Disparity Cues Research Articles

A trained perceptual bias that lasts for weeks

Classical (Pavlovian) conditioning procedures can be used to bias the appearance of physical stimuli. Under natural conditions this form of perceptual learning could cause perception to become more accurate by changing prior belief to be in accord with what is statistically likely. However, for learning to be of functional significance, it must last until similar stimuli are encountered again. Here, we used the apparent rotation direction of a revolving wire frame (Necker) cube to test whether a learned perceptual bias is long lasting. Apparent rotation direction was trained to have a different bias at two different retinal locations by interleaving the presentation of ambiguous cubes with presentation of cubes that were disambiguated by disparity and occlusion cues. Four groups of eight subjects were subsequently tested either 1, 7, 14, or 28 days after initial training, respectively, using a counter-conditioning procedure. All four groups showed incomplete re-learning of the reversed contingency relationship during their second session. One group repeated the counter-conditioning and showed an increase in the reverse bias, showing that the first counter-conditioning session also had a long-lasting effect. The fact that the original learning was still evident four weeks after the initial training is consistent with the operation of a mechanism that ordinarily would improve the accuracy and efficiency of perception.

Integration of 3D Structure from Disparity into Biological Motion Perception Independent of Depth Awareness

Images projected onto the retinas of our two eyes come from slightly different directions in the real world, constituting binocular disparity that serves as an important source for depth perception - the ability to see the world in three dimensions. It remains unclear whether the integration of disparity cues into visual perception depends on the conscious representation of stereoscopic depth. Here we report evidence that, even without inducing discernible perceptual representations, the disparity-defined depth information could still modulate the visual processing of 3D objects in depth-irrelevant aspects. Specifically, observers who could not discriminate disparity-defined in-depth facing orientations of biological motions (i.e., approaching vs. receding) due to an excessive perceptual bias nevertheless exhibited a robust perceptual asymmetry in response to the indistinguishable facing orientations, similar to those who could consciously discriminate such 3D information. These results clearly demonstrate that the visual processing of biological motion engages the disparity cues independent of observers’ depth awareness. The extraction and utilization of binocular depth signals thus can be dissociable from the conscious representation of 3D structure in high-level visual perception.

Depth perception of illusory surfaces

The perception of an illusory surface, a subjectively perceived surface that is not given in the image, is one of the most intriguing phenomena in vision. It strongly influences the perception of some fundamental properties, namely, depth, lightness and contours. Recently, we suggested (1) that the context-sensitive mechanism of depth computation plays a key role in creating the illusion, (2) that the illusory lightness perception can be explained by an influence of depth perception on the lightness computation, and (3) that the perception of variations of the Kanizsa figure can be well-reproduced by implementing these principles in a model (Kogo, Strecha, et al., 2010). However, depth perception, lightness perception, contour perception, and their interactions can be influenced by various factors. It is essential to measure the differences between the variation figures in these aspects separately to further understand the mechanisms. As a first step, we report here the results of a new experimental paradigm to compare the depth perception of the Kanizsa figure and its variations. One of the illusory figures was presented side-by-side with a non-illusory variation whose stereo disparities were varied. Participants had to decide in which of these two figures the central region appeared closer. The results indicate that the depth perception of the illusory surface was indeed different in the variation figures. Furthermore, there was a non-linear interaction between the occlusion cues and stereo disparity cues. Implications of the results for the neuro-computational mechanisms are discussed.

