VIOLA - A multi-purpose and web-based visualization tool for neuronal-network simulation output

Neuronal network models and corresponding computer simulations are invaluable tools to aid the interpretation of the relationship between neuron properties, connectivity and measured activity in cortical tissue. Spatiotemporal patterns of activity propagating across the cortical surface as observed experimentally can for example be described by neuronal network models with layered geometry and distance-dependent connectivity. The interpretation of the resulting stream of multi-modal and multi-dimensional simulation data calls for integrating interactive visualization steps into existing simulation-analysis workflows. Here, we present a set of interactive visualization concepts called views for the visual analysis of activity data in topological network models, and a corresponding reference implementation VIOLA (VIsualization Of Layer Activity). The software is a lightweight, open-source, web-based and platform-independent application combining and adapting modern interactive visualization paradigms, such as coordinated multiple views, for massively parallel neurophysiological data. For a use-case demonstration we consider spiking activity data of a two-population, layered point-neuron network model subject to a spatially confined excitation originating from an external population. With the multiple coordinated views, an explorative and qualitative assessment of the spatiotemporal features of neuronal activity can be performed upfront of a detailed quantitative data analysis of specific aspects of the data. Furthermore, ongoing efforts including the European Human Brain Project aim at providing online user portals for integrated model development, simulation, analysis and provenance tracking, wherein interactive visual analysis tools are one component. Browser-compatible, web-technology based solutions are therefore required. Within this scope, with VIOLA we provide a first prototype.Comment: 38 pages, 10 figures, 3 table

Reconciliation of weak pairwise spike-train correlations and highly coherent local field potentials across space

Chronic and acute implants of multi-electrode arrays that cover several mm$^2$ of neural tissue provide simultaneous access to population signals like extracellular potentials and the spiking activity of 100 or more individual neurons. While the recorded data may uncover principles of brain function, its interpretation calls for multiscale computational models with corresponding spatial dimensions and signal predictions. Such models can facilitate the search of mechanisms underlying observed spatiotemporal activity patterns in cortex. Multi-layer spiking neuron network models of local cortical circuits covering ~1 mm$^2$ have been developed, integrating experimentally obtained neuron-type specific connectivity data and reproducing features of in-vivo spiking statistics. With forward models, local field potentials (LFPs) can be computed from the simulated spiking activity. To account for the spatial scale of common neural recordings, we extend a local network and LFP model to 4x4 mm$^2$. The upscaling preserves the neuron densities, and introduces distance-dependent connection probabilities and delays. As detailed experimental connectivity data is partially lacking, we address this uncertainty in model parameters by testing parameter combinations within biologically plausible bounds. Based on model predictions of spiking activity and LFPs, we find that the upscaling procedure preserves the overall spiking statistics of the original model and reproduces asynchronous irregular spiking across populations and weak pairwise spike-train correlations observed in sensory cortex. In contrast with the weak spike-train correlations, the correlation of LFP signals is strong and distance-dependent, compatible with experimental observations. Enhanced spatial coherence in the low-gamma band may explain the recent experimental report of an apparent band-pass filter effect in the spatial reach of the LFP.Comment: 44 pages, 9 figures, 5 table

Estimation of neural network model parameters from local field potentials (LFPs)

publishedVersio

Conditions for wave trains in spiking neural networks

Spatiotemporal patterns such as traveling waves are frequently observed in recordings of neural activity. The mechanisms underlying the generation of such patterns are largely unknown. Previous studies have investigated the existence and uniqueness of different types of waves or bumps of activity using neural-field models, phenomenological coarse-grained descriptions of neural-network dynamics. But it remains unclear how these insights can be transferred to more biologically realistic networks of spiking neurons, where individual neurons fire irregularly. Here, we employ mean-field theory to reduce a microscopic model of leaky integrate-and-fire (LIF) neurons with distance-dependent connectivity to an effective neural-field model. In contrast to existing phenomenological descriptions, the dynamics in this neural-field model depends on the mean and the variance in the synaptic input, both determining the amplitude and the temporal structure of the resulting effective coupling kernel. For the neural-field model we employ liner stability analysis to derive conditions for the existence of spatial and temporal oscillations and wave trains, that is, temporally and spatially periodic traveling waves. We first prove that wave trains cannot occur in a single homogeneous population of neurons, irrespective of the form of distance dependence of the connection probability. Compatible with the architecture of cortical neural networks, wave trains emerge in two-population networks of excitatory and inhibitory neurons as a combination of delay-induced temporal oscillations and spatial oscillations due to distance-dependent connectivity profiles. Finally, we demonstrate quantitative agreement between predictions of the analytically tractable neural-field model and numerical simulations of both networks of nonlinear rate-based units and networks of LIF neurons.Comment: 36 pages, 8 figures, 4 table

