lecture 9: sleep, dreaming and memory Flashcards
Electroencephalogram (EEG)
measures gross brain electrical activity
Electrooculogram (EOG)
measures eye movements
Electromyogram (EMG)
measures muscle activity and tone
sleep stages as measured on an EEG
- awake = low voltage, high frequency beta waves
- drowsy = alpha waves prominent
- stage 1 sleep = theta waves prominent
- stage 2 sleep = sleep spindles and mixed EEG activity
- slow wave sleep (stage 3 and stage 4 sleep) = progressively more delta waves ( stage 4 shown)
- REM sleep = low voltage, high frequency waves
what is detected during REM sleep
EOG = detects rapid eye movements
EMG = shows loss of muscle tone
how long does it normally take to go from one cycle of REM sleep to the next
around 90mins
at what times of the night are we in SWS sleep and REM sleep
first 4hrs = mostly SWS
last 4hrs = mostly REM
REM sleep
- paradoxical sleep
- high correlation with dreaming
80% report dreaming during REM
7% report dreaming during SWS
how does the amount of sleep we get change across the lifespan
- sleep the most as infants
- middle as children
- sleep less as we get older
time in spent in REM sleep across the lifespan
- highest percentage of REM as infants
- REM is roughly the same throughout childhood and adulthood
- slightly higher around 19-30yrs
declarative memory
the type of memory which consciously allows us to recall facts and events
procedural memory
long term memory that stores how to perform actions and skills
connections between sleep and memory for procedural and declarative memory
- declarative memory is enhanced by early or SWS rich sleep
- procedural memory is enhanced by late or REM-rich sleep
connection between sleep and insight
- when the subjects are asleep they have the most insight
- there tends to be more insight after sleep and after wake compared to wake-day and wake-night
the creative sweet spot
- the wake sleep transition during sleep stage 1 is associated with involuntary spontaneous dream like experiences that incorporate recent wake experience
- it was proposed that a technique that qoke people during this wake-sleep transition led to creative insights
Hypnagogia
the transitional state of consciousness between wakefulness and sleep, often characterised by vivid, involuntary sensory experiences, such as hallucinations
what do hippocampal cells encode
they encode experience
Sharp-wave ripple events
- during slow wave sleep the hippocampus replays previous experience as sequences of cell firing during sharp wave ripple events
- hippocampal cells fire in the same order they did during experience, but the sequence is sped up 10-20x
sleep spindles
- EEG spindle density in neocortex during sleep predicts subsequent memory performance
- short bursts of brain activity (oscillatory activity) occurring during non-rapid eye movement (NREM) sleep, particularly in stage 2
what happens during slow wave sleep
the hippocampus replays previous experience as sharp wave ripple events. these events coincide with cortical spindles, which suggests coordinated activity between the two regions
Mechanisms of memory consolidation
- experience is initially encoded in the hippocampus
- the representation of experience is replayed at high speed during slow wave sleep
- sleep spindles may reflect engagement of that replayed experience with information in neocortex
- these events may underlie memory consolidation
