sleep Flashcards
sleep
important and mostly quiescent phase of our circadian rhythms (24hr natural rhythm)
proposed functions of sleep
adaptive immobilization or energy allocation/conservation (dont make noise ie/ for predators)
protective/restorative phase (decreased immune function and memory when deprived
neural network reorganization
enhanced synaptic efficiency
neurotoxic chemical clearance
memory consolidation, enhancement, and/ or erasure
REM sleep
paradoxical sleep, looks as if you are awake
dreaming
sharp wave ripple (SWR)
occurs in the hippocampus, thought to support “replay”/”reactivation” during sleep
serotonergic (raphe nuclei)
promotes arousal, wakefulness
turns off during sleep
noradrenergic (locus coeruleus)
promotes arousal, wakefulness
subcoerulus: inhibits motor neurons, promotes muscle atonia during sleep
the part that ensures we do not act out our dreams
turn off during sleep
GABA-ergic (basal forebrain)
promotes sleepiness, SWS
active for us to sleep
cholinergic (pedunculopontine)
promotes REM (PGO waves)
rapid eye movements - state where people report the dreams most often
hyhypothalamic nucli regulate sleep
activation of ventrolateral preoptic nucleus (VLPO) induces sleep
orexin neurons produce arousal
activation of ventrolateral preoptic nucleus (VLPO) induces sleep
GABA projections to reticular activating system in the brainstem
RAS keeps you awake so this shuts it down
orexin neurons produce arousal
Peptide NT
orexin peptides are produced by neurons in the lateral hypothalamus
projections of orexin neurons connect to other areas of the hypothalamus (ie/ tuberomammillary nucleus) TMN and brainstem (e.g. locus coeruleus) - helps keep us awake
dual orexin receptor antagonists (DORAs) are being developed as sleep- promoting medications
cerebrospinal fluid (CSF)
for the ventricles and subarachnoid space flow into the extracellular space
increased space between extracelluar space between neurons and glial cells but a lot - allows CSF to flow
space between cells expaning
glymphatic system
CSF
contributes to removing debris and depositing it in perivascular vein space
this mostly occurs while we sleep, offering a clue to the purpose of sleep
the extracellular space increases in volume and removes waste to sharpen signal quality and to reduce synaptic noise
intrinsic immune response in brain
during SWS
increased synaptic activity, less signal to noise signal will not have to get though debris - get slower throughout the day because debris is accumalating
slow - wave sleep is linked to the glymphatic system through hemodynamic oscillation
EEG slow (delta wave sleep)
causes large changes in cerebral blood flow, cerebral blood volume and cerebral spinal fluid
sleep spindles: thalamocortical loop
12-15 Hz
behavioural evidence suggests that sleep spindles are associated with sleep-dependent cognitive and motor performance - fewer you have the worst you are going to be in cognitive and motor tasks the next day
physiologically, spindles have been shown to support plasticity
- sleep deprivation suppresses neurogenesis in hippocampus
hippocampal ripples
during behavioural exploration, the hippocampus displays a strong ~7-8 Hz oscillatory activity, nown as the theta rhythm
during sleep and quiet wakefulness theta is replaced by large irregular activity characterized. by the occurrence of sharp wave events called ripples
play a causal role in memory consolidations
this is created by broad excitation of CA1 neurons by CA3 pyramidal cells via the Schaffer collaterals
synchronization of the interneuron network at ~200 Hz generates a ripple in the pyramidal layer
the role of sleep in memory
sleep quality, duration, and consistency are associated with better academic performance
intrinsic neural activity reactivates this circuit with the consequence that new proteins are synthesized
sleep and motor learning
motor sequence learning is often used to study the effects of sleep on motor memory
sleep spindles increase after motor sequence learning (better motor learning with more sleep spindles)
motor-skill learning correlates postitively with the amount of stage 2 NREM sleep, when sleep spindles reach peak density
schizophrenia
fewer sleep spindles and no sleep-associated motor sequence improvement
SWS: offline memory replay
when rats explore a novel space (ie/ a maze), place cells are trained to be activated in a specific sequence (we do this when we familiarize ourselves with a room)
while awake, place cells fire in revered order sequence- this may allow for reward signal to assign decaying value to reverse sequence
during SWS, place cells fire in sequence but at ~20 times the rate
SWS short wave sleep
is the stage most implicated in memory consolidation
stimulus cues presented during SWS can bias which memories are replayed
sleep spindles
arise from the thalamus and travel to the cortex
stimulate early gene expression and glutamate receptors for LTP
Ripples
arise in the hippocampus
associated with offline replay of learned sequences during encoding
long duration ripples improve memory
- artificially prolong sharp wave ripples improved working memory
- artificially inhibiting sharp wave ripples decreases performance on learned tasks
synchronizations of Slow oscillations, sleep spindles and ripples in SWS sleep
believed to ensure memory replay and transfer of learned sequences from the hippocampus of the cortex
when synchronized we get the strongest consolidation
slow oscillation
slow oscillations arise in the cortex and spread to subcortical areas
enhancing these with tDCS in humans causes an improvement in memory recall
forming schemas
when distinct memories are consolidated, abstracted reqularities are extracted
the schemaof “dog” can be formed by extracting regularities from instances of poodle, retriever and hound
distinct memory instances of the dogs have overlapping cortical representations
during SWS, the common parts of each are reactivated and reinforced as a generalized schema for a “dog”, followed by synaptic downscaling to remove features not fully common
Integrating new memories
Assimilating new memories is easier when related schemas are available
when a new memory shares features with one or more established schemas, it is more easily appended through reactivation of the schema and hebbian synapse strengthening
synaptic downscaling makes memory-to-schema activation more likely than schema-to-memory re-activation
additional memories are similarly appended, which occasionally cause and update to the schema
proposed function of REM sleep
schema disintegration
this involves associative thinking, in which pieces of info are combined in novel ways (ie/ creativity)
in multiple studies of creative problem solving, associative thinking benefits after being awakened from only REM sleep
ie/ anagram word puzzles
effects of sleep deprivation
attention and working memory
- common lapses and microsleeps, causing increases in omission failures
- diminished WM capacity
- sleep deprivation causes more frequent switching between frontoparietal and default mode brain networks
emotion perception and production
- both positive and negative emotion discrimination and expression are diminished after sleep deprivation
sleep and dementia
sleep disturbances are common in Alzheimer’s disease
growing evidence that sleep disturbances are a symptom and risk factor for AD - less sleep in the long run = more risk
patients with AD exhibit less time in SWS
improving sleep holds promise as AD prevention or treatment