Near-eye light field displays

We propose near-eye light field displays that enable thin, lightweight head-mounted displays (HMDs) capable of presenting nearly correct convergence, accommodation, binocular disparity, and retinal defocus depth cues. Sharp images are depicted by out-of-focus elements by synthesizing light fields corresponding to virtual objects within a viewer's natural accommodation range. We formally assess the capabilities of microlens arrays to achieve practical near-eye light field displays. Building on concepts shared with existing integral imaging displays and light field cameras, we optimize performance in the context of near-eye viewing. We establish fundamental trade-offs between the quantitative parameters of resolution, field of view, and depth of field, as well as the ergonomic parameters of form factor and ranges of allowed eye movement. As with light field cameras, our design supports continuous accommodation of the eye throughout a finite depth of field; as a result, binocular configurations provide a means to address the accommodation-convergence conflict occurring with existing stereoscopic displays. We construct a complete prototype display system, comprising: a custom-fabricated HMD using modified off-the-shelf parts and real-time, GPU-accelerated light field renderers (including a general ray tracing method and a "backward compatible" rasterization method supporting existing stereoscopic content). Through simulations and experiments, we motivate near-eye light field displays as thin, lightweight alternatives to conventional near-eye displays.

Joint Representation of Depth from Motion Parallax and Binocular Disparity Cues in Macaque Area MT

Perception of depth is based on a variety of cues, with binocular disparity and motion parallax generally providing more precise depth information than pictorial cues. Much is known about how neurons in visual cortex represent depth from binocular disparity or motion parallax, but little is known about the joint neural representation of these depth cues. We recently described neurons in the middle temporal (MT) area that signal depth sign (near vs far) from motion parallax; here, we examine whether and how these neurons also signal depth from binocular disparity. We find that most MT neurons in rhesus monkeys (Macaca Mulatta) are selective for depth sign based on both disparity and motion parallax cues. However, the depth-sign preferences (near or far) are not always aligned: 56% of MT neurons have matched depth-sign preferences ("congruent" cells) whereas the remaining 44% of neurons prefer near depth from motion parallax and far depth from disparity, or vice versa ("opposite" cells). For congruent cells, depth-sign selectivity increases when disparity cues are added to motion parallax, but this enhancement does not occur for opposite cells. This suggests that congruent cells might contribute to perceptual integration of depth cues. We also found that neurons are clustered in MT according to their depth tuning based on motion parallax, similar to the known clustering of MT neurons for binocular disparity. Together, these findings suggest that area MT is involved in constructing a representation of 3D scene structure that takes advantage of multiple depth cues available to mobile observers.

Accommodation and Vergence Response Gains to Different Near Cues Characterize Specific Esotropias

Aim: To describe preliminary findings of how the profile of the use of blur, disparity, and proximal cues varies between non-strabismic groups and those with different types of esotropia.Design: This was a case control study.Methodology: A remote haploscopic photorefractor measured simultaneous convergence and accommodation to a range of targets containing all combinations of binocular disparity, blur, and proximal (looming) cues. Thirteen constant esotropes, 16 fully accommodative esotropes, and 8 convergence excess esotropes were compared with age- and refractive error–matched controls and 27 young adult emmetropic controls. All wore full refractive correction if not emmetropic. Response AC/A and CA/C ratios were also assessed.Results: Cue use differed between the groups. Even esotropes with constant suppression and no binocular vision (BV) responded to disparity in cues. The constant esotropes with weak BV showed trends for more stable responses and better vergence and accommodation than those without any BV. The accommodative esotropes made less use of disparity cues to drive accommodation (p = 0.04) and more use of blur to drive vergence (p = 0.008) than controls. All esotropic groups failed to show the strong bias for better responses to disparity cues found in the controls, with convergence excess esotropes favoring blur cues. AC/A and CA/C ratios existed in an inverse relationship in the different groups. Accommodative lag of >1.0 D at 33 cm was common (46%) in the pooled esotropia groups compared with 11% in typical children (p = 0.05).Conclusion: Esotropic children use near cues differently from matched non-esotropic children in ways characteristic to their deviations. Relatively higher weighting for blur cues was found in accommodative esotropia compared to matched controls.

