Topographical recognition memory and autobiographical memory in amnestic mild cognitive impairment: a longitudinal study
RITTER, Emilie (2007) Topographical recognition memory and autobiographical memory in amnestic mild cognitive impairment: a longitudinal study. Thèses de doctorat, Université Louis Pasteur.
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Mild cognitive impairment (MCI) is defined as one or more cognitive deficit(s) of not sufficient severity to constitute a dementia but of greater severity than that of healthy individuals of the same age and education level (Petersen et al., 2001). When the cognitive deficit concerns memory, it is called amnestic MCI (aMCI). It has been shown that individuals with aMCI are at a high risk of developing dementia of Alzheimer type (Petersen et al., 1999). Moreover, the finding of medication for slowing cognitive decline of Alzheimer’s disease (AD) and waiting for new more efficient ones (Roberson & Mucke, 2006) renders research on aMCI, and thereby preclinical markers, of crucial interest. However, the aMCI syndrome may have causes other than neurodegenerative diseases, such as depression, and no standardized method exists to distinguish incipient demented aMCI patients from those who will not develop dementia. The main purpose of this study is to detect specific markers of preclinical dementia to discriminate aMCI patients who will develop dementia from those who will not. To this end, we performed a two-year longitudinal study aiming to examine cognitive evolution of aMCI patients in order to discriminate declining from non-declining aMCI patients. At the end of the study, we compared declining aMCI’s cognitive performances at baseline with those of the non-declining to detect markers of preclinical dementia. Based on their neural substrates, we theorized that deficits in topographical recognition memory and autobiographical memory (AbM) could be neuropsychological markers of incipient dementia. The aMCI patients who declined cognitively were considered as evolving aMCI. Results showed that aMCI was an heterogeneous syndrome leading to evolving aMCI in a limited proportion whereas additional depression strongly increased the risk of becoming evolving aMCI. With regard to topographical recognition memory, aMCI patients were impaired and this memory was not sensitive to depression. Nevertheless, longitudinal results indicated that deficits in topographical recognition memory were not specific to the evolving aMCI condition. In the case of AbM, no specific deficit was found. These preliminary results may be useful for very large scale studies targeting neuropsychological markers of AD. Only a very accurate diagnosis of evolving aMCI will allow efficient early medical treatment.
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