Advantage of Hole Stimulus in Rivalry Competition

Mounting psychophysical evidence suggests that early visual computations are sensitive to the topological properties of stimuli, such as the determination of whether the object has a hole or not. Previous studies have demonstrated that the hole feature took some advantages during conscious perception. In this study, we investigate whether there exists a privileged processing for hole stimuli during unconscious perception. By applying a continuous flash suppression paradigm, the target was gradually introduced to one eye to compete against a flashed full contrast Mondrian pattern which was presented to the other eye. This method ensured that the target image was suppressed during the initial perceptual period. We compared the initial suppressed duration between the stimuli with and without the hole feature and found that hole stimuli required less time than no-hole stimuli to gain dominance against the identical suppression noise. These results suggest the hole feature could be processed in the absence of awareness, and there exists a privileged detection of hole stimuli during suppressed phase in the interocular rivalry

How does binocular rivalry emerge from cortical mechanisms of 3-D vision?

AbstractUnder natural viewing conditions, a single depthful percept of the world is consciously seen. When dissimilar images are presented to corresponding regions of the two eyes, binocular rivalry may occur, during which the brain consciously perceives alternating percepts through time. How do the same brain mechanisms that generate a single depthful percept of the world also cause perceptual bistability, notably binocular rivalry? What properties of brain representations correspond to consciously seen percepts? A laminar cortical model of how cortical areas V1, V2, and V4 generate depthful percepts is developed to explain and quantitatively simulate binocular rivalry data. The model proposes how mechanisms of cortical development, perceptual grouping, and figure-ground perception lead to single and rivalrous percepts. Quantitative model simulations of perceptual grouping circuits demonstrate influences of contrast changes that are synchronized with switches in the dominant eye percept, gamma distribution of dominant phase durations, piecemeal percepts, and coexistence of eye-based and stimulus-based rivalry. The model as a whole also qualitatively explains data about the involvement of multiple brain regions in rivalry, the effects of object attention on switching between superimposed transparent surfaces, monocular rivalry, Marroquin patterns, the spread of suppression during binocular rivalry, binocular summation, fusion of dichoptically presented orthogonal gratings, general suppression during binocular rivalry, and pattern rivalry. These data explanations follow from model brain mechanisms that assure non-rivalrous conscious percepts

How does binocular rivalry emerge from cortical mechanisms of 3-D vision?

AbstractUnder natural viewing conditions, a single depthful percept of the world is consciously seen. When dissimilar images are presented to corresponding regions of the two eyes, binocular rivalry may occur, during which the brain consciously perceives alternating percepts through time. How do the same brain mechanisms that generate a single depthful percept of the world also cause perceptual bistability, notably binocular rivalry? What properties of brain representations correspond to consciously seen percepts? A laminar cortical model of how cortical areas V1, V2, and V4 generate depthful percepts is developed to explain and quantitatively simulate binocular rivalry data. The model proposes how mechanisms of cortical development, perceptual grouping, and figure-ground perception lead to single and rivalrous percepts. Quantitative model simulations of perceptual grouping circuits demonstrate influences of contrast changes that are synchronized with switches in the dominant eye percept, gamma distribution of dominant phase durations, piecemeal percepts, and coexistence of eye-based and stimulus-based rivalry. The model as a whole also qualitatively explains data about the involvement of multiple brain regions in rivalry, the effects of object attention on switching between superimposed transparent surfaces, monocular rivalry, Marroquin patterns, the spread of suppression during binocular rivalry, binocular summation, fusion of dichoptically presented orthogonal gratings, general suppression during binocular rivalry, and pattern rivalry. These data explanations follow from model brain mechanisms that assure non-rivalrous conscious percepts

Neural processing of orientation differences between the eyes’ images

The aim of this study was to explore the neural mechanisms underlying visual processing of brief stimuli that were either the same in the two eyes or differed in orientation between the two eyes. To examine the neural mechanisms, I measured event-related potentials (ERPs) to 200-ms sine-wave gratings differing in orientation between the eyes from 08 to 908. The gratings were either both of high contrast or both of low contrast. They elicited typical ERPs at occipital electrodes, with a first major component (P100) 100 ms after stimulus onset and a second major component (N170) 170 ms after stimulus onset. Global electrical field strength and focal amplitudes of both components were affected by grating contrast: Highcontrast gratings elicited larger amplitudes than low-contrast gratings, confirming that neural responses depend on stimulus salience. P100 amplitude followed a U-shaped function: It was larger when the orientations were the same in the two eyes (yielding binocular fusion), intermediate when the orientations were maximally different between the eyes (leading to binocular rivalry), and smallest for in-between orientation differences. N170 amplitude followed a linear function: It was smallest when the orientations were the same and increased with orientation difference between the eyes. These results suggest that the P100 reflects processes in which the binocular input are offset against each other, and that the N170 reflects binocular rivalry. I argue that the N170 shows the effects of reciprocal inhibition and adaptation-both critical factors in theories of binocular rivalry

Binocular interactions

Contains fulltext : 62061.pdf (Publisher’s version ) (Open Access)RU Radboud Universiteit Nijmegen, 23 september 2002Promotor : Weert, C.M.M. de164 p

A cross-modal investigation into the relationships between bistable perception and a global temporal mechanism

When the two eyes are presented with sufficiently different images, Binocular Rivalry (BR) occurs. BR is a form of bistable perception involving stochastic alternations in awareness between distinct images shown to each eye. It has been suggested that the dynamics of BR are due to the activity of a central temporal process and are linked to involuntary mechanisms of selective attention (aka exogenous attention). To test these ideas, stimuli designed to evoke exogenous attention and central temporal processes were employed during BR observation. These stimuli included auditory and visual looming motion and streams of transient events of varied temporal rate and pattern. Although these stimuli exerted a strong impact over some aspects of BR, they were unable to override its characteristic stochastic pattern of alternations completely. It is concluded that BR is subject to distributed influences, but ultimately, is achieved in neural processing areas specific to the binocular conflict