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Author Fadi Dornaika; Abdelmalik Moujahid; Bogdan Raducanu edit   pdf
url  doi
openurl 
  Title Facial expression recognition using tracked facial actions: Classifier performance analysis Type Journal Article
  Year 2013 Publication Engineering Applications of Artificial Intelligence Abbreviated Journal EAAI  
  Volume 26 Issue 1 Pages 467-477  
  Keywords Visual face tracking; 3D deformable models; Facial actions; Dynamic facial expression recognition; Human–computer interaction  
  Abstract In this paper, we address the analysis and recognition of facial expressions in continuous videos. More precisely, we study classifiers performance that exploit head pose independent temporal facial action parameters. These are provided by an appearance-based 3D face tracker that simultaneously provides the 3D head pose and facial actions. The use of such tracker makes the recognition pose- and texture-independent. Two different schemes are studied. The first scheme adopts a dynamic time warping technique for recognizing expressions where training data are given by temporal signatures associated with different universal facial expressions. The second scheme models temporal signatures associated with facial actions with fixed length feature vectors (observations), and uses some machine learning algorithms in order to recognize the displayed expression. Experiments quantified the performance of different schemes. These were carried out on CMU video sequences and home-made video sequences. The results show that the use of dimension reduction techniques on the extracted time series can improve the classification performance. Moreover, these experiments show that the best recognition rate can be above 90%.  
  Address  
  Corporate Author Thesis  
  Publisher Elsevier Place of Publication Editor  
  Language Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN ISBN Medium  
  Area Expedition Conference  
  Notes (down) OR; 600.046;MV Approved no  
  Call Number Admin @ si @ DMR2013 Serial 2185  
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Author Bogdan Raducanu; Fadi Dornaika edit   pdf
doi  openurl
  Title Texture-independent recognition of facial expressions in image snapshots and videos Type Journal Article
  Year 2013 Publication Machine Vision and Applications Abbreviated Journal MVA  
  Volume 24 Issue 4 Pages 811-820  
  Keywords  
  Abstract This paper addresses the static and dynamic recognition of basic facial expressions. It has two main contributions. First, we introduce a view- and texture-independent scheme that exploits facial action parameters estimated by an appearance-based 3D face tracker. We represent the learned facial actions associated with different facial expressions by time series. Second, we compare this dynamic scheme with a static one based on analyzing individual snapshots and show that the former performs better than the latter. We provide evaluations of performance using three subspace learning techniques: linear discriminant analysis, non-parametric discriminant analysis and support vector machines.  
  Address  
  Corporate Author Thesis  
  Publisher Springer-Verlag Place of Publication Editor  
  Language Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 0932-8092 ISBN Medium  
  Area Expedition Conference  
  Notes (down) OR; 600.046; 605.203;MV Approved no  
  Call Number Admin @ si @ RaD2013 Serial 2230  
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Author Xavier Otazu; Olivier Penacchio; Xim Cerda-Company edit  url
openurl 
  Title Brightness and colour induction through contextual influences in V1 Type Conference Article
  Year 2015 Publication Scottish Vision Group 2015 SGV2015 Abbreviated Journal  
  Volume 12 Issue 9 Pages 1208-2012  
  Keywords  
  Abstract  
  Address Carnoustie; Scotland; March 2015  
  Corporate Author Thesis  
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  ISSN ISBN Medium  
  Area Expedition Conference SGV  
  Notes (down) NEUROBIT;CIC Approved no  
  Call Number Admin @ si @ OPC2015a Serial 2632  
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Author Olivier Penacchio; Xavier Otazu; A. wilkins; J. Harris edit  url
openurl 
  Title Uncomfortable images prevent lateral interactions in the cortex from providing a sparse code Type Conference Article
  Year 2015 Publication European Conference on Visual Perception ECVP2015 Abbreviated Journal  
  Volume Issue Pages  
  Keywords  
  Abstract  
  Address Liverpool; uk; August 2015  
  Corporate Author Thesis  
  Publisher Place of Publication Editor  
  Language Summary Language Original Title  
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  Series Volume Series Issue Edition  
  ISSN ISBN Medium  
  Area Expedition Conference ECVP  
  Notes (down) NEUROBIT;CIC Approved no  
  Call Number Admin @ si @ POW2015 Serial 2633  
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Author Xavier Otazu; Olivier Penacchio; Xim Cerda-Company edit  openurl
  Title An excitatory-inhibitory firing rate model accounts for brightness induction, colour induction and visual discomfort Type Conference Article
  Year 2015 Publication Barcelona Computational, Cognitive and Systems Neuroscience Abbreviated Journal  
  Volume Issue Pages  
  Keywords  
  Abstract  
  Address Barcelona; June 2015  
  Corporate Author Thesis  
  Publisher Place of Publication Editor  
