Assessment of memory: cognitive processes and measurement

Memory Models and Assessment

The most famous typology of memory was originally proposed by Atkinson and Shiffrin (1968). Their research suggested that two distinctly different types of memory exist: short-term memory, and long-term memory. Later Baddley and Hitch (1974) proposed a third type of memory storage device, that of sensory memory (Wilson 1996, p. 135). Two forms of sensory memory exist: sensory memory for vision, called iconic memory, which lasts for approximately .5 to 1 second and auditory or echoic memory, which lasts for about 4-5 seconds. Short-term memory lasts slightly longer, about 18-20 seconds, but only approximately seven individual chunks of memory can reside in STM. "Long-term memory," in contrast "is the relatively permanent memory store in which you hold information even when you are no longer attending to it. Information held in LTM is not represented as patterns of neural activity (as in STM), but rather as changes in brain wiring" (Human Memory, 2010, Atkinson-Shiffrin Model).

Individuals with brain damage may exhibit deficits in memory in all three areas, or many only show cognitive deficits in one area, although usually sense memory deficits are related to physical perceptual impairments rather than purely neurological impairments (Wilson 1996, p. 136). Distinctions between long-term memory deficits such as amnesia and STM are important to note: both are different forms of processing disorders, and exhibit different neurological features. This can influence how the individual is rehabilitated for his or her condition.

A number of different types of tests exist to screen patients' memory capacity. For example, in school children, the Wide Range Assessment of Memory and Learning (WRAML) can be used because of its inclusion of age-appropriate instruments. Its nine subtests (Verbal Learning, Story Memory, Sound Symbol, and Visual Learning) demand the test taker to exhibit both immediate and delayed recall responses. The use of recalling stories and pictures enable the test to be comprehensible to a young child, and to reduce the anxiety the child might feel. Tension and emotion are two factors which can affect test results, and can limit the accuracy of the assessment, if the administrator does not manage these emotions correctly.

Matching the right type of memory test to the target population is essential, to ensure that the results are useful and other extraneous factors, such as cultural barriers, do not inhibit the assessment. Other highly specific tests include the Scales of Cognitive Ability for Traumatic Brain Injury (SCATB), which focuses on cognitive issues that may specifically arise in individuals with problems that occur as a result of head trauma, including perception/discrimination, orientation, organization, recall, and reasoning. More generalized assessments include the Wechsler Memory Scale, created by the founder of the IQ test of that name, which offers a generalized assessment of different memory types (sensory, short, and long-term) and is most appropriate for adults.

In general, two basic types of neuropsychological memory tests exist. "In almost all objective tests, quantitative results are compared with some normative standard, including data from groups of non-brain injured persons and groups of persons with various kinds of brain injury. If the norms are based on age and educational achievement, valid comparison can be made between an individual's performance and that of persons in known diagnostic categories as well as persons who do not have a diagnosis of brain injury. Qualitative assessment of neuropsychological tests provides a look at the processes an individual may use in producing the quantitative scores. Analysis of the pattern of performance among a large number of tests is vital to a neuropsychological assessment" (Swiercinsky, 2001). For example, a patient might be subjected to the SCATB or the Wechsler, which are both quantitatively 'normed' tests. Then, the patient might be subject to tests that examine different processes that might have been affected. These might include the Grooved Pegboard test, which "examines flexibility of thinking and openness to learning" and the Finger Tapping (Oscillation) Test of reproducing rhythm patterns, which assesses if different sides of the brain were impacted to varying degrees through replicating tapping sounds (Swiercinsky, 2001). These latter tests are not normed upon a scale, but are meant to examine the capacity of the individual, to determine more specifically what processes were affected and conspired to produce a memory deficit on the normed tests.