Cadre générique pour le recalage dense combinant un coût dense et et un coût basé sur des correspondances de primitives

National audienceL'estimation dense de correspondances entre deux images est un sujet essentiel de la vision par ordinateur et s'exprime sous plusieurs formes : déformations rigides ou flexibles avec de faibles ou grandes amplitudes de déplacements. De nombreuses solutions spécifiques existent mais aucune méthodologie unifiée n'a été formulée. Cet article propose une nouvelle approche générale qui combine de manière robuste un coût dense par pixel et un coût basé sur des correspondances de primitives. Ce dernier utilise une distance robuste permettant d'exploiter des correspondances de points ou de segments. Les correspondances permettent d'empêcher l'optimisation dense de tomber dans un minimum local. En utilisant un coût dense robuste, associé à une régularisation au second ordre et une détection explicite des auto-occultations, nous obtenons des résultats égalant ou surpassant l'état de l'art pour les applications de flot optique 2D, stéréo à fortes disparité et recalage de surfaces déformables. De plus, le faible couplage des modules permet une grande flexibilité en fonction de l'application

Caméras virtuelles pour la calibration d'un système de réalité augmentée composé d'un écran transparent et deux caméras à champs disjoints

National audienceUne nouvelle méthode de calibration extrinsèque pour systèmes de réalité augmentée sur affichages transparents est proposée. Elle est principalement destinée à un système composé d'un écran semi-transparent, d'une caméra de suivi de l'utilisateur et d'une autre caméra, à champ dis- joints, pour localiser le système au sein de l'environne- ment mais facilement généralisable. L'algorithme se base sur des indications fournies par l'utilisateur sur la projection apparente sur l'écran de points de référence d'un objet connu. Une estimation convexe est calculée grâce à la calibration de caméras virtuelles et sert d'initialisation à un ajustement de faisceaux global. Des expériences sur données synthétiques et réelles montrent le bien-fondé de cette approche. Ceci est une traduction de la publication originale

Subcortical amyloid relates to cortical morphology in cognitively normal individuals

Purpose Amyloid (Aβ) brain deposition can occur in cognitively normal individuals and is associated with cortical volume abnormalities. Aβ-related volume changes are inconsistent across studies. Since volume is composed of surface area and thickness, the relative contribution of Aβ deposition on each of these metrics remains to be understood in cognitively normal individuals. Methods A group of 104 cognitively normal individuals underwent neuropsychological assessment, PiB-PET scan, and MRI acquisition. Surface-based cortical analyses were performed to investigate the effects of cortical and subcortical Aβ burden on cortical volume, thickness, and surface area. Mediation analyses were used to study the effect of thickness and surface area on Aβ-associated volume changes. We also investigated the relationships between structural metrics in clusters with abnormal morphology and regions underlying resting-state functional networks and cognitive performance. Results Cortical Aβ was not associated with cortical morphology. Subcortical Aβ burden was associated with changes in cortical volume, thickness, and surface area. Aβ-associated volume changes were driven by cortical surface area with or without thickness but never by thickness alone. Aβ-associated changes overlapped greatly with regions from the default mode network and were associated with lower performance in visuospatial abilities, episodic memory, and working memory. Conclusions In cognitively normal individuals, subcortical Aβ is associated with cortical volume, and this effect was driven by surface area with or without thickness. Aβ-associated cortical changes were found in the default mode network and affected cognitive performance. Our findings demonstrate the importance of studying subcortical Aβ and cortical surface area in normal agein

Education as a moderator of the relationship between episodic memory and amyloid load in normal aging

