771 research outputs found
Sang et dérivés sanguins:vers le risque zéro
No full textTreize années de présence dans le service de standardisation biologique et de virologie de l'ISP ont permis à Esther Mathys de posséder une connaissance approfondie de la sécurité des produits dérivés du sang. Des produits dont la disponibilité est totalement dépendante de la bonne volonté des donneurs (un acte purement gratuit dans notre pays) et dont la qualité doit être irréprochable.</p
Hierarchical Gaussian Filtering of Sufficient Statistic Time Series for Active Inference
No full textActive inference relies on state-space models to describe the environments that agents sample with their actions. These actions lead to state changes intended to minimize future surprise. We show that surprise minimization relying on Bayesian inference can be achieved by filtering of the sufficient statistic time series of exponential family input distributions, and we propose the hierarchical Gaussian filter (HGF) as an appropriate, efficient, and scalable tool for active inference agents to achieve this
Funktionelle und effektive Konnektivität
No full textZusammenfassung
Neurophysiologische und bildgebende Verfahren zur Messung von Hirnaktivität, wie fMRI oder EEG, werden in den Neurowissenschaften eingesetzt, um Prozesse funktioneller Spezialisierung und funktioneller Integration im menschlichen Gehirn zu untersuchen. Funktionelle Integration kann auf zwei verschiedene Arten beschrieben werden: funktionelle Konnektivität und effektive Konnektivität. Während die funktionelle Konnektivität lediglich statistische Abhängigkeiten zwischen Zeitreihen beschreibt, erfordert das Konzept der effektiven Konnektivität ein mechanistisches Modell der kausalen Effekte, die den beobachteten Daten zu Grunde liegen. Dieser Artikel fasst die konzeptionellen und methodischen Grundlagen moderner Techniken für die Analyse funktioneller und effektiver Konnektivität auf der Basis von fMRI und elektrophysiologischen Daten zusammen. Ein besonderer Schwerpunkt liegt dabei auf dem Dynamic Causal Modelling (DCM), einem neuen Verfahren zur Analyse nichtlinearer neuronaler Systeme. Diese Methode besitzt ein vielversprechendes Potenzial für klinische Anwendungen, z. B. zur Entschlüsselung pathophysiologischer Mechanismen bei Hirnerkrankungen und zur Etablierung neurophysiologisch fundierter diagnostischer Klassifikationen.
Abstract
Neurophysiological and imaging procedures to measure brain activity, such as fMRI or EEG, are employed in neuroscience to investigate processes of functional specialisation and functional integration in the human brain. Functioal integration can be described in two distinct ways: functional connectivity and effective connectivity. Whereas functional connectivity merely describes the statistical dependence between two time series, the concept of effective connectivity requires a mechanistic model of the causative effects upon which the data to be observed are based. This article summarises the conceptual and methodological principles of modern techniques for the analysis of functional and effective connectivity on the basis of fMRI and electrophysiological data. Particular emphasis is placed on dynamic causal modelling (DCM), a new procedure for the analysis of non-linear neuronal systems. This method has a highly promising potential for clinical applications, e. g., for decoding pathological mechanisms in brain diseases and for the establishment of neurologically valid diagnostic classifications
Economic importance of the Belgian ports: Flemish maritime ports, Liège port complex and the port of Brussels – Report 2009
No full textThis paper is an annual publication issued by the Microeconomic Analysis service of the National Bank of Belgium. The Flemish maritime ports (Antwerp, Ghent, Oostende, Zeebrugge), the Autonomous Port of Liège and the port of Brussels play a major role in their respective regional economies and in the Belgian economy, not only in terms of industrial activity but also as intermodal centres facilitating the commodity flow. This update paper provides an extensive overview of the economic importance and development of the Flemish maritime ports, the Liège port complex and the port of Brussels in the period 2004 - 2009, with an emphasis on 2009. Focusing on the three major variables of value added, employment and investment, the report also provides some information about social balance and the financial situation in these ports as a whole. These observations are linked to a more general context, along with a few cargo statistics. Annual accounts data from the Central Balance Sheet Office were used for the calculation of direct effects, the study of financial ratios and the analysis of the social balance sheet. The indirect effects of the activities concerned were estimated in terms of value added and employment, on the basis of data from the National Accounts Institute. In terms of maritime cargo traffic, the downturn recorded during the last quarter of 2008 continued throughout 2009. Direct value added declined in all the ports in Flanders. Maritime branches as a whole contracted. Only the value added of the maritime branches in the port of Ostend remained stable. The non-maritime branches as a whole saw a contraction in all the Flemish ports. It was the port of Antwerp that suffered the most from the drop in the value added. Its maritime branches shrank by nearly one third. While the non-maritime branches were slightly down. The port of Ghent recorded a bigger decrease in the non-maritime branches. Conversely, the value added in the port of Zeebrugge fell more sharply in the maritime branches. Direct