neurobiology of sleep and circadian rhythms Flashcards
how does adenosine relate to sleep? how does it relate to the 19th century view of hypotoxins?
it accumulates in the body as sleep debt and dimishes during sleep
- similar to the view that hypotoxins accumulate in the body during waking and need to be purged out during sleep
what do imaging studies look for during sleep?
functional connectivity and anatomical correlates of EEG events
in terms of global activity (glucose metabolism) describe wakefulness, sws, and rem
WAKEFULNESS: brain uses a lot of energy
SWS: way less energy
REM: looks like wakefulness but not quite
what does brain activity look like in non rem sleep
· Cerebral blood flow decreases in a lot of areas
○ Basal ganglia
○ Prefrontal cortex
○ Basal forebrain
○ Hypothalamus
○ Etc
Compared to wake: cbf, glucose and oxygen metabolism decreases by 5-19% in N2 and by 25-40% in N3 (sws)
what does brain activity look like in rem sleep?
Unique pattern of activation (compared to nrem and wake)
Areas that are more active in rem:
- Thalamus, basal forebrain, amygdala, hyppocampus, anterior cingulate (memory, emotions, etc), motor areas, visual associative areas
Areas that are less active:
Dorsolateral prefrontal cortex, posterior cingulate, precuneus, inferior parietal cortex (executive attentional areas)
what are pgo waves
(in other mammals - cats and such)
Thought to initiate REM sleep (Hobson-wanted to prove that dreams are purely physiology)
Hobson: brainstem sends waves from PONs, activating neocortex bottom up and blocking motor and sensory input. Eye movements are generated for no good reason and hallucinations are also generated.
brain connectivity
how much of the brain is doing something together?
· In wake we have high connectivity between regions(have to do so much) · Things get less integrated as we fall asleep · In slow wave sleep, things are *really* local - nrem sleep stage of locally generated slow waves In REM sleep, things get more interconnected - prefrontal cortex stays disconnected (why we dream about things that aren't entirely logical and not directly related to our real life)
why are our dreams often so illogical?
because the prefrontal cortex is disconnected from the rest of brain activity in rem sleep
what are some types of time scales that our bodies are attuned to?
□ Seasons (hard to be as productive in the winter, need more sleep) *have to think about seasonal changes in circadian rhythm when doing studies
□ Day-night - planetary changes 🌎🪐
□ Sleep-wake
□ Activity-rest
□ Heart rate
□ Respiration
□ Cell metabolism
Neuronal firing
what is the connection between homeostatic drive and our circadian rhythm
Homeostatic drive is inhibited by circadian alerting signal - by noon we actually have a lot of homeostatic drive (sleep debt/load), however our circadian alerting signal tells us to stay awake because its day
Or… Think of how if you sleep in really really late, then you might not be able to fall asleep in the evening because although your circadian alerting system is telling you to fall asleep, you don’t have enough homeostatic drive
describe the sleep deprivation study graph that includes three parts: homeostatic, ultradian, circadian
⭐️Sleep deprivation study that shows us the interaction of three processes⭐️
- Shows circadian rhythm persisting regardless of how tired you are (at least for some time)
- Homeostatic drive accumulates when you are sleep deprived
Ultradian process: regulation of sleep architecture during a period of sleep - changes with more sleep deprivation - with prioritize getting rid of sws pressure first - will increase sws and length of sws
what are the three processes that regulate sleep:
HOMEOSTATIC PROCESS:
- Homeostatic debt, sleep pressure
- Sleep pressure starts upon awakening and diminishes with sleep
CIRCADIAN PROCESS:
- Circadian phase - high/los sleep propensity, largely independent of preceding sleep period
ULTRADIAN PROCESS: sleep architecture within a period of sleep, alternating structure of REM/NREM sleep
ultradian processes
. Last less than 24 hours and are modulated by circadian and homeostatic processes
Refer to the distribution of sleep stages - tend to be differently distributed during early and late night
- Slow wave sleep pressure predominance early in the night
- Rem sleep pressure predominant late in the night
- naps in the day have a higher propensity for rem
circadian rhythm
…are rhythms of living organisms that last approximately 1 day (pretty flexible - seasons, time zones, changing needs)
It is a dynamic balance between stability of the system and adaptability to demands of the environment
Balance: between modulation of internal organization and external
suprachiasmatic nucleus
Is the circadian “master clock” - other organs and peripheral tissues have their own circadian clocks, but are subordinate to the SCN
