Conservation of the morphology, by people with Alzheimer' disease, at the severe stage

The aim of this communication is to show how Alzheimer's disease does not disrupt the implicit morphological knowledge. We present two studies in order to reveal the semantic abilities of patients, through both understanding and producing morphological markers. We consider categorization process, not from a taxonomic model (Rosch), but through the information conveyed by morphology. According to this model, the properties of linguistic signs determine the structure of categories (Dubois and Poitou). We will try to show that people with Alheimer's Disease (AD) use morphological information (lexical and derivational) to succeed in doing a categorical inclusion task. We proposed to 30 AD people and 30 matched healthy subjects, a task of category-specific inclusion. We created an experimental protocol constituted by items bringing in 3 variables: (1) membership or not in the category ``Tree'' or ``Work'', (2) with or without derivational morpheme-'' ier `` and (3) lexical bound (or pseudo-bound) morpheme or not bound to the fruit / function. The aim was to highlight the respective effects of the lexical morpheme and the derivational morpheme. The results show that the combined information carried by lexical morpheme and the derivational morpheme-'' ier `` is effective, for the AD people as for the matched healthy subjects. People with AD use more the information carried by the language than the others. The results point out a resilience of morphology, in memory implicit, which allows the subjects to succeed the task of category-specific inclusion. So, the lexico-semantic difficulties of the patients do not depend only on difficulty of access or loss of the semantic representations as well as supposes it cognitive psychology, because AD patients can process items as linguistic signs, a well as do healthy subjects. The goal of second research is to study production of neoforms, through the analysis of corpus of an AD patient at the severe stage. We shall try to show how the production of these terms increases with the advance of the disease. Furthermore, these productions are to be considered not as mark of an irreversible destruction of the language but as of real mechanisms of compensation, which take on the morpholexicales and morphosyntactic characteristics of the linguistic code. These results tend to demonstrate that the productions, apparently meaningless, can be considered in reality as idiolects. This idiolects respect the rules of the linguistic code, implicitly built by each one, even at the ultimate stage of the disease. Thus, speech difficulties, cannot be considered as a `` loss of the language `` and nor a `` regress of language''.