep stages
Basic rest-activity cycle (BRAC)

Question 3

Sleep Stages - each cycle of sleep consists of both REM and NREM sleep

Answer 3

The first four stages are called NREM sleep (non-rapid eye movement) and the fifth stage is REM sleep (rapid eye movement).
One sleep cycle goes through all 5 stages and lasts ~ 90 minutes
The number of sleep cycles depends on how long an individual sleeps for

Question 4

Describe the Sleep Stages

Answer 4

The different stages of sleep are measured by the electrical activities of the brain, with each stage showing a distinct EEG pattern.
Stages 1 and 2 are light/shallow sleep.
As the person enters deep sleep (stages 3 and 4), their brainwaves slow and their breathing and heart rate decreases.
In deep sleep (SWS – Slow Wave Sleep) most of the body’s physiological ‘repair work’ is undertaken and important biochemical processes occur i.e. the production of growth hormones.
During the 5th stage (REM), the EEG pattern resembles that of an awake person and it is in this stage that most dreaming occurs.

Question 5

Dement and Kleitman (1957)
Procedure

Answer 5

Connected 9 participants (7 males; 2 females) to an EEG machine in a lab, which took measurements throughout a night’s sleep. The findings were:

Question 6

Dement and Kleitman (1957
Findings

Answer 6

Everyone had periods of REM every night.
There were high incidences of dream recall when participants are awakened during REM sleep. If awakened in the other stages, very few reported dreaming.
The brain activity of very vivid dreams was different to the less clear dreams.
The rapid eye movements of REM sleep varied according to dream type and mirrored brain activity whilst awake and completing a similar task to the one they had dreamt about e.g. climbing a series of ladders and looking up and down = vertical eye movements.

Question 7

Dement and Kleitman (1957)
Conclusions

Answer 7

Conclusion: The stages of sleep follow a typical pattern throughout the night; dreams mostly occur in REM sleep.

Question 8

Evaluation of Dement and Kleitman (1957) study

Answer 8

Negative:
Ppts were studied in a sleep laboratory, which could have caused an atypical reaction from ppts.
The frequency of REM sleep might be different in a non-experimental setting.
Dreaming is difficult to assess, in terms of type/vividness.

Positive:
EEG is an objective measure and is therefore scientific.

Question 9

The Basic Rest Activity Cycle (Kleitman, 1969)

Answer 9

Kleitman (1969) referred to the 90-minute cycle of sleep as the Basic Rest Activity Cycle (BRAC).
He suggested that this ultradian rhythm continues during the day, even when we are awake: we move progressively from a state of alertness into a state of physiological fatigue ~ every 90 minutes.
Research suggests that the human mind can focus for a period of ~90 minutes and towards the end of these 90 minutes the body begins to run out of resources, resulting in loss of concentration, fatigue and hunger.

Question 10

what did Friedman and fisher do

Answer 10

Friedman and Fisher (1967) observed the eating and drinking behaviour in a group of psychiatric patients over a period of 6 hours and found a 90 minute cycle in eating and drinking behaviour, thus adding support to the BRAC.