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Summary of the slides 0HM200 psychology of light and time
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Lecture 1 SleepSleep: naturally recurring state of mind and body, characterized by altered consciousness,
relatively inhibited sensory activity, inhibition of nearly all voluntary muscles and reduced
interactions with surroundings.
Wakefulness: a spectrum of behavioral states during which an animal exhibits voluntary
motor activation and is responsive to internal and external stimuli. EEG shows low
amplitude, fast frequencies and the EMG shows variable amounts of muscle activity.
Hypnogram: measures sleep pattern. Normally 4/5 sleep cycles. Short
awakenings are normal.
Measuring sleep
Are used to characterize sleep as either rapid eye movement (REM) or non-rapid eye
movement (NREM).
Electroencephalogram (EEG): brain activity
o For NREM slower frequencies in the delta (0-4Hz) and theta (4-7Hz) ranges
o For REM low amplitutde, fast activity much like that of wake with modest
amount of theta activity
Electrooculogram (EOG): eye movements
Electromyogram (EMG): Muscle activity
Heart, respiration, leg movements
NREM: consciousness fades and in the deepest stages.
Consist of 3 substages from light to deep and starts after
falling asleep. Your in the NREM sleep majority of night
and there is a lower body temperature and heart rate
(saving energy).
Moving memories from short term to long term storage
REM: dreams, rapid eye movements and fluctuations in heart rate and respiration.
Relaxation of muscles. Visual information processing. Thermoregulation impaired, so when
very cold less REM.
Stabilization of memories in long-term storage and filtering information. It reduces strong
emotions associated with negative events (less fear).
Eldery are more in stage awake, REM, stage 1 and stage 2 and young adults have longer
periods of stages and also in stage 4 and 3.
Melatonin: sleep hormone, highest when you try to fall a sleep
Sleep regulation
Process S: homeostatic process. During the day your probability to fall asleep rises
and during night it decreases
Process C: Circadian clock. Probability to fall a sleep is highest during middle of
sleep period and lowest during middle of the day since you are most exposed to light
Sleep deprivation (slaap tekort): more slow wave sleep and is a marker for process
S
,Functions of sleep:
- Conserve energy
- Concentration
- Process emotions
- Synaptic homeostaiss
- Memory consolidation
- Rest muscles
- Sense of humor
- Obesity
- Cardiovascular disease
Effects of sleep deprivation are irritability, memory loss (result of REM deprivation),
impaired moral judgement, hallucinations, adhd symptoms, impaired immune system, risk
diabetes, increased rt and decreased accuracy. Risk of obesity and growth suppression.
Less than 6h sleep: increased risk obesity, stroke, diabetes and CAD
Circadian sleep disorders
Delayed sleep phase disorder (DSPD): sleep >2h later (later melatonin secretion),
but have consistent bed times. Hard times getting out of bed and are often tired. Not
the same as insomnia)
o solution: melatonin earlier, light therapy, chronotherapy (start delaying your
clock, so from 3 AM 6 AM 9 AM, till 10 PM)
Advanced Sleep Phase Disorder (ASPD): sleepiness in the evening, early morning
insomnia, relatively rare but more elderly.
o solution: melatonin morning, light therapy early evening
Non 24-hour sleep-wake disorder :free running rhythm delayed internal clock
(delays 2h each day)
?shift work: reduction of quality and quantity of sleep, tired anxiety and depression
Insomnia: problems with sleeping, and indicates clinical depression
o Vicious cycle of insomnia: unhelpful thinking, emotions and behavior all
result in feeling more awake and alert
o Solution: drug therapy, cognitive behavioral therapy
Obstructive sleep apnea: blocked airway (colapsed muscle in back of throat). Loud
snoring, gasping for air , morning headche and attention problems
o Treatment: continuous positive airway pressure therapy
Narcolepsy: fall asleep without warning (cataplexy), feel sleepy during day
o Hypocretin: sleep wake stabilization
o Treatment: lifestyle, medication
Restless legs syndrome: urge to move, arises during rest and night. Can be
caused by disturbed dopamine regulation in brain or due to diabetes or parkinson.
o Treatment: sleep hygiene, regular exercise, medication
Parasomnias: a group of sleep disorders that involve unwanted events or experiences that
occur while you are falling asleep, sleeping or waking up
Nrem parasomnias (disorder of arousal): confusional arousals, sleepwalking, night
terrors harmful and dangerous
REM parasomnias: nightmare disorder, recurrent isolated slep paralysis, REM
behavioral sleep disorder (no reduced muscle tone, damage of brain stem)
, Lecture 2: light and time
Melatonin onset is earlier for natural light than when exposed to electrical lighting
Circadian rhythms: various metabolic, chemical, endocrine & behavioural process
cycle alternately through high and low activity phases with a periodicity of 24hrs
o Circadian hour = FRP/24
Free running (FRP) sleep-wake rhythm: participant delays sleep with 30min each
day if there is no light
?Forced desynchrony: 27h
Sleep latency: how long it takes to fall asleep after putting the lights off
Sleep wake regulation
Circadian principle: the longer we are active, the shorter we sleep
Homeostatic principle: the longer we are active, the deeper our sleep
Tow process model
Homeostatic process (S): need for sleep. increases as an
exponential saturating function during waking and decreases as
an exponential function during sleep. i
o Sleep pressure: increaes during waking and decreases during sleep
o Borbély: S increases till threshold during awakening and declines
monotonically during sleep till threshold L
Somnostat: conscious decisions and environmental conditions affect
threshold H, e.g. social stimulation
Circadian pacemaker (C): drive to be active. driven by the SCN, the neural master
pacemaker. Sinusoide and has a period, phase and amplitude
o Circadian sleep propensity: not constant over time but varies with the time
of day
o After 24h values return to baseline (not the case by homeostatic)
Greatest urge to sleep: when the distance between S and C is biggest
Constant routine: constant wakefulness, conditions, position and food intake
Biological clock: not driven by sunlight but are rather synchronized by the 24h
pattern of light and temperature produced by the earth’s rotation. Keep existing
without environmental cues
SCN: suprachiasmatic nuclei, master circadian pacemaker located in ventral
hypothalamus. More master synchronizer than strict pacemaker
Endogenous circadian rhythm
Circadian pacemaker is exquisitely sensitive to light as a synchronizer
Light is primary synchronizer
Light to entrain
Without rods and cones, mice still had normal circadian functioning iprgc’s (intrinsically
photosensitive retinal ganglion cells)
Melanopsin: photopigment with max 480 nm (blue)
scotopic: 500nm
photopic: 550
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