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)