  Language Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN ISBN Medium  
  Area Expedition Conference BARCCSYN  
  Notes (down) NEUROBIT;CIC Approved no  
  Call Number Admin @ si @ OPC2015b Serial 2634  
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Author Domicele Jonauskaite; Nele Dael; C. Alejandro Parraga; Laetitia Chevre; Alejandro Garcia Sanchez; Christine Mohr edit   pdf
url  doi
openurl 
  Title Stripping #The Dress: The importance of contextual information on inter-individual differences in colour perception Type Journal Article
  Year 2018 Publication Psychological Research Abbreviated Journal PSYCHO R  
  Volume Issue Pages 1-15  
  Keywords  
  Abstract In 2015, a picture of a Dress (henceforth the Dress) triggered popular and scientific interest; some reported seeing the Dress in white and gold (W&G) and others in blue and black (B&B). We aimed to describe the phenomenon and investigate the role of contextualization. Few days after the Dress had appeared on the Internet, we projected it to 240 students on two large screens in the classroom. Participants reported seeing the Dress in B&B (48%), W&G (38%), or blue and brown (B&Br; 7%). Amongst numerous socio-demographic variables, we only observed that W&G viewers were most likely to have always seen the Dress as W&G. In the laboratory, we tested how much contextual information is necessary for the phenomenon to occur. Fifty-seven participants selected colours most precisely matching predominant colours of parts or the full Dress. We presented, in this order, small squares (a), vertical strips (b), and the full Dress (c). We found that (1) B&B, B&Br, and W&G viewers had selected colours differing in lightness and chroma levels for contextualized images only (b, c conditions) and hue for fully contextualized condition only (c) and (2) B&B viewers selected colours most closely matching displayed colours of the Dress. Thus, the Dress phenomenon emerges due to inter-individual differences in subjectively perceived lightness, chroma, and hue, at least when all aspects of the picture need to be integrated. Our results support the previous conclusions that contextual information is key to colour perception; it should be important to understand how this actually happens.  
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  Notes (down) NEUROBIT; no proj Approved no  
  Call Number Admin @ si @ JDP2018 Serial 3149  
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Author Xim Cerda-Company; Olivier Penacchio; Xavier Otazu edit   pdf
url  openurl
  Title Chromatic Induction in Migraine Type Journal
  Year 2021 Publication VISION Abbreviated Journal  
  Volume 5 Issue 3 Pages 37  
  Keywords migraine; vision; colour; colour perception; chromatic induction; psychophysics  
  Abstract 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.  
  Address  
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  Series Editor Series Title Abbreviated Series Title  
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  ISSN ISBN Medium  
  Area Expedition Conference  
  Notes (down) NEUROBIT; no proj Approved no  
  Call Number Admin @ si @ CPO2021 Serial 3589  
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Author Arash Akbarinia; Karl R. Gegenfurtner edit  doi
openurl 
  Title Metameric Mismatching in Natural and Artificial Reflectances Type Journal Article
  Year 2017 Publication Journal of Vision Abbreviated Journal JV  
  Volume 17 Issue 10 Pages 390-390  
  Keywords Metamer; colour perception; spectral discrimination; photoreceptors  
  Abstract The human visual system and most digital cameras sample the continuous spectral power distribution through three classes of receptors. This implies that two distinct spectral reflectances can result in identical tristimulus values under one illuminant and differ under another – the problem of metamer mismatching. It is still debated how frequent this issue arises in the real world, using naturally occurring reflectance functions and common illuminants.

We gathered more than ten thousand spectral reflectance samples from various sources, covering a wide range of environments (e.g., flowers, plants, Munsell chips) and evaluated their responses under a number of natural and artificial source of lights. For each pair of reflectance functions, we estimated the perceived difference using the CIE-defined distance ΔE2000 metric in Lab color space.

The degree of metamer mismatching depended on the lower threshold value l when two samples would be considered to lead to equal sensor excitations (ΔE < l), and on the higher threshold value h when they would be considered different. For example, for l=h=1, we found that 43.129 comparisons out of a total of 6×107 pairs would be considered metameric (1 in 104). For l=1 and h=5, this number reduced to 705 metameric pairs (2 in 106). Extreme metamers, for instance l=1 and h=10, were rare (22 pairs or 6 in 108), as were instances where the two members of a metameric pair would be assigned to different color categories. Not unexpectedly, we observed variations among different reflectance databases and illuminant spectra with more frequency under artificial illuminants than natural ones.

Overall, our numbers are not very different from those obtained earlier (Foster et al, JOSA A, 2006). However, our results also show that the degree of metamerism is typically not very strong and that category switches hardly ever occur.