Personality traits and hardiness as risk- and protective factors for mental distress during the COVID-19 pandemic: a Norwegian two-wave study

Background Several risk factors for anxious-depressive symptomatology during the COVID-19 pandemic have been established. However, few studies have examined the relationship between personality traits, hardiness, and such symptomatology during the pandemic. These constructs might serve as risk- and/or protective factors for such mental distress through the pandemic. Methods A sample of 5783 Norwegians responded to a survey at two time points within the first year of the pandemic. The first data collection was in April 2020 (T1) and the second in December 2020 (T2). Measures included the Ten-Item Personality-Inventory, the Revised Norwegian Dispositional Resilience Scale, and the Patient Health Questionnaire Anxiety and Depression Scale. Analyses were performed using Pearson’s correlations, multiple linear regression, and a moderation analysis. Results Anxious-depressive symptomatology in early phases (T1) of the pandemic was the strongest predictor for the presence of such symptomatology 9 months after the outbreak (T2). Personality and hardiness correlated significantly with mental distress at T1 and T2. Personality traits explained 5% variance in symptoms when controlling for age, gender, solitary living, negative economic impact, and mental distress at baseline. Higher neuroticism predicted higher mental distress, whereas higher conscientiousness and extraversion predicted less mental distress. Hardiness did not explain variance in outcome beyond personality traits. Hardiness did not significantly moderate the relationship between neuroticism and mental distress. Conclusion Individuals with high levels of neuroticism had greater difficulties adapting to the circumstances of the COVID-19 pandemic and were more prone to mental distress. Contrastingly, higher conscientiousness and extraversion may have served as protective factors for mental distress during the pandemic. The current findings might aid identification of vulnerable individuals and groups. Consequently, preventive interventions could be offered to those who need it the most.publishedVersio

VIOLA—A Multi-Purpose and Web-Based Visualization Tool for Neuronal-Network Simulation Output

Neuronal network models and corresponding computer simulations are invaluable tools to aid the interpretation of the relationship between neuron properties, connectivity, and measured activity in cortical tissue. Spatiotemporal patterns of activity propagating across the cortical surface as observed experimentally can for example be described by neuronal network models with layered geometry and distance-dependent connectivity. In order to cover the surface area captured by today's experimental techniques and to achieve sufficient self-consistency, such models contain millions of nerve cells. The interpretation of the resulting stream of multi-modal and multi-dimensional simulation data calls for integrating interactive visualization steps into existing simulation-analysis workflows. Here, we present a set of interactive visualization concepts called views for the visual analysis of activity data in topological network models, and a corresponding reference implementation VIOLA (VIsualization Of Layer Activity). The software is a lightweight, open-source, web-based, and platform-independent application combining and adapting modern interactive visualization paradigms, such as coordinated multiple views, for massively parallel neurophysiological data. For a use-case demonstration we consider spiking activity data of a two-population, layered point-neuron network model incorporating distance-dependent connectivity subject to a spatially confined excitation originating from an external population. With the multiple coordinated views, an explorative and qualitative assessment of the spatiotemporal features of neuronal activity can be performed upfront of a detailed quantitative data analysis of specific aspects of the data. Interactive multi-view analysis therefore assists existing data analysis workflows. Furthermore, ongoing efforts including the European Human Brain Project aim at providing online user portals for integrated model development, simulation, analysis, and provenance tracking, wherein interactive visual analysis tools are one component. Browser-compatible, web-technology based solutions are therefore required. Within this scope, with VIOLA we provide a first prototype

Evaluation of genetic effects on wild salmon populations from stock enhancement

Many salmonid populations are of conservation concern, and the release of hatchery-produced juveniles is a frequently used measure to alleviate declines and increase harvest opportunities. While such releases may be of conservation value for some populations, stocking may also decrease the effective population size and subsequently impose additional strain on already threatened populations. In this study, we assessed how the cohort-wise effective number of breeders in five populations of Atlantic salmon (Salmo salar) were affected by supplementation. Altogether, 19 cohorts were studied (2–7 cohorts per population) by estimating the proportion hatchery-released individuals and the effective number of wild and captive breeders in each cohort of the respective populations. We show that the effect of releasing captive-bred individuals varies both between populations and between years within the same population. A Ryman–Laikre effect—where the effective number of breeders has decreased as a consequence of supplementation—was observed for 11 cohorts. We discuss how supplementation can be adapted to optimize the effective population size, demonstrate that evaluation of supplementation can be reliably achieved, and show that supplementation programmes that lead to high proportions of hatchery-origin fish on spawning grounds are more likely to induce a Ryman–Laikre effect. Atlantic salmon, effective population size, population genetics, Ryman–Laikre effect, Salmo salar, stockingpublishedVersio

