Reliability of working memory assessment in neurocognitive disorders: a study of the Digit Span and Corsi Block-Tapping tasks.

Working memory (WM) is a core aspect of executive function, related to temporary storage of information to be manipulated and used by other cognitive processes. Despite the lack of a consensus definition and theoretical model to explain this function, its assessment is a key aspect in clinical practice, both for diagnostic and intervention purposes. Furthermore, as a cognitive process, WM is key to understanding functional capacity in clinical samples. The Digit Span and Corsi Block-Tapping tasks are frequently used in WM assessment. In both tests, the subject must repeat a series of stimuli in the presented order (forward) or in the inverse order (backward). The Digit Span uses escalating series of numbers from 1 to 9, presented in a randomized fashion, to assess verbal WM. The Corsi Block-Tapping task uses nine cubes placed on a wooden board to assess visuospatial WM. Both tests are commonly used in neuropsychological assessment of older adults with a diagnostic hypothesis of pathological aging (e.g., minor and major neurocognitive disorders). However, we are unaware of studies investigating the reliability of these tasks for WM assessment in older adults diagnosed with neurocognitive disorders. Test reliability is an important measure used to estimate test precision and to create reliable change coefficients. These are simple statistical procedures used to examine whether changes in test scores over time (e.g., pre-intervention vs. post-intervention, baseline vs. follow-up) are likely due to measurement error (imprecision of test measures) or are associated with an external factor (the intervention, a placebo, or other non-documented causes). To analyze the reliability of the Digit Span and Corsi Block-Tapping tasks, we assessed 25 older adults with low formal education referred for neuropsychological assessment due to cognitive-functional complaints (13 patients with mild and 12 with major neurocognitive disorder, irrespective of etiological diagnosis). Diagnosis involved cognitive and functional assessment, performed with the Brazilian versions of the Mattis Dementia Rating Scale and Functional Activities Questionnaire. All participants gave written consent. The study was approved by the Universidade Federal de Minas Gerais Ethics Committee and conducted in accordance with the Declaration of Helsinki. The same examiner administered and scored both tasks in all participants. Two trials were administered for each span (sequence length ranging from 2 to 8), in forward and reverse order, in both tasks. Two errors in the