Depth spreading through empty space induced by sparse disparity cues

A key goal of visual processing is to develop an understanding of the three-dimensional layout of the objects in our immediate vicinity from the variety of incomplete and noisy depth cues available to the eyes. Binocular disparity is one of the dominant depth cues, but it is often sparse, being definable only at the edges of uniform surface regions, and visually resolvable only where the edges have a horizontal disparity component. To understand the full 3D structure of visual objects, our visual system has to perform substantial surface interpolation across unstructured visual space. This interpolation process was studied in an eight-spoke depth spreading configuration corresponding to that used in the neon color spreading effect, which generates a strong percept of a sharp contour extending through empty space from the disparity edges within the spokes. Four hypotheses were developed for the form of the depth surface induced by disparity in the spokes defining an incomplete disk in depth: low-level local (isotropic) depth propagation, mid-level linear (anisotropic) depth-contour interpolation or extrapolation, and high-level (anisotropic) figural depth propagation of a disk figure in depth. Data for both perceived depth and position of the perceived contour clearly rejected the first three hypotheses and were consistent with the high-level figural hypothesis in both uniform disparity and slanted disk configurations. We conclude that depth spreading through empty visual space is an accurately quantifiable perceptual process that propagates depth contours anisotropically along their length and is governed by high-level figural properties of 3D object structure.

Combining texture and stereo disparity cues for real-time face detection

Intuitively, integrating information from multiple visual cues, such as texture, stereo disparity, and image motion, should improve performance on perceptual tasks, such as object detection. On the other hand, the additional effort required to extract and represent information from additional cues may increase computational complexity. In this work, we show that using biologically inspired integrated representation of texture and stereo disparity information for a multi-view facial detection task leads to not only improved detection performance, but also reduced computational complexity. Disparity information enables us to filter out 90% of image locations as being less likely to contain faces. Performance is improved because the filtering rejects 32% of the false detections made by a similar monocular detector at the same recall rate. Despite the additional computation required to compute disparity information, our binocular detector takes only 42ms to process a pair of 640×480 images, 35% of the time required by the monocular detector. We also show that this integrated detector is computationally more efficient than a detector with similar performance where texture and stereo information is processed separately.

Perceived depth magnitude with a combination of motion parallax and binocular disparity cues

Perceived depth magnitude with a combination of motion parallax and binocular disparity cues

The Clinical Near Gradient Stimulus AC/A Ratio Correlates Better With the Response CA/C Ratio Than With the Response AC/A Ratio

Aim: To provide evidence that a near clinical gradient AC/A ratio could instead reflect the CA/C relationship (the accommodation driven by response to disparity).Design: Case control study.Methodology: 27 emmetropic participants with heterophoria <4 PD, 19 with intermittent distance exotropia, and 17 with near exophoria >6 PD were tested. A remote haploscopic photorefractor, which can measure simultaneous convergence and accommodation to a range of targets containing all combinations of presence or absence of binocular disparity, blur, and proximal (looming) cues, was used to assess response AC/A and CA/C relationships. These were compared with clinical gradient AC/A ratios at near and distance fixation using alternate prism cover test and plus or minus lenses.Results: Although the near and distance clinical AC/A ratios correlated weakly with each other (p = 0.03), neither clinical method correlated with the more accurate response AC/A ratio from the laboratory method (p = 0.88 and p = 0.93, respectively). The laboratory CA/C ratio correlated strongly with the near clinical AC/A ratio (p = 0.004) but only very weakly with the distance ratio (p = 0.16).Conclusions: The “near gradient AC/A ratio” may actually reflect the CA/C linkage as the dissociation of the prism cover test disrupts vergence accommodation. If the near deviation diverges more with plus lenses, it may be because the lenses allow clear near vision without needing to recruit convergence accommodation to achieve it.

