Week 5 - Sleep Flashcards
Function of sleep
- Immune system functioning
- Neurological development
- Memory processing
- Many, many other functions
Every living animal with a _____ sleeps
CNS
Food chain and how long we sleep
- Those higher on the food chain tend to sleep longer than those lower down (e.g., python sleeps 18 hours versus a giraffe, which sleeps 1.9 hours)
- Humans tend to fall right in the middle at
around 8 hours per night
Measuring sleep stages
Measured with
electroencephalogram (EEG)
Gold standard: polysomnography (Tracks brain waves, blood oxygen
levels, heart rate, breathing, and
eye and leg movements)
Synchronous delta activity: If the cells are active at about the same time, their electrical messages are synchronized and appear as a large, clear wave in the EEG data
Desynchronous beta wave activity: If neurons are active at
different times, their electrical messages are desynchronized and
appear as small, chaotic waveforms without a clear pattern in the EEG data.
5 stages of sleep
Wakefulness
NREM stage 1
NREM stage 2
NREM stage 3
REM
Stages of sleep and their waves
Wakefulness - alpha and beta
NREM stage 1 - theta
NREM stage 2 - k complex and sleep spindles
NREM stage 3 - delta
REM - theta and beta
*The Silly Kids Don’t Think Bout (sleep)
Total time in sleep for each NREM Stage
NREM stage 1 - 2/5%
NREM stage 2 - 50%
NREM stage 3 - 20%
NREM 1
- Transition between wakefulness and sleep
- Lightest stage of sleep (may not realize you were sleeping)
- Theta waves (4/7Hz)
- 2-5% of total sleep time
- Hypnic jerks
- Increased proportion suggests sleep fragmentation
–> E.g., chronic pain
NREM 2
About half the night is spent in N2
Experience:
* Slowed heartrate, breathing, muscle activity, eye movements
* Reduced body temperature
Characterized by:
* Sleep spindles
* K complexes
NREM 3
- Commonly referred to as deep sleep or slow wave sleep (SWS)
- Low frequency, high amplitude DELTA waves
- 20% time spent (increases with physical exertion)
- MOST restorative sleep stage (memory consolidation, waste clearance)
- Predominates the first half of the night
REM Sleep
- Rapid eye movement sleep
- Muscle paralysis
- Dreams
- Easily awoken from this stage
- Desynchronized EEG
- Absence of movement on EMG
Slep Cycles
Each cycle lasts
approximately 90 minutes
- Alternates between REM
and NREM - SWS (NREM stage 3) predominates first
half of the night - REM predominates second
half
Brain activity in REM and Dreaming
Prefrontal cortex: low activity (why dreams have no planning, etc.)
Cerebral blood flow is high in the
extrastriate cortex (visual) but low in the striate (primary) visual cortex and
prefrontal cortex
Brain regions active during a dream are same as in real life
Lucid dreaming: eye movements maybe correlated to visual movements in dreams
Deficiency in REM sleep
Called the rebound phenomenon
Made up later
Lucid dreams
A state where one is “physiologically asleep while at
the same time aware that they are dreaming, able to intentionally
perform diverse actions, and in some cases remember their waking
life” (Baird, Mota-Rolim, & Dresler, 2019)
Brain Activity in Slow-Wave Sleep
- Involves slow oscillations synchronized across large neuronal regions –> memory consolidation
- Initiation of cortically-based slow wave oscillations largely based in the prefrontal cortex
- Prior work suggested global decrease in neural activity during SWS
Sleep deprivation
record: 11 days
See issues in daylight savings (increase MI, traffic accidents, sucide, etc.)
Fatal familial insomnia: neurological disorder, damages thalamus, death after 12 months
Is sleep important following physical exertion?
probably not!
Is sleep important following cognitive exertion?
YES!
