The Cognitive Substrates of Action Fluency: A Multivariate Analysis in Parkinson's Disease.
The Cognitive Substrates of Action Fluency: A Multivariate Analysis in Parkinson's Disease.
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Original abstract
PURPOSE: Action fluency (AF), the rapid generation of verbs, has been proposed as a sensitive marker of cognitive impairment in Parkinson's disease (PD). However, it is unclear whether AF reflects domain-general executive-generative abilities or a disease-specific motor semantic deficit. This study examined the cognitive predictors of AF in individuals with PD without dementia (PD-ND). METHOD: Thirty-one older adults (14 PD-ND, 17 healthy controls) matched on age, sex, and education completed AF, letter fluency, semantic fluency, design fluency, processing speed, and global cognition tasks. AF responses were scored for unique verbs. A multiple regression model examined whether PD status, other fluency scores, processing speed, and global cognition predicted AF performance while controlling for demographic covariates. RESULTS: Letter, semantic, and design fluency each independently explained variance in AF, whereas processing speed, global cognition, age, education, and PD status were not significant predictors. Thus, group differences between PD-ND and controls were not observed once domain-general fluency abilities were considered. CONCLUSIONS: AF performance in PD-ND reflects domain-general executive-generative mechanisms rather than an isolated verb semantic deficit. Clinically, AF should be interpreted as an integrative measure of executive control. Incorporating a multidimensional fluency battery may improve diagnostic sensitivity and inform targeted interventions for cognitive-communication impairments in PD.