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Biopsych - Sleep (Y2) - Coggle Diagram
Biopsych - Sleep (Y2)
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The Sleep Cycle
Chronotypes - preferences that manifest in personal sleep-wake rhythms, measured using the Munich Chronotype questionnaire (MCTQ)
- Types -
-> Lion - early bird; conscientious and agreeable, productive in mornings
-> Bear - able to follow normal schedule such as office hours and follow the sun so can socialise in the evening
-> Wolf - night owl - neuroticism and openess
-> Dolphin - insomniacs
Measuring sleep -
- Polysomnography - physiological information e.g. brain activity and eye movement inferences - electrodes allows researchers to measure electrophysiological activity in the brain, muscles in the face and around the eyes
- EEG
- Actigraphy - watch-like device measures movements - inferences about sleep are made with this information
- Sleep diaries - completed in morning, self rated
- Questionnaires - self, parent or observer rater
- Smartphone applications - use high quality sensors of movements and sound to infer sleep
Questionnaires -
- Pittsburgh Sleep Quality Index (PSQI) - 9 item self report questionnaire of sleep quality within the past month
- Insomnia sleep index - 7 item self report questionnaire to measure insomnia
The brain during wakefulness - delta (deep), alpha (transitional), and beta (waking) waves
Sleep stages -
Sleep is not a uniform state; it is composed of different stages differentiated by patterns of brain wave activity that occur during each stage
- These changes can be visualised using EEG and are distinguished from one another by the frequency and amplitude of brain waves
- Divided in two general phases - REM and non-REM
- Rapid eye movement sleep is characterized by darting movement of the eyes under closed eyelids; brain waves in this stage appear similar to wakefulness brain waves
Waking - Alpha (8-12 Hz) - relaxed, and Beta (13-30 Hz)
- Stage 1 - NREM sleep, consists of theta activity (3.5-7.5 Hz)
-> Transitional phase that occurs between wakefulness and sleep; the period during which a person drifts to sleep
- Stage 2 - NREM sleep, contains sleep spindles and K complexes
-> Body goes into deep relaxation - characterised by the appearance of sleep spindles
- Stage 3 - slow wave sleep, consists of delta activity (< 3.5 Hz)
-> Deep sleep characterised by low frequency, high amplitude delta waves
- Stage 4 - similar to stage 3
- REM sleep - consists of theta and beta activity - brain areas involved in during dreaming is the same one involved in waking activity; therefore, brain waves look similar to wakefulness
Brain wave characteristics -
- Alpha wave - relativaly high freuqency, relatively low amplitude brain wave that becomes synchronised; characteristic of stage 1 sleep and rest - alpha amplitude increases when we close our eyes
- Beta wave - high frequency, low amplitude, can be erratic, waking wave
- Theta - transitional between waking and sleep
- K complex - very high amplitude pattern of brain activity associated with stage 2 sleep
- Sleep spindle - rapid burst of high frequency brain waves during stage 2 sleep that may be important for learning and memory
- Delta wave - low frequency, high amplitude brain wave characteristic of slow wave sleep
NREM - period outside REM
REM - disorganised dreams = underused planning area of frontal lobe
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Basic-rest activity cycle -
- Derment and Kleitman - violinist study about cognitive alertness - post lunch dips
- Mammals sleep for varying amounts of the day - humans; 8 hours, horses; 3 hours, cats; 14 hours and giant sloth; 20 hours a day
Sleep disorders
Six main categories of sleep disorder - Gregory and Sadeh (2016)
- Insomnia - persistent sleep problems - no single definition, hard to measure, occasional and regular insomnia, depression
- Sleep related breathing disorders - Apnea
-> Condition in which individuals cannot get air into their lungs when they sleep
-> This causes them to wake up everytime they cannot breathe, resulting in fatigue issues of accidents, attention difficulty, irritability and other adverse effects such as stroke risk, cardiovascular risk increase and obesity as well as diabetes
- Central disorders of hypersomnolence - excessive sleepiness
