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Summary
In neuropsychological practice, the availability of effective and reliable tests is crucial. The Symbol Digit Modalities Test (SDMT) is widely used because it is easy to administer, reliable and also evaluates information processing speed.
We set out to obtain normative data (currently unavailable for the Italian population) for the oral version of this test.
Both age and education influenced performance on the SDMT; therefore, correction scores were obtained on the basis of these factors. The cut-off for normality was 34.2. The availability of Italian normative data for the SDMT will allow wider application of this test in clinical practice.
KEY WORDS: information processing speed, normative data, SDMT oral version.
Introduction
Among the various parameters to consider when evaluating a subject's ability to process information, the speed at which information is analysed and inserted into the patrimony of data available for other cognitive processes is crucial. Sustained attention and selective attention both help to determine information processing speed. The term "sustained attention" indicates "the ability to maintain a consistent behavioural response during continuous and repetitive activities" (1). This function comprises two sub-components: vigilance and working memory. "Working memory" (2) is a functional component of short-term memory; it is part of an integrated system that holds and processes information for brief periods of time during the performance of a complex cognitive task (3). The term "selective attention", on the other hand, refers to the ability to avoid distractions induced by other conflicting stimuli (1).
In neuropsychological practice, effective and reliable tests are necessary to assess the various aspects of cognitive functioning. The Symbol Digit Modalities Test (SDMT) (4), a modified version of the WAIS Digit Symbol sub-test (5), is a neuropsychological test used, in clinical settings, to assess information processing speed, which is possibly determined by attentional capacity (scanning and tracking in the visuo-spatial domain) (6) and working memory (7). Performance on the written version also depends on motor speed and agility (visuo-motor coordination) (7).
Aaron Smith developed this test to screen cognitive state. It was originally published in 1973 and subsequently revised in 1982. It consists of a sheet of paper with, at the top, a sequence of nine symbols and nine corresponding numbers (key). The task sequence consists of a series of...