Disparity Modulation Research Articles

Late development of sensory thresholds for horizontal relative disparity in human visual cortex in the face of precocial development of thresholds for absolute disparity.

Immaturities exist at multiple levels of the developing human visual pathway, starting with immaturities in photon efficiency and spatial sampling in the retina and on through immaturities in early and later stages of cortical processing. Here we use Steady-State Visual Evoked Potentials (SSVEPs) and controlled visual stimuli to determine the degree to which sensitivity to horizontal retinal disparity is limited by the visibility of the monocular half-images, the ability to encode absolute disparity or the ability to encode relative disparity. Responses were recorded from male and female human participants at average ages of 5.3 +/- 1.6 months, 4.7 +/- 1.3 years, and 25.3 +/ -6 years. Horizontal disparity sensitivity was measured using planar stereograms that modulated absolute disparity and in stereograms portraying disparity gratings that additionally contained relative disparity. Disparity thresholds for absolute disparity changed little over development, but those for relative disparity changed by a factor of ∼10. SSVEPs were also recorded in response to contrast and blur modulation of dynamic random dot patterns to measure sensitivity to the spatio-temporal content of the monocular half-images. Equating subjective contrast and blur levels between infants, children and adults based on these measurements did not equate disparity sensitivity. The protracted developmental sequence for horizontal relative disparity coding shown in our measurements is not simply inherited from immaturities in encoding absolute disparity or retinal image contrast, but rather reflects immaturities in the computations needed to represent relative disparity that likely involve extra-striate cortical areas where relative disparity is first extracted.Significance Statement The lateral separation of the eyes creates horizontal image disparities that provide the primary cue for depth. These disparities reflect the distance of a point from the plane of fixation (absolute disparities) or depth relationships between two or more points in the image (relative disparity). By recording SSVEPs driven by disparity modulation and stimuli that contain only absolute disparity versus those that also contain relative disparity, we find that sensitivity to absolute disparity develops to near adult levels within the first 6 months of life, but that relative disparity develops beyond 5 years of age. These developmental changes are dissociable from changes in the visibility of the half-images and reflect specific immaturities in disparity processing.

Nested patterns of commensals and endosymbionts in microbial communities of mosquito vectors

BackgroundMosquitoes serve as vectors for numerous pathogens, posing significant health risks to humans and animals. Understanding the complex interactions within mosquito microbiota is crucial for deciphering vector-pathogen dynamics and developing effective disease management strategies. Here, we investigated the nested patterns of Wolbachia endosymbionts and Escherichia-Shigella within the microbiota of laboratory-reared Culex pipiens f. molestus and Culex quinquefasciatus mosquitoes. We hypothesized that Wolbachia would exhibit a structured pattern reflective of its co-evolved relationship with both mosquito species, while Escherichia-Shigella would display a more dynamic pattern influenced by environmental factors.ResultsOur analysis revealed different microbial compositions between the two mosquito species, although some microorganisms were common to both. Network analysis revealed distinct community structures and interaction patterns for these bacteria in the microbiota of each mosquito species. Escherichia-Shigella appeared prominently within major network modules in both mosquito species, particularly in module P4 of Cx. pipiens f. molestus, interacting with 93 nodes, and in module Q3 of Cx. quinquefasciatus, interacting with 161 nodes, sharing 55 nodes across both species. On the other hand, Wolbachia appeared in disparate modules: module P3 in Cx. pipiens f. molestus and a distinct module with a single additional taxon in Cx. quinquefasciatus, showing species-specific interactions and no shared taxa. Through computer simulations, we evaluated how the removal of Wolbachia or Escherichia-Shigella affects network robustness. In Cx. pipiens f. molestus, removal of Wolbachia led to a decrease in network connectivity, while Escherichia-Shigella removal had a minimal impact. Conversely, in Cx. quinquefasciatus, removal of Escherichia-Shigella resulted in decreased network stability, whereas Wolbachia removal had minimal effect.ConclusionsContrary to our hypothesis, the findings indicate that Wolbachia displays a more dynamic pattern of associations within the microbiota of Culex pipiens f. molestus and Culex quinquefasciatus mosquitoes, than Escherichia-Shigella. The differential effects on network robustness upon Wolbachia or Escherichia-Shigella removal suggest that these bacteria play distinct roles in maintaining community stability within the microbiota of the two mosquito species.

