210 Introduction to Anatomy and Physiology
What Research Tells Us
...about
Studying the Brain
An increasing variety of
approaches is available for
studying the functional roles
of different parts of the central
nervous system. As technology
advances, more sophisticated
techniques emerge.
fMRI Scans
One procedure extremely
useful for both scientifi c and clinical
evaluation of the brain is called
functional magnetic resonance
imaging (fMRI). This technology
creates images of changes in
blood fl ow to activated brain
structures. This is made possible
by the slightly different magnetic
properties of oxygenated and
deoxygenated blood. The images
show which brain structures
are activated and the amount of
time they are activated during
performance of different tasks. The
individual undergoing the brain
scan is presented with certain
tasks that can cause activation
(increased blood fl ow) to the
regions of the brain responsible for
perception, thought, and a stimulated
motor action, such as raising an
arm or smiling (Figure 6.11).
Increasingly, physicians are
using fMRI to diagnose disorders
and diseases of the brain. With a
fi ne sensitivity to changes in blood
fl ow, fMRI is particularly useful for
evaluating patients who may have
suffered a stroke. Early diagnosis
of stroke is important because
treatment can be signifi cantly more
effective the earlier it is given.
PET Scans
Another approach for studying
brain function involves positron
emission tomography (toh-MAHG-
ra-fee), or PET. This procedure
tracks the locations of radioactively
labeled chemicals in the
bloodstream. PET scans can show
blood fl ow, oxygen absorption, and
glucose absorption in the active
brain, indicating where the brain
is active and inactive. Although
fMRI has largely replaced PET
for the study of brain activation
patterns, PET scans still provide
the advantage of showing where
particular neurotransmitters are
concentrated in the brain. PET
scans are also still widely used
in diagnosing various forms of
brain disease because they can
be analyzed and interpreted more
quickly than fMRI scans.
Taking It Further
1. How is an fMRI used to
help diagnose disease and
disorders?
2. Why is the blood-fl ow pattern
to the brain a revealing factor
in the diagnosis of a particular
brain disease or disorder?
3. In what situations might a
doctor prefer to use an fMRI or
PET scan?
Figure 6.11 Functional magnetic resonance imaging (fMRI) scans of the
brain show different areas of activation.
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