RESUMO
Alzheimer's disease (AD) studies on animal models, and humans showed a tendency of the brain tissue to become hyperexcitable and hypersynchronized, causing neurodegeneration. However, we know little about either the onset of this phenomenon or its early effects on functional brain networks. We studied functional connectivity (FC) on 127 participants (92 middle-age relatives of AD patients and 35 age-matched nonrelatives) using magnetoencephalography. FC was estimated in the alpha band in areas known both for early amyloid accumulation and disrupted FC in MCI converters to AD. We found a frontoparietal network (anterior cingulate cortex, dorsal frontal, and precuneus) where relatives of AD patients showed hypersynchronization in high alpha (not modulated by APOE-ε4 genotype) in comparison to age-matched nonrelatives. These results represent the first evidence of neurophysiological events causing early network disruption in humans, opening a new perspective for intervention on the excitation/inhibition unbalance.
Assuntos
Doença de Alzheimer/diagnóstico por imagem , Encéfalo/diagnóstico por imagem , Disfunção Cognitiva/diagnóstico por imagem , Rede Nervosa/diagnóstico por imagem , Doença de Alzheimer/genética , Doença de Alzheimer/fisiopatologia , Apolipoproteína E4/genética , Encéfalo/fisiopatologia , Disfunção Cognitiva/genética , Disfunção Cognitiva/fisiopatologia , Potenciais Pós-Sinápticos Excitadores/fisiologia , Feminino , Humanos , Imageamento por Ressonância Magnética/métodos , Magnetoencefalografia/métodos , Masculino , Pessoa de Meia-Idade , Rede Nervosa/fisiopatologia , Inibição Neural/fisiologiaRESUMO
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Assuntos
Humanos , Masculino , Adulto , Disfunção Cognitiva , Diagnóstico Diferencial , Transtornos da Memória , Neurossífilis/diagnóstico , Lobo Temporal/patologia , Antibacterianos/administração & dosagem , Encefalite Viral/diagnóstico , Imageamento por Ressonância Magnética , Neurossífilis/tratamento farmacológico , Neurossífilis/epidemiologia , Penicilinas/administração & dosagem , Treponema pallidum/imunologiaAssuntos
Disfunção Cognitiva , Diagnóstico Diferencial , Transtornos da Memória , Neurossífilis/diagnóstico , Lobo Temporal/patologia , Adulto , Antibacterianos/administração & dosagem , Encefalite Viral/diagnóstico , Humanos , Imageamento por Ressonância Magnética , Masculino , Neurossífilis/tratamento farmacológico , Neurossífilis/epidemiologia , Penicilinas/administração & dosagem , Treponema pallidum/imunologiaRESUMO
The objective of this study was to analyze image quality of chest examinations in pediatric patients using computed radiography (CR) obtained with a wide range of doses to suggest the appropriate parameters for optimal image quality. A sample of 240 chest images in four age ranges was randomly selected from the examinations performed during 2004. Images were obtained using a CR system and were evaluated independently by three radiologists. Each image was scored using criteria proposed by the European Guidelines on Quality Criteria in Pediatrics. Mean global scoring and scoring of individual criteria more sensitive to noise were used to evaluate image quality. Agfa dose level (DL) was in the range 1.20 to 2.85. It was found that there was not significant correlation (R < 0.5) between image quality and DL for any of the age ranges for either global score or for individual criteria more related to noise. The mean value of DL was in the ranges 1.9-2.1 for the four age bands. From this study, a DL value of 1.6 is proposed for pediatric CR chest imaging. This could yield a reduction of approximately a factor of 2.5 in mean patient entrance surface doses.