Disparity modulations from both fixational vergence and version contribute to stereopsis

Disparity modulations from both fixational vergence and version contribute to stereopsis

Automated image processing pipeline for adaptive optics scanning light ophthalmoscopy

To mitigate the substantial post-processing burden associated with adaptive optics scanning light ophthalmoscopy (AOSLO), we have developed an open-source, automated AOSLO image processing pipeline with both "live" and "full" modes. The live mode provides feedback during acquisition, while the full mode is intended to automatically integrate the copious disparate modules currently used in generating analyzable montages. The mean (±SD) lag between initiation and montage placement for the live pipeline was 54.6 ± 32.7s. The full pipeline reduced overall human operator time by 54.9 ± 28.4%, with no significant difference in resultant cone density metrics. The reduced overhead decreases both the technical burden and operating cost of AOSLO imaging, increasing overall clinical accessibility.

基于视差和条纹调制度分析的多物体场景分割

基于视差和条纹调制度分析的多物体场景分割

基于视差和条纹调制度分析的多物体场景分割

基于视差和条纹调制度分析的多物体场景分割

Dynamic Cancellation of Perceived Rotation from the Venetian Blind Effect.

Geometric differences between the images seen by each eye enable the perception of depth. Additionally, depth is produced in the absence of geometric disparities with binocular disparities in either the average luminance or contrast, which is known as the Venetian blind effect. The temporal dynamics of the Venetian blind effect are much slower (1.3 Hz) than those for geometric binocular disparities (4–5 Hz). Sine-wave modulations of luminance and contrast disparity, however, can be discriminated from square-wave modulations at 1 Hz, which suggests a non-linearity. To measure this non-linearity, a luminance or contrast disparity modulation was presented at a particular frequency and paired with a geometric disparity modulation that cancelled the perceived rotation induced by the luminance or contrast modulation. Phases between the luminance or contrast and the geometric modulation varied in 50 ms increments from −200 and 200 ms. When phases were aligned, observers perceived little or no rotation. When not aligned, a perceived rotation was induced by a contrast or luminance disparity that was then cancelled by the geometric disparity. This causes the perception of a slight jump. The Generalized Difference Model, which is linear in time, predicted a minimal probability in cases when luminance or contrast disparities occurred before the geometric disparities due to the slower dynamics of the Venetian blind effect. The Gated Generalized Difference Model, which is non-linear in time, predicted a minimal probability for offsets of 0 ms. Results followed the Gated model, which further suggests a non-linearity in time for the Venetian blind effect.

A systematic review of gut-immune-brain mechanisms in Autism Spectrum Disorder.

Despite decades of research, the etiological origins of Autism Spectrum Disorder (ASD) remain elusive. Recently, the mechanisms of ASD have encompassed emerging theories involving the gastrointestinal, immune, and nervous systems. While each of these perspectives presents its own set of supporting evidence, the field requires an integration of these modular concepts and an overarching view of how these subsystems intersect. In this systematic review, we have synthesized relevant evidences from the existing literature, evaluating them in an interdependent manner and in doing so, outlining their possible connections. Specifically, we first discussed gastrointestinal and immuno-inflammation pathways in-depth, exploring the relationships between microbial composition, bacterial metabolites, gut mucosa, and immune system constituents. Accounting for temporal differences in the mechanisms involved in neurodevelopment, prenatal and postnatal phases were further elucidated, where the former focused on maternal immune activation (MIA) and fetal development, while the latter addressed the role of immune dysregulation in contributing to atypical neurodevelopment. As autism remains, foremost, a neurodevelopmental disorder, this review presents an integration of disparate modules into a "Gut-Immune-Brain" paradigm. Existing gaps in the literature have been highlighted, and possible avenues for future research with an integrated physiological perspective underlying ASD have also been suggested.