Goal-directed grasping: The dimensional properties of an object influence the nature of the visual information mediating aperture shaping

An issue of continued debate in the visuomotor control literature surrounds whether a 2D object serves as a representative proxy for a 3D object in understanding the nature of the visual information supporting grasping control. In an effort to reconcile this issue, we examined the extent to which aperture profiles for grasping 2D and 3D objects adheres to, or violates, the psychophysical properties of Weber’s law. Specifically, participants grasped differently sized 2D and 3D objects (20, 30, 40, and 50mm of width) and we computed the just-noticeable-difference scores associated with aperture profiles at decile increments of normalized grasping time. The aperture profiles for 2D objects showed an early through late (i.e., 10% through 90%) adherence to Weber’s law, whereas the late stages of grasping 3D objects (i.e., >50% of grasping time) produced a fundamental violation of the law’s principles. As such, results suggest that grasping a 2D object is a top-down and cognitive task mediated via relative visual information. In contrast, the enriched shape information provided by a 3D object (i.e., stereoscopic vergence and disparity cues) allows for later aperture specification via absolute (Euclidean) visual information. Most notably, our results establish that the dimensional properties of an object influence the visual information mediating motor output, and further indicate that 2D and 3D objects are not representative proxies for one another in understanding the visual control of grasping.

Audio–visual interactions for motion perception in depth modulate activity in visual area V3A

Multisensory signals can enhance the spatial perception of objects and events in the environment. Changes of visual size and auditory intensity provide us with the main cues about motion direction in depth. However, frequency changes in audition and binocular disparity in vision also contribute to the perception of motion in depth. Here, we presented subjects with several combinations of auditory and visual depth-cues to investigate multisensory interactions during processing of motion in depth. The task was to discriminate the direction of auditory motion in depth according to increasing or decreasing intensity. Rising or falling auditory frequency provided an additional within-audition cue that matched or did not match the intensity change (i.e. intensity-frequency (IF) "matched vs. unmatched" conditions). In two-thirds of the trials, a task-irrelevant visual stimulus moved either in the same or opposite direction of the auditory target, leading to audio-visual "congruent vs. incongruent" between-modalities depth-cues. Furthermore, these conditions were presented either with or without binocular disparity. Behavioral data showed that the best performance was observed in the audio-visual congruent condition with IF matched. Brain imaging results revealed maximal response in visual area V3A when all cues provided congruent and reliable depth information (i.e. audio-visual congruent, IF-matched condition including disparity cues). Analyses of effective connectivity revealed increased coupling from auditory cortex to V3A specifically in audio-visual congruent trials. We conclude that within- and between-modalities cues jointly contribute to the processing of motion direction in depth, and that they do so via dynamic changes of connectivity between visual and auditory cortices.

Efficiency of extracting stereo-driven object motions

Most living things and many nonliving things deform as they move, requiring observers to separate object motions from object deformations. When the object is partially occluded, the task becomes more difficult because it is not possible to use two-dimensional (2-D) contour correlations (Cohen, Jain, & Zaidi, 2010). That leaves dynamic depth matching across the unoccluded views as the main possibility. We examined the role of stereo cues in extracting motion of partially occluded and deforming three-dimensional (3-D) objects, simulated by disk-shaped random-dot stereograms set at randomly assigned depths and placed uniformly around a circle. The stereo-disparities of the disks were temporally oscillated to simulate clockwise or counterclockwise rotation of the global shape. To dynamically deform the global shape, random disparity perturbation was added to each disk's depth on each stimulus frame. At low perturbation, observers reported rotation directions consistent with the global shape, even against local motion cues, but performance deteriorated at high perturbation. Using 3-D global shape correlations, we formulated an optimal Bayesian discriminator for rotation direction. Based on rotation discrimination thresholds, human observers were 75% as efficient as the optimal model, demonstrating that global shapes derived from stereo cues facilitate inferences of object motions. To complement reports of stereo and motion integration in extrastriate cortex, our results suggest the possibilities that disparity selectivity and feature tracking are linked, or that global motion selective neurons can be driven purely from disparity cues.

