Impact of the pulvinar on the ventral pathway of the cat visual cortex

Signals from the retina are relayed to the lateral geniculate nucleus from which they are sent to the primary visual cortex. At the cortical level, the information is transferred across several visual areas in which the complexity of the processing increases progressively. Anatomical and functional evidence demonstrate the existence of two main pathways in visual cortex processing distinct features of the visual information: the dorsal and ventral streams. Cortical areas composing the dorsal stream are implicated mostly in motion processing while those comprising the ventral stream are involved in the processing of form and colour. This classic view of the cortical functional organization is challenged by the existence of reciprocal connections of visual cortical areas with the thalamic nucleus named pulvinar. These connections allow the creation of a trans-thalamic pathway that parallels the cortico-cortical communications across the visual hierarchy. The main goal of the present thesis is twofold: first, to obtain a better comprehension of the processing of light increments and decrements in an area of the cat ventral stream (area 21a); second, to characterize the nature of the thalamo-cortical inputs from the cat lateral posterior nucleus (LP) to area 21a. In study #1, we investigated the spatiotemporal response profile of neurons from area 21a to light increments (brights) and decrements (darks) using a reverse correlation analysis of a sparse noise stimulus. Our findings showed that 21a neurons exhibited stronger responses to darks with receptive fields exhibiting larger dark subfields. However, no differences were found between the temporal dynamics of brights and darks. In comparison with the primary visual cortex, the dark preference in area 21a was found to be strongly enhanced, supporting the notion that the asymmetries between brights and darks are transmitted and amplified along the ventral stream. In study #2, we investigated the impact of the reversible pharmacological inactivation of the LP nucleus on the contrast response function (CRF) of neurons from area 21a and the primary visual cortex (area 17). The thalamic inactivation yielded distinct effects on both cortical areas. While in area 17 the LP inactivation caused a slight decrease in the response gain, in area 21a a strong increase was observed. Thus, our findings suggest that the LP exerts a modulatory influence on the cortical processing along the ventral stream with stronger impact on higher order extrastriate areas. Taken together, our findings allowed a better comprehension of the functional properties of the cat ventral stream and contributed to the current knowledge on the role of the pulvinar on the cortico-thalamo-cortical processing of visual information.Les signaux provenant de la rétine sont relayés dans le corps géniculé latéral où ils sont envoyés au cortex visuel primaire. L’information passe ensuite à travers plusieurs aires visuelles où la complexité du traitement augmente progressivement. Des données tant anatomiques que fonctionnelles ont démontré l’existence de deux voies principales qui traitent différentes propriétés de l’information visuelle : les voies dorsale et ventrale. Les aires corticales composant la voie dorsale sont impliquées principalement dans le traitement du mouvement tandis que les aires de la voie ventrale sont impliquées dans le traitement de la forme et de la couleur. Cette vision classique de l’organisation fonctionnelle du cortex est toutefois remise en question par l’existence de connections réciproques entre les aires corticales visuelles et le pulvinar, un noyau thalamique. En effet, ces connections permettent la création d’une voie trans-thalamique parallèle aux connections cortico-corticales à travers la hiérarchie visuelle. Le but principal de la présente thèse consiste en deux volets : le premier est d’obtenir une meilleure compréhension du traitement des incréments et décréments de la lumière dans une aire de la voie ventrale du chat (aire 21a); le second est de caractériser la nature des inputs thalamo-corticaux du noyau latéral postérieur (LP) à l’aire 21a chez le chat. Dans l’étude #1, nous avons investigué le profil spatiotemporel des réponses des neurones de l’aire 21a aux incréments (blancs) et décréments (noirs) de lumière en utilisant l’analyse de corrélation inverse d’un stimulus de bruit épars. Les neurones de l’aire 21a ont répondu plus fortement aux stimuli noirs, en montrant des champs récepteurs avec des sous-champs noirs plus larges. Cependant, aucune différence n’a été trouvée en ce qui concerne les dynamiques temporelles des réponses aux blancs et aux noirs. En comparaison avec le cortex visuel primaire, la préférence aux stimuli noirs dans l’aire 21a s’est avérée fortement augmentée. Ces données indiquent que les asymétries entre les réponses aux blancs et aux noirs sont transmises et amplifiées à travers la voie ventrale. Dans l’étude #2, nous avons investigué l’impact de l’inactivation pharmacologique réversible du noyau LP sur la fonction de réponse au contraste (CRF) des neurones de l’aire 21a et du cortex visuel primaire (aire 17). L’inactivation a eu différents effets dans les deux aires corticales. Alors que, dans l’aire 17, l’inactivation du LP a causé une légère réduction du gain de la réponse, une forte augmentation a été observée dans l’aire 21a. Ainsi, nos résultats suggèrent que le LP exerce une influence modulatrice dans le traitement cortical à travers la voie ventrale avec un impact plus important dans des aires extrastriées de plus haut niveau. Nos résultats ont permis d’avoir une meilleure compréhension des propriétés fonctionnelles de la voie ventrale du chat et de contribuer à enrichir les connaissances actuelles sur le rôle du pulvinar dans le traitement cortico-thalamo-cortical de l’information visuelle

