Biological Rhythms & Sleep

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  • Siffre (1972)
    • Stayed in a cave for 6 months - separated from light/dark cycles. His sleep-wake cycle extended to between 25-32 hrs (days became longer). His body also maintained a circadian rhythm - eventually his body temp & sleep-wake cycle decoupled (internal desynchronisation)
      • Innate mechanism for circadian rhythms that will function without external cues.
  • SCN [Suprachiasmatic nucleus] - a tiny cluster of cells in HYPOTHALAMUS could be site for at least 1 EP.
    • [A01] Stehan & Zucker (1972) - compared rats with damage to the SCN & normal rats. Found that those with damaged SCN eliminated the normal circadian patterns of drinking & activity.
      • Suggets SCN is a key EP in controlling circadian rhythms
        • [A02] Morgan (1995) found that if a  damaged SCN is transplanted into a normal hamster they now showed distorted circadian rhythms
          • BIOLOGICALLY REDUCTIONIST - this may be relevant for understanding animal behaviours it is likely that other external factors eg. social cues play a role in shaping human circadian rhythms eg. sleep/wake cycle.
            • ETHICAL ISSUES - Stephan & Zucker study, out of 25 hamsters only 11 survived. Although can be argued that the costs of animal suffering is justified by the potential benefits for understanding sleep/wake disorders.
              • EVOLUTION - Biological clock may be adjusted by EP's. Therefore not constrained to rigid, innate schedule. Could have an advantage in having EP's reset by EZ's - keeping in tune with seasonal changes: to rely solely on EZ's could threaten survival, internal cues are important too
  • Stage 1: Light Sleep (Ocassional muscle activity 4-5%).     Stage 2: Heart rate slows (45-55%)            Stage 3: Deep Sleep [SLOW Delta waves produced] (4-6%).   Stage 4: Very Deep Sleep [Delta waves produced] (12-15%).        REM: Dreams [High activtity, muscle paralysis] (20-25%)
    • Stages of Sleep
      • Dement & Kleitman (1957) - Observed if pps awakened in periods of REM/NREM. REM sleepers able to recall dream easier. All pps showed periods of REM during sleep. REM never occurred at the beginning of sleep.
        • Objective Evidence - EEG, EOG, EMG provide objective measures of sleep (less bias)
          • Lacks mundane realism - too artificial findings lack generalisability & ecological validity
            • Sleep varies from individual - not everyone will have the same sleep pattern
    • Dement & Kleitman (1957) - Observed if pps awakened in periods of REM/NREM. REM sleepers able to recall dream easier. All pps showed periods of REM during sleep. REM never occurred at the beginning of sleep.
      • Objective Evidence - EEG, EOG, EMG provide objective measures of sleep (less bias)
        • Lacks mundane realism - too artificial findings lack generalisability & ecological validity
          • Sleep varies from individual - not everyone will have the same sleep pattern
  • Predatory Theory (Meddis,1975) Sleep is adaptive because the immobility of sleep keeps animals safe from predators at most vulnerable. It is also a time when normal activities are impossible. Also it is during a time when normal activities are impossible.
    • Evolutionary
      • [A02] Sleep leaves animals more vulnerable as they are in a state of unconsciousness & paralysis. Thus protection is unlikely the main function.
  • Only NREM has evolved for energy conservation. Alison (1976) larger animals had less NREM but not less REM.
    • NREM evolued first for energy conservation, REM evolved later to maintain brain activity. Supported by the need for REM in infants whose brains are developing.
  • To repair & recharge the brain & body through restoring energy resources.
    • Restoration Theory
      • Sleep Deprivation
        • Peter Tripp - Radio DJ stayed awake for 8 days. He experiences delusions and hallucinations. No effect on physicality
        • Rechtschafffen (1983) - Placed 2 rats on a disc above water. One was able to sleep the other was not. All of the sleep deprived rats died by 33 days: The rats that were not sleep deprived appeared to suffer no ill effects as the study (died due to inability to regulate body temp)
        • Lab setting - increases internal validity but may have affected the sleep pattern not in their natural setting.
      • Functions of Sleep
        • Evolutionary
          • [A02] Sleep leaves animals more vulnerable as they are in a state of unconsciousness & paralysis. Thus protection is unlikely the main function.
    • Many restorative processes - digestion & protein synthesis occur in sleep.
      • REM is far higher in babies than adults and even higher in premature babies. With the development of synaptic connections & neurotransmitters.
        • [AO2] Krueger 1985 - Lack of SWS associated with reduced functioning of the immune system. Immune system is 'regenerated' during cell growth & protein synthesis in SWS
          • [A02] Ryback & Lewis (1971) - Found healthy pps who speant 6 weeks resting in a sleep lab showed no changes in their sleep patterns
  • Lifespan changes of Sleep
    • Ohayon (2004) Sleep tends to become lighter with age. Stage 2 used to be 42& of sleeptime by 70 takes up 55%.
      • Suggests sleep has different functions @ different ages. eg. - babies = more REM for development.
    • Restorative/   Adaptive Function - Long unresponsive REM sleep in infants may have allowed parents to rest .
      • Sentinel theory - that REM in adults evolved to allow checking for signs of danger in the short periods of wakefulness that occurs @ end of each episode of REM sleep.
    • Functions of Sleep
    • Insomnia
      • Primary = Not attributed to medical, psychiatric or environmental cause.
      • Secondary = caused by psychiatric disorder or medical disorder
      • Spielman's Cumulative Model (1987) Predisposing Fctors - perfectionism, sensitive types etc. precipitating factors (environmental factors) can trigger disorder. Perpetuating factors may maintain the disorder even when stressors have gone (bad thoughts/habits)
        • [A03] - Allows for an eclectic approach to understanding & treatment. It is flexible as each persons factors may vary and this avoids a simplistic explanation
      • Psychophysiological Insomnia -  learn to associate sleep with anxiety (classical conditioning)
        • Dauvillers (2005) - Primary insomniacs completed clinical interview, questionnaire on family history and polysomnography . 72% reported familial insomnia compared with 24% in control. Sugegst familial link to primary insomnia
      • FOR A02+A03 CHECK PAST HW
    • Gregory (2006) - Family conflict & Insomnia. Family conflict at 5-15 resulted in insomnia at age 18.
      • Correlational so may be other variables at play like individual personalities.
      • Secondary = caused by psychiatric disorder or medical disorder
    • Psychophysiological Insomnia -  learn to associate sleep with anxiety (classical conditioning)
      • Dauvillers (2005) - Primary insomniacs completed clinical interview, questionnaire on family history and polysomnography . 72% reported familial insomnia compared with 24% in control. Sugegst familial link to primary insomnia
    • Inherit a genetic variation that increases the risk of SW.  10 x more likely if a 1st degree relative has a history of SW.
      • Bassati (2002) - found that 50% of 74 SW studied had a specific HLA gene that was only seen in 24% of the non-SW (HLA helps pregulate immune system & implicated in other sleep disorders.
        • Suggests a genetic link to SW

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