Une approche structurale de la memoire : correlations clinico-metaboliques a l'aide de la tomographie par emission de positions dans la maladie d'alzheimer
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Abstract EN:
The aim of this study was to contribute to the organization of human memory, using cognitive and metabolic data from patients with alzheimer's disease. The framework of this study is tulving's model which postulates a monohierarchical organization between five memory systems : episodic memory, short term memory, semantic memory, perceptual representations system and procedural memory. These systems were assessed in 24 patients and the results were compared to those of 30 control subjects. A multiple single case study was also performed in order to look for dissociations between abilities preserved and those disturbed in the same patient. The cerebral metabolic rate of glucose was measured, in the resting state, in 19 patients from the initial group. The metabolic data were analyzed both with the method of "regions of interest" and the "statistical parametric mapping". The cognitive study showed a pattern of disorders which fits in with tulving's model (episodic, short term and semantic memory, i. E. , the most specialized systems, are the most affected by the disease and the "inferior" systems, perceptual representations systems and procedural memory, are relatively preserved). However, the multiple case study showed a few dissociations that are not compatible with this model. Most of the correlations between memory performances and metabolic values were consistent with the initial hypotheses and the recent literature on functional anatomy of memory. Furthermore, this study allows a better understanding of memory deficits and of their neurobiological bases in alzheimer's disease.
Abstract FR:
L'objectif de ce travail est de contribuer a la modelisation de la memoire a partir de donnees cognitives et metaboliques recueillies chez des patients atteints de maladie d'alzheimer. Le cadre de cette etude est celui du modele de tulving qui postule une organisation hierarchique entre cinq systemes de memoire : memoire episodique, memoire a court terme, memoire semantique, systeme de representations perceptives et memoire procedurale. Ces cinq systemes ont ete evalues chez 24 patients et les resultats ont ete compares a ceux de 30 sujets temoins. Une approche de cas uniques multiples a egalement ete utilisee afin de mettre en evidence des dissociations entre des capacites preservees et des capacites perturbees. Des mesures de consommation cerebrale de glucose au repos ont ete effectuees chez 19 patients issus de la population precedente. Les donnees metaboliques ont fait l'objet de deux types d'analyse, la methode des regions d'interet et la methode spm ("statistical parametric mapping"). Les donnees de l'etude cognitive montrent un profil d'atteinte compatible avec 'arrangement monohierarchique du modele de tulving (atteinte de la memoire episodique, la memoire a court terme et la memoire semantique, systemes les plus eleves dans la hierarchie et relative preservation des systemes "inferieurs", systeme de representations perceptives et memoire procedurale). En revanche, l'analyse de cas multiples a revele des dissociations qui contredisent cette organisation. L'etude des correlations entre les scores mnesiques et les valeurs metaboliques montre de nombreux resultats en accord avec nos hypotheses initiales ainsi qu'avec la litterature actuelle concernant la neuroanatomie fonctionnelle de la memoire. Outre sa contribution a la modelisation de la memoire humaine, cette etude permet de mieux connaitre les deficits mnesiques dans la maladie d'alzheimer et leurs bases neurobiologiques.