How Objective Memory Performance is Assessed
Studies have utilized a variety of tests to measure cognition in relation to SMC.
Most of these are pencil and paper tests that take anywhere fromfive to 35 min to
complete. Global screening measures are very brief tests that broadly measure
cognitive status with a variety of cognitive functions, such as attention, language,
and memory, and use a summary score to see whether an individual scores above or
below a predetermined cutoff that indicates impairment. As these screening mea-
sures are relatively easy, many individuals perform at 100% accuracy. Thus, it is
difficult to detect subtle relationships between SMC and global screening outcomes
in healthy individuals. A preferred approach is to utilize more complex, reliable,
and validated neuropsychological measures of memory functioning. Verbal mem-
ory measures typically consist of a list-learning task in which individuals hear a list
of words and are asked to immediately recall as many of the words on the list in
each of several learning trials and then again after a 20- to 30-min delay. Another
verbal memory task is paragraph recall, in which individuals are presented with a
short story and are asked to recall as much of that story as possible immediately and
after some delay period. Nonverbal memory measures typically involve drawing
geometricfigures or designs. For example, an individual is shown a series of four
designs arranged on a sheet of paper that they must then draw immediately and then
again after some period of delay. Recognition memory for the design is tested by
showing individuals a series of designs and asking them to choose the designs they
saw from an array of drawings—some previously studied and some not.
Here, we focus on the more commonly used verbal memory measures, but in
some studies, researchers use a battery of tests to assess a wide range of cognitive
functions. The use of a broader cognitive battery helps to address important
questions such as whether the memory problems an individual reports are related to
memory or to difficulty concentrating or to difficulties using effective strategies to
better remember the items they studied.
Assessing Brain Structure and Function
Brain structure is typically assessed with magnetic resonance imaging (MRI). MRI
scanners use strong magneticfields and radio waves to form images of the brain.
Specific regions of the brain can be measured to look at volume changes in regions
of the brain that are critical for memory function.
Brain function is frequently measured by two techniques,functionalMRI (fMRI)
and positron emission tomography (PET) , which can be used while an individual is
engaged in a cognitive task. In the former, MRI technology is utilized to measure
brain activity by detecting associated changes in bloodflow. In the latter, a
radioactive trace is introduced in the body, and concentrations of the tracer will
indicate metabolic activity.
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