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Author |
Oriol Pujol |
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Title |
Model-based three dimensional interpolation of IVUS images |
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Report |
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1999 |
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CVC Technical Report #27 |
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CVC (UAB) |
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HuPBA;MILAB |
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no |
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BCNPCL @ bcnpcl @ Puj1999 |
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49 |
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Author |
Oriol Pujol |
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Title |
A semi-Supervised Statistical Framework and Generative Snakes for IVUS Analysis |
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2004 |
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PhD Thesis, Universitat Autonoma de Barcelona-CVC |
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CVC (UAB), Bellaterra |
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Ph.D. thesis |
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Petia Radeva |
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HuPBA;MILAB |
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no |
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BCNPCL @ bcnpcl @ Puj2004 |
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512 |
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Author |
Oriol Martinez |
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Title |
Semantic Retrieval of Memory Color Content |
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Report |
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2004 |
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CVC Technical Report #80 |
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no |
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Admin @ si @ 38047 |
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508 |
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Author |
Onur Ferhat; Fernando Vilariño; F. Javier Sanchez |
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Title |
A cheap portable eye-tracker solution for common setups. |
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Journal Article |
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Year |
2014 |
Publication |
Journal of Eye Movement Research |
Abbreviated Journal |
JEMR |
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Volume |
7 |
Issue |
3 |
Pages |
1-10 |
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Abstract |
We analyze the feasibility of a cheap eye-tracker where the hardware consists of a single webcam and a Raspberry Pi device. Our aim is to discover the limits of such a system and to see whether it provides an acceptable performance. We base our work on the open source Opengazer (Zielinski, 2013) and we propose several improvements to create a robust, real-time system which can work on a computer with 30Hz sampling rate. After assessing the accuracy of our eye-tracker in elaborated experiments involving 12 subjects under 4 different system setups, we install it on a Raspberry Pi to create a portable stand-alone eye-tracker which achieves 1.42° horizontal accuracy with 3Hz refresh rate for a building cost of 70 Euros. |
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Notes |
;SIAI |
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no |
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Call Number |
Admin @ si @ FVS2014 |
Serial |
2435 |
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Permanent link to this record |
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Author |
Onur Ferhat; Fernando Vilariño |
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Title |
A Cheap Portable Eye-Tracker Solution for Common Setups |
Type |
Conference Article |
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Year |
2013 |
Publication |
17th European Conference on Eye Movements |
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Keywords |
Low cost; eye-tracker; software; webcam; Raspberry Pi |
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Abstract |
We analyze the feasibility of a cheap eye-tracker where the hardware consists of a single webcam and a Raspberry Pi device. Our aim is to discover the limits of such a system and to see whether it provides an acceptable performance. We base our work on the open source Opengazer (Zielinski, 2013) and we propose several improvements to create a robust, real-time system. After assessing the accuracy of our eye-tracker in elaborated experiments involving 18 subjects under 4 different system setups, we developed a simple game to see how it performs in practice and we also installed it on a Raspberry Pi to create a portable stand-alone eye-tracker which achieves 1.62° horizontal accuracy with 3 fps refresh rate for a building cost of 70 Euros. |
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Lund; Sweden; August 2013 |
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ECEM |
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Notes |
MV;SIAI |
Approved |
no |
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Call Number |
Admin @ si @ FeV2013 |
Serial |
2374 |
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Author |
Onur Ferhat; Fernando Vilariño |
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Title |
Low Cost Eye Tracking: The Current Panorama |
Type |
Journal Article |
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Year |
2016 |
Publication |
Computational Intelligence and Neuroscience |
Abbreviated Journal |
CIN |
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Article ID 8680541 |
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Abstract |
Despite the availability of accurate, commercial gaze tracker devices working with infrared (IR) technology, visible light gaze tracking constitutes an interesting alternative by allowing scalability and removing hardware requirements. Over the last years, this field has seen examples of research showing performance comparable to the IR alternatives. In this work, we survey the previous work on remote, visible light gaze trackers and analyze the explored techniques from various perspectives such as calibration strategies, head pose invariance, and gaze estimation techniques. We also provide information on related aspects of research such as public datasets to test against, open source projects to build upon, and gaze tracking services to directly use in applications. With all this information, we aim to provide the contemporary and future researchers with a map detailing previously explored ideas and the required tools. |
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MV; 605.103; 600.047; 600.097;SIAI |
Approved |
no |
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Call Number |
Admin @ si @ FeV2016 |
Serial |
2744 |
