Psychology Sleep Chapter Summary

Sleep-wake cycle:

• Circadian = 24 hours
• Cycle persists despite isolation from light

Evaluation:

• Participants not isolated from artificial light in early research
• Demonstrated by Siffre and Aschoff and Weaver
• External cues important too (Folkard et al)
• Cycle length varies in individuals

Core Body Temperature:

• Lowest at 4:30am
• Highest at 6pm
• Post-lunch dip, even without food

Evaluation:

• Linked to cognitive abilities (Folkard et al)
• Evidence that change is caused by temperature (Giesbrecht et al, 1993)
• Other research sugest link is spurious

Hormones:

• Cortisol = lowest at midnight
• Melatonin and growth hormone = highest at midnight

IDA:

• Biological and deterministic
• Real world application - chronotherapeutics

Ultradian Rhythms:

• Less than one day
• First four stages of sleep = NREM
• Fifth stage = REM
• BRAC = 90 minutes within 24 hour rhythm

Evaluation:

• REM does not equal dreaming
• BRAC = important because it ensures biological processes work in unison

Infradian Rhythms:

• Female menstrual cycle regulates ovulation
• Males have 20 day cycle of body temperature and alertness
• SAD = caused by melatonin during winter months

Evaluation:

• Menstrual cycle = subject to exogenous cues
• PMS
• SAD could also be consequence of disrupted circadian rhythms

IDA:

• Determisitic but can change through willpower (Born et al)
• Real world application = phototherapy

Endogenous Pacemakers:

• SCN = main endogenous pacemaker
• Contains protein mechanism
• Pinal gland controls melatonin secretion

Evaluation:

• SCN evidence = 'mutant' hamsters (Morgan)
• Desynchronisation can lead to symptoms of jet lag

Exogenous Zeitgebers:

• Light is dominant zeitgeber
• Social cues also important
• Biological rhythms can be entrained by temperature

Evaluation:

• Artificial lighting may also reset biological clock
• Failure of biological clock leads to sleep-phase disorders
• Biological clck is really a blend of endognous and exogenous factors

IDA:

• Non-human animal studies
• Ethics and relevance

Children:

• Babies sleep 16 hours a day, but not continuously
• Shorter sleep cycles than adults
• Circadian rhythm established at six months
• At 5, sleep patterns like those of adults
• May experience parasomnias

Evaluation:

• Sleep differences in babies - adaptive (for parents)
• Immature brain

Adolescence:

• Need for sleep increases (9-10)
• Circadian rhythms change
• Slight phase delay

Evaluation:

• May be linked to hormone production
• Implications in school day

Adulthood and Old Age:

• Increase in sleep disorders
• Patterns of sleep changes in old age
• Reduction in REM and SWS
• Older = phase advance effect

Evaluation:

• Increased mortality rate with too much sleep (Kripke et al)
• Sleep deficit in old age may explain impaired functioning in other areas

IDA:

• Developmental Approach
• Cultural bias (overlooked)
• Real-world application

SWS:

• SWS = stages three and four
• Growth hormones secreted during SWS
• Decline of GH in older age = reduced SWS
• Lack of SWS = low immune functioning

REM:

• Important for brain growth
• Restoring neurotransmitter sensitivity
• Link between REM and procedural memory

Shift work and Shift Lag:

• Nightworkers experience 'trough' of decreased alertness
• Sleep deprivation due to sleeping problems during the day
• Relationship between shift work and organ disease

Evaluation:

• Shift work effects not solely due to disruption of biological rhythms
• More problems with rotating shifts
• Forward rotating less harmful
• Artificial lighting can eset rhythm but not dim lighting

Jet travel and Jet lag:

• Caused by disruption of circadian rhythms
• Phase delay less disruptive than phase advance

Evaluation:

• Jet lag symptoms may be caused by other factors
• Melatonin may reduce symptoms
• Social customs also help
• Individual differences exist in coping with disruption

Energy Conservation:

• Period of inactivity to conserve energy
• Essential for animals with high metabolic rates

Foraging:

• Herbivores spend less time sleeping
• Carnivores more because food rich in nutrients

Predator Avoidance:

• Sleep constrained by predation risk
• Predators sleep more, prey sleep less

Waste of time:

• Staying still at times when an animal cannot forage
• Subject to predatation

Evaluation:

• Evidence about animal sleep patterns incomplete
• Evidence suggests that species with a higher metabolic rate sleep more
• Evidence suggests that species with higher predatation risk sleep less
• Evidence to support foraging and predator avoidance
• NREM evolved first for energy conservation
• Then REM to maintain brain activity
• Phylogenetic signal supports evolution of sleep patterns

IDA:

• Evolutionary approach can be combined
• Restoration using core and optional sleep
• Horne (1988)

Short term Insomnia:

• Caused by worry, noise, jet lag or temporary medical conditions

Long term Insomnia:

• Primary = not associated with medical conditions
• Secondary = symptom of a medical disorder or some other issue

Evaluation:

• Diagnosis has implications for treatment
• May be cause rather than effect
• Consequences include cognitive impairment, accidents, psychological disturbance, anxiety disorders or immune system underfunctioning
• Predisposing factors (genetics)
• Precipitating factors (environemental stressors)
• Perpetuating factors (expectations)

• Psychological (Disguishing sexual fantasies)
• Early explanations = failure of REM regulation
• HLA mutation causes reduced immune system functioning
• Low levels of neurotransmitter hypocretin in hypothalamus affects wakefulness 

Evaluation:

• REM hypothesis (some evidence, not convincing)
• HLA varient cannot be sole explanation because common in general population
• Hypocretin support from studies of dogs and humans
• Low levels of hypocretin rarely inherited
• Most likely to due brain injury or autoimmune attack
• Link to HLA

• Person wakes during SWS but brain arousal incomplete
• Other factors = sleep deprivation, alcohol, hormone changes
• May affect children more because underdeveloped SWS inhibition

Evaluation:

• Evidence for genetic basis
• Diathesis-stress model
• Sleep deprivation triggers sleep walking in vulnerable people
• Psychological cause unlikely because not in REM sleep