Structurally well-formed narrative production in the face of severe conceptual deterioration: A longitudinal case study of a woman with semantic dementia

Language production was examined in a woman with semantic dementia (SD) over a three-year time period. Narratives were analyzed for their propositional content, syntactic structure, morphological complexity, and lexical makeup. An additional analysis looked at the proportion of vague terms and pronouns out of all nominal expressions. Investigation of verb frequency, light/heavy verbs, verb type/token ratio, and verb argument structure was also conducted. Findings suggest that alongside a severe deterioration of the general message level and continual degradation of lexical retrieval mechanisms, syntactic and morphological aspects of connected speech remain essentially unaffected by SD. It is argued that SD leads to a dissociation between impaired conceptual knowledge and intact structure in language production.