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3.5 Eating, sex and other needs week 3 summary on sleep
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SLEEPLearning Goals
- Describe the stages of sleep and age-related differences
- Explain the concepts of sleep timing, social factors, diurnal preference, and chronotype.
- Report the criteria of all sleeping disorders described in the DSM V (Hypersomnolence
disorder, Narcolepsy, Central sleep apnea, Sleep-related hypoventilation, Circadian
rhythm sleep-wake disorders, Non–rapid eye movement (NREM) sleep arousal
disorders, Nightmare disorder, Rapid eye movement (REM) sleep behavior disorder,
Restless legs syndrome, Substance/medication-induced sleep disorder)
- Report in-depth knowledge of all aspects of Insomnia disorder and Obstructive sleep
apnea-hypopnea, as described in the DSM V
- Describe the most common sleep disorders and possible treatments in children
- Describe the most common sleep disorders and possible treatments in adults/elderly
- Report the associations between screen time and sleep in children and adolescents and
the limitations of currents studies
Carskadon & Dement
HUMAN SLEEP
Sleep: reversible behavioral state of perceptual disengagement from and unresponsiveness to
the environment
Within sleep, there are two separate states: rapid eye movement (REM) and non-REM (NREM).
NREM, is further subdivided into four stages (mentioned later), has characteristic waveforms as
sleep spindles, k-complexes and high-voltage slow waves & with different arousal
thresholds (lowest in stage 1 and higher in stage 4), inactive yet actively regulating brain in a
movable body.
Vs REM, defined by EEG activation, muscle atonia, and episodic bursts of rapid eye
movements. Dreaming, w/ inhibition of spinal motor neurons by brainstem mechanisms →
suppression postural motor tonus in REM, activated brain in a paralyzed body.
● Sleep onset
Among normal adults, the onset of sleep is through NREM sleep.
How do we know the onset of sleep?
- Electromyogram (EMG): diminution of muscle tonus
- Electrooculogram: slow, asynchronous eye movements
- Electroencephalogram: activity in the occipital, to a relatively low-voltage, mixed
frequency pattern (Stage 1) → going into stage 2 w/ K-complex or sleep spindles
Is it the same for everyone? Is ‘falling asleep’’ a unitary event? Different functions, such as
sensory awareness, memory, self-consciousness, latency of response to a stimulus etc.
,Behavioral concomitants of sleep onsets
Simple behavioral task: failure to perform a simple behavioral task at the onset of sleep
Visual response: perceptual disengagement from the environment
Auditory response: (subjects asked to respond each time a tone is heard) reaction times
become longer in proximity to the onset of stage 1 sleep, and absent later
Olfactory response: (subjects asked to respond when they smell something), responses
maintained during initial stage 1 sleep, other stages poorer (more response for unpleasant than
pleasant smells later on)
Response to meaningful stimuli: sensory sensitivity to meaningful vs non meaningful stimuli,
response usually measured as evoked K-complexes or arousal.
- E.g. people have a lower arousal threshold for their own names
It seems clear that sensory processing at some level does continue after the onset of sleep.
fMRIs also show regional brain activity in response to stimuli during sleep and that different
brain regions are activated in response to meaningful vs non meaningful stimuli.
Hypnic myoclonia: visual imagery present in stage 1 sleep, as well as general or localized
muscle contraction very often associated with rather vivid visual imagery.
Vs in REM sleep → hypnagogic hallucination with motor inhibitory component
Memory near sleep onset: memory is impaired by sleep, lost for the few minutes before sleep -
because the info in the short-term are not consolidated into long-term memory stores, no
primacy and recency effects
- Inability to grasp the instant sleep onset in your memory
- Forgetting a phone call that had come in the middle of the night
- Not remembering the ringing of your alarm clock
- Morning amnesia for coherent sleep talking
Etc.
NOTE: patients with syndromes of excessive sleepiness can experience similar memory
problems in the daytime if sleep becomes intrusive.
