Psychology of sleep - neural basis of sleep

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How is sleep measured?
EEG-Electroencephalogram EOG- Electrooculogram EMG-Electromyogram Together these a called polysomnography.
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What are electrical brain potentials used for?
to classify different levels of arousal and states of sleep.
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Order of EEG
Beta, Alpha, Theta, Delta
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Stages of sleep
Non-Rapid Eye Movement (NREM) sleep - stage 1 NREM, stage 2 NREM, stage 3 NREM, stage 4 NREM (3 and 4 are slow wave sleep. Then Rapid Eye Movement (REM) sleep
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EEG - stage 1 - awake
Alpha and beta activity
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EEG - stage 1 - stage 1 sleep
Theta activity
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EEG - stage 2
sleep spindles and k-complex. Sleep spindles-burst of activity, originating in the thalamus and projecting to the cortex.
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EEG: Stage 3 & 4
delta activity
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EEG: REM
Theta and beta activity
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REM- loss of...
muscle tone
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Sleep cycle
Spend more time in slow wave sleep in first half of night and more time in REM sleep in second half of night
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Circadian Rhythms
Functions of living organisms that display a rhythm of about 24 hours. Diurnal- active during the day. Nocturnal- active during the night. The animals activity and sleep cycles are tied to their circadian rhythm.
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Sleep-wake regulation
Circadian clock
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Circadian rhythms
We have an internal representation of time. Suprachiasmatic nucleus
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Mohawk & Takahashi (2011)
The network properties of the SCN lead to coordination of circadian rhythms amongst its neurons and neuronal subpopulations.
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Ibuka & Kawamura (1975)
Male albino rats had complete bilateral electrolytic SCN lesions. Instantly after recovery from anesthesia, circadian rhythm of the sleep-wakefulness cycle was entirely eliminated after SCN lesions.
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Our circadian rhythm is particularly sensitive to...
blue light
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Zaidi et al (2007) - background
the eye has a dual role in detecting light for a variety of functions independent from sight.These responses are mainly driven by stimulation of photosensitive retinal ganglion cells (pRGCs) which stay functional in the absence of rods and cones.
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Zaidi et al (2007) - what they did
examined the spectral sensitivity of non-image-forming responses in two profoundly blind subjects lacking functional rods and cones
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Zaidi et al (2007) - what they found
Collectively the data demonstrates that photosensitive retinal GCs contribute to both circadian physiology and basic visual awareness in humans and dispute the theory that rod- and cone-based photoreception mediate all "visual" responses to light.
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Our internal clock (SCN) is dependent on...
dependent on external cues such as light. This helps set the clock to local time
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Another important factor in regulating sleep-wake is...
sleep homeostasis
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Sleep homeostasis
As homeostatic drive for sleep accumulates, circadian drive for arousal decrease. This increases as we are awake, but wake is maintained by progressively increasing circadian drive for arousal (Moore, 2007)
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What two key components regulate the timing and duration of sleep?
Circadian Pacemaker (SCN) and Sleep Homeostasis
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We also have this structure in the brain called the...
pineal which produces melatonin feeds back on this master clock and gives a biological representation of the darks as melatonin is released at night.
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We also have to add in...
light is critically important. The light dark cycle will set the clock to local time so that your internal clock is in line with the external clock. Light also inhibits the production of melatonin. Light will also have an alerting affect.
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If any of these are disrupted it has a significant impact on this sleep wake cycle e.g.....
shift work/jet lag
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Excitatory (wake-promoting) neurotransmitters:
Acetylcholine, dopamine, histamine, noradrenaline, serotonin (Schwartz & Roth, 2008)
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Wake promoting neuromodulator
Hypocretin (Schwartz & Roth, 2008)
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Hypocretin is...
Synthesised in a small group of cells in the lateral and posterior hypothalamus (Schwartz & Roth, 2008)
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Acetylcholine from...
LDT and PPT send signals to the thalamus (Schwartz & Roth, 2008)
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Hypocretin is a neuromodulator which is involved in...
Flipping this sleep wake switch (Schwartz & Roth, 2008)
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Individuals with narcolepsy have problems with...
stabilizing sleep/wake states this is due to dysfunctional hypocretin activity
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Primary inhibitory (sleep-promoting) system
Located in the ventrolateral preoptic area of the hypothalamus (VLPO) Inhibits arousal system This VLPO is the sleep promoting area, but very importantly is it inhibits the neurotransmitters invovled in arousal (Schwartz & Roth, 2008)
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The inhibitory neurotransmitters include:
GABA, Galanin (Schwartz & Roth, 2008)
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Normal wakefulness
-Wake promoting neurotransmitters may promote cortical arousal -Wake promoting neurotransmitters may inhibit sleep promoting neurons Hypocretin helps stabilize transitions between wakefulness and sleep
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Normal Sleep
Sleep promoting neurons inhibit wake promoting neurons, decreasing cortical arousal and promoting sleep.
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Polysomnography is used to measure
Sleep
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Different types of Polysomnography
EEG, EOG and EMG
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The sleep stages are characterised by differences in...
EEG, EOG and EMG activity.
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Schwartz & Roth, 2008
Ascending Arousal System
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The two key processes that regulate sleep wake behaviour are
circadian rhythm and sleep homeostasis.
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Awake:
Reticular activating system Active Hypothalamic sleep system Inhibited
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Sleep:
Reticular activating system Inhibited Hypothalamic sleep system Active
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***Beersma & Gordijn, 2007***
In humans it is recognised that the circadian pacemaker in the suprachiasmatic nucleus (SCN) of the hypothalamus exerts gentle control over the sleep–wake cycle, as is shown by the extreme circumstances by which we can nap during the day or stay awak
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******Inouye & Kawamura, 1979******
Evidence that the SCN is a principal circadian pacemaker in the mammalian brain includes the finding that isolation of the SCN in an intact animal does not affect SCN rhythmicity but abolishes the sleep–wake cycle
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******Michel et al., 2009******
Cell-to-cell communication is clearly required for transporting inputs to and outputs from the SCN and might be involved in ensuring the high precision of the observed rhythm.
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******Saper et al, 2005******
PPT/LDT neurons are most active during wakefulness and rapid eye movement (REM) sleep and release more slowly during non-REM (NREM) sleep, a period when cortical activity is decreased
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***Independent research - Lim & Szymusiak, 2015***
Arousal systems can have an effect on neocortical activity indirectly via projections to the thalamus, lateral hypothalamus, or basal forebrain, while others send direct projections to the cortex.
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Card 2

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What are electrical brain potentials used for?

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to classify different levels of arousal and states of sleep.

Card 3

Front

Order of EEG

Back

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Card 4

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Stages of sleep

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Card 5

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EEG - stage 1 - awake

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