ClustGeo: an R package for hierarchical clustering with spatial constraints

In this paper, we propose a Ward-like hierarchical clustering algorithm including spatial/geographical constraints. Two dissimilarity matrices $D_0$ and $D_1$ are inputted, along with a mixing parameter $\alpha \in [0,1]$. The dissimilarities can be non-Euclidean and the weights of the observations can be non-uniform. The first matrix gives the dissimilarities in the "feature space" and the second matrix gives the dissimilarities in the "constraint space". The criterion minimized at each stage is a convex combination of the homogeneity criterion calculated with $D_0$ and the homogeneity criterion calculated with $D_1$. The idea is then to determine a value of $\alpha$ which increases the spatial contiguity without deteriorating too much the quality of the solution based on the variables of interest i.e. those of the feature space. This procedure is illustrated on a real dataset using the R package ClustGeo

Multivariate Analysis of Mixed Data: The R Package PCAmixdata

Mixed data arise when observations are described by a mixture of numerical and categorical variables. The R package PCAmixdata extends standard multivariate analysis methods to incorporate this type of data. The key techniques/methods included in the package are principal component analysis for mixed data (PCAmix), varimax-like orthogonal rotation for PCAmix, and multiple factor analysis for mixed multi-table data. This paper gives a synthetic presentation of the three algorithms with details to help the user understand graphical and numerical outputs of the corresponding R functions. The three main methods are illustrated on a real dataset composed of four data tables characterizing living conditions in different municipalities in the Gironde region of southwest France

Diversité ethno-culturelle et différentiel de pauvreté multidimensionnelle au Cameroun

Peu de recherches ont concilié le caractère multidimensionnel de la pauvreté avec le conditionnement culturel des populations pour orienter les politiques. La démarche de la MES (Modélisation en Équations Structurelles) à travers sa technique de comparaison de modèles nichés a permis de formuler et de tester les hypothèses de recherche. Les résultats montrent que les différences de niveau observées sur les dimensions de pauvreté résultent significativement (ce qui ne veut pas dire exclusivement) des systèmes de valeurs culturelles partagés au sein des groupes. Les facteurs par lesquels transite l'élément culturel vers le domaine de la pauvreté sont de deux ordres. Il s'agit du différentiel des perceptions et des déterminants de la pauvreté. Compte tenu de ces résultats et pour une stratégie crédible de réduction de la pauvreté, nous proposons une approche participative et décentralisée prudente pour définir les actions de lutte répondant aux besoins exprimés par les populations concernées.Pauvreté multidimensionnelle, culture, différentiel de pauvreté, MES, modèles nichés, variables latentes, indicateurs de pauvreté

Effector-Specific Characterization of Brain Dynamics in Manual vs. Oculomotor Go/NoGo Tasks.

Motor inhibitory control (IC), the ability to suppress unwanted actions, has been previously shown to rely on domain-general IC processes that are involved in a wide range of IC tasks. Nevertheless, the existence of effector-specific regions and activation patterns that would differentiate manual vs. oculomotor response inhibition remains unknown. In this study, we investigated the brain dynamics supporting these two response effectors with the same IC task paradigm. We examined the behavioral performance and electrophysiological activity in a group of healthy young people (n = 25) with a Go/NoGo task using the index finger for the manual modality and the eyes for the oculomotor modality. By computing topographic analysis of variance, we found significant differences between topographies of scalp recorded potentials of the two response effectors between 250 and 325 ms post-stimulus onset. The source estimations localized this effect within the left precuneus, a part of the superior parietal lobule, showing stronger activity in the oculomotor modality than in the manual modality. Behaviorally, we found a significant positive correlation in response time between the two modalities. Our collective results revealed that while domain-general IC processes would be engaged across different response effectors in the same IC task, effector-specific activation patterns exist. In this case, the stronger activation of the left precuneus likely accounts for the increased demand for visual attentional processes in the oculomotor Go/NoGo task

Sélection de variables pour la construction d'indicateurs de qualité de vie pour des données structurées en groupes

International audienceThe analysis and measurement of quality of life may be made via two complementary approaches. The first one, based on survey of individuals, concerns the analysis of levels of life satisfaction. We focus here on the second one, based on national data, which analyses living conditions of people. The aim is to create composite indices of living conditions.According to authors, the components of quality of life are related to different themes (groups of variables): ``Family conditions", ``Employment", ``Housing",... For this purpose, dimension reduction methods are particularly suitable.Multiple Factor Analysis (MFA) is a method designed to handle data structured into groups of quantitative variables. In our study, each theme is composed of a group of quantitative and/or categorical variables. Since our data are naturally structured in groups of variables, we develop an extension of MFA for mixed data type, called MFAmix. Thus the principal components from MFAmix are our composite indices for measuring quality of life. However, the creation of these indices raises two questions. How many principal components keep to create indices? How select a limited number of variables to get similar indices for easier interpretation? We propose answers to these questions in this communication

Rotation orthogonale en ACP de données mixtes. Le package PCAmixdata et une application en sociologie culturelle.

