Ultradian Rhythms Ultradian Rhythms, AO1 and AO2 0.0 / 5 ? PsychologySleepA2/A-levelAQA Created by: Caitriona DohertyCreated on: 05-04-14 10:57 AO1 - Sleep Stages 1 Ultradian rhythms are biological rhythms that last less than 24 hours Researchers have identified 5 distinct 90-minute stages of sleep Stages 1 and 2 (NREM) Relaxed state, easily woken Slow alpha and theta waves, accompanied by bursts of activity (sleep spindles) and increased wave amplitude (k complexes) Heart rate slows, temperature drops Stages 3 and 4 (NREM) Delta waves, metabolic rate slowest Hard to wake them up, but not unconscious Physiological 'repair work' takes place Growth hormone produced 1 of 6 AO1 - Sleep Stages 2 REM (a.k.a Stage 5) Fast, desynchronised EEG activity resembling the awake brain Rapid eye moments (which is where it gets its name from) Called 'paradoxical sleep' because brain and eyes are active but body is paralysed 2 of 6 AO2 - Basic Rest-Activity Cycle SUPPORTS Researcher have found that the 90-minute 'clock' is also ticking throughout the day It is called the basic rest-activity cycle Friedman and Fisher: observed eating and drinking in a group of psychiatric patients over periods of six hours Detected a clear 90-minute cycle in eating and drinking behaviour Shows that ultradian rhythms do exist and not just in sleep 3 of 6 AO2 - REM sleep and Dreams 1 UNDERMINES An issue with studies on REM sleep is the assumption that it is for dreams Dement and Kleitman: woke participants up at times when their brain waves were characteristic of REM They were highly likely to report dreaming HOWEVER, dreams were also recorded outside of REM sleep When awoken in REM, sleepers were not always dreaming Questions the ecological validity of the experiments 4 of 6 AO2 - REM sleep and Dreams 2 UNDERMINES The importance of the REM-dream link is that it potentially provides a way to identify when someone is dreaming It therefore might provide theorists with a way to explain dreaming Hobson and McCarely: proposed that dreams are just a psychological read-out of the random electrical signals typical of REM sleep Such theories are based on the erroneous assumption that REM activity = dreaming Which, as has previously been noted, is not the case 5 of 6 AO2 - Support for the BRAC SUPPORTS The BRAC shows that sleep stages are part of a continuum: a 90-minute cycle that occurs throughout the day within the circadian rhythm The importance of this 90-minute rhythm is probably as a form of timing to ensure that biological processes in the body work in unison Much like how a conductor keeps time in an orchestra 6 of 6
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