Grammatical ability predicts relative action naming impairment in primary progressive aphasia

Background: Findings from several studies have indicated that participants with nfvPPA and participants with svPPA exhibit different patterns on action and object naming tasks, while other recent studies have found that neither participants with nfvPPA nor participants with svPPA show a significant difference in accuracy between object naming and action naming. Aims: The goal of this study was to test the hypothesis that relative action naming impairment is associated with grammatical ability in PPA, rather than a specific subtype of PPA. Methods & Procedures: Thirty-four participants with PPA completed the Boston Naming Test, the Action Naming subtest of the Boston Diagnostic Aphasia Examination, and the Northwestern Anagram Test, which was used to measure grammatical ability. Z-scores for the two naming tasks were calculated based on normative data from unimpaired controls. For each participant with PPA, the relative action naming impairment was calculated by subtracting the object naming z-score from the action naming z-score. Linear regression analysis was then used to evaluate the role of grammatical ability as a predictor of relative action naming impairment, while controlling for age, education, cognitive ability (as measured by the Montreal Cognitive Assessment), and semantic ability (as measured by the Pyramids and Palm Trees test). The interaction between grammatical ability and each control variable was also examined. Outcomes & Results: The main effect of grammatical ability was a significant predictor of relative action naming impairment, while none of the control variables was a significant predictor. However, the interaction between grammatical ability and semantic ability was also significant. Conclusions: Individuals who have both grammatical impairment and semantic impairment have the largest relative action naming impairment. These individuals may benefit from a treatment that focuses on the retrieval of verbs and their arguments.