Surface continuity and discontinuity bias the perception of stereoscopic depth.

Binocular disparity signals can provide high acuity information about the positions of points, surfaces, and objects in three-dimensional space. For some stimulus configurations, however, perceived depth is known to be affected by surface organization. Here we examine the effects of surface continuity and discontinuity on such surface organization biases. Participants were presented with a series of random dot surfaces, each with a cumulative Gaussian form in depth. Surfaces varied in the steepness of disparity gradients, via manipulation of the standard deviation of the Gaussian, and/or the presence of differing forms of surface discontinuity. By varying the relative disparity between surface edges, we measured the points of subjective equality, where surfaces of differing steepness and/or discontinuity were perceptually indistinguishable. We compare our results to a model that considers sensitivity to different frequencies of disparity modulation. Across a series of experiments, the observed patterns of change in points of subjective equality suggest that perceived depth is determined by the integration of measures of relative disparity, with a bias toward sharp changes in disparity. Such disparities increase perceived depth when they are in the same direction as the overall disparity. Conversely, perceived depth is reduced by the presence of sharp disparity changes that oppose the sign of the overall depth change.

The perceived depth from disparity as function of luminance contrast.

Does human vision show the contrast invariance expected of an ideal stereoscopic system for computing depth from disparity? We used random-dot stereograms to investigate the luminance contrast effect on perceived depth from disparity. The perceived depth of disparity corrugations was measured by adjusting the length of a horizontal line to match the perceived depth of the corrugations at various luminance contrasts. At each contrast, the perceived depth increased with disparity up to a critical value, decreasing with further increases in disparity. Both the maximum perceived depth and the disparity modulation level where this maximum occurred changed as a sigmoid function of luminance contrast. These results show that perceived depth from disparity depends in a complex manner on the luminance contrast in the image, providing significant limitations on depth perception at low contrasts in a lawful manner but that are incompatible with existing models of cortical disparity processing.

Pooled, but not single-neuron, responses in macaque V4 represent a solution to the stereo correspondence problem.

Binocular disparity is an important cue for depth perception. To correctly represent disparity, neurons must find corresponding visual features between the left- and right-eye images. The visual pathway ascending from V1 to inferior temporal cortex solves the correspondence problem. An intermediate area, V4, has been proposed to be a critical stage in the correspondence process. However, the distinction between V1 and V4 is unclear, because accumulating evidence suggests that the process begins within V1. In this article, we report that the pooled responses in macaque V4, but not responses of individual neurons, represent a solution to the correspondence problem. We recorded single-unit responses of V4 neurons to random-dot stereograms of varying degrees of anticorrelation. To achieve gradual anticorrelation, we reversed the contrast of an increasing proportion of dots as in our previous psychophysical studies, which predicted that the neural correlates of the solution to correspondence problem should gradually eliminate their disparity modulation as the level of anticorrelation increases. Inconsistent with this prediction, the tuning amplitudes of individual V4 neurons quickly decreased to a nonzero baseline with small anticorrelation. By contrast, the shapes of individual tuning curves changed more gradually so that the amplitude of population-pooled responses gradually decreased toward zero over the entire range of graded anticorrelation. We explain these results by combining multiple energy-model subunits. From a comparison with the population-pooled responses in V1, we suggest that disparity representation in V4 is distinctly advanced from that in V1. Population readout of V4 responses provides disparity information consistent with the correspondence solution.

Shading Beats Binocular Disparity in Depth from Luminance Gradients: Evidence against a Maximum Likelihood Principle for Cue Combination.