Integration of motion and disparity cues to depth in monkey brain

Event Abstract Back to Event Integration of motion and disparity cues to depth in monkey brain Marcelo Armendariz1*, Andrew Welchman2, Hiroshi Ban2 and Wim Vanduffel1 1 KU Leuven, Neuroscience, Belgium 2 University of Birmingham, School of Psychology, United Kingdom Recognising and interacting with objects depends on knowing the three-dimensional (3D) structure of the world around us. Estimating the depth structure of the environment is a principal function of the visual system in primates, enabling many key computations, such as segmentation, object recognition, material perception and the guidance of movements. The brain exploits a range of depth cues to estimate depth, combining information from shading and shadows to linear perspective, motion and binocular disparity. To solve the depth perception there are two computationally distinct ways: independence or fusion. Traditionally, this process has been broadly conceived in modular terms, with the independent processing of individual cues followed by a combination stage in which the influence of each cue reflects the reliability with which it is encoded. However, a recent study with humans (Ban et al., 2012), using fMRI for decoding depth from binocular disparity and motion parallax cues, provided evidence that dorsal visual areas are involved in the fusion mechanism that combines the two cues into a single depth perception. They found that fMRI responses are more discriminable when two cues (binocular disparity and relative motion) concurrently signal depth, since the variance is significantly reduced. Our present study aims to investigate cue integration in monkey (Macaca mulatta) with fMRI. We presented the monkey a set of stimuli representing near or far depths defined by motion parallax, binocular disparity and the combination of both in congruent and incongruent ways. We performed statistical data analysis to obtain all the activation areas in the brain involved in depth processing: V1, V2, V3, V3A, V4, MST, MT, FST, F5 and MIP. Once the regions of interest are defined, we will use multivoxel pattern analysis (MVPA) to reveal depth selectivity in macaque cortex (Preston et al., 2008) and assess the fusion mechanism for cue integration. References Ban, H., Preston, T.J., Meeson, A.,& Welchman, A.E. The integration of motion and disparity cues to depth in dorsal visual cortex. Nature Neuroscience 15, 636–643 (2012). Preston, T.J., Li, S., Kourtzi, Z. & Welchman, A.E. Multivoxel pattern selectivity for perceptually relevant binocular disparities in the human brain. J. Neurosci. 28, 11315–11327 (2008). Keywords: fMRI, monkey, Depth Perception, binocular diparity, motion parallax Conference: Imaging the brain at different scales: How to integrate multi-scale structural information?, Antwerp, Belgium, 2 Sep - 6 Sep, 2013. Presentation Type: Poster presentation Topic: Poster session Citation: Armendariz M, Welchman A, Ban H and Vanduffel W (2013). Integration of motion and disparity cues to depth in monkey brain. Front. Neuroinform. Conference Abstract: Imaging the brain at different scales: How to integrate multi-scale structural information?. doi: 10.3389/conf.fninf.2013.10.00042 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 23 Aug 2013; Published Online: 31 Aug 2013. * Correspondence: Mr. Marcelo Armendariz, KU Leuven, Neuroscience, Leuven, Belgium, m.zimarron@gmail.com Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Marcelo Armendariz Andrew Welchman Hiroshi Ban Wim Vanduffel Google Marcelo Armendariz Andrew Welchman Hiroshi Ban Wim Vanduffel Google Scholar Marcelo Armendariz Andrew Welchman Hiroshi Ban Wim Vanduffel PubMed Marcelo Armendariz Andrew Welchman Hiroshi Ban Wim Vanduffel Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Cortical responses to congruent and incongruent stereo cues for objects on a collision path with the observer

We explored the cortical responses to visual collision events that were presented via stimuli that changed in size (looming) or stereo-depth (binocular motion), or both. In particular we examined the differences in cortical response when the looming and binocular cues were congruent or incongruent in the collision information they provided. A stereoscopic goggle system was used within the fMRI environment and allowed us to present looming and disparity cues in isolation, or in congruent or incongruent combinations. Comparison across conditions showed that incongruent cues elicited additional activation in cortical areas know to both process error and locate objects in spatio-topic coordinates. Results are discussed in terms of cognitive and motor responses to seeing incongruent cues.