Molecular studies in schizophrenia

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INFLUÊNCIA DO USO DE HERBICIDAS SOB AS CARACTERÍSTICAS DE CRESCIMENTO E PRODUÇÃO DO SORGO FORRAGEIRO (Sorghum bicolor (L.) Moench)

The sorghum (Sorghum bicolor (L.) Moench) has shown tremendous growth in recent years, it has great potential both productive and economical for agriculture in various regions of Brazil, especially in regions where rainfall is scarce or irregular, and with this growth comes the culture will demand for pre and post-emergence herbicides in order to reduce the damage caused by plants that compete directly with the culture. This study aimed to evaluate the efficiency of the use of herbicides in weed control and its influence on growth characteristics and production of the sorghum crop. The experiment in rainfed conditions with irrigation salvation was conducted under field conditions, the Department of Agronomy at the Center for Agricultural Sciences (CCA), Campus II of the Federal University of Paraiba (UFPB), located in the City of Areia-PB. The experiment was arranged in a randomized block design, where treatments were constituted of pre and post-emergence herbicide dosages, Herbadox® 400 EC and the DMA® 806 BR applied alone and in combination where: (T1: control, T2: weeded, T3: DMA (100%) T4: DMA (150%), T5: Herbadox (100%) T6: Herbadox (150%) T7: DMA (100%) Herbadox + (150%), T8: DMA (150%) Herbadox + (100%), 9T: DMA (150%) Herbadox + (150%)), which were applied at 15 DAS. The stem diameter variables were analyzed, plant height, and the number of green leaves every 10 days, and total production per treatment. We conclude that the height variable, did not own characteristics and values to differentiate from the others who did not have the use of herbicides in cultivation; Sorghum plants reached a desired development in height and diameter in the periods were evaluated; The higher number of leaves was obtained witness in the weeded treatment and treatment with application of DMA® (100%); The weed control was greater when weeded, and was more efficient in treatments with herbicides DMA® (100% and 150%), and the DMA® mixtures (100%) + HERBADOX® (150%) and DMA® (150%) HERBADOX® + (150%); The phytotoxicity in treatments with the application of DMA® (100% and 150%) and HERBADOX® (150%) was considered low or zero; Applications with DMA® (100%) and HERBADOX® (100%) showed the best results in the production of grains.A cultura do sorgo (Sorghum bicolor (L.) Moench) vem apresentando um enorme crescimento nos últimos anos, pois possui um grande potencial tanto produtivo quanto econômico para a agricultura em diversas regiões do Brasil, principalmente em regiões onde as chuvas são escassas ou irregulares, e juntamente com este crescimento da cultura vem á demanda por herbicidas de pré e pós-emergência a fim de diminuir os danos causados por plantas que competem diretamente com a cultura. Neste trabalho, objetivou-se avaliar a eficiência do uso de herbicidas no controle de plantas daninhas e sua influência nas características de crescimento e produção da cultura do Sorgo Forrageiro. O experimento em regime de sequeiro com irrigação de salvação foi realizado, em condições de campo, no Departamento de Fitotecnia do Centro de Ciências Agrárias (CCA), Campus II da Universidade Federal da Paraíba (UFPB), localizado no Município de Areia-PB. O experimento foi disposto em delineamento de blocos casualizados, onde os tratamentos foram constituídos de dosagens de herbicidas pré e pós-emergentes, Herbadox® 400 EC e o DMA® 806 BR, aplicados isolados e em mistura onde: (T1: Testemunha, T2: Capinado, T3: DMA (100%), T4: DMA (150%), T5: Herbadox (100%), T6: Herbadox (150%), T7: DMA (100%) + Herbadox (150%), T8: DMA (150%) + Herbadox (100%), T9: DMA (150%) + Herbadox (150%)), os quais foram aplicados aos 15 DAS. Foram analisadas as variáveis de diâmetro de caule, altura de plantas, e o número de folhas verdes a cada 10 dias, e produção total por tratamento. Conclui-se que a variável altura, não possuiu características e valores que às diferenciassem das demais que não tiveram a utilização dos herbicidas em seu cultivo; As plantas de sorgo atingiram um desenvolvimento desejado na altura e diâmetro nos períodos que foram avaliados; O Maior número de folhas foi obtido na testemunha, no tratamento capinado e no tratamento com aplicação de DMA® (100%); O controle das plantas daninhas foi maior quando capinado, e se mostrou mais eficiente nos tratamentos com os herbicidas DMA® (100% e 150%), e com as misturas DMA® (100%) + HERBADOX® (150%) e DMA® (150%) + HERBADOX® (150%); A fitotoxidade nos tratamentos com a aplicação de DMA® (100% e 150%) e HERBADOX® (150%), foi considerada baixa ou nula; As aplicações com DMA® (100%) e HERBADOX® (100%), apresentaram os melhores resultados na produção de grãos

