Ultradian Rhythms Flashcards
What is an ultradian rhythm?
A rhythm that has less than 24 hours periodicity
What is the main ultradian rhythm?
The different stages of sleep
How are the stages of sleep measured?
By an EEG which measures brain waves
How many stages of sleep are there?
5
How long do all of the stages of sleep take?
90 minutes
Outline the 5 stages of sleep
1 & 2 are light sleep (change in electrical electricity activity in the brain )
3 & 4 are slow wave sleep (SWS)
5 is REM sleep
What characterises light sleep?
Alpha waves
What characterises slow wave sleep?
Delta waves
What occurs during slow wave sleep?
Biochemical processes like the production of growth hormones
What characterises REM sleep?
Fast, desynchronised EEG activity resembling the waking brain
What stages are NREM sleep?
The first 4
What does BRAC stand for?
Basic Rest-Activity Cycle
What is the BRAC?
The 90 minute cycle that occurs throughout the day
What evidence is there for the BRAC?
Friedman & Fisher (1967)
What does Friedman & Fisher (1967) show?
The existence of the BRAC
Outline Friedman & Fisher (1967)
They observed eating and drinking behaviour in psychiatric patients over 6 hours and detected a clear 90 minute cycle
What is the main research study for the different stages of sleep?
Kleitman & Dement (1957)
Outline Kleitman & Dement (1957)
10 participants in a sleep lab for 61 nights, in which EEG readings were taken to determine the stage of sleep and thus woke them at different stages and asked about experiences and emotions. They found that during REM, 80-90% reported dreams in great detail. However, only 7% reported dreams during NREM and in deep sleep, reported confusion and thought they were dreaming but could not describe them. They displayed similar EEG, EMG, ECG & EOG patterns showing 90 minute cycles. Also, they showed progressively more REM and less deep sleep and that we have about 4 or 5 cycles every night
Other than research evidence, what is another positive of the sleep cycles?
It has stood the test of time and is accepted by the scientific community
What are 4 negative points about Kleitman & Dement (1957)?
1) Some studies contradict as they have found 70% report dreams in NREM sleep - but what constitutes a dream?
2) Small sample, mainly men - generalisability
3) Sleep lab not a real life setting so lacks ecological validity
4) Shows a close correlation between REM & dreaming but the nature of the relationship remains unclear - dreams may just be recalled easier in REM sleep than NREM because NREM is a deeper stage of sleep so it is just harder to recall?
What is the importance of BRAC?
It is a form of timing biological processes in body unison
What evidence is there for the importance of BRAC?
Klein & Armitage (1979)
Outline Klein & Armitage
They found 90 minute rhythms during the day in cognitive vigilance with participants showing regular peaks and troughs in performance on spatial and verbal tasks
