Hippocampal subregional volume changes in elders classified using positron emission tomography-based Alzheimer's biomarkers of ß-amyloid deposition and neurodegeneration.

Changes in hippocampal subfield volumes (HSV) along the Alzheimer's disease (AD) continuum have been scarcely investigated to date in elderly subjects classified based on the presence of ß-amyloid aggregation and signs of neurodegeneration. We classified patients (either sex) with mild dementia compatible with AD (n = 35) or amnestic mild cognitive impairment (n = 39), and cognitively unimpaired subjects (either sex; n = 26) using [11 C]PIB-PET to assess ß-amyloid aggregation (A+) and [18 F]FDG-PET to account for neurodegeneration ((N)+). Magnetic resonance imaging-based automated methods were used for HSV and white matter hyperintensity (WMH) measurements. Significant HSV reductions were found in A+(N)+ subjects in the presubiculum/subiculum complex and molecular layer, related to worse memory performance. In both the A+(N)+ and A+(N)- categories, subicular volumes were inversely correlated with the degree of Aß deposition. The A-(N)+ subgroup showed reduced HSV relative to the A-(N)- subgroup also in the subiculum/presubiculum. Combining all (N)- subjects, HSV were lower in subjects presenting significant cognitive decline irrespective of A+/A- classification (controlling for WMH load); these between-group differences were detected again in the presubiculum, but also involved the CA4 and granular layer. These findings demonstrate that differential HSV reductions are detectable both in (N)+ and (N)- categories along the AD continuum, and are directly related to the severity of cognitive deficits. HSV reductions are larger both in A+(N)+ and A+(N)- subjects in direct proportion to the degree of Aß deposition. The meaningful HSV reductions detected in the A-(N)+ subgroup highlights the strength of biomarker-based classifications outside of the classical AD continuum.

Modelo matemático para o estudo da propagação de informações por campanhas educativas e rumores / Mathematical model to study the spread of information from educative campaigns and rumors

Formulamos um modelo matemático determinístico baseado no princípio de ação de massas, em analogia aos trabalhos que estudam a dinâmica de doenças infecciosas em Epidemiologia. Analisamos a dinâmica do espalhamento de rumores levando em conta a simetria no número de contatos diretos entre suscetíveis e infectados pelo rumor e estudamos as implicações de uma campanha publicitária educativa na dinâmica do modelo. Posteriormente, propomos uma simplificação do modelo e desconsideramos o contato entre os indivíduos suscetíveis e infectados supostamente mais resistentes às novidades. Discutimos suas implicações no espalhamento do rumor e a conexão com os parâmetros que descrevem o comportamento social.

We have developed a deterministic mathematical model based on the mass-action principle, in analogy to the works that study the dynamics of infectious diseases in Epidemiology. We analyzed the dynamic of rumors spreading, taking into account the symmetry of contacts among susceptible and infectious individuals and studied the implications of an educative broadcasting advertising in the model. Afterwards, we proposed a simplification ot the model excluding the contact among susceptible and infected individuals supposedly more resistant to novelities. Their implications to the spread of rumor and its connection with parameters describing social behavior are discussed.