ultradian rhythms

• ultradian rhythms last less than 24 hours, for e.g. the 5 sleep cycle.
• the 5 sleep cycle starts at light sleep, the progresses onto deep sleep and then dream sleep (REM - rapid eye movement). this cycle repeats itself every 90 minutes during sleep.
• stages 1-2: light sleep, where the heart rate is slowed and temperature drops.
• stages 3-4: deep sleep, difficult to wake person up, metabolic rate slows and the growth hormone is produced.
• REM stage 5: dream sleep, the body is paralysed and brain + eye activity resembles that of an awake person.
• dement + kleitman (1957): monitored sleep patterns of 9 adults in a sleep lab using EEGS, researchers controlled for effects of caffeine and alcohol. found that REM activity was highly correlated with dreaming, brain activity varied according to how vivid the dreams were. when p's woke up during dream, they had impressive recall of their dream.
• in conclusion: this study suggests REM sleep is associated with dreaming and thus distinct from other stages in the ultradian sleep cycle.