● Progression of sleep across the night
Pattern of sleep in a normal young adult:
Enters sleep through NREM, and REM sleep occurs until about 80 minutes after, then NREM
and REM continue to alternate through the night, with an approximately 90-minute cycle
First sleep cycle
Stage 1 sleep:
- usually persists for only a few (1 to 7) minutes at the onset of sleep
- Easily discontinued
- Low arousal threshold
, - This stage occurs as a transitional stage throughout the night
- Common sign of severely disrupted sleep is an increase in the amount and percentage
of stage 1 sleep
Stage 2 NREM sleep:
- Sleep spindles or K-complexes in the EEG
- Approximately 10 to 25 minutes
- More intense stimulus required to produce arousal
NOTE: the same stimulus that produces arousal from stage 1 often results in evoked K-complex
but NO awakening
- High-voltage slow-wave – which continues onto the next stage
The last two stages also called slow-wave sleep (SWS), delta sleep, or deep sleep
Stage 3 NREM sleep:
- Lasts only a few minutes in the first cycle, and transitional to stage 4 sa a more and
more high-voltage slow wave activity occurs
Stage 4 NREM sleep:
- Lasts approximately 20 to 40 minutes in the first cycle
- Incrementally larger stimulus required to produce arousal for the last 2 stages than the
first 2
The initial REM episode:
- Usually short lived in the first cycle (1 to 5 minutes)
- Arousal threshold is variable
NOTE: the first cycle overall approximately lasts 70 to 100 minutes in total
The NREM-REM sleep continue to alternate through the night in a cyclic fashion
- REM episodes usually become larger across night
- Stages 3 and 4 (SWS) occupy less time in the second cycles, and might disappear
altogether from later cycles
- Stage 2 expands to occupy the NREM portion of the cycle
- The second and later cycles are longer (90-120 minutes)
SWS → reflects the homeostatic sleep system (regulated balance between sleep and waking),
highest at sleep onset and diminishing across the night as sleep pressure wanes.
Disruption of sleep stages across the night:
- Brief episodes of wakefulness tend to interlude later in the night, usually near REM sleep
transitions (usually do not last long enough to be remembered in the morning)
- REM sleep - longest in the last one third of the night, this preferential distribution is
thought to be linked to a circadian body temperature oscillation (mentioned later)
- SWS - the preferential distribution of SWS toward the beginning of a sleep episode is
thought to be a marked response to the length or prior wakefulness (and not to
circadian)
Length of sleep
- High variability from person to person and from night to night
- Also depends on genetic determinants
, - Length of prior waking
- Associated with circadian rhythms
SO, when one sleeps helps to determine how long one sleeps.
Generalizations about sleep in the normal young adult
• Sleep is entered through NREM sleep.
• NREM sleep and REM sleep alternate with a period near 90 minutes.
• SWS predominates in the first third of the night and is linked to the initiation of sleep and the
length of time awake.
• REM sleep predominates in the last third of the night and is linked to the circadian rhythm of
body temperature.
• Wakefulness in sleep usually accounts for less than 5% of the night.
• Stage 1 sleep generally constitutes approximately 2% to 5% of sleep.
• Stage 2 sleep generally constitutes approximately 45% to 55% of sleep.
• Stage 3 sleep generally constitutes approximately 3% to 8% of sleep.
• Stage 4 sleep generally constitutes approximately 10% to 15% of sleep.
• NREM sleep, therefore, is usually 75% to 80% of sleep.
• REM sleep is usually 20% to 25% of sleep, occurring in four to six discrete episodes.
Factors modifying sleep stage distribution
Age: the strongest and most consistent factor affecting the pattern of sleep stages across the
night
- First year of life: transition from wake to sleep is often accomplished through REM sleep
(called active sleep in newborns) vs NREM in healthy adults. Fully developed EEG
patterns of the NREM sleeps are not present
- When brain structure and function achieve a level that can support high-voltage
slow-wave EEG activity, NREM stages 3 and 4 sleep become prominent.
- SWS is maximal in young children and decreases with age
- By age 60 - SWS no longer present particularly in men. Women appear to maintain SWS
later into life than men.
NOTE: REM sleep → the absolute amount of REM sleep at night has been correlated with
intellectual functioning, and declines markedly in the case of organic brain dysfunctions of th
elderly
- Arousals during sleep markedly increase with age
- Extended wake episodes of which the individual is awake and report, as well as bried
unremembered arousals increase with aging
- Elderly also have higher interindividual variability
Prior sleep history: experienced sleep loss on one or more nights – recovery is through SWS,
with prolonged and deeper (thus having a higher arousal threshold throughout) the basal sleep.
- The REM sleep tends to recover only after the recuperation of the SWS,
So, SWS usually comes first, but there are also cases where a person is deprived from REM
sleep (e.g. by being awakened each time the sleep pattern occurs) etc., in that case there is a
preferential rebound of REM stage
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