Sleep Flashcards
Which animals show unihemispheric and asymmetric non-REM sleep?
Marine animals and birds
What has been observed in humans when sleeping in a novel environment for the first time?
Interhemispheric asymmetry - the dominant hemisphere does not appear to fall asleep as deeply, showing increased vigilance in response to deviant stimuli
Where does interhemispheric asymmetry occur in the brain?
The default-mode network
Sleep is…..
✨dangerous
✨omnipresent
✨universal
✨irresistible
✨strictly regulated
✨serious consequences
How many hours sleep are recommended for adults?
7-9 hours
What happens to REM sleep as we get older?
It decreases
Why is REM hypothesised to be greatest in the first 2 years of life?
REM is when the brain is most active during sleep, during which new connections can be made
What is post-REM important for?
Cognition
What did Yetishi et al find in their study of sleep patterns around the world?
People in preindustrial societies can function on less sleep BUT this is likely because they engage in less demanding cognitive tasks
When do we need more sleep?
▪️As babies/children
▪️When under stress
▪️When engaging in complex cognitive tasks
What two EEG sleep patterns are seen in mammels and birds across evolution?
REM and non-REM
What happens to the body in extreme sleep deprivation?
▪️Metabolic overdrive
▪️Food intake increased 80% and body weight decreases 20%
▪️Increased levels of plasma noradrenaline, T3, and T4
▪️Sepsis
▪️Thermoregulatory and metabolic imbalance
▪️Death
What is fatal familial insomnia?
An autosomal dominant inherited prion disease that causes increasing insomnia before death
What are the first symptoms of FFI and how long do these last?
Increasing insomnia, resulting in anxiety, paranoia, and phobias for approximately 4 months
What is the second stage of FFI?
Hallucinations and panic attacks for approximately 5 months
What is the third stage of FFI?
Catatonia, complete inability to sleep and rapid weight loss for approximately 3 months
What is the final stage of FFI?
Dementia, during which they become unresponsive or mute, following by death. This usually occurs over 6 months.
What are the Roiter family known for?
The majority of research into fatal familial insomnia
What is the main neurological finding in those with FFI?
Decreasing activity in the thalamus (hypometabolism)
Where and when does neurodegeneration begin in FFI?
In the thalamus, approximately 13-21 months before clinical presentation
What are the main stages of the sleep cycle?
▪️N1 (stage 1)
▪️N2 (stage 2)
▪️N3 (stage 3&4)
▪️REM
How long is each sleep cycle?
80-100 minutes
How many sleep cycles do people usually have in a night?
4-6
What percentage of sleep is non-REM sleep in adults?
75-80%
What percentage of sleep is REM sleep in adults?
20-25%
What happens in the first stage of sleep (N1) and how long does this last?
The body falls asleep and starts to relax. This usually takes 5-10 minutes (3-8% of sleep)
What happens during N2 and how much of sleep is this?
Stable light sleep - brain activity, heart rate and breathing slows, body temperature drops, and the brain produces sleep spindles. This stage is very important for cognition.
It is approximately 45-55% of sleep
What happens during N3 and what proportion of sleep is it?
Deep restorative sleep aka slow wave sleep - body and tissue is restored, increased delta brain waves.
It is approximately 15-20% of sleeo
What is REM sleep and what happens during it?
Dreaming sleep
▪️Brain activity increases again
▪️Learning and memory consolidation
▪️Muscle atonia (low muscle tone)
What are the main brain regions involved in sleep?
The thalamus and a complex set of nuclei in the brainstem
What state is the brain in during waking?
A catabolic state:
▪️Breaking down or losing tissue
▪️Sympathotpnic
▪️Type 2 humoral immune responses
Are hallucinations in DLB and narcolepsy intrusions of REM into wakefulness?
Maybe!
What state is the brain in during NREM sleep?
An anabolic state:
▪️Building and preparing tissue - plasticity?
▪️Parasympathetotonic
▪️Pulsed release of GH, insulin, prolactin, and neuroprotective factors
▪️Unrequired synapses and compounds?
How does blood flow change in REM sleep compared to waking?
▪️Increased flow towards the brain stem, limbic forebrain, and parietal operculum related to increased hallucinatory experience
▪️Decreased blood flow to dorsolateral prefrontal cortex related to decreased thinking
Activity in which areas decrease during REM sleep?
Frontal and parietal areas, particularly the DLPFC (associated with decreased thinking and lack of sense of entity)
Which type of memory is predominantly activated during REM sleep and why?
Emotional memories - enables us to reply them without emotion, aiding the reduction of associated emotional charge
What state is the brain in during REM sleep?
An antihomeostatic state - muscle atonia, decreased sleep drive
Very important not to go into REM too early on extreme expeditions!
What happens to metabolism during slow wave sleep?
It drops by 40%
Atrophy in the medial PFC is associated with _________________ disruption in sleep, which leads to impaired ___________________
▪️Slow wave activity
▪️Memory consolidation
What is hypothesised to happen to astrocytes during sleep and why?
They tuck in, decreasing contact with neurons and synapses, due to decreased noradrenaline
Which stage of sleep is thought to be most influential in the development of neuropsychiatric disorder?
Non-REM
What is the SHY hypothesis?
The synaptic homeostasis hypothesis - it claims that sleep, particularly slow wave, is needed to reestablish synaptic homeostasis which is challenged by neuroplasticity (a systematic bias towards net increase of synaptic strength)
What is obstructive sleep apnoea (OSA)?
A sleep related breathing disorder where the walls of the throat relax and narrow during sleep, interrupting normal breathing (repeatedly stops and starts)
How does OSA affect cognition?
OSA in adults is associated with cognitive deficits, particularly in working memory, attention, and executive function
Does CPAP therapy improve OSA-related cognitive deficits?
Yes!
Why does OSA affect cognition?
Intermittent hypoxia may affect brain structure and function, possibly due to interrupted production and clearance of metabolic products and toxins in the brain
What does iRBD stand for?
Idiopathic Rapid Eye Movement Sleep Behaviour Disorder
What is iRBD?
A parasomnia characterised by dream-enacting and motor behaviours due to the loss of muscle atonia during REM sleep
IRBD is prodromal to what category of neurodegenerative disorders?
Alpha-synucleinopathies such as Parkinson’s disease, dementia with Lewy bodies, or multiple system atrophy
Why might use of antidepressants be associated with worse iRBD?
▪️Unmasking of alpha-synucleinopathy process through the serotonergic system?
▪️High prevalence of depression in the prodromal stages of PD?
What themes are common in iRBD dreams and behaviours?
▪️Aggression
▪️Animals
▪️Learned behaviours in accordance with cultural and social norms
What sleep disorder is associated with sleepwalking?
Non-REM parasomnia
How do you distinguish REM parasomnia from NREM parasomnia?
▪️Patients don’t tend to move around, sticking to dreamscape coordinates
▪️Video telemetry
▪️Occurs later on in sleep
▪️More frequently in older adults
What is GBA mutation associated with?
High likelihood of developing alpha-synucleinopathy (parkinsonism), with high degree of cognitive impairment and sleep disturbance
How does REM change through the night?
It increases in length, from ~10 minutes in the first cycle to ~30 minutes
What are the two main processes needed for sleep?
- Homeostatic (toxins accumulate as a biproduct of metabolism that induce sleep once at a certain level)
- Circadian
What kind of dysfunction can commonly occur with narcolepsy and why?
Metabolic as they are both regulated by the thalamus
