sleep

Question 1

sleep

Answer 1

important and mostly quiescent phase of our circadian rhythms (24hr natural rhythm)

Question 2

proposed functions of sleep

Answer 2

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

Question 3

REM sleep

Answer 3

paradoxical sleep, looks as if you are awake

dreaming

Question 4

sharp wave ripple (SWR)

Answer 4

occurs in the hippocampus, thought to support “replay”/”reactivation” during sleep

Question 5

serotonergic (raphe nuclei)

Answer 5

promotes arousal, wakefulness

turns off during sleep

Question 6

noradrenergic (locus coeruleus)

Answer 6

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

Question 7

GABA-ergic (basal forebrain)

Answer 7

promotes sleepiness, SWS

active for us to sleep

Question 8

cholinergic (pedunculopontine)

Answer 8

promotes REM (PGO waves)

rapid eye movements - state where people report the dreams most often

Question 9

hyhypothalamic nucli regulate sleep

Answer 9

activation of ventrolateral preoptic nucleus (VLPO) induces sleep

orexin neurons produce arousal

Question 10

activation of ventrolateral preoptic nucleus (VLPO) induces sleep

Answer 10

GABA projections to reticular activating system in the brainstem

RAS keeps you awake so this shuts it down

Question 11

orexin neurons produce arousal

Answer 11

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

Question 12

cerebrospinal fluid (CSF)

Answer 12

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

Question 13

glymphatic system

Answer 13

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

Question 14

EEG slow (delta wave sleep)

Answer 14

causes large changes in cerebral blood flow, cerebral blood volume and cerebral spinal fluid

Question 15

sleep spindles: thalamocortical loop

Answer 15

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

Question 16

hippocampal ripples

Answer 16

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

Question 17

the role of sleep in memory

Answer 17

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

Question 18

sleep and motor learning

Answer 18

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

Question 19

schizophrenia

Answer 19

fewer sleep spindles and no sleep-associated motor sequence improvement

Question 20

SWS: offline memory replay

Answer 20

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

Question 21

SWS short wave sleep

Answer 21

is the stage most implicated in memory consolidation

stimulus cues presented during SWS can bias which memories are replayed

Question 22

sleep spindles

Answer 22

arise from the thalamus and travel to the cortex

stimulate early gene expression and glutamate receptors for LTP

Question 23

Ripples

Answer 23

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

Question 24

synchronizations of Slow oscillations, sleep spindles and ripples in SWS sleep

Answer 24

believed to ensure memory replay and transfer of learned sequences from the hippocampus of the cortex

when synchronized we get the strongest consolidation

Question 25

slow oscillation

Answer 25

slow oscillations arise in the cortex and spread to subcortical areas

enhancing these with tDCS in humans causes an improvement in memory recall

Question 26

forming schemas

Answer 26

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

Question 27

Integrating new memories

Answer 27

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

Question 28

proposed function of REM sleep

Answer 28

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

Question 29

effects of sleep deprivation

Answer 29

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

Question 30

sleep and dementia

Answer 30

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