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Chapter 9

PSYC 211 Chapter Notes - Chapter 9: Retina, Oxidative Stress, Night Terror

Course Code
PSYC 211
Yogita Chudasama

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Chapter 9: Sleep and Biological Rhythms
Notes taken by: Ashley Brown
Contact for mistakes: Ashley.brown@mail.mcgill.ca
A Physiological and Behavioral Description of Sleep
Sleep is a behavior but not distinguished by movement.
Stages of Sleep
Sleep is studied in a sleep laboratory
- electromyogram (EMG): an electrical potential recorded from an electrode
placed on or in a muscle; attached at the chin
- electroencephalogram (EEG): record electrical activity of the brain; attached
at the scalp
- electro-oculogram (EOG): an electrical potential recorded from the eyes,
recorded by means of electrodes placed on the skin around them; detect eye
During wakefulness the EEG of a normal person shows two basic patterns of activity
- alpha activity: smooth electrical activity of 8 12 Hz recorded from the
brain, generally associated with a state of relaxation
o more prevalent when eyes are closed
- beta activity: irregular electrical activity of 13 30 Hz recorded from the
brain, generally associated with a state of arousal
o the desynchrony shown reflects the fact that many different neural
circuits in the brain are actively processing information
Stage 1 of Sleep
- when we get drowsy and the transition from wakefulness to sleep occurs
we show theta activity
o EEG activity of 3.5 to 7 Hz that occurs intermittently during early
stages of slow-wave sleep and REM sleep
- This is a transition phase
Stage 2 of Sleep
- occurs 10 minutes after stage one
- EEG becomes irregular with mixture of theta activity, sleep spindles, and
K complexes
o Sleep spindles are short burst of waves (12 14 Hz) which occur 2
to 5 times a minute during stages 1 4 of sleep
The sleep of older people contains fewer sleep spindles
Represents the activity of a mechanism that is involved in
keeping a person asleep

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o K-complexes are sudden, sharp waveforms which are found in
stage 2 only. They occur spontaneously at approximately 1 per
minute but can be triggered by unexpected noise
Represents an inhibitory mechanism that is involved in
keeping a person asleep
Forerunner of delta waves
- Even though the subject is sleeping soundly if suddenly awoken they will
report that they hadn’t been asleep
Slow-wave sleep: collective term for stages 3 and 4 of sleep, characterized by
synchronized EEG activity during its deeper stages and predominated by slow-wave
EEG activity
- 15 minutes later enter stage 3 sleep which is signaled by occurrence of
high amplitude delta activity (less than 3.5 Hz)
- Stage 3 contains 20 50 % delta activity
- Stage 4 contains more than 50% delta activity
o During stage 4, the deepest stage of sleep, only loud noises will
cause them to wake and when awakened the person acts groggy
and confused
o Cerebral blood flow and oxygen consumption decrease
- Most important feature of slow-wave activity during sleep are slow
oscillations less than 1 Hz
o Each consist of a single high-amplitude biphasic (down and up)
o First part of the wave indicates a down state a period of
inhibition during which neurons in the neocortex are absolutely
silent, and presumably able to rest
o The second part indicates an up state a period of excitation
during which neurons briefly fire at a high rate
o The other components of SWS like sleep spindles and delta waves
are synchronized with these slow wave oscillations
o Important for learning and memory
- Lack of this sleep affects cognitive abilities rather than physical in
- Never regain lost SWS after sleep deprivation
- SWS is for the brain to restore the effects of oxidative stress
About 90 minutes after the beginning of sleep (or 45 minutes after the onset of stage
4 sleep) there is an abrupt change REM sleep
- EEG suddenly becomes desynchronized, with a sprinkling of theta waves,
very similar to the record obtained during stage 1of sleep
- Eyes rapidly dart back and forth beneath closed eyelids
- The EMG becomes silent, there is a profound loss of muscle tone and
besides the occasional twitching, muscles are totally inactive during REM
- Don’t react to noise but can be aroused by meaningful stimuli
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