Morphosyntactic characteristics of agrammatism in Persian post-stroke aphasia: a comprehensive description

Objective This study provides a comprehensive grammatical-encoding profile of Persian-speaking individuals with agrammatism (PSWA) after stroke across domains of verb production, functional morphology, and syntactic structure.Methods Forty-two participants (21 PSWA; 21 non-brain-damaged [NBD] controls) completed an action-naming task, five sentence-production tasks, and eight discourse elicitation tasks (picture description, narratives, story retelling). Responses were recorded, transcribed, and coded. Quantitative and error analyses were conducted across domains and tasks, and proportional accuracy scores were calculated.Results Verb retrieval was reduced in PSWA (action-naming accuracy: PSWA, M = 35.95%, SD = 22.63; NBD, M = 100%). In discourse, PSWA produced fewer simple (12.06% vs 58.21%) and compound verbs (16.16% vs 74.72%). Naming errors were dominated by omissions (no response: 36.31%) and compound-verb disruptions, including verbal element substitution (40.30%) and non-verbal element deletion (23.95%). Argument structure was simplified: in discourse PSWA produced fewer two-argument (16.71% vs 90.00%) and three-argument verbs (1.13% vs 5.97%), and in sentence tasks fewer three-argument verbs (0.16% vs 1.07%). Functional morphology was especially reduced in discourse: present 32.23% vs 64.55%; past 14.83% vs 61.09%; subjunctive 2.18% vs 42.39%; perfective 14.67% vs 38.88%; SVA errors were low (0.57% sentence; 1.61% discourse). Clitic production was also markedly reduced: sentence 6.88% vs 59.78%; discourse 18.21% vs 87.26%. Syntax was truncated, with shorter discourse MLU (1.72, SD = 0.57 vs 7.90, SD = 1.32), near-absent relative clauses (0.33% vs 21.48%), and high verb deletion (45.04%) and absent sentential structure (56.50%) in discourse.Conclusion Persian agrammatism reflects broad, task-sensitive impairment, with discourse revealing greatest vulnerability in compound verbs, argument structure, inflectional marking and clitic cohesion, and syntactic complexity, while agreement remains relatively spared.