Search results for "Visual Processing"

Psychophysically Tuned Divisive Normalization Approximately Factorizes the PDF of Natural Images

2010

The conventional approach in computational neuroscience in favor of the efficient coding hypothesis goes from image statistics to perception. It has been argued that the behavior of the early stages of biological visual processing (e.g., spatial frequency analyzers and their nonlinearities) may be obtained from image samples and the efficient coding hypothesis using no psychophysical or physiological information. In this work we address the same issue in the opposite direction: from perception to image statistics. We show that psychophysically fitted image representation in V1 has appealing statistical properties, for example, approximate PDF factorization and substantial mutual informatio…

Editorial: Face Perception across the Life-Span

2016

Anger superiority effect for change detection and change blindness

2013

Abstract In visual search, an angry face in a crowd “pops out” unlike a happy or a neutral face. This “anger superiority effect” conflicts with views of visual perception holding that complex stimulus contents cannot be detected without focused top-down attention. Implicit visual processing of threatening changes was studied by recording event-related potentials (ERPs) using facial stimuli using the change blindness paradigm, in which conscious change detection is eliminated by presenting a blank screen before the changes. Already before their conscious detection, angry faces modulated relatively early emotion sensitive ERPs when appearing among happy and neutral faces, but happy faces only…

Symmetry in Computer Vision

2002

Symmetry properties establish the invariance of a system to a given set of transformations. Physicists assign special meaning whenever symmetry is broken in nature; for example, groups of symmetry have been used to explain and predict the spatial organization of atoms in a crystal. Psychologists consider relevant the property of symmetry in the perception of visual signals. The paper will briefly describe different approaches, introduced in computer vision, to measure symmetry. A review of some applications at the Computer Vision Group (Department of Mathematics and Applications of Palermo University) is presented. They regard attentive visual processing, the analysis of faces, the recognit…

Differences in visual information processing style between Idiopathic Generalized Epilepsy with and without photosensitivity.

2021

Purpose: Recently, altered visual cortical processes i.e., lack of habituation to visual evoked potentials (VEP), has been highlighted in both photosensitive epilepsy and in a specific i.e., analytic mode of processing visual inputs. In this study we aimed at evaluating the relationship between photosensitivity (PS) and analytic style of processing visual information, in a sample of 30 patients with Idiopathic Generalized Epilepsy (IGE) and matched healthy controls. Methods: At our Epilepsy unit of the Sapienza University of Rome, we consecutively enrolled 15 patients with IGE with PSand matched them with 15 patients with IGE without PS and 15 Healthy Volunteers. All patients underwent EEG …

Panel Summary: Plasticity and Reconfigurability in Sensory Systems

1997

Natural neural network are highly plastic in structure and function and may adapt to long lasting environmental changes. Plasticity and adaptation are not confined to lower level of processing, or to lower vertebrates, but also at the higher levels of visual processing in higher vertebrates are highly dynamic and perform considerable spatial integration. There are numerous influences that play a role in the functional architecture of the retina and the, cortex, the dynamics of the outside environment, the context within which a feature is presented, the history of previous visual stimulation and attention or expectation. The brief report on the visual system is integrated by the report of G…

Wider Letter-Spacing Facilitates Word Processing but Impairs Reading Rates of Fast Readers

2020

Previous reports of improved oral reading performance for dyslexic children but not for regular readers when between-letter spacing was enlarged led to the proposal of a dyslexia-specific deficit in visual crowding. However, it is in this context also critical to understand how letter spacing affects visual word recognition and reading in unimpaired readers. Adopting an individual differences approach, the present study, accordingly, examined whether wider letter spacing improves reading performance also for non-impaired adults during silent reading and whether there is an association between letter spacing and crowding sensitivity. We report eye movement data of 24 German students who sile…

Position Coding in Two-Digit Arabic Numbers

2011

Digit position coding in two-digit Arabic numbers was examined in two masked priming experiments. In Experiment 1, participants had to decide whether the presented stimulus was a two-digit Arabic number (e.g., 67) or not (e.g., G7). Target stimuli could be preceded by a prime which (i) shared one digit in the initial position (e.g., 13-18), (ii) shared one digit but in a different position (83-18), and (iii) was a transposed number (81-18). Two unrelated control conditions, equalized in terms of the distance between primes and targets with the experimental conditions, were also included (e.g., 79-18). Results showed a priming effect only when prime and target shared digits in the same posi…

David Marr: A Theory for Cerebral Neocortex

1986

This paper is an important contribution to the understanding of the visual system, it contains a part of those ideas which have become the commonly accepted basis of current research. Although some of these principles already had a history in 1970, Marr clearly deserves the credit for their sharp formulation and for a series of attempts leading to a formalization of the problems. His way of dividing the approach into the levels of computational theory, of the algorithm and of the implementation clarified the problems. His creed that human visual processing is modular, and that different types of information, which are encoded in the image can be decoded independently by modules, has been ge…

Near- and Far-Surround Suppression in Human Motion Discrimination.

2018

The spatial context has strong effects on visual processing. Psychophysics and modeling studies have provided evidence that the surround context can systematically modulate the perception of center stimuli. For motion direction, these center-surround interactions are considered to come from spatio-directional interactions between direction of motion tuned neurons, which are attributed to the middle temporal (MT) area. Here, we investigated through psychophysics experiments on human subjects changes with spatial separation in center-surround inhibition and motion direction interactions. Center-surround motion repulsion effects were measured under near-and far-surround conditions. Using a sim…