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PS101 Lecture Notes - Slow-Wave Sleep, Theta Wave, Delta Wave

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Eileen Wood

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Psychology Study Notes: States of Consciousness (Chapter 5)
By: Yen Hoang
The Nature of Consciousness:
Consciousness is the awareness of internal and external stimuli
Your consciousness is continually changing
o This continuous flow is referred to as the stream of consciousness
Described by William James
Some thoughts entering your stream of consciousness are the result of
intention: we seem to be easily able to shift our attention to things of
importance or interest in our environment
Variations in Awareness and Control:
o Attention and consciousness are closely related but they are not identical
o Most of what enters our consciousness seems intentional and designed to further
specific goals or motivations however, there are other thoughts that enter the mind
Mind wandering refers to people’s experience of task-unrelated thoughts
Ie thoughts that are not related to what they are intentionally trying
to do at a given moment
It’s something that we all have experience with
It seems less likely to occur if the task you are engaged in is one
that requires significant cognitive resources
o The distinction between what we control about our mental processes and what just
seems to happen is often referred to as the difference between controlled and
automatic processes
In contrast to controlled processes- judgments or thoughts that we exert
some control over that we intend to occur- automatic processing and its
effects happen without our intentional control or effort
Consciousness and Brain Activity:
o At this point, research suggests that consciousness does not arise from any distinct
structure in the brain but rather from activity in distributed networks of neural
o One of the best physiological indicators of variations in consciousness is the EEG
The electroencephalograph (EEG) is a device that monitors the electrical
activity of the brain over time by means of recording electrodes attached
to the surface of the scalp
Ultimately, it summarizes the rhythm of cortical activity in the brain in
terms of line tracings called brain waves
Brain waves vary in amplitude and frequency
Human brain wave activity is usually divided into four principal
bands called alpha, beta, theta and delta
o Beta: normal waking thought, alert problem solving
o Alpha: deep relaxation, blank mind, meditation
o Theta: light sleep
o Delta: deep sleep
Biological Rhythms and Sleep:

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Variations in consciousness are shaped in part by biological rhythms
o Biological rhythms are periodic fluctuations in physiological functioning
The existence of these rhythms means that organisms have internal
“biological clocks” that somehow monitor the passage of time
The Role of Circadian Rhythms:
o Circadian rhythms are the 24 hour biological cycles found in humans and many
other species
In humans, circadian rhythms are particularly influential in the regulation
of sleep
Daily cycles also produce rhythmic variations in blood pressure, urine
production and other physical functions
o Body temperature varies rhythmically in a daily cycle, usually peaking in the
afternoon and reaching its low point in the depths of the nights
Research indicates that people generally fall asleep as their body
temperature begins to drop and awake as it begins to ascend once again
Circadian rhythms can leave individuals physiologically primed to fall
asleep most easily at a particular time of day
This optimal time caries from person to person, depending on their
schedules but it’s interesting to learn that each individual may have
an “ideal” time for going to bed
o This ideal bedtime may also promote better quality of sleep
during the night
Daily exposure to light readjusts people’s biological clocks
When subjects were cut off from exposure to the cycle of day and night
and all other external time cues, the circadian rhythms still persisted
except that the cycles ran on longer (24.2 hours)
Regular cycles are 24 hours
o When exposed to light, some receptors in the retina send direct inputs to a small
structure in the hypothalamus called the suprachiasmatic nucleus (SCN)
The SCN sends signals to the pineal gland, whose secretion of the
hormone melatonin plays a key role in adjusting biological clocks
Neurons in SCN are active during daytime so they inhibit melatonin
secretion and raises the body temp. and alertness
Neurons in SCN are inactive at night so they allow melatonin secretion to
increase and melatonin promotes relaxation and sleepiness
o Circadian rhythms in humans are regulated by multiple internal clocks with a
central pacemaker
Ignoring Circadian Rhythms:
o Typically the quality of your sleep suffers when you go to sleep at an unusual
o If you get less sleep than the amount of sleep you need, you accumulate “sleep
In order for things to return to normal, it must be paid back by getting
extra sleep
o Getting out of sync with your circadian rhythms also causes jet lag

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o People get less sleep when they go on rotating shifts and when they do sleep their
quality of sleep is poor
Lack of sleep or poor quality sleep can also increase workers’ accident
proneness and their mental and physical health
o Sleep lost when the clock is set ahead in the spring shift to Daylight Saving Time
is associated with an increase in traffic accidents during the week after the switch
Melatonin and Circadian Rhythms:
o Giving small doses of melatonin has proven to reduce the effects of jet lag by
helping travelers resynchronize their biological clocks
The Sleep and Waking Cycle:
An electromyograph (EMG) records muscular activity and tension
An electrooculograph (EOG) records eye movements
Cycling Through the Stages of Sleep:
o During sleep, people cycle through 5 stages
Stages 1-4:
Length of time it takes for a person to fall asleep varies
o It depends on many factors such as how long its been since
the person has slept, where the person is in his/her
circadian cycle, the amount of noise or light in the sleep
environment, etc
Stage 1 is a brief transitional stage of light sleep that usually lasts
only a few (1-7) minutes
o Breathing and heart rate slow as muscle tension and body
temp. decline
o Alpha waves that dominated the EEG activity just before
falling asleep give way to lower frequency EEG activity in
which theta waves are prominent
o Hypnic jerks are brief muscular contractions that occur
during stage 1 drowsiness
As the sleeper descends through stages 2, 3 and 4 of the cycle,
respiration rate, heart rate, muscle tension and body temp. continue
to decline
Stage 2 typically lasts about 10-25 mins
o Brief bursts of higher frequency brain waves called sleep
spindles appear against a background of EEG activity
Gradually brain waves become higher in amplitude
and slower in frequency as the body moves into a
deeper form of sleep called slow-wave sleep
Slow-wave sleep (SWS) consists of sleep stages 3 and 4 during
which high amplitude, low frequency delta waves become
prominent in EEG recordings
o Typically individuals reach SWS in about 30 mins and stay
in it for 30 mins
The cycle reverses itself and the sleeper gradually moves back
upward through the lighter stages
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