Sleep Flashcards
(36 cards)
What is sleep
A dynamic and actively produced brain state with accompanying changes to physiology
not static or passive
some brain regions are more active during sleep than wake
some hormones are secreted selectively during sleep
urge of sleepiness that compels one to seek out a quiet, warm, comfortable place; lie there, and remain there for several hours
How to measure sleep
electroencephalograph (EEG): brain activity across cortex
Electromyogram (EMG): muscle activity
Electro-oculogram (EOG): eye movements
what does EEG reflect?
EEG records activity from neurons at same time (neuronal spiking)
at scalp level, this activity corresponds to the sum of these neurons electrical activity
if neurons are active at random, electrical signals are desynchronised and appear small, chaotic EEG waves (like awake)
if neurons are active at same time, electrical signals are synchronised and appear large EEG waves (like sleep)
types of brain wave frequencies in sleep
gamma waves (higher than 30Hz) (concentrating, focusing, learning) - very irregular on EEG, low amplitude waves
beta waves (13-30Hz) (most activities when awake)
alpha waves (8-12.99Hz) (when relaxed or sleepy)
Theta waves (4-7.99) (during stage 1 or 2 of sleep)
N2 sleep = K-complexes (less than 2Hz) and spindles (12-16Hz)
delta waves (1-3.99) (during stage 3 of sleep) (very slow waves)
Tooth waves in REM sleep (after 90 minutes)
it’s proposed that sleep spindles in all stages as a mechanism to disconnect brain, and K-complexes only occur in stage 2 as triggered by noises
BUT it’s also suggested they both relate to consolidation of memories or are a possible mechanism of neural inhibition
NREM-REM Sleep Cycle Stages
- transition between awake and asleep, 5-10 mins long
- body temperature drops and heart rate begins to slow, brain begins to produce sleep spindles, 20mins long
- muscles relax, blood pressure and breathing rate drop, deepest sleep
- REM sleep = brain is active, body is relaxed and immobilised, dreams, eyes move rapidly
Sleep and Health
American Heart Association added sleep to its cardiovascular health checklist (8 factors a person can modify to stay healthy)
EEG procedure for measuring sleep
sensors measure electrical activity of neurons, eyes and muscles
brain waves displayed on computer in real time and show stage of sleep
sleep spindles =
brain activity at top, then eye movements in middle, then chin muscles are bottom
data can be analysed for characteristics of persons sleep in more detail
characteristics of sleep cycles
first sleep cycle shows more deep sleep then last sleep cycle is more REM sleep
in young adults with 8 hours of sleep there are 4.5 sleep cycles across the night
digital health and sleep
sleep headband = 7 sensors measure brain activity (EEG), heart rate, respiration and movement
Wrist-worn trackers = 3-axis accelerometer on wearable tracker record movements - sleep algorithms are used to estimate sleep parameters
Sleep PSG in labs is still best way to measure sleep but the accuracy of sleep wearables is promising
brain activity in REM sleep: dreaming
80% of awakening during REM lead to dream recall
intense brain activity during REM sleep dreams - less activity in prefrontal cortex reflecting the lack of organisation and planning that occurs in dreams
high activity in extrastriate cortex during REM sleep reflecting visual “hallucinations” during dreaming
brain activity during REM sleep: lucid dreaming
dreamer is aware they’re dreaming
some control over dream characters/narrative/environment
increased activity in 40Hz brainwaves in frontal cortex (DLPFC) associated with consciousness
Sleep Deprivation
worse cognitive abilities, especially on tasks that require attention and vigilance
regular sleep deprivation is associated with adverse health outcomes, including weight gain and obesity, diabetes, hypertension, heart disease and stroke, depression, risk of death, breast cancer
hypothesis: sleep deprivation increases oxidative stress leading to inflamed molecules and worse neurogenesis/learning/memory/synaptic plasticity so anxiety and cog impairment
How does slow wave sleep improve memory processing
STUDY ONE: ppts learned a declarative learning task (paired words list) and non-declarative learning task (mirror tracing)
after nap with slow-wave sleep, ppts who learned declarative task improved performance compared to those who stayed awake
STUDY TWO: ppts learning non-declarative learning task (visual discrimination task) - nap with slow-wave sleep and REM sleep - ppts who learned non-declarative task improved performance compared to those who stayed awake
Sleep’s role in emotional processing
sleep loss amplifies brain activity in response to emotionally aversive stimuli -