A propriedade sem registro : o contrato e aquisição da propriedade imóvel na perspectiva civil-contitucional

Orientador : Prof. Dr. Eroulths Cortiano JuniorTese (doutorado) - Universidade Federal do Paraná, Setor de Ciências Jurídicas, Programa de Pós-Graduação em Direito. Defesa: Curitiba, 12/08/2014Inclui referênciasResumo: Esta tese objetiva uma releitura da obrigatoriedade do registro nas aquisições da propriedade imóvel, a partir do reconhecimento do contrato como dotado de função social, que realiza, igualmente, a função social como liberdade de acesso aos bens. A propriedade imobiliária no Direito Civil brasileiro está qualificada como direito real, conforme o art. 1225, I, do Código Civil, e sua transferência negocial se orienta pelo sistema da separação parcial dos planos dos direitos obrigacionais e reais, o qual prevê a necessidade do contrato de transmissão (compra e venda, doação ou permuta) com posterior registro no Cartório Imobiliário, nos termos do art. 1245 e seguintes. A Constituição Federal de 1988 garante o direito de propriedade, que deve atender à sua função social, considerando-a como direito fundamental (art. 5.o, XXII e XXIII) e como princípio geral da ordem econômica (art. 170, II e III). A necessária interação entre o Direito Civil e a Constituição, sob a supremacia hierárquica desta, conduz a entender que o direito de propriedade atual, para além da literalidade do Código Civil, deve nortear-se pela sintonia entre ambos os diplomas legais, mas a partir da observação dos princípios e dos valores constitucionais. O Direito Civil-Constitucional surge, então, como uma opção de desenvolvimento do pensamento jurídico, que visa oferecer espaço de reflexão que supere a dogmática unicamente codificada, pois, com fundamento nos princípios e na axiologia constitucional, auxilia na ressignificação de institutos clássicos, como a propriedade e o contrato. O acesso à propriedade, então, pode ser considerado para além da letra da lei, o que permite relevar o registro, com a funcionalização do contrato que, a partir de sua teleologia, da solidariedade, da alteridade e da boa-fé, pode ser o elemento constitutivo da propriedade, com base no caso concreto. A aplicação direta e imediata da Constituição nas relações interprivadas favorece a ressignificação do contrato, que alçará significado de título suficiente para garantir o direito à propriedade (acesso). A complexidade e a pluralidade das relações sociais conduzem a uma transição do modelo abstrato e individualista da propriedade para o da propriedade concreta, que se constrói na funcionalização como liberdade(s) com vistas à realização das necessidade da pessoa concretamente considerada.Abstract: The aim of this thesis is to re-read the mandatory registration on acquisition of immovable property, from the social function of contract's recognition, which also performs its social function as freedom of access to assets. The immovable property in the Brazilian Civil Law is qualified as a real right, according to art. 1225, I, Civil Code, and its negotiating transferring is guided by the partial separation between obligations and real rights, which predicts the registration of transmission's contract (sale, donation or exchange) with the state registration authority, according to art. 1245 and on Civil Code. The 1988 Federal Constitution guarantees the right to property, which must meet its social function, considering it as a fundamental right (art. 5, XXII and XXIII) and as a general principle of economic order (art. 170, II and III). The necessary interaction between the civil law and the Constitution, under the hierarchical supremacy of this leads to understand that the current property law, beyond its literal meaning of the Civil Code, shall be guided by the line between the two enactments, but from the observation of constitutional principles and values.The Civil-constitutional Law arises, then, as an option for legal thinking development, which aims to provide a reflection space that overcomes the consolidated dogmatic, therefore, on the basis of principles and the constitutional axiology, assists in reframing classical institutes, as property and contract. The access to the property can then be considered beyond the letter of the law, which allows to release the register, with the functionalization's contract which, from its teleology, solidarity, alterity and good faith, may be the constituent element of the property, based on the case. The direct and immediate constitutional applying in privates relations cooperate to the contract redefinition, which obtain the sufficient title to guarantee the right to property (access). The complexity and plurality of social relations lead to a transition from abstract and individualistic model of property to concrete one which is constructed on functionalization as freedom (s) to intending to accomplish persons needs concretely considered