Structural language knowledge -mainly morphology and syntax- is systematically argued to be preserved during the course of Alzheimer’s disease (AD). Against impaired semantic and lexical knowledge, and important dementia-related shifts in acoustic phonetics, structural language levels are usually defined as unimpaired until severe stages of dementia.
Based on a multidisciplinary approach to language assessment, including corpus analysis and discourse analysis, we propose a methodological revision of approaches to studying structural language knowledge as candidates to dementia-driven language changes. In this work we discuss the possibility of applying discourse annotation for detecting morphological and syntactic deviations in oral production of speakers at different stages of dementia (early AD, moderate AD and severe AD) in order to show how qualitative approaches can reveal structural changes during cognitive impairment. Furthermore, we show how such structural changes can be classified into dementia-related and healthy-aging-related traits by using an annotation system we developed for our corpus CORDEM (Annotated corpus of oral speech production in MCI and AD for European Spanish language).
Our main findings prove that structural levels of language may undergo dementia-driven changes, like spontaneous production of inflectional mistakes, lack of syntagma agreement, omission of referents or systematic failure to process complex and subordinate clauses. In view of these results, we discuss how these changes may be discriminated from parallel phenomena occurring in healthy aging, and how an annotated corpus approach we undertake can help in such discrimination.