Episodic and working memory function in Primary Progressive Aphasia: A meta-analysis

OBJECTIVE: The distinction between Primary Progressive Aphasia (PPA) variants remains challenging for clinicians, especially for the non-fluent (nfv-PPA) and the logopenic variants (lv-PPA). Previous research suggests that memory tests might aid this differentiation. This meta-analysis compares memory function among PPA variants. METHOD: Effects sizes were extracted from 41 studies (N = 849). Random-effects models were used to compare performance on episodic and working memory tests among PPA patients and healthy controls, and between the PPA variants. RESULTS: Memory deficits were frequently observed in PPA compared to controls, with large effect sizes for lv-PPA (Hedges' g = -2.04 [-2.58 to -1.49]), nfv-PPA (Hedges' g = -1.26 ([-1.60 to -0.92], p < .001)), and the semantic variant (sv-PPA; Hedges' g = -1.23 [-1.50 to -0.97]). Sv-PPA showed primarily verbal memory deficits, whereas lv-PPA showed worse performance than nfv-PPA on both verbal and non-verbal memory tests. CONCLUSIONS: Memory deficits were more pronounced in lv-PPA compared to nfv-PPA. This suggests that memory tests may be helpful to distinguish between these PPA variants.