employment in the ports of Flanders as a whole declined during the year 2009. Except in Ghent, direct employment in the maritime branches fell in all the Flemish ports. Similarly, only one of them, the port of Ostend, recorded a rise in employment in the non-maritime branches. Thanks to this, it has been the only Flemish port to register direct employment growth. Investment decreased in all the ports in Flanders. The decline in investment was between one-sixth and one-fifth in the ports of Ghent, Antwerp and Zeebrugge. While Ostend recorded a cut of more than one third in its investment levels in 2009. The volume of cargo handled in the port of Liège decreased strongly in 2009. Direct value added and employment registered a significant decline. Maritime and non-maritime branches were down for both value added and employment. Thanks to the "other services" branch of activity, investment rose steadily. The volume of cargo handled at the port of Brussels declined in 2009. Value added in this port remained steady. But employment contracted slightly. After the growth seen in 2008, investment was down by more than a quarter. This report provides a comprehensive account of these issues, giving details for each economic sector, although the comments are confined to the main changes that occurred in 2009.branch survey, maritime cluster, subcontracting, indirect effects, transport intermodality, public investments
Morphological evolution of birds recently introduced to islands: patterns of diversification
No full textEvolution was originally considered to be observable only over geological time scales. It has recently become apparent that evolutionary changes can be detected over contemporary time periods. Exotic species often experience intense selection, making them good model systems for investigating evolutionary changes over contemporary time. We often know details of the introductions, such as exact time, location of the source population, founding propagule size, and establishment history. These details allow us to formulate hypotheses concerning the evolutionary changes expected in these species' exotic ranges.
I examined contemporary morphological evolution of passerine birds introduced to islands. Passerine birds have been introduced to many islands world-wide, making them conducive for examining patterns of insular evolution. In chapters one and two, I evaluated whether these species conform to the Island Rule, an ecogeographic rule based on the study of native insular species. It states that, on islands, small species should increase in body size while large species should decrease body size. All of the species I studied are small, therefore they were expected to increase in body size. I found equivocal results concerning the Island Rule. In chapter one, I found that the great kiskadee (Pitangus sulphuratus) follows the Island Rule, as it is larger in its exotic island range than in the native source range. However, in chapter two, I found no clear Island Rule pattern examining 39 insular populations. However, I did find a clear pattern of decrease in wing length and increase in tail length. Although these populations may not be following an overall Island Rule pattern, they are still adapting to their exotic environments. In chapter three, I evaluated among-island diversification of six passerine species introduced to the Hawaiian archipelago. Five of these six species show some morphological differentiation between islands, and at least some of this differentiation cannot be accounted for by genetic drift.
The results of this dissertation provide further support for the idea that evolutionary divergence can happen over contemporary time scales. The passerine bird populations examined in these chapters have adapted to local conditions, giving us insights into the genesis of evolutionary diversity.Ph.D.Includes bibliographical referencesby Blake Mathy
Bayesian modelling captures inter-individual differences in social belief computations in the putamen and insula
No full textComputational models of social learning and decision-making provide mechanistic tools toinvestigate the neural mechanisms that are involved in understanding other people. Whilemost studies employ explicit instructions to learn from social cues, everyday life is characterizedby the spontaneous use of such signals (e.g., the gaze of others) to infer on internalstates such as intentions. To investigate the neural mechanisms of the impact of gaze cues on learning and decision-making, we acquired behavioural and fMRI data from50 participants performing a probabilistic task, in which cards with varying winningprobabilities had to be chosen. In addition, the task included a computer-generated facethat gazed towards one of these cards providing implicit advice. Participants’ individualbelief trajectories were inferred using a hierarchical Gaussian filter (HGF) and used aspredictors in a linear model of neuronal activation. During learning, social prediction errorswere correlated with activity in inferior frontal gyrus and insula. During decision-making,the belief about the accuracy of the social cue was correlated with activity in inferiortemporal gyrus, putamen and pallidum while the putamen and insula showed activity as afunction of individual differences in weighting the social cue during decision-making. Ourfindings demonstrate that model-based fMRI can give insight into the behavioural andneural aspects of spontaneous social cue integration in learning and decision-making.They provide evidence for a mechanistic involvement of specific components of thebasal ganglia in subserving these processes
