Referential adjustment during discourse production in Alzheimer's disease.

Several studies have shown that people with Alzheimer's disease (AD) tend to use more pronouns than healthy aged adults when referring to entities during discourse. This referential behavior has been associated with the decrease of cognitive abilities, such as lexical retrieval difficulties or reduced abilities in working memory. However, the influence of certain important discourse factors on the referential choices made by people with AD has yet to be established. This study examines referential choices made at three discourse stages during narrative discourse (the introduction of a referent, the maintaining of the referent in focus, and the shift from one referent in focus to another). These referential choices are examined in increasingly complex referential contexts. In addition, this study investigates the relationships between referential choices and various cognitive abilities. To do so, the narrative discourses of 21 people with AD and 21 healthy adults were elicited using a newly developed storytelling in sequence task. The analyses focused on the production of three major referential expressions (indefinite expressions, definite expressions and pronouns) which are expected to vary according to discourse stage and the referential complexity of the stories. The results show that AD participants produce significantly fewer of the referential expressions expected at the introduction and shift stages than healthy aged adults produce. Nevertheless, the variation in the categories of referential expressions produced by the AD participants between the discourse stages is similar to that produced by the healthy aged adults, suggesting a preserved sensitivity to the factors manipulated in the task (i.e., discourse stages and referential complexity). This study also highlights the fact that different cognitive competences, especially executive abilities, are greatly involved in referential choices. The results add further evidence that referential choices rely on a variety of cognitive skills, depending on the discourse context in which they are made.