The current study explored whether education, a proxy of cognitive reserve, modifies the association between episodic memory (EM) performance and βeta-amyloid load (Aβ), a biomarker of Alzheimer’s disease, in a cohort of cognitively normal older adults. One hundred and four participants (mean age 73.3 years) evenly spread out in three bands of education were recruited. Participants underwent neuropsychological assessment, structural MRI as well as PET imaging to quantify Aβ load. Moderation analyses and the Johnson–Neyman technique were carried out to examine the interaction of education with Aβ load to predict EM performance. Linear regressions were then performed within each group of education to better illustrate the interaction effect (all analyses were controlled for age and sex). The interaction between education and Aβ load was significant (p < .05) for years of education, reaching a cutoff point of 13.5 years, above which the relationship between Aβ load and EM was no longer significant. Similarly, significant associations were found between Aβ and EM among participants with secondary (p < .01) and preuniversity education (p < .01), but not with a university degree (p = .253). EM performance is associated with Aβ load in cognitively normal older individuals, and this relationship is moderated by educational attainment

Amyloid burden and white matter hyperintensities mediate age-related cognitive differences

This study examined the additive versus synergistic contribution of beta-amyloid (Aβ) and white matter hyperintensities (WMHs) across 7 cognitive domains in 104 cognitively normal older adults. It also measured the extent to which age-related differences in cognition are driven by measurable brain pathology. All participants underwent neuropsychological assessment along with magnetic resonance imaging and Pittsburg compound B-positron emission tomography imaging for Aβ quantification. WMH severity was quantified using the age-related white matter changes scale. Stepwise regressions, moderation, and mediation modeling were performed. Our findings show that Aβ deposition single-handedly predicts poorer episodic memory performance and that Aβ and WMHs contribute additively to poorer performance in working memory and language while carrying synergistic associations with executive functions and attention. Through mediation modeling, we demonstrated that the influence of age over episodic memory, working memory, executive functions, and language is fully mediated by brain pathology. This study permits to conclude that, in healthy older adults, (1) Aβ burden and WMHs have synergistic associations with some cognitive domains and (2) age-related differences in most cognitive domains are driven by brain pathology associated with dementia

Cytokines as mediators of chemotherapy-associated cognitive changes: Current evidence, limitations and directions for future research

10.1371/journal.pone.0081234PLoS ONE812-POLN

Estimation of acute and chronic Q fever incidence in children during a three-year outbreak in the Netherlands and a comparison with international literature

Background:  In the Dutch 2007-2009 Q fever outbreak Coxiella burnetii was transmitted aerogenically from dairy goat farms to those living in the surrounding areas. Relatively few children were reported. The true number of pediatric infections is unknown. In this study, we estimate the expected number of acute and chronic childhood infections. Methods:  As Coxiella was transmitted aerogenic to those living near infected dairy goat farms, we could use adult seroprevalence data to estimate infection risk for inhabitants, children and adults alike. Using Statistics Netherlands data we estimated the number of children at (high) risk for developing chronic Q fever. Literature was reviewed for childhood (0-15 years) Q fever reports and disease rates. We compared this with Dutch reported and our estimated data for 2007-2009. Results:  In The Netherlands epidemic, 44 children were reported (1.2 % of total notifications). The childhood incidence was 0.15 compared to 2.6 per 10,000 inhabitants for adults. No complications were reported. Based on the expected similarity in childhood and adult exposure we assume that 9.8 % of children in the high-risk area had Q fever infection, resulting in 1562 acute infections during the Q fever epidemic interval. Based on the prevalence of congenital heart disease, at least 13 children are at high risk for developing chronic Q fever. In medical literature, 42 case reports described 140 childhood Q fever cases with a serious outcome (four deaths). In chronic Q fever, cardiac infections were predominant. Four outbreaks were reported involving children, describing 11 childhood cases. 36 National and/or regional studies reported seroprevalences varying between 0 and 70 %. Conclusion:  In the 3-year Dutch epidemic, few childhood cases were reported, with pulmonary symptoms leading, and none with a serious presentation. With an estimated 13 high-risk children for chronic infection in the high exposure area, and probably forty in the whole country, we may expect several chronic Q fever complications in the coming years in paediatric practice