EEG and the stages of sleep Flashcards

1
Q

EEG EOG and EMG

A

EEG measures cortical activity

  • electrodes on the scalp at front, centre and back most important for sleep research
  • bilateral in case on side comes loose during sleep

EOG measures eye movement

  • corneoretinal potential (difference in potential between cornea and retina)
  • electrodes above right and below left eye

EMG measures muscle tone

  • electrodes under the chin
  • muscle tone lowered during REM sleep
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2
Q

EEG stages of sleep

A

Deeper sleep = lower frequency

Wake

  • alpha waves 8 - 12Hz
  • beta waves

Stage 1

  • Theta waves 4 - 7Hz

Stage 2

  • Sleep spindles similar to alpha waves - more easily found by centre electrodes
  • K complexes - large wave
  • Can be up to 1/2 your sleep

Stage 3

  • Delta (slow) waves 0.5 - 2 Hz
  • Stage 3 and 4 now one type, known as N-3 sleep

REM

  • slightly higher amplitude than wakefulness
  • Theta and beta activity - waking- and light-sleep-type activity
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3
Q

Slow eye movement

A

Eyes slowly rolling back into the head

With theta waves as you fall asleep

  • LAMF - low amplitude mixed frequency : ‘dropping off’
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4
Q

Discovery of REM sleep

A

Ladd 1892

  • noticed eyes moving during sleep
  • hypothesised they were watching their dreams
  • idea of REM wasn’t popularised until

Aserinsky and Kleitman 1953

  • EEG - into and out of deep sleep
  • looked like they went back into stage 1 but there were also rapid eye movements — REM sleep!
  • REM occurs periodically during the night

Berger & Oswald 1962

  • EMG suppressed during REM - lungs and heart only muscles still fully active
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5
Q

Hypnograms

A

Show sleep architecture - transition through sleep stages during the night

REM periods get longer throughout the night - explains why when we wake in the morning we can remember long dreams - can be 40mins long!

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6
Q

Induction of SWS

A

Ngo et al., 2013

  • 3 conditions
    1. with tones presented at a rate of 0.8Hz
    2. tones presented at random
    3. no tones (sham)
  • acoustic stimulation began during wakefulness, through first 90mins of sleep
  • 0.8Hz gave significantly delayed sleep onset and increased slow wave activity during sleep
  • sleep after stimulation was not affected
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7
Q

Functionality of K complexes

A

Wauquier et al., 1995

  • K complexes and sometimes spindles occur when there is external noise
  • people with sleep disorders e.g. apnoea or insomnia have very few K complexes … K complexes keep you asleep

Amzica and Steriade 2002

  • K complexes are more spontaneous than evoked
  • generated spontaneously by slow waves
  • impair transmission of incoming stimuli - keep you asleep
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8
Q

Functionality of sleep spindles

A

Can occur in response to environmental stimuli like K complexes (keep us asleep) but have recently been linked to memory consolidation _____ STUDY

Generated by the thalamus. As spindle power increases, the thalamus is less active

Veto sensory activation of the cortex

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9
Q

Slow wave sleep

A

Association with ventral medial pre frontal cortex (vMPFC) - generated here?

Confirms frontal predominance of slow wave activity during NREM seep seen in EEG studies

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10
Q

REM sleep

A
  • PGO (pontine geniculate occipital) waves generated in the pons in the brain stem
    • Which stimulates the geniculate area
      • Which stimulates the occipital area
  • Theta waves (4-7Hz) in the hippocampus and cortex during REM and wake
    • associated with memory consolidation during REM
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11
Q

First night effect

A

Sleep architecture is slightly different from normal

  • longer to fall asleep
  • less REM, more time in lighter stages
  • basic architecture is more or less the same

Often exclude first night data if using physiological data - not an issue if using dream data and REM sleep still occurs, just not as often as usual

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12
Q

Waking from sleep during the night

A

Agnew & Webb, 1972

  • 44% woken from stage 1 or 2 said they weren’t asleep
  • 15% woken from N-3 sleep said they weren’t asleep

Number of arousals during the night increases with age

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