experiment assessed anxiety responses using emotional aversive or neutral visual clips during fMRI neuroimaging sessions - total sleep loss amplified emotional-stimulus in many brain regions associated with processing of fear (ACC, amygdala, hypothalamus, thalamus) and amplified neutral-stimulus suggesting “overactive” brain, regions activated = ACC and amygdala
what is sleep homeostasis
sleep pressure increases with time awake due to increases in sleep-promoting substances
adenosine
adenosine increases when awake and decreases when asleep, and vice versa for glycogen (energy for brain)
adenosine causes cognitive deficits
adenosine releases ATP which converts into adenosine in extracellular space
adenosine accumulates during wakefulness and is reduced during slow-wave sleep (mice with mutation to reduce adenosine production has less slow-wave sleep AND people with recessive genes for slower acting enzyme which destroy adenosine have more slow-wave sleep)
caffeine blocks adenosine receptors, preventing inhibitory effects on neural activity and reducing effects of sleep deprivation by adenosine lingering in synaptic cleft
neural control of arousal
acetylcholine, produced in pons and basal forebrain, activates the brain (cortical desynchrony)
norepinephrine, produced by neurons in locus coeruleus in brainstem, is released along the neurons’ axons that branch widely in the brain for alertness
serotonin: serotonergic neurons in the raphe nuclei (medullary/pontine regions of reticular formation) project to many brain regions and stimulation causes cortical arousal
histamine: histaminergic neurons in tuberomammillary nucleus branch widely throughout cerebral cortex and increase cortical activation
lateral hypothalamus secretes orexin and orexinergic neurons project to regions involved in arousal, including locus coeruleus, raphe nuclei, tubermammillary nucleus (TMN) and Ach neurons in dorsal pons and basal forebrain - it has excitatory effects here - narcolepsy is treated with modafinil which suppresses drowsiness by stimulating orexin release in tuberomammillary nucleus
the flip-flop switch
major sleep promoting region (vlPOA) and wakefulness promoting regions (basal forebrain and pontine regions and locus coeruleus and raphe nuclei and tuberomammillary nucleus of hypothalamus - these are connected by inhibitory GABAergic neurons)
when flip-flop is “awake”, arousal systems are active and vlPOA is inhibited
when “asleep”, vlPOA is active and arousal systems are inhibited
biological clocks and hunger signal to the orexinergic neurons in lateral hypothalamus to stablise the flip-flop switch
orexins role
homeostatic = when awake, orexinergic neurons receive signals from brain mechanisms that monitor nutritional state - hunger-related signals activate orexinergic neurons and satiety-related signals inhibit them
circadian = when awake, orexinergic neurons receive an excitatory signal from biological clock
allostatic = when asleep, orexinergic neurons are inhibited by vlPOA due to accumulation of adenosine - this overcomes the excitatory input to orexinergic neurons and sleep occurs
what is insomnia
issues with falling asleep, staying asleep or waking up too early
issue with fatigue/attention/memory, social/family/occupational PERFORMANCE, MOOD disturbance, daytime sleepiness/less ENERGY/motivation, prone to ERRORS or DISSATISFACTION with sleep
these must have lasted at least 3 months
insomnia and mental health
people with typical sleep encode new emotional experiences during sleep (REM especially) and recall them without abnormal activation of limbic system
BUT
chronic insomnia = new emotional experiences are encoded with abnormal activity in limbic system and, with reduced REM and more sleep fragmentation, problems with processing emotions arise - over years, emotions are seen as overwhelming, increasing mental health disorder risk
CBT for insomnia
trained CBT-I provider helps identify thoughts/feelings/behaviours contributing to insomnia symptoms
thoughts/feelings tested for accuracy
behaviours examined as promoting or inhibiting sleep
provider reframes challenges as conductive to restful sleep
CBT-I = multicomponent treatment
cognitive interventions = cognitive restructuring changes inaccurate/unhelpful thoughts about sleep
behavioural interventions = sleep hygiene (appropriate bedroom environment/avoid screen-based devices/coffee/alcohol), relaxation training (short and long relaxations during day), stimulus control (using bedroom only to sleep/leaving bedroom when cannot fall asleep), sleep restriction (restricting sleep times/increasing in-bed sleep times) - establish healthy sleep habits
psychoeducational interventions = provide info about connection between thoughts/feelings/behaviours
what is sleep apnea
breathing repeatedly stops and starts in sleep
symptoms of sleep apnea
loud snoring
sleepiness despite full night’s sleep