SWS permits the brain to rest and recover from its daily cognitive activity
SWS increases after a day or weeks of intense cerebral activity
Neurologically, sleep is important for many processes, including:
- Waste clearance
- Memory consolidation
Sleep and memory consolidation
SWS: there is a reactivation of recently encoded memory representations
* Thought to be important for transferring them
to long-term memory store
* AKA playing through through again
REM sleep: stabilizes transformed memories
(May occur across physiological systems: Immunological memories encoded/stored
during sleep)
Synaptic Homeostasis theory
During SWS, synapses are pruned back (increases efficiency of brain)
REM and neurological development
Highest proportion of REM sleep is during the most active phase of brain development: infancy and childhood
Becasue REM sleep supports memory and learning
REM and SWS: Long term memories (nondelcarative vs declarative)
- REM sleep facilitates consolidation of nondeclarative memories
- Slow-wave sleep facilitates consolidation of declarative memories (The brain rehearses newly learned information during slow-wave sleep)
REM: NONDECLARATIVE
SWS: DECLARATIVE
Chemicals at play
Adenosine (inhibitory)
Inhibitory response
Steps:
1) Astrocytes store glycogen for “emergency energy,” break down into glucose to give to neurons
2) By product of that is adenosine,
3) Accumulation of adenosine triggers DELTA sleep
4) throughout day body naturally accumulates adenosine, which helps us feel sleepy at night
5) during the night, body recycles adenosine
Sleep Deprivaon = ↓ Glycogen Stores & ↑ Adenosine = SLEEPINESS
Adenosine and Caffine
Caffeine blocks adenosine receptors, so you don’t feel sleepy but are still sleepy
Adenosine and Caffeine
Caffeine blocks adenosine receptors, so you don’t feel sleepy but are still sleepy
Histamines
produced in hypothalamus, relays to brain
MAKES YOU FEEL AWAKE
Histamines also activate release of ACH
Antihistamines: makes you sleepy
Acetylcholine
High during wakefulness and REM, low during SWS
Hallmark of REM sleep
1 neuron in the Hippocampus, 2 located in the Pons and Forebrain
Produce cortical desyncrhony and activation
Cortical Desynchrony = low voltage mixed
frequencies
Serotonin
Serotonin plays a role in activating behavior, stimulation causes locomotion and cortical arousal. IT AROUSES
SO most active during waking, low during REM becasue you have limited movement
Norepinephrine
BOTH Arousal & Sleeplessness controlled by norepinephrine
This is mediated by the Locus Coeruleus in the PONS.
↑ Locus Coeruleus Firing = ↑ Vigilance/Focus
Orexin
Secreted by hypothalamus
Stimulates other neurons to promote alertness & energy metabolism in response to stress in the environment.
High during alert or active waking, especially exploratory activity
WHere is melatnonin produced
Pineal Gland
Melatnonin
Produced by the Pineal Gland in response to evening/darkness about 2 hours
before normal sleep time
Serotonin is converted into melatonin
Exogenous melatonin = take 1-2mg 30 to 1 hr before bedtime (higher just peed out)
Doesn’t keep you asleep, just puts you to sleep
Sleep disorders: Trends in sleep in USA
- 25% less sleep than earlier generations
- 20% Americans employed in shift work
- 40% of adults report falling asleep during the day without meaning to at least once a
month
Insomnia
effects 30% of adults, mostly women (40 vs 30)
Insomnia disorder has a high comorbidity rate with chronic medical conditions
CBTI most effective
Chronic use of sleep-promoting drugs can cause rebound insomnia
Primary and secondary insomnia
Primary insomnia = difficulty falling asleep after going to bed or after awakening during the night.
Secondary insomnia = inability to sleep due to another mental or physical condition (e.g., pain, medication)
Narcolepsy
Orexin-related neurological d/o (missing 85%)
Narcolepsy
Orexin-related neurological d/o (missing 85%)
Most people have sleep attacks (overwhelming urge to sleep during something boring) -> but people with narcolepsy just fall asleep
Narcolepsy: cataplexy
sudden muscle weakness/paralysis
- Triggered by strong emotional reaction or physical exertion
- Remain fully conscious.
- Loss of muscle control d/t massive inhibition of motor neurons in spinal cord
Narcolepsy: Sleep paralysis
inability to move before onset of sleep or waking
hypnagogic Hallucinations (visual)
Narcolepsy
Treatment = modafinil
REM Sleep Behavior D/O
Lack of muscle paralysis during REM –> acting out of dreams
Can be comorbid narcolepsy
later in life, neurodegenerative
Clonazepam
Sleep Apnea
Difficulties sleeping and breathing at the same time ↑CO2 = stimulates
chemoreceptors –> wake up gasping for air & decreased slow wave activity
Untreated causes significant deficits in attention, memory, & exec fxns, and anxiety (wake up anxious because of extra co2)
CPAP and BIPAP
Two types of sleep apnea
Obstructive Sleep Apnea = d/t narrowing of airway (obesity, enlarged tonsils,
hormonal changes)
Central Sleep Apnea = brain does not signal need to breath.
Maladaptive Slow-Wave Sleep Bxs in Children
Children typically outgrow
bedwetting, sleepwalking, night terrors
Could be all three or a combination.
Night terrors vs nightmares
terror = Wake up with no memory of the nightmare
Disordered Circadian Rhythms: Alzheimers
body temp lowers at off time (9-noon vs. 4-5 a.m), see return of sleep walking
Disordered Circadian Rhythms: schizo
Melatonin production lags, so starts around 2-3am
Disordered Circadian Rhythms: Depression
40-65% report sleep px
Disordered Circadian Rhythms: suicide
Sleep deprivation independent risk factor
Sleep D/O’s Post- TBI
Up to 80% report sleep problems after injury
–> typically dropped to 50% by half year mark
Poor sleep = poorer recovery trajectory d/t increased risk for mood d/o’s, ongoing cog deficits, and neurodegeneration.
Nap lengths
10-20: feel alert after, because only in NREM
30 minutes: BAD, feel groggy
60 minutes: groggy, but do learn some
90: Best
