- the alpha waves seen above(9-13 hz) are a clear
indication of restful, relaxed wakefulness.
- a sudden sound or light, or any kind of focused mental
activity (like
doing mental arithmethic) would replace the alpha with beta
waves which are even faster (>13 hz) and which are typical of alert wakefulness.
In general, the frequency of the EEG is correlated with
alertness and arousal...more arousal = higher frequency (and
lower amplitude).
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- Onset of "sleep blindness" in which the brain
stops processing information from the eyes.
- Easily aroused.
- If aroused, person is likely to say "I was half
asleep"
- Movements of L & R eyes become uncoordinated
- myoclonic jerks and hypnogogic imagery may occur
- theta waves (5-8 hz) are typical
- Typically spend relatively little time in stage I...time
increases in old age
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- often considered the first stage of "true" sleep
- relatively easily awakened
- theta waves (5-8 hz) mixed with sleep spindles
- this stage is prominent in the sleep of the elderly
- this stage is only minimally replaced following prolonged
sleep deprivation
- often see sleep spindles and K-complexes in EEG
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- III and IV are very similar---depends on % of EEG that
shows delta waves (<5 hz). Less than 50%
delta = III, more than 50% delta = IV. Many sources now combine them and call them SWS or deep sleep or delta sleep.
- increase during a night following exercise
- awakening from III and IV shows "sleep inertia"
- duration of these stages decrease across the night
- III and IV decline w/ age (19% @ 20 yrs; 3-4% @ 50 yrs)
- HGH secretion is highly correlated w/ SWS
- Do we dream during III/IV?
- dream reports tend to be brief &
"thought-like" rather than visual; most reports
score less than 5 on the
Orlinsky
scale
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- Note the very low EMG...so low that the muscles lose tone and
"REM paralysis" sets in. What would happen if the EMG
remained high during REM? Click here
to see.
- REM is consistently accompanied by arousal of sexual organs in
both males and females. This is sometimes used to test for
the causes of impotency in men.
- REM stages become longer as the night progresses
- half of a newborn's sleep (this includes premature infants) is
REM
- 80%-90% of awakenings produce dream reports of at least 5 on
the 8-point Orlinsky
scale.
- Do EEG recordings tell us what the dream is about?
No, but...Click Here
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