Hierarchical bayesian models of social inference for probing persecutory delusional ideation
No full textWhile persecutory delusions (PDs) have been linked to fallacies of reasoning and social inference, computational characterizations of delusional tendencies are rare. Here, we examined 151 individuals from the general population on opposite ends of the PD spectrum (Paranoia Checklist [PCL]). Participants made trial-wise predictions in a probabilistic lottery, guided by advice from a more informed human and a nonsocial cue. Additionally, 2 frames differentially emphasized causes of invalid advice: (a) the adviser’s possible intentions (dispositional frame) or (b) the rules of the game (situational frame). We applied computational modeling to examine possible reasons for group differences in behavior. Comparing different models, we found that a hierarchical Bayesian model (hierarchical Gaussian filter) explained participants’ responses better than other learning models. Model parameters determining participants’ belief updates about the adviser’s fidelity and the contribution of prior beliefs about fidelity to trial-wise decisions, respectively, showed significant Group × Frame interactions: High PCL scorers held more rigid beliefs about the adviser’s fidelity across both experimental frames and relied less on advice in situational frames than low scorers. These results suggest that PD tendencies are associated with rigid beliefs and prevent adaptive use of social information in “safe” contexts. This supports previous proposals of a link between PD and aberrant social inference. (PsycInfo Database Record (c) 2021 APA, all rights reserved
A new twist on spinning (A)dS correlators
No full textAbstract Massless spinning correlators in cosmology are extremely complicated. In contrast, the scattering amplitudes of massless particles with spin are very simple. We propose that the reason for the unreasonable complexity of these correlators lies in the use of inconvenient kinematic variables. For example, in de Sitter space, consistency with unitarity and the background isometries imply that the correlators must be conformally covariant and also conserved. However, the commonly used kinematic variables for correlators do not make all of these properties manifest. In this paper, we introduce twistor space as a powerful way to satisfy all kinematic constraints. We show that conformal correlators of conserved currents can be written as twistor integrals, where the conservation condition translates into holomorphicity of the integrand. The functional form of the twistor-space correlators is very simple and easily bootstrapped. For the case of two- and three-point functions, we verify explicitly that this reproduces known results in embedding space. We also perform a half-Fourier transform of the twistor-space correlators to obtain their counterparts in momentum space. We conclude that twistors provide a promising new avenue to study conformal correlation functions that exposes their hidden simplicity
Modeling subjective relevance in schizophrenia and its relation to aberrant salience
No full textIn schizophrenia, increased aberrant salience to irrelevant events and reduced learning of relevant information may relate to an underlying deficit in relevance detection. So far, subjective estimates of relevance have not been probed in schizophrenia patients. The mechanisms underlying belief formation about relevance and their translation into decisions are unclear. Using novel computational methods, we investigated relevance detection during implicit learning in 42 schizophrenia patients and 42 healthy individuals. Participants underwent functional magnetic resonance imaging while detecting the outcomes in a learning task. These were preceded by cues differing in color and shape, which were either relevant or irrelevant for outcome prediction. We provided a novel definition of relevance based on Bayesian precision and modeled reaction times as a function of relevance weighted unsigned prediction errors (UPE). For aberrant salience, we assessed responses to subjectively irrelevant cue manifestations. Participants learned the contingencies and slowed down their responses following unexpected events. Model selection revealed that individuals inferred the relevance of cue features and used it for behavioral adaption to the relevant cue feature. Relevance weighted UPEs correlated with dorsal anterior cingulate cortex activation and hippocampus deactivation. In patients, the aberrant salience bias to subjectively task-irrelevant information was increased and correlated with decreased striatal UPE activation and increased negative symptoms. This study shows that relevance estimates based on Bayesian precision can be inferred from observed behavior. This underscores the importance of relevance detection as an underlying mechanism for behavioral adaptation in complex environments and enhances the understanding of aberrant salience in schizophrenia
Der Menschgewordene als Ebenbild Gottes. Zum frühchristlichen Verständnis der Imago Dei
No full textThe author interprets the image of God in relation to the disparity between various Old and New Testament statements and examines it in the light of contemporary questions posed by the theory of evolution. He shows that the disparate biblical statements do not permit us to develop an anthropology based on the concept of the image of God. Nevertheless the author shows that this concept – even against the New Testament background of the christological exclusivity of the Imago Dei – is relevant for the understanding of humans as mediators
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