Lecture Genzel Flashcards
What is the function of sleep
Metabolic ( e.g. sleep deprivation –> insulin resistance)
Homeostatic (e.g. cleansing of extracellular space)
Immunological (e.g. sleep deprivation –> smaller vaccination effect)
Memory consolidation (e.g. memory reactivation)
interaction between oscillation between cortex and hippocampus in replay
memories are mainly reactivated during non-rem sleep
What happens during sleep (memory consolidation)
Replay:
- capture oscillations (slow and sleep k-complex spindles) –> non-rem sleep, light non-rem sleep and deep non-rem sleep. In both surface of EEG and deeper areas. In Hippocampus we see SWR (sharp wave ripple)
Downscaling:
- more during slow wave activity and REM sleep. decreasing synaptic strength. Otherwise brain would only potentiate. Also : prooning happening but in adults more adjustemt of size of synapse
mostly about homeostasis
How is sleep and memory consolidation related to Alzheimers disease?
- disregulation of sleep – linked with beta amyloid protein
- memory will initially be more reliant on hyppocampus and later on cortex – systems consolidation
glucose deoxit imaging (which brain areas are used during learning):
- Recent memory retrieval ( more hippocampus)
- Remote memory retrieval (more cortex)
water mase –> after one weeks (use cortex more for memory retrieval), but in alzheimer models cortex is used less.
Ripples do not look compleatly normal in memory reactivation (suggesting that ripples are important for memory replay and systems consolidation)
Vicious cycle between sleep and beta amyloid. Which one is connected to memory?
Mander et al., –>
healthy controls and testing of amount of beta amyloid protein
High, intermediate an low group
the more beta amyloid protein they had in their prefrontal cortex, the fewer of the slow oscillations
slow-wave activity vs beta amyloid and memory compared with slow-wave/beta amyloid
The fewer of slow oscillations –> the more beta amyloid
System consolidation:
How much is hippocampus LESS active at retrieval
Amount of beta amyloid in frontal cortex correlates with how much slow oscillations are found and correlates with how good you are with memory and with how much less activity is found in the hippocampus.
How are memories consolidated during sleep and what is the directionality according to Mander et al., model?
memories are consolidated from the hyppocampus to the cortex during sleep, what they found is that beta Amyloid protein causes sleep disruption which causes problems with memory consolidation (Mander et al.)
Depression/Schizophrenia relationship with sleep
Genzel Biol Psych 2015:
Finger-tapping task (ask subjects to tap as quickly and correctly as possible)
Increase in correctly tapped sequences with sleep (jump, benefit of sleep on memory). Benefit of sleep in memory consolidation is not as affective in depression and schizophrenia.
Scanner: connectivity between hippocampus and prefrontal cortex predicted how much they would benefit from sleep for memory consolidation.
Research slow oscillations, spindels, ripples in rodents schizophrenia
Philipps Neuron 2012, Wamsley et al. Biol Psych 2011
mouse model of schizophrenia, research found
Cross frequency coupling (slow oscillation coupled with spindle, which is coupled to the ripple) disappears in schizophrenia mouse models.
Sleep spindels look different as well in humans with schizophrenia.
Is replay propper replay? In healthy mice yes, in schizophrenic mice, no.
So there are more ripples but less oscillation coherence and less replay.
When they are engaging in learning then there will be less hippocampal connectivity, but the connectivity problem is also present during sleep
How is sleep regulated?
You can describe sleep regulation with 2 main factors:
- Homeostatic sleep pressure (If I take away your sleep you get sleepier) –> buildup over the day and decreases in night
- cicardian (regulates with sun)
process 1 can be changed with Adenosine antagonist (coffee)
Process 2 can be influences with Light (Melatonin)
Schlaf-Wach-Zyklus
Schlafentzug
Two Process Model from Borbely
Chronotypes
11-7 with chronotype being in the middle of the night (3)
average in Germans (midnight and 9 am)
Multidien Effects: Seizure incidence
10 day peak and 26 peak day. Every 26th day they are more likely to have a seizure. Seisonal cycle, daily cycle etc.
Important!
Sleep stages – what comprises them and how they cycle through the night and that they do exist in rodents but shorter and polyphasic
oscillations and coupling of oscillations
and coupling of brain areas is important for memory replay during sleep which leads to memory consolidation
cleansing of brain (beta amyloid) vicious cycle with alzheimers
Chronotypes
