ultradian rhythms

• Ultradian Rhythm - a type of biological rhythm with a frequency of more than one cycle in 24 hours, such as the stages of sleep
• Sleep has 5 stages that occur through the night, each lasts approx 90 minutes
• Activity in each stage of sleep is measured using an EEG
• Stage 1. Drowsiness
• Stage 2. Asleep - theta waves
• Stage 3. Delta waves
• Stage 4. Deepest stage of NREM - hard to wake, growth hormone released
• the first 4 stages are NREM
• in stages 1-2, EEG readouts record alpha and beta wave patterns in the brain accompanied by sleep spindles (bursts of activity)
• stage 5. REM sleep - fast desynchronised EEG, body effectively paralysed, dreaming
• in NREM sleep, the body is in a relaxed easily-awoken state, with a slowed heart rate and a drop in temperature
• Research by Dement and Kleitman monitored stages of sleep and found REM activity was highly correlated to dreaming. Replications of this study reported similar findings, suggesting REM is an important component of the ultradian sleep cycle
• This research has implications for identifying when dreams take place and thus explain dreams
• Hobson and McCarley (1977) proposed that dreams are just a psychological read-out of random electric signals typical of REM, however this explanation can be ruled out as it is based on the erroneous assumption that dreams take place in REM
• caution must be applied as some have criticised the small sample size and have questioned the generalisability of the findings of research into ultradian rhythms