 
  Address Florida, USA; May 2017  
  Corporate Author Thesis  
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  Series Editor Series Title Abbreviated Series Title  
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  Notes (down) NEUROBIT; no menciona Approved no  
  Call Number Admin @ si @ AkG2017 Serial 2899  
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Author Hans Stadthagen-Gonzalez; Luis Lopez; M. Carmen Parafita; C. Alejandro Parraga edit  doi
openurl 
  Title Using two-alternative forced choice tasks and Thurstone law of comparative judgments for code-switching research Type Book Chapter
  Year 2018 Publication Linguistic Approaches to Bilingualism Abbreviated Journal  
  Volume Issue Pages 67-97  
  Keywords two-alternative forced choice and Thurstone's law; acceptability judgment; code-switching  
  Abstract This article argues that 2-alternative forced choice tasks and Thurstone’s law of comparative judgments (Thurstone, 1927) are well suited to investigate code-switching competence by means of acceptability judgments. We compare this method with commonly used Likert scale judgments and find that the 2-alternative forced choice task provides granular details that remain invisible in a Likert scale experiment. In order to compare and contrast both methods, we examined the syntactic phenomenon usually referred to as the Adjacency Condition (AC) (apud Stowell, 1981), which imposes a condition of adjacency between verb and object. Our interest in the AC comes from the fact that it is a subtle feature of English grammar which is absent in Spanish, and this provides an excellent springboard to create minimal code-switched pairs that allow us to formulate a clear research question that can be tested using both methods.  
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  Area Expedition Conference  
  Notes (down) NEUROBIT; no menciona Approved no  
  Call Number Admin @ si @ SLP2018 Serial 2994  
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Author C. Alejandro Parraga edit  doi
openurl 
  Title Colours and Colour Vision: An Introductory Survey Type Journal Article
  Year 2017 Publication Perception Abbreviated Journal PER  
  Volume 46 Issue 5 Pages 640-641  
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  Notes (down) NEUROBIT; no menciona Approved no  
  Call Number Par2017 Serial 3101  
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Author Hans Stadthagen-Gonzalez; M. Carmen Parafita; C. Alejandro Parraga; Markus F. Damian edit   pdf
url  openurl
  Title Testing alternative theoretical accounts of code-switching: Insights from comparative judgments of adjective noun order Type Journal Article
  Year 2019 Publication International journal of bilingualism: interdisciplinary studies of multilingual behaviour Abbreviated Journal IJB  
  Volume 23 Issue 1 Pages 200-220  
  Keywords  
  Abstract Objectives:
Spanish and English contrast in adjective–noun word order: for example, brown dress (English) vs. vestido marrón (‘dress brown’, Spanish). According to the Matrix Language model (MLF) word order in code-switched sentences must be compatible with the word order of the matrix language, but working within the minimalist program (MP), Cantone and MacSwan arrived at the descriptive generalization that the position of the noun phrase relative to the adjective is determined by the adjective’s language. Our aim is to evaluate the predictions derived from these two models regarding adjective–noun order in Spanish–English code-switched sentences.
Methodology:
We contrasted the predictions from both models regarding the acceptability of code-switched sentences with different adjective–noun orders that were compatible with the MP, the MLF, both, or none. Acceptability was assessed in Experiment 1 with a 5-point Likert and in Experiment 2 with a 2-Alternative Forced Choice (2AFC) task.
 
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  Area Expedition Conference  
  Notes (down) NEUROBIT; no menciona Approved no  
  Call Number Admin @ si @ SPP2019 Serial 3242  
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Author David Berga; Xavier Otazu; Xose R. Fernandez-Vidal; Victor Leboran; Xose M. Pardo edit  openurl
  Title Generating Synthetic Images for Visual Attention Modeling Type Journal Article
  Year 2019 Publication Perception Abbreviated Journal PER  
  Volume 48 Issue Pages 99  
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  Notes (down) NEUROBIT; no menciona Approved no  
  Call Number Admin @ si @ BOF2019 Serial 3309  
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Author David Berga; Xavier Otazu edit  openurl
  Title Computations of inhibition of return mechanisms by modulating V1 dynamics Type Conference Article
  Year 2019 Publication 28th Annual Computational Neuroscience Meeting Abbreviated Journal  
  Volume Issue Pages  
  Keywords  
  Abstract In this study we present a unifed model of the visual cortex for predicting visual attention using real image scenes. Feedforward mechanisms from RGC and LGN have been functionally modeled using wavelet filters at distinct orientations and scales for each chromatic pathway (Magno-, Parvo-, Konio-cellular) and polarity (ON-/OFF-center), by processing image components in the CIE Lab space. In V1, we process cortical interactions with an excitatory-inhibitory network of fring rate neurons, initially proposed by (Li, 1999), later extended by (Penacchio et al. 2013). Firing rates from model’s output have been used as predictors of neuronal activity to be projected in a map in superior colliculus (with WTA-like computations), determining locations of visual fxations. These locations will be considered as already visited areas for future saccades, therefore we integrated a spatiotemporal function of inhibition of return mechanisms (where LIP/FEF is responsible) to feed to the model with spatial memory for next saccades. Foveation mechanisms have been simulated with a cortical magnifcation function, which distort spatial viewing properties for each fxation. Results show lower prediction errors than with respect no IoR cases (Fig. 1), and it is functionally consistent with human psychophysical measurements. Our model follows a biologically-constrained architecture, previously shown to reproduce visual saliency (Berga & Otazu, 2018), visual discomfort (Penacchio et al. 2016), brightness (Penacchio et al. 2013) and chromatic induction (Cerda & Otazu, 2016).  
