Brain Imaging Technologies
Technology
Description
Strengths
Limitations
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Combines computer and X-ray technology.
Uses a series of X-ray beams passed through the
head. Images are then developed on sensitive
film. This method creates cross-sectional images
of the brain.
Shows structure of the brain.
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Extremely useful
for showing
structural
damage to the
brain.
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Monitors glucose metabolism in the brain
Patient is injected with a harmless dose of
radioactive glucose, and the radioactive particles
emitted by the glucose are detected by the PET
scanner
When radioactive material gets into the
bloodstream, it goes to areas of the brain that
use it. Usually this is a form of sugar that
produces gamma rays as it is metabolized by the
brain. Gamma rays produced can be detected by
the machine in which the person is placed.
Eventually the signal is turned into a computer
image that displays a colorful map of activity in
different parts of the brain.
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Can record
ongoing activity
in the brain, such
as thinking
Useful in
conditions (such
as Alzheimer’s
disease) that do
not show
structural
changes early
enough to be
detected by MRI
or CT scans
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CT
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PET
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EEG
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fMRI
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Electrodes that detect changes in the electrical
activity below them are placed on the outside of
a person’s head in specific locations. When
areas of the brain are active, the EEG produces a
graphical representation of the activity from
each electrode.
Electrical activity is caused by the electrical
charge generated by neurons transporting
information through the brain
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Measures changes in blood flow in the active
brain. This is associated with use of oxygen and
linked to neural activity during information
processing. When participants are asked to
perform a task, the scientist can observe the part
of the brain that corresponds to that function.
Provides a 3-dimensional picture of brain
structures, using magnetic fields and radio
waves.
Takes advantage of the fact that when neurons
in a particular region are active, more blood is
sent to that region
Indicates which areas of the brain are active
when engaged in a behavior, or as certain
thoughts or emotions occur, by detecting
changes in blood flow to particular areas of the
brain
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Commonly used
in sleep research
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Provides both an
anatomical and a
functional view
of the brain
More precise
than a PET scanhigher resolution
and easier to
carry out
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Only shows structural
images, cannot show brain
function.
Exposure to X-ray radiation
can be a cause for concern.
Expensive to use
Radioactive material used
may be problematic for
individuals with certain
health problems
Scanner is not a natural
environment for cognition,
question of ecological
validity
Use of colors may
exaggerate the different
activities of the brain
Brain areas activate for
different reasons
Much less precise than the
fMRI
Does not show localization
of function because
electrodes are outside the
skull and detect the activity
of an unaccountable
number of neurons
Provides limited
information, does not show
actual function
MRI scanner is not a natural
environment for cognition,
question of ecological
validity
Use of colors may
exaggerate the different
activities of the brain
Brain areas activate for
different reasons
Focus is mostly on localized
functioning and does not
take into account the
distributed nature of
processing in neural
networks
Brain Imaging Technologies
Technology
Description
Strengths
Limitations
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MRI
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Gives detailed pictures of internal structures
in the body. The body consists to a large
extent, of water molecules. In the MRI
scanner a radio frequency transmitter is
turned on and it produces an
electromagnetic field.
Detects radio frequency signals produced by
displaced radio waves in a magnetic field
Provides an anatomical view of the brain
When body is exposed to strong magnetic field,
the protons in the water inside the body
change their alignment. When a magnetic field
is used in conjunction with radio frequency
fields, the alignment of the hydrogen atoms is
changed in a way to be detectable by a scanner.
Signal from the scanner can be transformed
into visual representation of area of part of
body being studied
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No X-rays or
radioactive material
used
Provides a detailed
view of the brain in
different dimensions
Safe, painless, noninvasive
No special
preparation required
from patient
Image that is
produced can
represent a slice of
the brain taken from
any angle and can be
used to create a 3-D
image of the brain.
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Expensive to use
Cannot be used on
patients with metallic
devices (such as metal
screws or pacemakers)
Movement can affect
pictures- Cannot be used
with uncooperative
patients because patients
must lie still
Cannot be used with
patients who are
claustrophobic
Cannot determine causeeffect relationships
Research Methods Used at the Biological Level of Analysis
Method
Description
Strengths
Limitations
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Investigator manipulates a variable under
carefully controlled conditions and observes
whether any changes occur in a second
variable as a result
Used to establish cause and effect
relationships between variables studied
May be used to test the effects of changes in
physiology or to test the effectiveness of a
new medication
May also be used to study what effects can
be observed when particular parts of the
brain are damaged
An in-depth investigation of an individual
subject
Allows researchers to take advantage of
naturally occurring irregularities (e.g. brain
damage or long-term drug use) by obtaining
detailed information about the participant’s
condition
Produces primarily descriptive info
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Examines the extent to which two variables
are related to each other by taking scores on
two or more measures and working out the
relationship between them
Many techniques used to observe brain
activity, such as fMRI and PET, are essentially
correlating brain activity with behavior,
cognition or emotion
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Experiments
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Case Studies
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Correlational 
Studies
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May be used to
determine cause
and effect
Increased control
over extraneous
variables
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Relatively little
harm that can be
done to
participants
Possible to study
cases that could
not ethically be
investigated via
experiments
Frequently used
in twin and
adoption studies
which are
important sources
of information
about the link
between genetics
and behavior
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Ethical issues with
experimenting on humans
Placebo effect may occur in
humans
Ethical issues even with
animal research
Questions over validity of
doing experiment on animals
and generalizing to humans
Artificiality may lead to
questions of ecological
validity
Depth of information
obtained and possible
uniqueness of the case make
it difficult to maintain
anonymity of the
participants
Questions of generizability
Although a relationship can
be established, we cannot
infer causation