Memory systems and memory distorsions : neuropsychological and neurophysiological approaches
The relationship between episodic memory (EM) and semantic memory (SM) encompasses a major interest for understanding the functional architecture of the long-term memory and the mechanisms underlying the different types of memory deficits. Our main objective was to study the functionning of these two memory systems and their dysfunction, through the study of symptoms known as 'negative', such as forgetfulness and positive symptoms, such as confabulation. The first part of this work concerns the study of the organization of these two memory systems using a paradigm suitable for magnetoencephalography (MEG). A first MEG study in healthy elderly subjects showed a clear dissociation between neurophysiological correlates of EM for famous and unknown faces, showing the interdependence between EM and SM in faces recognition. A second comparative study between a group of patients with Alzheimer's disease (AD) and a group of healthy subjects performed with the same experimental paradigm, allowed us to show an alteration of the relationship between EM and SM from a neuropsychological point of view and the physiopathological correlates of memory deficits in AD. The second part focuses on the expression of the dysfunction of the EM and SM in confabulation. Our studies show that confabulation cannot be considered as a pure memory deficit, but rather as a disorder of consciousness, especially temporal consciousness. Overall, our findings suggest that the link between memory, consciousness and temporality encompasses a major interest in studying the organization of memory systems and in a better understanding of memory disorders