- Processing of thematic and taxonomic relationships in ageing and in Alzheimer's disease: Evidences from an EEG study and a semantic priming task.

The knowledge stored in semantic memory includes information about categories and features, as well as the semantic relationship between concepts (Murphy & Medin, 1985; Spellman, Holyoak, & Morrison, 2001). In the semantic network, taxonomic (which refers to similarity relations based on shared features) and thematic (which refers to contiguity relations based on co-occurrence in events or scenarios) links are both salient. In Alzheimer's disease (AD), semantic memory is early impaired. However, there are contrasting results regarding the pattern of taxonomical and thematical deterioration in the semantic network of AD. Also, a remaining issue is to determine whether semantic processing of both kinds of links is embodied, as suggested by the upholders of the embodied cognition (e.g. Barsalou, 1999, 2008) and if the sensorimotor system takes differentially part in the semantic process in ageing and in AD.
In order to investigate these questions, sensorimotor sensitive electroencephalogram rhythm will be analyze through young adults (study 1), healthy elderly people (study 2) and AD participants (study 3) performing a semantic priming task in which the target could be preceded either by a thematically (milk-cow) or a taxonomically (pig-cow) related prime compared to an unrelated condition (lemon-cow) or neutral (random meaningless pattern-cow).. The stimuli used in the different conditions were controlled for lexical frequency, familiarity, age of acquisition and visual complexity. Within the framework of the extended sensory-functional theory, the sensory and motor properties of our targets were investigated in order to explore the impact of those variables on the semantic processing. The protocol of our experiment as well as the preliminary results regarding the impact of the variables recruited on young adults semantic processing (study 1) will be presented.