PSYC30020 Lecture Notes - Lecture 9: Rebound Effect, Vasotocin, Caffeine
10 May 2018
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Lecture 9
- What is sleep?
- A condition of body and mind which typically recurs for several hours per day, in
which the eyes are closed, the postural muscles are relaxed, and consciousness is
practically
- suspended/reduced
- Factors to help guess whether somebody is asleep without measuring in EEG:
- Specific postures - humans lay down or lean or get comfortable, somewhere dark
and quiet and safe, conducive to sleep
- Relative inactivity
- Reduced responsiveness
- Rapidly reversible
- Eyes closed
- Behavioural preludes (dog walking in circles)
- Reduced consciousness
- Measures of Sleep:
- Electroencephalogram (EEG): summated brain wave activity, electrode on surface of
skin
- ↠ active eyes open wakefulness: beta activity (13-30 Hz) is present in the EEG
record (desynchrony: low amplitude, high frequency waveforms)
- ↠ eyes closed wakefulness: alpha activity (8-12 Hz) appears in the EEG record, sine
wave, some neurons firing synchronously (simultaneously)
- ↠ with sleep EEG synchrony develops: high amplitude, low frequency waveforms
- Electrooculogram (EOG): eye movements, eyes roll up into back of head
- Electromyogram (EMG): muscle tone [typically in face, cheeks and neck [neck also
for animal research]], REM sleep - most muscles near paralysed, non-REM sleep -
most muscles relaxed but generally have some tone
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-
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- Wakefulness
- 3rd ⇒ EMG of chin muscle activity
- 4th ⇒ EEG behind ear
- 30 seconds page
- 5 - 10 blinks a minute
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- Stage 1 Non-REM sleep
- No blinks, slow rolling movements of eyes, rolling backward and forward
- Muscle tone slightly reduced but still present
- EEG clearly slowed down, lost alpha EEG activity (sinusoidal 8-12 Hz), more 4-7 Hz
[theta EEG activity]
- Don’t always know you’re falling asleep at this stage
- K complex → stereotypical wave of negative EEG followed by positive then back to
baseline, 0.5 - 2 seconds, 75 microvolts
- Once see a few K complex → person said to enter stage 2 sleep
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- Stage 2 Non-REM sleep
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- Person is sure they dozed off
- K complexes
- Sleep spindle: about a second long, a bit faster than alpha, 12-14 Hz
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- Stage 3 Non-REM sleep
- Group of K complexes: delta waves, 0.5-2 seconds, at least 75 microvolts
- More than 20% of 30 seconds is delta waves → means stage 3
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- Stage 4 Non-REM sleep
- More than 50% is delta waves
- Muscle tone still there, not paralysed
- Non-REM sleep:
- Theta [4-7 Hz] and delta activity, and K complexes and Sleep Spindles are present
in the EEG record (Stages 1 and 2 [N1, N2]; Stages 3 and 4: delta activity
(synchronised), termed slow-wave sleep [SWS, N3])
- Light, even respiration and regular heart rate
- Muscle tone is present (lower than wake), wake about 20 times an hour (not
always conscious of waking, to shift, turn)
- Cognitive activity (thought like, rational) : difficult to rouse from SWS
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