Impaired perceptual processing and conceptual cognition in patients with anxiety disorders: A pilot study with the binocular depth inversion paradigm

The Binocular Depth Inversion Test (BDIT) measures a common illusion of visual perception whereby implausible objects are seen as normal, e.g., a hollow face is perceived as a normal, convex face. Such inversion is frequent, especially for objects with a high degree of familiarity. Under normal conditions, cognitive factors apparently override the binocular disparity cues of stereopsis. This internal mechanism of “censorship” of perception, which balances “top-down” and “bottom-up” processes of perception to come to a cognitive coherence, which is congruent to previous experience and concepts, appears to be disturbed in (pro-)psychotic states. The BDIT has been shown to be a sensitive measure of impaired higher visual processing and conceptual cognition common to conditions including schizophrenia, cannabinoid-intoxication, and sleep deprivation but not depression. In this pilot study, we tested the performance of patients with anxiety disorders (ICD-10 F40 and F41) compared to matched controls using the BDIT paradigm. Anxiety patients scored significantly higher on the BDIT than controls, in a range comparable to propsychotic conditions. The findings suggest that anxiety patients could have abnormalities in central perceptual processing, top-down processing (conceptual cognition), and reality testing similar to (pro-)psychotic conditions. Implications of these findings are discussed in relation to therapeutic interventions with anxiety disorders.

P1-26: Influence of Depth from Luminance Contrast on Vergence Eye Movements

A vergence eye movement is the simultaneous movement of both eyes in opposite directions to obtain or maintain single binocular vision. It has been shown that a vergence movement is induced not only by binocular depth but also by the changing size of the stimuli, which produces perception of motion in depth. That is, a monocular depth cue influences the direction of the eye movement, even when the eye movement contradicts depth from the disparity cue. Despite that a number of monocular depth cues are known, the influence on the vergence movement is known only with changing size. In this study, we focused on luminance contrast as a monocular depth cue and examined whether it influences the vergence movement. The stimuli were a Gabor patch with contrast changing sinusoidally in time at a given temporal frequency. When the observer looks at the stimuli, apparent depth changes with the contrast change. Eye movement measurements showed vergence movements synchronizing with luminance changes. Change in perceive...

P2-1: Visual Short-Term Memory Lacks Sensitivity to Stereoscopic Depth Changes but is Much Sensitive to Monocular Depth Changes

Depth from both binocular disparity and monocular depth cues presumably is one of most salient features that would characterize a variety of visual objects in our daily life. Therefore it is plausible to expect that human vision should be good at perceiving objects' depth change arising from binocular disparities and monocular pictorial cues. However, what if the estimated depth needs to be remembered in visual short-term memory (VSTM) rather than just perceived? In a series of experiments, we asked participants to remember depth of items in an array at the beginning of each trial. A set of test items followed after the memory array, and the participants were asked to report if one of the items in the test array have changed its depth from the remembered items or not. The items would differ from each other in three different depth conditions: (1) stereoscopic depth under binocular disparity manipulations, (2) monocular depth under pictorial cue manipulations, and (3) both stereoscopic and monocular depth....

Where do the eyes really go in the hollow-face illusion?

The hollow-face illusion refers to the finding that people typically perceive a concave (hollow) mask as being convex, despite the presence of binocular disparity cues that indicate the contrary. Unlike other illusions of depth, recent research has suggested that the eyes tend to converge at perceived, rather than actual, depths. However, technical and methodological limitations prevented one from knowing whether disparity cues may still have influenced vergence. In the current study, we presented participants with virtual normal or hollow masks and asked them to fixate the tip of the face’s nose until they had indicated whether they perceived it as pointing towards or away from them. The results showed that the direction of vergence was indeed determined by perceived depth, although vergence responses were both somewhat delayed and of smaller amplitude (by a factor of about 0.5) for concave than convex masks. These findings demonstrate how perceived depth can override disparity cues when it comes to vergence, albeit not entirely.

The integration of disparity and shading cues to 3D shape in dorsal visual cortex

The integration of disparity and shading cues to 3D shape in dorsal visual cortex