sleep architecture Flashcards
what are three mechanisms thought to regulate sleep?
(1) autonomic nervous system balance
- Sleep requires decreased sympathetic activation and increased parasympathetic balance
(2) homeostatic sleep drive
- We get sleepy when we don’t sleep
(3) circadian rhythms
Biological clock in suprachiasmatic nucleus
match stages of alterness with their types of brain waves
wake: beta
resting wake: alpha
sleep onset, nrem1,2, and REM: theta
SWS,NREM3: delta
what is sleep architecture?
the organization of a person’s sleep stages. For example, we have a different sleep architecture in the beginning of the night compared to late at night.
· More slow wave sleep at the beginning
· More REM sleep late at night
what is sleep microarchitecture
Refers to smaller phasic events during sleep. Examples include sleep spindles, k complexes, delta/slow waves, rapid eye movements, cyclic alternating patterns
what are possible functions/clinical implications of sleep spindles
Possible functions include:
· Memory consolidation
· Possible marker of neuroplasticity - promote recovery after serious brain injury?
· Controversial: spindles and intelligence??
Clinical implications:
· Some disorders like schizophrenia have altered sleep spindles
· Indirect indicator more widespread deficits in thalamocortical functioning - neurodegenerative diseases?
· Changes with age - less spindles as we get older (spindles are a dynamic, age dependant phenomenon)
what is the connection between sleep spindles and memory?
People who learnt a task before bed have more spindles than people who didn’t learn a task.
K complexes - when do they happen
Similar to sleep spindles in that they are a NREM sleep phenomenon - mark the beginning of N2 sleep. They can be spontaneous or evoked (ex. By external stimulation - like a sound - during sleep). Play a role in thalamocortical gating.
Individual thresholds of intensity/ ‘do we care’ for arousal in sleep
slow waves - where do they occur?
Sleep is usually considered a global phenomenon - however, slow waves tend to be generated locally. In other words, different brain regions can be in their own state of synchrony
potential functions of slow wave sleep
· Memory consolidation
· Synaptic homeostasis - getting rid of the synaptic connections made during the day that take up too much room
· Restorative function
Reactivity - highest threshold of responsiveness
Rapid eye movements
Happen when we look around in our dreams. (maybe) This is the “scanning hypothesis.”
We aren’t still fully sure on the function of rapid eye movements but we’re pretty sure that they can act as an index of intensity of dream experience.
Could also be a marker for depression - less REM?
cyclic alternating patterns
are any events in sleep that don’t mark a change in sleep stages. These types of patterns are composed of phasic events and are used as markers of sleep instability.
· Ex. Sleep spindles, bursts of slow waves, etc
Can be used to create an index of sleep instability
what is the significance behind cyclic alternating patterns in comatose patients?
CAP started to be studied in comatose patients to predict recovery - once a patients sleep starts to look closer to normal sleep, it becomes more likely that they are recovering
why do some people think we should look at sleep as processes instead of stages?
because sleep ‘stages’ aren’t confined to sleep and vice versa for stages of wakefulness:
SLEEP PROCESSES IN WAKE:
· Sleepiness
· Fatigue
· Mind-wandering
· Attentional lapses
WAKE PROCESSES IN SLEEP
· “windows of wakefulness”
· Responsiveness to stimuli
· Motor behaviours
Lucid dreams
why is sleep quality a poorly defined concept?
Sleep quality is actually quite a poorly defined concept. Because the correlation between objective markers and subjective experience of sleep is so modest, EEG markers may be separate from the experience of sleep
what do we know about getting ‘good’ sleep?
Slow wave sleep is likely the most crucial to feeling of good sleep and to recovery functions (memory, executive functions, etc)
· Remember: slow wave sleep is more concentrated early in the night
Continuity of sleep might be more important than duration of sleep - in relation the subjective experience and performance
