Les bases cognitives et cérébrales du traitement sémantique des personnes célèbres : étude chez le jeune adulte et la personne âgée saine, atteinte de TCL, ou de dépression

The knowledge that we have on familiar and famous people represents one of the most important areas of semantic memory. They have an important social value because they allow us to recognize and identify people we know and distinguish them from people we do not know. This thesis consists of two parts: the first part focuses on the study of the cerebral substrates of semantic processing of famous people in young adults, while the second part focuses on the study of the semantic knowledge about famous people in elderly person without cognitive impairment, with amnestic Mild cognitive impairment (aMCI), with amnestic Mild cognitive impairment and depressive symptoms (aMCI-D) or with late-life depression (LLD). More specifically, this last part discusses the relationship between semantic disorders and the presence of depressive symptoms.  Thus, the first part aims to explore in functional magnetic resonance imaging (fMRI) brain substrates underlying semantic processing of famous faces compared to perceptual processing (Article 1). The role of the posterior temporal regions (occipito-temporal) in the perceptual processing of faces is now well established. The anterior temporal lobes (ATL) seem to have a particularly important role in the identification of known and familiar faces, but the precise role of this region in semantic processing of familiar faces remains poorly understood. The first article highlights the cortical regions involved in the process of recognition of faces, from perceptual processing to semantic processing that allows us to identify and retrieve biographical information on the face that is presented to us. The results of this study support the model proposed by Haxby and colleagues (2000) in which the region of the ATL is associated with the semantic processing of faces of famous people.  As for the second part, it aims to investigate at behavioral level the integrity of specific and general biographical semantic knowledge in aMCI individuals, in aMCI individuals with depressive symptoms (aMCI-D) and in individuals with LLD (Article 2). Depression is considered as an interdependent factor that may play a role in the variability of the clinical presentation of elderly with aMCI. Indeed, it appears that the presence of depressive symptoms influences the cognitive profile of aMCI individuals, especially for executive function and episodic memory. However, no study has investigated the impact of depressive symptoms on the semantic memory of famous people in aMCI individuals. The present results indicate that aMCI individuals show deficits for semantic processing of famous people, and that these deficits are modulated by the presence of depressive symptoms. Depression alone can not, however, lead to semantic deficits since the group with LLD showed no impairment of semantic memory. The theoretical and clinical implications of these findings are discussed, as well as limitations and future prospects.

Keyphrases: Semantic Memory, Face processing, Anterior temporal lobe, Mild cognitive impairment