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Author |
Onur Ferhat; Arcadi Llanza; Fernando Vilariño |
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Title |
A Feature-Based Gaze Estimation Algorithm for Natural Light Scenarios |
Type |
Conference Article |
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Year |
2015 |
Publication |
Pattern Recognition and Image Analysis, Proceedings of 7th Iberian Conference , ibPRIA 2015 |
Abbreviated Journal |
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Volume |
9117 |
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Pages |
569-576 |
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Keywords |
Eye tracking; Gaze estimation; Natural light; Webcam |
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Abstract |
We present an eye tracking system that works with regular webcams. We base our work on open source CVC Eye Tracker [7] and we propose a number of improvements and a novel gaze estimation method. The new method uses features extracted from iris segmentation and it does not fall into the traditional categorization of appearance–based/model–based methods. Our experiments show that our approach reduces the gaze estimation errors by 34 % in the horizontal direction and by 12 % in the vertical direction compared to the baseline system. |
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Santiago de Compostela; June 2015 |
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Springer International Publishing |
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LNCS |
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0302-9743 |
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978-3-319-19389-2 |
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IbPRIA |
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Notes |
MV;SIAI |
Approved |
no |
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Call Number |
Admin @ si @ FLV2015a |
Serial |
2646 |
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Permanent link to this record |
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Author |
Onur Ferhat; Arcadi Llanza; Fernando Vilariño |
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Title |
Gaze interaction for multi-display systems using natural light eye-tracker |
Type |
Conference Article |
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Year |
2015 |
Publication |
2nd International Workshop on Solutions for Automatic Gaze Data Analysis |
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Bielefeld; Germany; September 2015 |
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SAGA |
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MV;SIAI |
Approved |
no |
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Call Number |
Admin @ si @ FLV2015b |
Serial |
2676 |
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Permanent link to this record |
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Author |
Onur Ferhat |
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Title |
Eye-Tracking with Webcam-Based Setups: Implementation of a Real-Time System and an Analysis of Factors Affecting Performance |
Type |
Report |
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Year |
2012 |
Publication |
CVC Technical Report |
Abbreviated Journal |
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Volume |
172 |
Issue |
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Keywords |
Computer vision, eye-tracking, gaussian process, feature selection, optical flow |
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Abstract |
In the recent years commercial eye-tracking hardware has become more common, with the introduction of new models from several brands that have better performance and easier setup procedures. A cause and at the same time a result of this phenomenon is the popularity of eye-tracking research directed at marketing, accessibility and usability, among others.
One problem with these hardware components is scalability, because both the price and the necessary expertise to operate them makes it practically impossible in the large scale. In this work, we analyze the feasibility of a software eye-tracking system based on a single, ordinary webcam. Our aim is to discover the limits of such a system and to see whether it provides acceptable performances.
The significance of this setup is that it is the most common setup found in consumer environments, off-the-shelf electronic devices such as laptops, mobile phones and tablet computers. As no special equipment such as infrared lights, mirrors or zoom lenses are used; setting up and calibrating the system is easier compared to other approaches using these components.
Our work is based on the open source application Opengazer, which provides a good starting point for our contributions. We propose several improvements in order to push the system's performance further and make it feasible as a robust, real-time device. Then we carry out an elaborate experiment involving 18 human subjects and 4 different system setups. Finally, we give an analysis of the results and discuss the effects of setup changes, subject differences and modifications in the software. |
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Address |
Bellaterra |
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Corporate Author |
Computer Vision Center |
Thesis |
Master's thesis |
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Publisher |
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Place of Publication |
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Editor |
Fernando Vilariño |
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MV |
Approved |
no |
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Call Number |
Admin @ si @ Fer2012; IAM @ iam @ Fer2012 |
Serial |
2165 |
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Permanent link to this record |
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Author |
Onur Ferhat |
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Title |
Analysis of Head-Pose Invariant, Natural Light Gaze Estimation Methods |
Type |
Book Whole |
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Year |
2017 |
Publication |
PhD Thesis, Universitat Autonoma de Barcelona-CVC |
Abbreviated Journal |
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Eye tracker devices have traditionally been only used inside laboratories, requiring trained professionals and elaborate setup mechanisms. However, in the recent years the scientific work on easier–to–use eye trackers which require no special hardware—other than the omnipresent front facing cameras in computers, tablets, and mobiles—is aiming at making this technology common–place. These types of trackers have several extra challenges that make the problem harder, such as low resolution images provided by a regular webcam, the changing ambient lighting conditions, personal appearance differences, changes in head pose, and so on. Recent research in the field has focused on all these challenges in order to provide better gaze estimation performances in a real world setup.
