Chapter 4
States of consciousness
BY:
DR. UCHE AMAEFUNA (MD)
•THERE ARE MORE TO
LECTURES THAN JUST
SLIDES…….. 
• This area covers topics related to states of
consciousness such as waking consciousness,
sleep, dreams, and sleep deprivation.
Measurement of physiological responses
• Measurement of physiological responses
which can indicate different states of
consciousness: electrical activity of the brain
and other physiological responses, including
heart rate, body temperature and galvanic
skin response.
• A state of consciousness cannot be observed
or measured directly.
• However, psychologists use various tools to
detect changes in levels of consciousness.
• The electroencephalograph (EEG) is used to
measure the electrical activity of the brain.
• Changes in brain wave patterns provide
psychologists with information about a
person's level of consciousness.
• The EEG has proven most useful in the
identification of the different stages of sleep.
Measurement of heart rate
• The measurement of an individual's heart
rate, body temperature and breathing rate can
also provide psychologists with information
about the individual's state of consciousness.
• Generally, an altered state of consciousness
would reveal a decrease in heart rate and
body temperature.
• Psychologists also use the galvanic skin
response (GSR) to make inferences about the
changes in an individual's state of
consciousness.
• The GSR measures changes in electrical
conductivity in the skin by using two
electrodes placed on the skin and passing a
weak current between them.
• These changes indicate arousal of the
autonomic nervous system, as arousal causes
sweating and the consequent damp skin
increases its electrical conductivity.
• The ways to study sleep:
• The ways to study sleep;
(A) Electroencephalograph (EEG)
(B) Electromyograph (EMG)
(C) Electro-oculargram (eye movements) and
(D) Sleep laboratories.
• Researchers use many different devices to
study sleep and gain information about
particular stages of sleep.
• The most important apparatus of a sleep
laboratory is the polygraph.
• This is a machine which records on paper the
output of various devices that can be attached
to the person being studied.
• Sleep researchers use the following devices:
• The electroencephalograph (EEG) is used to
measure the electrical activity of the brain
through small metal discs pasted to the scalp.
• Changes in brain wave patterns provide
psychologists with information about a
person's level of consciousness and which
stage of sleep they are in.
• When a person is awake and alert, the output
of the EEG reveals brain wave patterns which
are high in frequency (15-30 cycles per
second) and low in amplitude.
• These small, irregular waves are called beta
waves. (Try to remember beta = busy, as the
person is active and alert.)
• Beta Waves.
• When a person is relaxed and somewhat
drowsy, the EEG recording shows a higher
amplitude and lower frequency rhythm (8-12
cycles per second).
• These brain waves are called alpha waves.
• These waves are characteristic of someone
falling asleep, entering stage 1 of sleep. (Try to
remember alpha = almost asleep.)
• Alpha Waves.
• As sleep progresses;
As sleep progresses and becomes deeper and
deeper, the EEG recordings reveal brain waves
which are slower in frequency and higher in
amplitude.
Stages three and four of sleep reveal these
slow waves which are called delta waves.(3-5
cycles per second). (Try to remember delta =
deep sleep.)
• Delta Waves
• An Electromyograph (EMG) is a device that
measures electrical activity in the muscles
through electrodes attached to the chin.
• This machine helps to establish if a person is
in rapid eye movement (REM) sleep, as the
output would show low activity due to relaxed
muscles (atonia) in REM sleep.
• The electro-oculargram (EOG) is used to
measure eye movements by attaching
electrodes to the skin around the eyes.
• It also assists in the recognition of REM sleep,
as the EOG shows high activity due to rapid
eye movements in REM sleep.
• Most sleep research takes place in a sleep
laboratory.
• As a person's sleep is affected by their
surroundings, a sleep laboratory attempts to
mimic a home.
• It contains one or more small bedrooms and
furnishings and decorations are as homelike
and comfortable as possible.
• A subject may spend a couple of nights in the
sleep laboratory before data is recorded from
them, as it is expected that they may be
unsettled for the first night or two because of
the new environment.
• However, by the third night, sleep is
essentially normal and from this point on,
observations can be considered useful.
• Characteristics and patterns of the stages of
sleep;
(1) Rapid eye movement sleep (REM sleep) and
(2) Non-rapid eye movement sleep (NREM
sleep).
• When we are awake and alert the
electroencephalograph (EEG) shows wave
lengths which are low in amplitude and high in
frequency called beta waves.
• As we relax the brain waves become alpha
waves, which are higher in amplitude and
lower in frequency.
• During sleep, periods of rapid eye movement
(REM) alternate with Non-REM (NREM) sleep.
The sleep cycle consists of four stages.
Stage one: This stage is characterised by
small, irregular waves which are a
combination of alpha and theta waves.
• During this stage the individual is drowsy and
is drifting off into a light sleep from which
they can be easily awoken.
• The person's heart rate slows down and their
muscles relax.
• Apart from the very first time the person
enters stage one sleep, this stage is known as
REM sleep.
• Stage two: In this stage sleep spindles begin
to occur.
• These are sharply pointed waves recorded by
the EEG.
• The EEG also shows rapid bursts of electrical
activity with irregular brain waves.
• Stage three: This stage is characterised by the
onset of slower delta waves.
• These brain waves are high in amplitude and
low in frequency.
• At this stage, the person becomes harder to
awaken, their breathing and pulse rate slow
down and their temperature drops.
• Stage four: This stage consists of pure delta
waves and it is extremely difficult to rouse the
sleeper.
• This is the stage when sleep walking, sleep
talking and night terrors occur.
• Once the sleeper reaches stage four (about an
hour after sleep begins) they then travel back
up through stages three, two and one.
• When stage one is reached for the second
time, REM sleep begins and the sleeper
engages in about ten minutes of dreaming.
• Most dreams occur during this REM stage.
• The EEG reveals brain wave patterns that are
very similar to beta waves when a person is
awake, active and alert.
• For this reason, REM sleep has been called
'paradoxical sleep'.
• It is also characterised by jerky movements of
the eyes beneath the eyelids, hence the label,
rapid eye movement.
• The person's heart rate also increases, their
blood pressure rises and their breathing
becomes faster and more irregular.
• Luckily for others, our muscles are paralysed,
preventing us from acting out our dreams.
• As the night progresses, the time spent in
stages three and four decreases while REM
sleep increases.
• The last stages or REM sleep can last up to one
hour or so.
• The entire cycle of stages one through to four
occurs approximately four to six times during
an average eight hour period of sleep.