Linguistic Features in the Connected Speech for Primary Progressive Aphasia: Evidence from a Meta-analysis

Abstract

Objectives: Primary progressive aphasia (PPA) is a neurodegenerative disease, where language disorder is a predominant symptom. Previous studies demonstrated that individuals with PPA shows different syntactic abilities when compared to other degenerative syndromes, suggesting that connected speech is the appropriate task for examining syntactic features. Therefore, the current study investigated the linguistic features of PPA in connected speech by conducting a systematic review.Methods: Thirteen studies were extracted from the three foreign databases (CINAHL EBSCO, PubMed, SCOPUS). Fluency, syntactic, and lexical features were converted to Hedges’ g to calculate the effect size of speech production among people with PPA and the control, and between linguistic features.Results: First, the PPA group showed a worse performance overall in the connected speech tasks compared to the control, having a moderate effect on only linguistic features. Second, the PPA group showed worse performance compared to the control in the fluency features, having PPA types as a moderator. Third, the control had better performance in the syntactic features, showing severity as a moderator. Lastly, performance between the PPA group and the control in lexical features had a moderate effect on PPA type.Conclusion: The current study demonstrated that the speech production of individuals with PPA in connected speech has a moderate effect on linguistic features. Moreover, the analysis of linguistic features of PPA in connected speech showed that each linguistic features has a different moderator. To be specific, fluency and lexical features were both discriminated by the PPA types, whereas syntactic features were differentiated by the severity, demonstrating that all people with all PPA types had difficulty in syntactic features.