In this work, we aim at tackling the gaze tracking problem in a single camera setup. We first analyze all the previous work in the field, identifying the strengths and weaknesses of each tried idea. We start our work on the gaze tracker with an appearance–based gaze estimation method, which is the simplest idea that creates a direct mapping between a rectangular image patch extracted around the eye in a camera image, and the gaze point (or gaze direction). Here, we do an extensive analysis of the factors that affect the performance of this tracker in several experimental setups, in order to address these problems in future works. In the second part of our work, we propose a feature–based gaze estimation method, which encodes the eye region image into a compact representation. We argue that this type of representation is better suited to dealing with head pose and lighting condition changes, as it both reduces the dimensionality of the input (i.e. eye image) and breaks the direct connection between image pixel intensities and the gaze estimation. Lastly, we use a face alignment algorithm to have robust face pose estimation, using a 3D model customized to the subject using the tracker. We combine this with a convolutional neural network trained on a large dataset of images to build a face pose invariant gaze tracker. |
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Address |
September 2017 |
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Ph.D. thesis |
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Publisher |
Ediciones Graficas Rey |
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Editor |
Fernando Vilariño |
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978-84-945373-5-6 |
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Notes |
MV |
Approved |
no |
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Call Number |
Admin @ si @ Fer2017 |
Serial |
3018 |
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Permanent link to this record |
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Author |
Olivier Penacchio; Xavier Otazu; Laura Dempere-Marco |
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Title |
A Neurodynamical Model of Brightness Induction in V1 |
Type |
Journal Article |
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Year |
2013 |
Publication |
PloS ONE |
Abbreviated Journal |
Plos |
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Volume |
8 |
Issue |
5 |
Pages |
e64086 |
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Abstract |
Brightness induction is the modulation of the perceived intensity of an area by the luminance of surrounding areas. Recent neurophysiological evidence suggests that brightness information might be explicitly represented in V1, in contrast to the more common assumption that the striate cortex is an area mostly responsive to sensory information. Here we investigate possible neural mechanisms that offer a plausible explanation for such phenomenon. To this end, a neurodynamical model which is based on neurophysiological evidence and focuses on the part of V1 responsible for contextual influences is presented. The proposed computational model successfully accounts for well known psychophysical effects for static contexts and also for brightness induction in dynamic contexts defined by modulating the luminance of surrounding areas. This work suggests that intra-cortical interactions in V1 could, at least partially, explain brightness induction effects and reveals how a common general architecture may account for several different fundamental processes, such as visual saliency and brightness induction, which emerge early in the visual processing pathway. |
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CIC |
Approved |
no |
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Call Number |
Admin @ si @ POD2013 |
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2242 |
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Author |
Olivier Penacchio; Xavier Otazu; Arnold J Wilkings; Sara M. Haigh |
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Title |
A mechanistic account of visual discomfort |
Type |
Journal Article |
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Year |
2023 |
Publication |
Frontiers in Neuroscience |
Abbreviated Journal |
FN |
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17 |
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Abstract |
Much of the neural machinery of the early visual cortex, from the extraction of local orientations to contextual modulations through lateral interactions, is thought to have developed to provide a sparse encoding of contour in natural scenes, allowing the brain to process efficiently most of the visual scenes we are exposed to. Certain visual stimuli, however, cause visual stress, a set of adverse effects ranging from simple discomfort to migraine attacks, and epileptic seizures in the extreme, all phenomena linked with an excessive metabolic demand. The theory of efficient coding suggests a link between excessive metabolic demand and images that deviate from natural statistics. Yet, the mechanisms linking energy demand and image spatial content in discomfort remain elusive. Here, we used theories of visual coding that link image spatial structure and brain activation to characterize the response to images observers reported as uncomfortable in a biologically based neurodynamic model of the early visual cortex that included excitatory and inhibitory layers to implement contextual influences. We found three clear markers of aversive images: a larger overall activation in the model, a less sparse response, and a more unbalanced distribution of activity across spatial orientations. When the ratio of excitation over inhibition was increased in the model, a phenomenon hypothesised to underlie interindividual differences in susceptibility to visual discomfort, the three markers of discomfort progressively shifted toward values typical of the response to uncomfortable stimuli. Overall, these findings propose a unifying mechanistic explanation for why there are differences between images and between observers, suggesting how visual input and idiosyncratic hyperexcitability give rise to abnormal brain responses that result in visual stress. |
