Lack of coherence in the narrative discourse of patients with dementia of the Alzheimer's type

Abstract

The lack of coherence in the narrative discourse of patients with dementia of Alzheimer's type (DAT) is attributed to the presence of irrelevant information. The definition of irrelevant information, however, varies across studies. For some authors, any utterance is considered as irrelevant, whether or not it is linked to the topic. In this study, we distinguished Relevant (expected), Related (unexpected but linked to the topic) and Irrelevant (unexpected not linked to the topic) utterances. We hypothesized that DAT patients produce more Irrelevant utterances than controls. We administered a narrative discourse test to 29 DAT and 29 controls. Results revealed that controls produced more Relevant than Irrelevant utterances whereas the proportions for these two utterance types did not differ in the DAT group. We conclude that the lack of coherence in the narrative discourse of DAT patients is due to the lower proportion of relevant information it contains.