ultradian rhythms- the cycles of sleep

what are ultradian rhythms and an example

what are ultradian rhythms and an example

a cycle that lasts for less than 24hrs and repeats itself over a period of less than 24hrs

for example, the stages of sleep

how long does one cycle of sleep usually last?

90mins

during a typical night’s sleep how many cycles do we go through?

4 or 5

stage 1

• ‘light sleep’ stage

• brain wave patterns become slower starting with alpha waves, progressing to theta waves

• muscle activity slows down

• occasional muscle twitching

stage 2

• ‘light sleep’ stage

• theta waves

• breathing pattern and heart rate slows

• slight decrease in body temperature

stage 3

• deep sleep begins

• brain begins to generate slow delta waves

stage 4

• deep sleep

• rhythmic breathing

• limited muscle activity

• delta waves

stage 5 (REM sleep)

• body is ‘paralysed’ to prevent acting out our dreams

• eyes rapidly move from side to side (REM=rapid eye movement)

• brain activity resembles a person who is awake

• brainwaves speed up

• dreaming occurs

• muscles relax

• heart rate increases

• breathing is rapid and shallow

what are stages 1-4 collectively known as

NREM stages (non REM)

how do the stages of sleep create a cycle of sleep?

1. as we fall asleep we enter stage 1 sleep which is high frequency and low amplitude sleep

2. as we progress through stages 1-4, sleep becomes deeper. Delta waves characterise deeper sleep

3. stage 4 sleep, which is the deepest sleep stage- it is hard to wake up at this point. Heart rate and blood pressure fall, muscles are very relaxed

4. we are in stage 4 sleep for about 30 minutes

5. after we have been asleep for about 1hr all together, we start to ascend back through these stages in reverse order.

6. but instead of going back to level 1, after just over an hour, we enter REM sleep

7. One cycle is completed

what type of sleep do we typically spend most of the first half of the night in?

deep sleep (NREM)

what type of sleep do we typically spend most of the second half of the night in?

REM sleep

aim of Dement and Kleitman’s research into the distinct stages of sleep and the role of REM sleep

to investigate the relationship between eye movements and dreaming

method of Dement and Kleitman’s research

• 7 adult males and 2 adult females.

• ps studied under controlled laboratory conditions

• ps had to report to the laboratory at bedtime where they were connected to an EEG

• the EEG took measurements throughout their time asleep all night

• ps were asked to not drink caffeine

results of Dement and Kleitman’s research

• REM sleep is predominantly, though not exclusively, associated with dreaming

• NREM sleep is associated with periods of non-dreaming sleep

• ps were able to recall dreams if awakened during REM periods. If they were awakened in other stages they were less likely to report dreaming

• the REM period occured at regular intervals during the night, though each p had their own patterm

• the mean period of each REM phase for the whole group was 92mins, with individual norms varying between 70 and 104mins

conclusions of Dement and Kleitman’s research

1. stages of sleep follow a pattern throughout the night

2. dreams mostly occur in REM

3. ps did go into REM on average every 90mins but there were still individual differences

positive of Dement and Kleitman’s research

relaible- there has been a lot of replication

Dement’s research into REM sleep- method and findings

• compared ps who had been deprived of REM sleep with a control group who had been deprived of the same amount of NREM sleep

• he found that the REM deprived group were more irritable, more aggressive and unable to concentrate on various tasks

Borbely’s research into REM sleep

REM deprived individuals made 31 attempts to re-enter REM on the first night of deprivation, 51 attempts on the second night and 60 on the third night

called REM re-bound

what does Dement’s and Borbely’s research suggest?

REM is a distinct and significant stage of the ultradian rhythm and also important for our psychological well-being

Randy Gardner’s research

• Randy Gardner remained awake for 264hrs

• while he experienced numerous problems- e.g. blurred vision and disorganised speech, he coped incredibly well despite his significant sleep deprivation

• after his experience, he slept for just 15hrs

• over several nights he recovered only 25% of his lost sleep

• he recovered about 70% of stage 4 sleep, 50% of REM sleep and very little of the other stages

• These results suggest the wide degree of flexibility in terms of the different stages within the sleep cycle and the variable nature of this ultradian rhythm

AO3- individual differences

p- a significant problem when studying sleep cycles is the differences observed in people

e- this can be seen in Dement and Kleitman’s research- sleep cycles varying in length 70-104mins

e- Tucker et al found differences in terms of duration of each stage, particularly stages 3 and 4 (NREM). Also sleep cycles differ with age

l- this research suggests there may be innate individual differences in ultradian rhythms- its worth focussing on these differences during investigations into sleep cycles

AO3- lack of ecological validity

p- sleep cycles are usually investigated with a high degree of control in sleep laboratories

e- ps wear caps with electrodes to monitor EEG patterns and are asked to sleep and then woken up at various points during their cycle

e- this is both invasive for the participant as well as being very artificial and may lead to them to sleep in a way that doesn’t represent their ordinary sleep cycle

l- this lack of ecological validity could lead to false conclusions being applied to our understanding of sleep cycles

AO3- flexible

p-Randy Gardner’s research suggested a degree of flexibility in sleep

e- His experience of remaining awake for 264hrs and subsequently recovering 70% of stage 4, 50% of REM and little of the other stages suggests the degree of flexibility in terms of the different stages may not be as ‘fixed’ as psychologists believed

e- however, we should consider that Gardner’s results could be unique to him, for example an older individual may have very different results in the sleep they recovered

l- generalisation of such specific cases could be difficult for the wider population