Ultradian rhythms are biological cycles lasting less than 24 hours, such as the sleep stages
Stages 1 & 2 of sleep is 'light sleep', brain wave patterns produced begin to slow down and become more rhythmic; producing alpha waves progressing to theta waves
Stages 3 & 4 of sleep are 'deep sleep', slow wave sleep; produces slower delta waves with greater amplitude
Stage 5 of sleep is REM sleep where the body is paralysed (stops person acting out their dreams), brain activity resembles someone that is awake; rapid eye movement (REM) due to fast, jerky activity of the eyes under the eyelids
An ultradian rhythm is a type of biological rhythm with a frequency of more than on cycle in 24 hours (e.g. stages of sleep)
Dreams:
Argued that REM sleep is not the only stage where dreams occur; hypnogogic dreams occur in stages 1 & 2 of sleep shortly after drifting off to sleep (feeling our of control/ falling)
These dreams are significant because we often wake up with a jolt (hypnic twitch) when we are about to hit the ground
Basic Rest-Activity Cycle:
90-minute rhythm carries throughout the day (Kleitman, 1969)
BRAC involves period of alertness alternating with periods of physiological fatigue and low concentration
W- Individual Differences (UR):
Studying sleep cycles is differences observed in people, making investigating patterns difficult. Tucker et al. (2007) found significant differences between participants in terms of duration of each stage, particularly 3 & 4 (just before REM). Study carried out in controlled lab, differences in sleep patterns cannot be attributed to situational factors. Demonstrates innate individual differences in ultradian rhythms, it is important to focus on these in research into sleep cycles
W- Ecological validity (UR):
Some research may tell us little about ultradian rhythms in humans. When investigating sleep patterns, participants must be subjected to a specific level of control and be attached to monitors that measure rhythms; may be invasive or uncomfortable for participant, leading them to sleep in a way that does not represent their ordinary sleep cycle when at home. Makes investigating ultradian rhythms difficult as their lack of ecological validity could lead to false conclusions
S- Supporting evidence (UR):
Distinct stages in sleep have been supported by Kleitman & Dement (1957) who monitored the sleep of 9 adults in a sleep lab. Brain-wave activity was recorded on EEG and researchers controlled for effects of alcohol and caffeine. REM activity during sleep was highly correlated with experiences of dreaming, brain activity varied with vividity of dreams and participants woken during sleep recorded very accurate reports of dreams