-> Narcolepsy - a neurological disorder characterised by sleep at inappropriate times - flip flop mechanism unstable, GABAergic neurons do not function well
-> Primary symptoms of sleep attacks and secondary symptoms of cataplexy and sleep paralysis
-> Inherited disorder, caused by immune system attacking and destroying hypocretin-secreting neurons
-> Treated with Ritalin and Modafinil
-> Gene mutation discovered that produces receptor for peptide neurotransmitter called hypocretin is associated with canine narcolepsy (Lin et al, 1999)
- Circadian rhythm sleep-wake disorders - misalignment of sleep-wake habits, autism
- Parasomnias e.g. sleep terrors
- Sleep related movement disorders - restless leg syndrome
Sleep behaviour disorder - Muscle paralysis in REM stage is lost, and so dreams are not prevented from being acted out as they should be
- Risk factors - Parkinson's, brain injury, Lewy body dementia, Psychiatric medicines
- Symptoms - sleepwalking, screaming, hitting, kicking and punching
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Problems associated with SWS - bed wetting, night terrors (most frequent in children and in stage 3) and sleep walking
Sleep and childhood psychiatric disorders - in the DSM-5 (APA, 2013) sleep plays a major role
- Category of sleep-wake disorders
- A major symptom within diagnoses of many other disorders
- Sleep problems are relevant in many disorders listed in the DSM-5
Why are sleep problems present in psychiatric disorders / neurodevelopmental conditions
- No single explanation - depends on disorder - depression; twin studies suggest these covary in adolescence due to genetic propensity (early childhood this overlap could be environmental)
- Trauma / abuse - often covary but mechanistic explanation needed
- Autism - one hypothesis is that autistic individuals have less endogenous melatonin secretion (Tordjman et al, 2005)
Treatment -
- A wide variety of effective treatments for sleep disorders
- Prevention of sleep problems in babies by offering advice booklets to parents
- Sleep hygiene for insomnia
- Behavioural interventions e.g. scheduled walking to avoid sleep
- Cognitive interventions e.g. image rehearsal therapy for nightmares
- Pharmacotherapy e.g. circadian rhythm sleep-wake disorders treated with melatonin
- Surgery e.g. removal of adenoids and tonsils for people with obstructive sleep apnoea
Genome-wide association study of mornings and sleep length - genetic variants identified which are associated with early bird chronotype and sleep length
Biological rhythms
- Circadian rhythms - repeat themselves every 24 hours, various rhythms for temperature, hormones, sleep-wake cycle - exogenous zeitgebers (Siffre) and endogenous pacemakers
- Infradian rhythms - these occur less than once a day e.g. hibernation, menstrual cycle, SAD
- Ultradian rhythms - repeat more than once a day e.g. dream cycles, cycles of cognitive arousal during day
Biological clocks
Suprachiasmic nucleus (SCN) of hypothalamus -
- Lesions of SCN disrupt daily activity cycles in rats (Ibuka and Kawamura, 1975) - Decoursey et al (chipmunks)
- Fundamental functions are protected in deeper brain areas
- Activity of SCN neurons correlates with day-night cycle (Foster and Kreitzman, 2013)
- Neural basis of sleep - hypothalamus and brainstem interaction
Melanopsin-containing ganglion (neurons that receive and transmit light signals) -
- Cortisol released in morning, melatonin released in light based on light signals
- Retinohypothalamic pathway -
-> Retinal ganglion cells containing melanopsin - night and daylight impact secretion which informs SCN
-> Circuit for biological rhythm
- Special photochemical - melanopsin
-> Transmit light information from eye to rest of brain and control pupil dilation
How does the SCN work -
- CLOCK genes encode proteins to regulate circadian rhythm (CLOCK = Circadian Locomotor Output Cycles Kaput)
- The neuron activity that makes the clock - this is the ticking cycle
-> The protein enters the nucleus, suppressing the gene responsible for production - no more messenger RNA is made when full
-> Level of the protein falls, so the gene becomes active again
-> The gene is active - messenger RNA leave the nucleus and causes production of the protein
-> 7 genes involved in the ticking
-> The time taken for this is the ticking
Two process model of sleep -
