Verbs and their thematic role processing abilities for people with aphasia

Objectives: The purpose of this study was to investigate the ability of people with aphasia (PWA) to process verbs and their thematic roles. We further examined the relationship between verb-related processing abilities and aphasia severity. Methods: Fifteen individuals with aphasia and 15 age- and education-matched normal individuals participated in the study. Experiment conditions consisted of thematic role-selection tasks (agent-selection vs. theme-selection) and verb-selection tasks when the two thematic roles were provided. Participants were asked to select the target among 3 choices. Results: PWA performed significantly worse in all conditions than normal elderly adults (NEA). Both groups performed worse on the agent-selection than theme-selection tasks. The group by thematic-role type interaction was significant, indicating that PWA demonstrated differentially greater difficulties in the agent-selection than theme-selection task compared to the NEA group. The verb-selection task was highly correlated with overall aphasia severity and verbal output measures from the standardized aphasia battery. Conclusion: These results indicated that PWA demonstrated deficits in selecting thematic roles associated with the verbs and choosing the verbs when the thematic roles were provided. Greater difficulties in the agent-selection than theme-selection task in both groups are likely due to the pro-drop phenomena, usually associated with the subject-deletion features in Korean. Overall high correlations of verb-selection task with aphasia severity and verbal output measures indicate that the verb-selection task may be a clinically useful method to evaluate word retrieval process deficits in PWA without using an overt naming task.