Dinâmica da Plasticidade Sináptica em neurônios do hipocampo durante ciclos de sono: um estudo computacional

Several research lines show that sleep favors memory consolidation and learning. It has been proposed that the cognitive role of sleep is derived from a global scaling of synaptic weights, able to homeostatically restore the ability to learn new things, erasing memories overnight. This phenomenon is typical of slow-wave sleep (SWS) and characterized by non-Hebbian mechanisms, i.e., mechanisms independent of synchronous neuronal activity. Another view holds that sleep also triggers the specific enhancement of synaptic connections, carrying out the embossing of certain mnemonic traces within a lattice of synaptic weights rescaled each night. Such an embossing is understood as the combination of Hebbian and non-Hebbian mechanisms, capable of increasing and decreasing respectively the synaptic weights in complementary circuits, leading to selective memory improvement and a restructuring of synaptic configuration (SC) that can be crucial for the generation of new behaviors ( insights ). The empirical findings indicate that initiation of Hebbian plasticity during sleep occurs in the transition of the SWS to the stage of rapid eye movement (REM), possibly due to the significant differences between the firing rates regimes of the stages and the up-regulation of factors involved in longterm synaptic plasticity. In this study the theories of homeostasis and embossing were compared using an artificial neural network (ANN) fed with action potentials recorded in the hippocampus of rats during the sleep-wake cycle. In the simulation in which the ANN did not apply the long-term plasticity mechanisms during sleep (SWS-transition REM), the synaptic weights distribution was re-scaled inexorably, for its mean value proportional to the input firing rate, erasing the synaptic weights pattern that had been established initially. In contrast, when the long-term plasticity is modeled during the transition SWSREM, an increase of synaptic weights were observed in the range of initial/low values, redistributing effectively the weights in a way to reinforce a subset of synapses over time. The results suggest that a positive regulation coming from the long-term plasticity can completely change the role of sleep: its absence leads to forgetting; its presence leads to a positive mnemonic change

Potencial de ocorrência de avarias ambientais em bacias hidrográficas com ocupação rural mediante análise morfométrica

The understanding of the geo-morphological characteristics allows the identification of flood areas and instability slopes among others important features for land use planning. The study of the hydrological net and the analysis of morphometric parameters help in the geomorphologic characterization, providing specific physics indicators that quantify the risks for environmental damages. The present work used Geographic Information Systems (GIS) and carried out the morphometric analysis of two watersheds in the Alto Rio Sorocaba, municipality of Ibiuna (SP). Using digitalized topographic bases in the scale 1:50,000, the main morphometric parameters were extracted and the Digital Elevation Model (DEM) was obtained. Hence the slope, ground illumination, hill orientation and relief feature maps were elaborated. The characteristics for the two watersheds were quite similar, both have low risks for floods and landslides. Therefore, the concave feature is the predominant hill shape for both watersheds. The morphometric parameters directly related to the river density of the watersheds showed some differences, because the Sorocabuçú watershed presents higher value, resulting in a higher level of relief development. Thus, with this characterization it is possible to provide subsidies for environmental planning actions to the area.

Igreja N. Sra. da Santa Cruz dos Militares

O desenho do frontispício apresenta monumentalidade pela proporção dos cinco tramos no primeiro pavimento e três no segundo encimado por um triângulo frontão com uma cruz sobre o acrotério na parte central. A horizontalidade advém das duas volutas laterais sobre o entalhamento das portas que dão acesso aos corredores. O corpo da igreja tem uma porta central ladeada por nichos e o pórtico com colunas em pedra com capitéis jônicos são de mármore. Unindo a sacada e janelas do coro há quatro nichos para os santos evangelistas. Mestre Valentim que lá trabalhou entre 1805 a 1811, esculpiu dois deles em cedro: São Mateus e São João, recolhidos atualmente no Museu Histórico e Nacional. As quatro esculturas em mármore de Carrara nos atuais nichos são do escultor acadêmico Jean-Louis Despré, vindas da Itália em 1926. Internamente a surpresa está na alvura da ornamentação, com o mínimo de policromia e mesmo douramento, permitindo que a rica talha rococó se revele aos pouco a partir da capela-mor, obra de mestre Valentim. Na entrada, o arco ornamentado que sustenta o coro é surpreendente pelas guirlandas e buquês de flores que se adensam até quase a altura dos olhos emoldurando toda a nave com relevos simbólicos cristãos e maçônicos, típicos do Iluminismo.