Memoria lexico-semantica no comprometimento cognitivo leve amnestico e doença de Alzheimer leve : aspectos neuropsicologicos, de neuroimagem estrutural e modelo de organização cerebral / Lexical semantic memory in amnestic mild cognitive impairment and mild Alzheimer´s disease : neuropsychological and neuroimaging aspects and model of cerebral organization

AUTOR(ES)
DATA DE PUBLICAÇÃO

2008

RESUMO

Cerebral organization of lexical-semantic memory, as well as its disruption in mild Alzheimer s disease (AD) and in amnestic Mild Cognitive Impairment (aMCI) is not fully understood. In this study, we evaluated the performance of mild AD, aMCI and normal aging subjects in lexical-semantic tests: Boston Naming Test (BNT), CAMCOG s Similarities item, Verbal Fluency (VF) for animals category and others cognitive domains. We detailed their performance on BNT by evaluating: 1) if they needed or were benefited by semantic and phonemic cues and 2) the pattern of general errors (classified as semantic errors, visual paragnosia, phonological errors, and omission errors). The semantic errors were further subcategorized into three subclasses (coordinate, superordinate, and circumlocutory). We also evaluated the pattern of brain atrophy in aMCI and mild AD patients by using structural neuroimaging methods: hippocampal volumetry (HV) and Voxel-based morphometry (VBM). We correlated HV with subjects performance on Rey Auditory Verbal Learning Test (RAVLT) delayed recall item, and the pattern of spontaneous and semantic errors on BNT with grey matter density, by using VBM. aMCI subjects performed worse than controls on VF for animals category, while mild AD performed worse than aMCI and controls in all lexical-semantic tests. However, after phonemic cues, mild AD subjects performed similar to aMCI and control subjects. They also had the same qualitative pattern of spontaneous and semantic errors, although quantitatively, AD patients committed the most errors, controls committed the fewest errors, and aMCI subjects showed an intermediate performance. Concerning structural neuroimaging, the three groups also presented a continuum pattern in HV, although there were no statistically differences between aMCI and AD HV. RAVLT delayed recall item was significantly related to HV, considering the three groups together. In relation to VBM analysis, mild AD patients had more areas with more grey matter atrophy than aMCI and control subjects. aMCI showed more atrophy mainly in parahippocampal gyri and thalami, when compared with control subjects. Considering white matter, mild AD group showed atrophy in periventricular regions, corpus callosum and areas adjacent to associative cortices. There was not white matter atrophy in aMCI patients in comparison with controls subjects. We found several areas with significant correlations between spontaneous naming errors on BNT and grey matter density, considering the three groups together. Medial temporal structures and thalami were correlated with all subtypes of errors; anterior temporal regions, mainly superior and inferior temporal gyri, were related with coordinate and circumlocutory errors; superior frontal gyri (left more than right) were related with superordinate errors, while inferior frontal gyri (left more than right) were related to circumlocutory errors. We discussed the possible role of each of these areas in the lexical-semantic mental processes, and their contribution to the understanding of cerebral organization of semantic memory.

ASSUNTO(S)

alzheimer disease memory doença de neuropsychology imagem por ressonancia magnetica neuropsicologia memória alzheimer magnetic resonance imaging

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