Sleep Flashcards
What does sleep polysomnography measure?
Brain activity EEG, eye movements EOG, muscle activity EMG, and heart activity ECG
What does EEG measure?
Measures the potential differences between two points on the scalp
Wakefulness EEG
Low amplitude fast rhythms
A relaxed subject with eyes closed is differentiated from sleep by the presence of alpha EEG activity in 50% or more of the time.
Stage 1 EEG
Similar to wakefulness, very superficial, small eye movements, slow, slightly higher amplitude EEG.
Alpha activity 50% or less of the time
Stage 2 EEG
Spindles and K complexes:
Characteristics include sleep spindles and K-complexes occurring on a low-voltage, mixed-frequency background EEG and minimal (<20% of the time) slow-wave activity.
Stage 3 EEG
High amplitude slow waves
Contains delta EEG activity with a 75 µV or greater amplitude enduring for 20% or more of the duration
REM EEG
Similar to wakefulness EEG, sensory disconnected from environment
Saccadic eye movements occur during epochs with low-voltage, mixed-frequency EEG in association with a very low level of EMG activity.
Proportions spent in each sleep phase?
REM sleep accounts for approximately 20% to 25% of total sleep time, stage N2 accounts for 50%, N3 accounts for 12.5% to 20%, and N1 accounts for the remainder.
Sleep oscillations
Rhythmic and/or repetitive electrical activity generated spontaneously and in response to stimuli by neural tissue in the central nervous system
Slow waves divided into
Slow oscillation (0.2-1 Hz)
Delta (1-4 Hz)
Spindle (7-15 Hz
Theta (4-10 Hz)
Three areas controlling sleep oscillations
Cortex, thalamus, reticular nucleus of thalamus
Thalamus sends what signals to RTN and cortex
Glutaminergic
Cortex sends what signals to RTN and thalamus
Glutaminergic
Reticular neurons sends what signals to where
GABAergic inhibitory output to the thalamocortical neurons
What is a sleep spindle
0.5-second (or longer) burst of 12- to 14-Hz activity
What initiates spindles
Thalamic reticular nucleus and regulated by thalamo-reticular and thalamo-cortical circuits.
What disorder leads to deficits in spindle activity?
Schizophrenia
What diffuse subcortical neuromodulatory systems regulate global brain states
Cholinergic Adrenergic Histaminergic Dopamine Serotonin Orexin/Hypocretin
Where are orexin neurons
Lateral nucleus of the hypothalamus
Cholinergic nuclei are located?
Lateral dorsal tegmentum and posterior pontine tegmentum
Basal forebrain
Cholinergic neuron effect on arousal
Maintain awake state
Monoaminergic nuclei that project to forebrain include
Noradrenergic locus coeruleus, histaminergic neurons in the TMN, serotoninergic neurons in the median raphe nuclei, dopaminergic neurons in the vPAG and VTA
Monoaminergic in wakefulness
Fire during wakefulness
Monoaminergic neuron in sleep and REM sleep
Decrease activity during non-REM sleep, and silent during REM sleep
Noradrenergic neurons in
Locus coeruleus
Histaminergic neurons in
TMN
Serotoninergic neurons in
Median raphe nuclei
Dopaminergic neurons in the
VTA and vPAG
Phenelzine can
Eliminate REM sleep
When do Orexin neurons fire
Fire predominantly during wakefulness, and particularly during motivated behaviours
Orexin neurons inhibited by
Glucose, (activated when glucose is low)
Orexin destruction leads to
Narcolepsy
What is the sleep promoting area
VLPO (ventral lateral preoptic nucleus)
What is the wake promoting area
TMN (histamine), LC (noradrenaline), LH (orexin), VTA (dopamine)
How do wake promoting and sleep promoting areas communicate?
Inhibitory connections
Sleep promoting neurons are
GABAergic neurons in preoptic hypothalamus
Why do benzodiazepines make you sleepy?
Potentiate GABA (preoptic sleep promoting area)
How is REM sleep controlled?
REM-on cells and REM-off cells
What is a circadian rhythm?
Natural, internal process that regulates the sleep–wake cycle and repeats on each rotation of the Earth roughly every 24 hours.
Any biological process that displays an endogenous, entrainable oscillation of about 24 hours.
Master circadian clock is?
SCN
SCN input
Light information by a direct retinohypothalamic tract (RHT) to entrain the clock to the 24-h day.
What is a zeitgeber?
Cue in the regulation of the body’s circadian rhythms.
What regulates the timing of melatonin synthesis?
The SCN clock
Where is melatonin released from?
Pineal
When is melatonin secreted?
At night
What does it mean to be able to synchronise and reset biological oscillations?
Chronobiotic effects
Responsiveness of SCN neurons to melatonin is greatest
Around subjective dusk
Role of melatonin
Chronobiotic, feedback to SCN clock
Sleep after sleep deprivation is
Deeper, not necessarily longer
Elderly sleep
Advanced sleep timing (i.e. earlier bedtimes and rise times)
Longer sleep-onset latency (i.e longer time taken to fall asleep)
Shorter overall sleep duration
Increased sleep fragmentation (i.e. less consolidated sleep with more awakenings, arousals, or transitions to lighter sleep stages)
More fragile sleep (i.e. higher likelihood of being woken by external sensory stimuli)
Reduced amount of deeper NREM sleep known as slow wave sleep (SWS), increased time spent in lighter NREM stages 1 and 2, shorter and fewer NREM-REM sleep cycles, increased time spent awake throughout the night.
Consequences of sleep deprivation
Decreased alertness
Increased attentional lapses
Decreased hand-eye coordination
Decreased attention and sustained vigilance
Decreased olfactory discrimination
Impaired verbal learning, deficit in temporal memory, impairment in working memory
Reduced verbal fluency
Reduced capacity to modify behaviour rapidly and flexibly to changing demands
Reduced inhibitory control
Impaired capacity to integrate emotional cues into the decision-making process, impaired judgement.
