Measuring the coherence of normal and aphasic discourse production in Chinese using rhetorical structure theory (RST)

The study investigated the difference in discourse coherence between healthy speakers and speakers with anomic aphasia using Rhetorical Structure Theory (RST). The effect of genre types on coherence and potential factors contributing to the differences were also examined. Fifteen native Cantonese participants of anomic aphasia and their control matched in age, education and gender participated. Sixty language samples were obtained using the story-telling and sequential description tasks of the Cantonese AphasiaBank protocol. Twenty naïve listeners provided subjective ratings on the coherence, completeness, correctness of order, and clarity of each speech sample. Results demonstrated that the control group showed significantly higher production fluency, total number of discourse units, and fewer errors than the aphasia group. Controls used a richer set of relations than the aphasic group, particularly those to describe settings, to express causality, and to elaborate. The aphasic group tended to omit more essential information content and was rated with significantly lower coherence and clarity than controls. The findings suggested that speakers with anomic aphasia had reduced proportion of essential information content, lower degree of elaboration, and more structural disruptions than the controls, which may have contributed to the reduced overall discourse coherence.published_or_final_versionSpeech and Hearing SciencesBachelorBachelor of Science in Speech and Hearing Science

Measuring Discourse Coherence In Anomic Aphasia Using Rhetorical Structure Theory

Purpose: The existing body of work regarding discourse coherence in aphasia has provided mixed results, leaving the question of coherence being impaired or intact as a result of brain injury unanswered. In this study, discourse coherence in non-brain-damaged (NBD) speakers and speakers with anomic aphasia was investigated quantitatively and qualitatively. Method: Fifteen native speakers of Cantonese with anomic aphasia and 15 NBD participants produced 60 language samples. Elicitation tasks included story-telling induced by a picture series and a procedural description. The samples were annotated for discourse structure in the framework of Rhetorical Structure Theory (RST) in order to analyse a number of structural parameters. After that 20 naïve listeners rated coherence of each sample. Result: Disordered discourse was rated as significantly less coherent. The NBD group demonstrated a higher production fluency than the participants with aphasia and used a richer set of semantic relations to create discourse, particularly in the description of settings, expression of causality, and extent of elaboration. People with aphasia also tended to omit essential information content. Conclusion: Reduced essential information content, lower degree of elaboration, and a larger amount of structural disruptions may have contributed to the reduced overall discourse coherence in speakers with anomic aphasia