Rotation orthogonale en ACP de données mixtes. Le package PCAmixdata et une application en sociologie culturelle

The modulation of event-related alpha rhythm during the time course of anticipation

Anticipation is the ability to accurately predict future actions or events ahead of the act itself. When attempting to anticipate, researchers have identified that at least two broad sources of information are used: contextual information relating to the situation in question; and biological motion from postural cues. However, the neural correlates associated with the processing of these different sources of information across groups varying in expertise has yet to be examined empirically. We compared anticipation performance and electrophysiological activity in groups of expert (n = 12) and novice (n = 15) performers using a video-based task. Participants made anticipation judgements after being presented information under three conditions: contextual information only; kinematic information only; and both sources of information combined. The experts responded more accurately across all three conditions. Stronger alpha event-related desynchronization over occipital and frontocentral sites occurred in experts compared to the novices when anticipating. The experts relied on stronger preparatory attentional mechanisms when they processed contextual information. When kinematic information was available, the domain specific motor representations built up over many years of practice likely underpinned expertise. Our findings have implications for those interested in identifying and subsequently, enhancing the neural mechanisms involved in anticipation

Executive control training does not generalize, even when associated with plastic changes in domain-general prefrontal areas

How executive function training paradigms can be effectively designed to promote a transfer of the effects of interventions to untrained tasks remains unclear. Here, we tested the hypothesis that training with a complex task involving motor, perceptual and task-set control components would result in more transfer than training with a simple motor control task, because the Complex training would lead to more involvement— and in turn modification—of domain-general executive control networks.We compared performance and electrophysiological activity before and after 10 days of executive control training with the complex (n = 18) versus the simple task (n = 17). We further assessed the effect of the two training regimens on untrained executive tasks involving or not one of the trained control components. A passive control group (n = 19) was used to assess retest effects.Both training groups improved at the trained task but exhibited different plastic changes within left-lateralized and medial frontal areas at 200–250 ms post-stimulus onset. However, contrary to our hypotheses, they showed equivalent improvement to the passive group to the transfer tasks.Our collective results reveal that the effect of training with a task involving multiple executive control components is highly specific to the trained task, even when the training modifies the functional networks underlying the trained executive components. Our findings corroborate current evidence that general cognitive enhancement cannot be achieved with training, even when the interventions modify domain-general brain areas

Growth of Yersinia pseudotuberculosis in human plasma: impacts on virulence and metabolic gene expression

<p>Abstract</p> <p>Background</p> <p>In man, infection by the Gram-negative enteropathogen <it>Yersinia pseudotuberculosis </it>is usually limited to the terminal ileum. However, in immunocompromised patients, the microorganism may disseminate from the digestive tract and thus cause a systemic infection with septicemia.</p> <p>Results</p> <p>To gain insight into the metabolic pathways and virulence factors expressed by the bacterium at the blood stage of pseudotuberculosis, we compared the overall gene transcription patterns (the transcriptome) of bacterial cells cultured in either human plasma or Luria-Bertani medium. The most marked plasma-triggered metabolic consequence in <it>Y. pseudotuberculosis </it>was the switch to high glucose consumption, which is reminiscent of the acetogenic pathway (known as "glucose overflow") in <it>Escherichia coli</it>. However, upregulation of the glyoxylate shunt enzymes suggests that (in contrast to <it>E. coli</it>) acetate may be further metabolized in <it>Y. pseudotuberculosis</it>. Our data also indicate that the bloodstream environment can regulate major virulence genes (positively or negatively); the <it>yadA </it>adhesin gene and most of the transcriptional units of the pYV-encoded type III secretion apparatus were found to be upregulated, whereas transcription of the pH6 antigen locus was strongly repressed.</p> <p>Conclusion</p> <p>Our results suggest that plasma growth of <it>Y. pseudotuberculosis </it>is responsible for major transcriptional regulatory events and prompts key metabolic reorientations within the bacterium, which may in turn have an impact on virulence.</p