The Impact of Sex and Performance Level on Pacing Behavior in a 24-h Ultramarathon

Purpose: We analyzed the impact of sex, performance level and substantial speed reductions (SSR) on pacing in the VI Rio 24-h Marines Ultramarathon. This will provide insights into the importance of minimizing speed variations in relation to optimal pacing in endurance events. Methods: Runners (30 males and 21 females), classified as high- (HP) and low-performance (LP) ran the race while having their time recorded every 400 m. The pacing was analyzed as the first 10% (initial epoch), the following 80% (intermediate epoch) and the last 10% of the race (final epoch). The time percentage spent at speeds 8.0 km·h−1 (running speed) was calculated. Results: Runners showed a reverse J-shaped pacing (P < 0.001) regardless of sex and performance level, although male (P < 0.004) and HP runners (P < 0.001) have preserved a higher mean speed throughout the race. Male and HP runners spent more time at running speed (P < 0.001) and less time at SSR (P < 0.001) than female and LP runners. Total distance was inversely correlated with the number of SSR and speed CV in male (r = −0.47 and r = −0.64, respectively) and female (r = −0.61 and r = −0.47, respectively). Conclusion: Male, HP runners showed less SSR, conserving a higher mean speed with less variation throughout the race. Results suggest that conservative pacing strategies, with lower speeds in the beginning and higher speeds toward the end, may be the most adequate for different endurance running disciplines. Results also show different competition dynamics between men and women, which warrants further exploration in ultramarathons as well as other IAAF events

Modelagem Computacional de uma Blindagem de Nêutrons Utilizando Métodos Determinísticos

In this paper, the so-called source-fixed problem (neutron shielding) in a non-multiplicative medium has been studied. Thus, neutron source shielding was computationally simulated using deterministic numerical methods to estimate the scalar and angular neutron fluxes in a one-dimensional domain. The linearized Boltzmann transport equation for neutral particles was employed in the modeling of the problems studied. In the numerical solution of the Boltzmann equation, certain approximations were considered and consolidated numerical methods were employed to generate accurate solutions. The Diamond Difference (DD), Step and Step Characteristic methods were used in the model problems addressed. The shielding configuration consisted of three materials, with the assembly sequence and material type varying as a function of the material-neutron interaction. Model problems were simulated and examined in order to identify efficient shielding for the emerging neutron flux.Neste artigo, o problema denominado de fonte-fixa (blindagem de nêutrons) em meio não multiplicativo foi estudado. Assim, foi simulada computacionalmente a blindagem da fonte de nêutrons utilizando métodos numéricos determinísticos para estimar os fluxos escalares e angulares de nêutrons em um domínio unidimensional. A equação de transporte linearizada de Boltzmann para partículas neutras foi empregada na modelagem dos problemas estudados. Na resolução numérica da equação de Boltzmann, foram consideradas certas aproximações e empregados métodos numéricos consolidados para gerar soluções precisas. Os métodos numéricos Diamond Difference (DD), Step (ou Degrau) e Step Characteristic (Degrau Característico) foram utilizados nos problemas-modelo abordados. A configuração das blindagens era constituída de três materiais, variando-se a sequência da montagem e o tipo de material em função da interação material-nêutron. Foram simulados e analisados problemas-modelo de modo a identificar blindagens eficientes para o fluxo emergente de nêutrons