week 7 - sleep and memory Flashcards
watch first 20 mins of this lecture!
how do you measure sleep?
EEG
During rem sleep. EEG trace is similar to awake stage. It is paradoxical because it sugests the person is awake. To measure REM sleep we must measure the EMG which measures signals from skeletal muscles. During REM sleep there is muscle atonia so there is very little signal from skeletal muscles.
NREM sleep:
N1: transient, half alseep
N2: K-complexes, spindles. Entering into deeper sleep
N3: Slow wave sleep, high amplitude low frequency oscillations.
whats the difference between human and rodent sleep stage cycles?
cycles are much shorter
how does sleep stages change throguhout the night
We experience more NREM sleep in the first half of the night, and more REM sleep in the second half of the night.
how does sleep impact memory?
sleep is beneficial for all types of memory
consolidating existing memorys and preparing the brain to learn the following day
how does sleep impact declerative memory
lehal et al 2007
positive correlation between words recalleed and sleep
even ultra short naps improved performance
what is the dual process hyptohesis?
plihal and born 1999
NREM facillllitates hippocampus dependent declerative memory consolidation
REM sleep facilitates non-declarative hippocampus independent memory
describe study plihal and born
what is the cost of staying awake
learning comes at a cost
sleep may function to restore the learning potential of the brain
what is the impact of sleep deprivation on ltp and memory?
read abel et al 2013
cAMP-PKA-CREb signalling required for long lasting LTP
reduced levels of CREB-containing genes transcribed during sleep deprivation.
cAMP-degrading phosphodiesterase (pdef_ upregulated by Sleep deprivation
Blocking PDE4 eliminates effect of Sleep deprivation on LTP and restores learning and memory
applied fear conditioning paradigm to rodents that had sleep deprivation
what happens to cortical neurons during sleep deprivation
read vyazovisky et al 2011
when animals are sleep deprived individual neurons in the cortex go into slow oscillatory sleep like states
what is the synaptic homeostasis hyptohesis
tononi and cirelli 2014
sleeps main function is the restoration of learning potential via synaptic homeostasis
when we are awake we make ‘noise synapses’ and when we are asleep we destrengthen these synapses to improve signal to noise ratio
waking = synaptic potentiation. Sleep = synaptic downscaling (de vivo et al, 2017)
what happens to synaptic proteins during sleep
evidence from flies and rodents suggest that synaptic proteins required for memory consolidated are downregulated during sleep - Gilestro et al., Science 2009, vyazovskiy et al, 2008
mechanism for synaptic plasticity during sleep according to SHY - tononi and cirelli 2018
Net (global) synaptic downscaling during NREM
Achieved by removal of AMPAR from spines
Sleep-dependent renormalization seems to spare neurons and/or synapses that are most active during sleep
UP states in slow oscillation of NREM can result in weakening or preservation of spines by a STDP mechanism.
Presence of co-active postsynaptic neurons crucial for preservation (and strengthening?).
Candidate molecules for positive tagging (preservation of spines): GSK3b phosphorylation (inactivates LTD)
Arc and Homer1a may localize in weaker spines and tag those for downscaling during sleep.
