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Chapter 9

PSYC 211 Chapter Notes - Chapter 9: Endocrine System, Catecholamine, Pedunculopontine Nucleus


Department
Psychology
Course Code
PSYC 211
Professor
Yogita Chudasama
Chapter
9

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CHAPTER(9(*(SLEEP(AND(BIOLOGICAL(RHYTHMS
Electrophysiological Measurement of Sleep
!Sleep research is conducted in a
sleep laboratory.
!Electrodes are attached to the
subjects scalp to record electrical
activity of the brain. The amplifier
records an
electroencephalogram (EEG).
!Electrodes are also attached to
the subjects chin to record
muscle activity recorded as an
electromyogram (EMG).
!Electrodes placed around the
eyes monitor eye movements
recorded as an electro -
oculogram (EOG).
Stages'of'Sleep
During'wakefulness,'the'EEG'shows 'alpha(ac:vity((regular'medium'frequency'waves 'of'8?12'Hx)
and' beta( ac:vity' (irregular,' mostly' low?amplitude' waves ' of' 13?30' Hz).' Beta' waves' shows'
desynchrony,'which'means 'it'reflects'the'fact'that'many'different'neural 'circuits 'in'the'brian'are'
acMvely'processing'informaMon/acMvely'thinking.
Brain activity when we’re are awake and at rest
When we are awake, our EEG shows two basic patterns:
- Alpha activity consists of regular, medium frequency waves
(8-12 Hz).
- Beta activity is generally associated wave forms that are
irregular at an amplitude of 13-30 Hz.
Beta activity is desynchronous; it’s a reflection of different
neural circuits actively processing information at the same time.

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When'a'person'becomes'drowsy,'they'enter'stage(1(sleep'characterized'by'theta(waves'(3.5?7.5'
Hz).'
Stage 1 of Sleep
When we get drowsy, we show theta activity (3.5-7.5 Hz). This is the
transition between wakefulness and sleep.
Stage 2 of Sleep
After about 10 minutes, the EEG becomes irregular with mixture of
theta activity, sleep spindles and K complexes.
- Sleep spindles are short bursts of waves (12-14 Hz) which occur
between 2-5 times a minute during sleep stages 1-4.
- Older people show more K complexes. K complexes are sudden,
sharp waveforms. They are found during stage 2 only. They
occur spontaneously at approximately 1 per minute and can be
triggered by unexpected noise.
A' study' showed'that' K' complexes'triggered'by' an'auditory' sMmulus,' represents 'an' inhibitory'

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mechanism' that' presumably' protects' the ' sleeper' from' awakening.' K' complexes ' are' the'
forerunner'of'delta'waves.
Stages 3 and 4 of Sleep
Stages 3 and 4 are characterised by high-amplitude delta waves
(less that 3.5 Hz). They occur more frequently in stage 4.
Neocortical neurons
oscillate during slow
wave activity
Stage( 3( sleep' is' signaled' by' high' amplitude' delta( waves' (less 'than'3.5' Hz).' The' disMncMon'
between'stage'3'sleep'and'stage(4(sleep' is 'not'clear,'but'stage'3'sleep'contains'20?50%'percent'
delta 'acMvity,'and 'stage'4'contains 'more'than'50%.'Stage '3'and'4'are'referred'to 'as 'slow(wave(
sleep.(
The'most'important'feature 'of'slow'wave'acMvity'during'sleep'are'slow'oscillaMons 'of'less 'than'
1'Hz.'Each'oscillaMon'consists 'of'single 'high?amplitude 'biphasic'(up'and'down)'wave 'of'slightly'
less'than'1'Hz.'The 'first' part' of'the'wave'indicates'a 'down(state,'a 'period'of'inhibiMon 'during'
which' neurons' in ' the' neocortex' are ' absolutely' silent.' This ' is' the' state' where' neocorMcal'
neurons'are 'able 'to'rest.' The'second'part' is 'an'up( state,' a 'period'of'excitaMon'during' which'
these'neurons'briefly' fire'at' a'high 'rate.' ' K' complexes,' sleep' spindles'and'delta 'waves 'are'
synchronized'with'these'slow'oscillaMons.'
In'the'picture'above,'you'can'seen'three'slow'oscillaMons'on'the'right.'
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