- Sleep-dependent process (Process S) - shows experimental decline during sleep and increase during waking i.e. it is a function prior to waking time and when you sleep
- Sleep independent circadian process (Process C) - controlled by circadian oscillator - how long you sleep
- Model proposes that sleep duration and sleep propensity are driven by these two processes
In zeitgeber free environments, these rhythms are free running and their duration is a free running period - very in length between all individuals (different cave studies) - around 24.2 hours
- Do not have to be learned
- Body temperature cycle is linked to their sleep wake - tend to sleep during falling phase of body temperature
-> However, in lab environments, sometimes there is internal desynchronisation of these two cycles
-> Many circadian rhythm cycles
-> This would be incompatible with restoration theories, as the clocks do not run on the same schedules
- Reducing jet lag - exposure to light to reset circadian rhythm (Burgess et al, 1980)
Drugs that impact sleep - hynpotics, anti-hypnotics and melatonin
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Why do we sleep?
Effects of sleep deprivation -
- Fatigue, irratability, poor performance on tasks requiring concentration, memory problems, hallucination, personality changes and rebound sleep (do not regain all sleep back)
- Can occur from stress - lab studies confounded as sleep deprivation can be from a stressful situation of the study not just the task itself
Rechtschaffen et al, 1983 - sleep deprivation in animals -
- Two mice in chambers on rotating platforms with water underneath
- When the experimental mouse falls asleep, they move the carousel so the mouse falls in the water and wakes up
- Control mouse can sleep when carousel is still
- Everything else is controlled
- The test rat deteriorates after 7-10 days, loses weight despite eating more, rats die in 2-3 weeks, metabolic and homeostasis failures; post mortem reveals large adrenal glands and high cortisol from stress
Record from sleep deprivation - Randy Gardener (264 hours) and Tony Wright (266 hours)
What's the limit to how long a human can stay awake?
- One man, Tripp, was tasked with staying awake in the 1950s and after 201 hours awake, during which he experienced hallucinations after 5 days on a similar REM cycle pattern
-> When he finally slept, he did so for 13 hours and had one of the longest REM episodes ever recorded
-> It was likely the Ritalin (stimulant) he took caused the hallucinations however, as others at a similar time reported sleeping longer with no ill effects
- However, it is not fully determined how long one can go without sleep - disregarding fatal insomnia, non fatal insomnia can lead to people going decades without sleep
Studies - Kleitman, 1963 - sleep deprived students - Students experienced similar effects from sleep deprivation
- After 1 night, they struggled at around 3:00am, and the next day could remain alert as long as not doing tasks
- After 2 nights, this worsened but they could not do anything as their sleepiness was so severe
- After nights 3 and 4, this worsened, but they could perform tasks in the lab as long as they were standing and moving
- Condition did not worsen after this point
Sleep deprivation can disrupt complex cognitive function (Krause et al, 2017)
- Only some cognitive functions appear to be susceptible - executive function is the main victim in sleep deprivation (Miller and Wallis, 2009)
- Attention is highly impacted, negative moods are caused and there is increase in sleepiness
Physiologically - increased blood pressure, reduced body temperature, decreased immune function, hormonal changes and metabolic changes - however, these changes have little impact in the long term
- Microsleeps - brief periods of sleep - typically 2 or 3 seconds sleep long during which the eyelids droop and volunteers become less responsive to external stimui
-> Vigilance decreases with depression
- Sleep deprivation is more subtle, selective and variable than deprivation of other needs
REM Deprivation effects -
- REM rebound - more than usual amount of REM sleep for the first two or three nights
- With each successive of deprivation, there is greater tendency for participants to initiate REM sleep
- This suggests REM sleep is regulated separately to slow-wave sleep
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