Premi Internacional al millor treball de fusió d'imatges de satèl·lit

Un grup de recerca multidisciplinari format per Xavier Otazu (Centre de Visió per Computador, Universitat Autònoma de Barcelona), Octavi Fors i Jorge Núñez (ambdós del Departament d'Astronomia i Meteorologia, Universitat de Barcelona) i María González-Audícana (Departament de Projectes i Enginyeria Rural, Universitat Pública de Navarra) ha estat guardonat amb un presitigiós premi internacional per desenvolupar una tècnica de fusió d'imatges obtingudes per satèl·lits.Un grupo de investigación multidisciplinario formado por Xavier Otazu(Centro de Visión per Computador, Universitat Autònoma de Barcelona),Octavi Fors y Jorge Núñez (ambos del Departamento de Astronomía yMeteorología, Universitat de Barcelona) y María González-Audícana(Departamento de Proyectos e Ingeniería Rural, Universidad Pública deNavarra) ha sido galardonado con un presitigioso premio internacionalpor desarrollar una técnica de fusión de imágenes obtenidas porsatélites

Tecnologia de la UAB millora imatges de satèl·lits

Els satèl·lits observen silenciosos els fenòmens naturals que succeeixen al nostre planeta. No obstant, les imatges reproduïdes per aquests ulls mecànics no són tan fiables com voldríem. Per alleugerir aquesta miopia dels satèl·lits, un equip de la UAB proposa un mètode de fusió d'imatges anomenat WiSpeR.Los satélites observan silenciosos los fenómenos naturales que ocurren en nuestro planeta. Sin embargo, las imágenes reproducidas por estos ojos mecánicos no son tan fiables como quisiéramos. Para atenuar esta miopía satelital un equipo de la UAB propone un método de fusión de imágenes llamado WiSpeR

Modeling Bottom-Up and Top-Down Attention with a Neurodynamic Model of V1

Previous studies in that line suggested that lateral interactions of V1 cells are responsible, among other visual effects, of bottom-up visual attention (alternatively named visual salience or saliency). Our objective is to mimic these connections in the visual system with a neurodynamic network of firing-rate neurons. Early subcortical processes (i.e. retinal and thalamic) are functionally simulated. An implementation of the cortical magnification function is included to define the retinotopical projections towards V1, processing neuronal activity for each distinct view during scene observation. Novel computational definitions of top-down inhibition (in terms of inhibition of return and selection mechanisms), are also proposed to predict attention in Free-Viewing and Visual Search conditions. Results show that our model outpeforms other biologically-inpired models of saliency prediction as well as to predict visual saccade sequences during free viewing. We also show how temporal and spatial characteristics of inhibition of return can improve prediction of saccades, as well as how distinct search strategies (in terms of feature-selective or category-specific inhibition) predict attention at distinct image contexts.Comment: 32 pages, 19 figure

Computations of top-down attention by modulating V1 dynamics

The human visual system processes information defining what is visually conspicuous (saliency) to our perception, guiding eye movements towards certain objects depending on scene context and its feature characteristics. However, attention has been known to be biased by top-down influences (relevance), which define voluntary eye movements driven by goal-directed behavior and memory. We propose a unified model of the visual cortex able to predict, among other effects, top-down visual attention and saccadic eye movements. First, we simulate activations of early mechanisms of the visual system (RGC/LGN), by processing distinct image chromatic opponencies with Gabor-like filters. Second, we use a cortical magnification function to reproduce foveation towards V1 retinotopy. Third, we feed these signals to an excitatory-inhibitory neurodynamic model of lateral interactions in V1 as a saliency mechanism. Fourth, projections towards the SC (modeled as WTA-like computations) determine the targets of fixations and saccade sequences. Fifth and last, we integrate a top-down inhibition process by simulating retrieval of visual representations as goal-directed selection processes (DLPFC/FEF), later projected towards V1/SC. These top-down representations will modulate the prediction of visual relevance during visual search tasks, where its weights (orientation, scale and opponency) are mapped as cortical signals from early visual areas for each exemplar/category. Our results show that our model predictions of eye movements improve by including the aforementioned top-down computations. In addition, our model has previously seen to simultaneously reproduce visual discomfort, brightness and chromatic induction effects

The contribution of luminance and chromatic channels to color assimilation

Luminance; Chromatic channelsLuminancia; Canales cromáticosLluminància; Canals cromàticsColor induction is the phenomenon where the physical and the perceived colors of an object differ owing to the color distribution and the spatial configuration of the surrounding objects. Previous works studying this phenomenon on the lsY MacLeod–Boynton color space, show that color assimilation is present only when the magnocellular pathway (i.e., the Y axis) is activated (i.e., when there are luminance differences). Concretely, the authors showed that the effect is mainly induced by the koniocellular pathway (s axis), but not by the parvocellular pathway (l axis), suggesting that when magnocellular pathway is activated it inhibits the koniocellular pathway. In the present work, we study whether parvo-, konio-, and magnocellular pathways may influence on each other through the color induction effect. Our results show that color assimilation does not depend on a chromatic–chromatic interaction, and that chromatic assimilation is driven by the interaction between luminance and chromatic channels (mainly the magno- and the koniocellular pathways). Our results also show that chromatic induction is greatly decreased when all three visual pathways are simultaneously activated, and that chromatic pathways could influence each other through the magnocellular (luminance) pathway. In addition, we observe that chromatic channels can influence the luminance channel, hence inducing a small brightness induction. All these results show that color induction is a highly complex process where interactions between the several visual pathways are yet unknown and should be studied in greater detail.Supported through the research projects: Grant PID2020-115734RB-C21 funded by MCIN/AEI/10.13039/501100011033 and Grant DPI2017-89867-C2-1-R funded by MCIN/AEI/10.13039/501100011033/ and FEDER Una manera de hacer Europa, by the Secretaria d'Universitats i Recerca del Departament d'Empresa i Coneixement de la Generalitat de Catalunya through 2017-SGR-649, and CERCA Programme/Generalitat de Catalunya

Chromatic induction in migraine

Funding: This work is partially supported by the Spanish Ministerio de Economía, Industria y Competitividad, Gobierno de España through research project DPI2017-89867-C2-1-R, by the Agen- cia de Gestió d’Ajuts Universitaris i de Recerca (AGAUR) through 2017-SGR-649, and CERCA Programme/Generalitat de Catalunya.The human visual system is not a colorimeter. The perceived colour of a region does not only depend on its colour spectrum, but also on the colour spectra and geometric arrangement of neighbouring regions, a phenomenon called chromatic induction. Chromatic induction is thought to be driven by lateral interactions: the activity of a central neuron is modified by stimuli outside its classical receptive field through excitatory–inhibitory mechanisms. As there is growing evidence of an excitation/inhibition imbalance in migraine, we compared chromatic induction in migraine and control groups. As hypothesised, we found a difference in the strength of induction between the two groups, with stronger induction effects in migraine. On the other hand, given the increased prevalence of visual phenomena in migraine with aura, we also hypothesised that the difference between migraine and control would be more important in migraine with aura than in migraine without aura. Our experiments did not support this hypothesis. Taken together, our results suggest a link between excitation/inhibition imbalance and increased induction effects.Publisher PDFPeer reviewe