  Address Barcelona; July 2019  
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  ISSN ISBN Medium  
  Area Expedition Conference CNS  
  Notes (down) NEUROBIT; no menciona Approved no  
  Call Number Admin @ si @ BeO2019a Serial 3373  
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Author David Berga; Xavier Otazu edit  openurl
  Title Computational modelingof visual attention: What do we know from physiology and psychophysics? Type Conference Article
  Year 2019 Publication 8th Iberian Conference on Perception Abbreviated Journal  
  Volume Issue Pages  
  Keywords  
  Abstract Latest computer vision architectures use a chain of feedforward computations, mainly optimizing artificial neural networks for very specific tasks. Although their impressive performance (i.e. in saliency) using real image datasets, these models do not follow several biological principles of the human visual system (e.g. feedback and horizontal connections in cortex) and are unable to predict several visual tasks simultaneously. In this study we present biologically plausible computations from the early stages of the human visual system (i.e. retina and lateral geniculate nucleus) and lateral connections in V1. Despite the simplicity of these processes and without any type of training or optimization, simulations of firing-rate dynamics of V1 are able to predict bottom-up visual attention at distinct contexts (shown previously as well to predict visual discomfort, brightness and chromatic induction). We also show functional top-down selection mechanisms as feedback inhibition projections (i.e. prefrontal cortex for search/task-based attention and parietal area for inhibition of return). Distinct saliency model predictions are tested with eye tracking datasets in free-viewing and visual search tasks, using real images and synthetically-generated patterns. Results on predicting saliency and scanpaths show that artificial models do not outperform biologically-inspired ones (specifically for datasets that lack of common endogenous biases found in eye tracking experimentation), as well as, do not correctly predict contrast sensitivities in pop-out stimulus patterns. This work remarks the importance of considering biological principles of the visual system for building models that reproduce this (and any other) visual effects.  
  Address San Lorenzo El Escorial; July 2019  
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  ISSN ISBN Medium  
  Area Expedition Conference CIP  
  Notes (down) NEUROBIT; no menciona Approved no  
  Call Number Admin @ si @ BeO2019b Serial 3374  
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Author Xavier Soria; Angel Sappa; Arash Akbarinia edit   pdf
openurl 
  Title Multispectral Single-Sensor RGB-NIR Imaging: New Challenges and Opportunities Type Conference Article
  Year 2017 Publication 7th International Conference on Image Processing Theory, Tools & Applications Abbreviated Journal  
  Volume Issue Pages  
  Keywords Color restoration; Neural networks; Singlesensor cameras; Multispectral images; RGB-NIR dataset  
  Abstract Multispectral images captured with a single sensor camera have become an attractive alternative for numerous computer vision applications. However, in order to fully exploit their potentials, the color restoration problem (RGB representation) should be addressed. This problem is more evident in outdoor scenarios containing vegetation, living beings, or specular materials. The problem of color distortion emerges from the sensitivity of sensors due to the overlap of visible and near infrared spectral bands. This paper empirically evaluates the variability of the near infrared (NIR) information with respect to the changes of light throughout the day. A tiny neural network is proposed to restore the RGB color representation from the given RGBN (Red, Green, Blue, NIR) images. In order to evaluate the proposed algorithm, different experiments on a RGBN outdoor dataset are conducted, which include various challenging cases. The obtained result shows the challenge and the importance of addressing color restoration in single sensor multispectral images.  
  Address Montreal; Canada; November 2017  
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  ISSN ISBN Medium  
  Area Expedition Conference IPTA  
  Notes (down) NEUROBIT; MSIAU; 600.122 Approved no  
  Call Number Admin @ si @ SSA2017 Serial 3074  
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