A – 117 Examining Working Memory in Frontotemporal Dementia Subtypes Using Digit Span

Abstract Objective This project examines working memory differences between two frontotemporal dementia (FTD) subtypes - behavioral variant (bvFTD) and primary progressive aphasia (PPA) - using Digit Span Forward (DSF) and Digit Span Backward (DSB), an area with limited prior research. Method Working memory was analyzed using participant data from the National Alzheimer’s Coordinating Center with diagnoses of either PPA or bvFTD and associated DSF and DSB performance scores (N = 2646, M(age) = 66.31, M(education) = 16.93). Cases missing assessment data or diagnosed with other/unspecified FTD subtypes were excluded from analysis. Results ANCOVA analyses controlling for age and education revealed significant group differences on DSF, F(1, 2642) = 167.14, p < .001, partial η2 = .06, and DSB, F(1, 2642) = 15.49, p < .001, partial η2 = .01. The bvFTD group outperformed the PPA group on both DSF (M = 6.60, 5.22; SE = 0.07, 0.08; 95% CI: [6.46, 6.73], [5.06, 5.38]) and DSB (M = 4.16, 3.77; SE = 0.06, 0.08; 95% CI: [4.04, 4.29], [3.62, 3.92]). Conclusion PPA patients performed significantly lower than bvFTD patients on both Digit Span subtests, likely reflecting additional verbal working memory demands that are more cognitively challenging for PPA patients due to their language-related deficits. In contrast, bvFTD may involve more relatively spared working memory processes, despite notable executive dysfunction. Findings highlight a need for further research into the clinical utility of various working memory measures to differentiate the roles of language and executive functioning in assessing cognitive profiles of FTD subtypes.