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NEUROBIT |
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no |
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Admin @ si @ POW2023 |
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3886 |
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Author |
Olivier Penacchio; Xavier Otazu; A. wilkins; J. Harris |
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Title |
Uncomfortable images prevent lateral interactions in the cortex from providing a sparse code |
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Conference Article |
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2015 |
Publication |
European Conference on Visual Perception ECVP2015 |
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Liverpool; uk; August 2015 |
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NEUROBIT;CIC |
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no |
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Admin @ si @ POW2015 |
Serial |
2633 |
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Permanent link to this record |
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Author |
Olivier Penacchio; Laura Dempere-Marco; Xavier Otazu |
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Title |
Switching off brightness induction through induction-reversed images |
Type |
Abstract |
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Year |
2012 |
Publication |
Perception |
Abbreviated Journal |
PER |
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Volume |
41 |
Issue |
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Pages |
208 |
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Keywords |
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Abstract |
Brightness induction is the modulation of the perceived intensity of an
area by the luminance of surrounding areas. Although V1 is traditionally regarded as
an area mostly responsive to retinal information, neurophysiological evidence
suggests that it may explicitly represent brightness information. In this work, we
investigate possible neural mechanisms underlying brightness induction. To this end,
we consider the model by Z Li (1999 Computation and Neural Systems10187-212)
which is constrained by neurophysiological data and focuses on the part of V1
responsible for contextual influences. This model, which has proven to account for
phenomena such as contour detection and preattentive segmentation, shares with
brightness induction the relevant effect of contextual influences. Importantly, the
input to our network model derives from a complete multiscale and multiorientation
wavelet decomposition, which makes it possible to recover an image reflecting the
perceived luminance and successfully accounts for well known psychophysical
effects for both static and dynamic contexts. By further considering inverse problem
techniques we define induction-reversed images: given a target image, we build an
image whose perceived luminance matches the actual luminance of the original
stimulus, thus effectively canceling out brightness induction effects. We suggest that
induction-reversed images may help remove undesired perceptual effects and can
find potential applications in fields such as radiological image interpretation |
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Olivier Penacchio; Laura Dempere-Marco; Xavier Otazu |
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A Neurodynamical Model Of Brightness Induction In V1 Following Static And Dynamic Contextual Influences |
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2012 |
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8th Federation of European Neurosciences |
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63-64 |
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Brightness induction is the modulation of the perceived intensity of an area by the luminance of surrounding areas. Although striate cortex is traditionally regarded as an area mostly responsive to ensory (i.e. retinal) information,
neurophysiological evidence suggests that perceived brightness information mightbe explicitly represented in V1.
Such evidence has been observed both in anesthetised cats where neuronal response modulations have been found to follow luminance changes outside the receptive felds and in human fMRI measurements. In this work, possible neural mechanisms that ofer a plausible explanation for such phenomenon are investigated. To this end, we consider the model proposed by Z.Li (Li, Network:Comput. Neural Syst., 10 (1999)) which is based on neurophysiological evidence and focuses on the part of V1 responsible for contextual infuences, i.e. layer 2-3 pyramidal cells, interneurons, and horizontal intracortical connections. This model has reproduced other phenomena such as contour detection and preattentive segmentation, which share with brightness induction the relevant efect of contextual infuences. We have extended the original model such that the input to the network is obtained from a complete multiscale and multiorientation wavelet decomposition, thereby allowing the recovery of an image refecting the perceived intensity. The proposed model successfully accounts for well known psychophysical efects for static contexts (among them: the White's and modifed White's efects, the Todorovic, Chevreul, achromatic ring patterns, and grating induction efects) and also for brigthness induction in dynamic contexts defned by modulating the luminance of surrounding areas (e.g. the brightness of a static central area is perceived to vary in antiphase to the sinusoidal luminance changes of its surroundings). This work thus suggests that intra-cortical interactions in V1 could partially explain perceptual brightness induction efects and reveals how a common general architecture may account for several different fundamental processes emerging early in the visual processing pathway. |
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