magnetic resonance imaging is a technique using very rapidly
acquired magnetic resonance images (MRIs). MRI
pictures are taken less than a second apart, and are used
to capture blood flow changes during a cognitive, sensory
or motor task. If a particular brain area has increased blood
flow during a task, it is assumed that the brain area is heavily
active and thus critically involved in that task. Typically,
fMRI images obtained during a task are compared against the
activity patterns obtained during a control task.
Because fMRI gives a snapshot of the functioning
brain, the technique is sometimes called "functional MRI".
It is useful both for identifying function in the normal brain
as well as detecting various abnormalities due to injury or
disease. In general, the results of these studies confirm
those of positron emission tomography (PET) studies in implicating
particular brain regions in particular kinds of activity.
fMRI provides better spatial resolution than PET, and is less
intrusive -- since PET requires injection of a radioactive
tracer into the bloodstream.
Further reading: Illustrated Guide to Diagnostic
Tests, 2nd edition. Springhouse Corporation, Springhouse PA,
by Catherine E. Myers. Copyright © 2006 Memory Loss and the Brain