Morphosyntactic Features of Korean Agrammatism in Primary Progressive Aphasia

Abstract

Objectives: Agrammatism is a core feature of nonfluent variant primary progressive aphasia (nfvPPA), characterized by impaired morphosyntactic processing that leads to substantial difficulty producing grammatically complex sentence structures. Although its manifestation varies across languages, systematic investigation of agrammatism remains underexplored in agglutinative languages such as Korean. This study aimed to identify the morphosyntactic characteristics of agrammatism in native Korean-speaking patients with nfvPPA. Methods: Participants included nfvPPA patients with agrammatism (Ag; N=5), nfvPPA patients without agrammatism (non-Ag; N=5), and age- and education-matched normal controls (NC; N=10). All participants completed connected speech tasks from which six linguistic measures were extracted: grammatical-to-lexical morpheme ratio, verb-to-noun ratio, mean length of utterance in morphemes, number of grammatical morphemes, number of semi-grammatical morphemes, and number of lexical case markers. Results: No significant group differences were found in grammatical-to-lexical morpheme or verb-to-noun ratios. The Ag group had significantly lower MLU-m, and fewer grammatical morphemes, semi-grammatical morphemes, and lexical case markers than the non-Ag and NC groups. In patient-only comparisons, only MLU-m and the number of grammatical morphemes per utterance remained significantly lower in the Ag group. Conclusion: Korean agrammatic speech showed morphosyntactic characteristics that both diverged from patterns reported in English and reflected cross-linguistically observed reductions in grammatical resources. These findings likely reflect the agglutinative and head-final properties of Korean, while also supporting the presence of a universal feature of agrammatism.