Perceived depth is conveyed by multiple cues, including binocular disparity and luminance shading. Depth perception from luminance shading information depends on the perceptual assumption for the incident light, which has been shown to default to a diffuse illumination assumption. We focus on the case of sinusoidally corrugated surfaces to ask how shading and disparity cues combine defined by the joint luminance gradients and intrinsic disparity modulation that would occur in viewing the physical corrugation of a uniform surface under diffuse illumination. Such surfaces were simulated with a sinusoidal luminance modulation (0.26 or 1.8 cy/deg, contrast 20%-80%) modulated either in-phase or in opposite phase with a sinusoidal disparity of the same corrugation frequency, with disparity amplitudes ranging from 0’-20’. The observers’ task was to adjust the binocular disparity of a comparison random-dot stereogram surface to match the perceived depth of the joint luminance/disparity-modulated corrugation target. Regardless of target spatial frequency, the perceived target depth increased with the luminance contrast and depended on luminance phase but was largely unaffected by the luminance disparity modulation. These results validate the idea that human observers can use the diffuse illumination assumption to perceive depth from luminance gradients alone without making an assumption of light direction. For depth judgments with combined cues, the observers gave much greater weighting to the luminance shading than to the disparity modulation of the targets. The results were not well-fit by a Bayesian cue-combination model weighted in proportion to the variance of the measurements for each cue in isolation. Instead, they suggest that the visual system uses disjunctive mechanisms to process these two types of information rather than combining them according to their likelihood ratios.

Dissociation of retinal and headcentric disparity signals in dorsal human cortex.

Recent fMRI studies have shown fusion of visual motion and disparity signals for shape perception (Ban et al., 2012), and unmasking camouflaged surfaces (Rokers et al., 2009), but no such interaction is known for typical dorsal motion pathway tasks, like grasping and navigation. Here, we investigate human speed perception of forward motion and its representation in the human motion network. We observe strong interaction in medial (V3ab, V6) and lateral motion areas (MT+), which differ significantly. Whereas the retinal disparity dominates the binocular contribution to the BOLD activity in the anterior part of area MT+, headcentric disparity modulation of the BOLD response dominates in area V3ab and V6. This suggests that medial motion areas not only represent rotational speed of the head (Arnoldussen et al., 2011), but also translational speed of the head relative to the scene. Interestingly, a strong response to vergence eye movements was found in area V1, which showed a dependency on visual direction, just like vertical-size disparity. This is the first report of a vertical-size disparity correlate in human striate cortex.

Consequences of traumatic brain injury for human vergence dynamics.

Purpose: Traumatic brain injury involving loss of consciousness has focal effects in the human brainstem, suggesting that it may have particular consequences for eye movement control. This hypothesis was investigated by measurements of vergence eye movement parameters.Methods: Disparity vergence eye movements were measured for a population of 123 normally sighted individuals, 26 of whom had suffered diffuse traumatic brain injury (dTBI) in the past, while the remainder served as controls. Vergence tracking responses were measured to sinusoidal disparity modulation of a random-dot field. Disparity vergence step responses were characterized in terms of their dynamic parameters separately for the convergence and divergence directions.Results: The control group showed notable differences between convergence and divergence dynamics. The dTBI group showed significantly abnormal vergence behavior on many of the dynamic parameters.Conclusion: The results support the hypothesis that occult injury to the oculomotor control system is a common residual outcome of dTBI.

Binocular contributions to linear vertical vection.

Compelling illusions of self-motion, known as vection, can be produced in a stationary observer by visual stimulation alone. The role of binocular vision and stereopsis in these illusions was explored in a series of three experiments. Previous research had provided evidence of stereoscopic enhancements for linear vection in depth (e.g., Palmisano, 1996, 2002). Here we examined for the first time the effects of binocular vision and stereopsis on linear vertical vection. Vertical vection was induced by the upward or downward translation of large stereoscopic surfaces. These surfaces were horizontally oriented depth corrugations produced by disparity modulation of patterns of persistent or short lifetime dot elements. We found that binocular viewing of such surfaces significantly increased the magnitudes and decreased the onset delays of vertical vection. Experiments utilizing short lifetime dot stereograms demonstrated that these particular binocular enhancements of vection were due to the motion of stereoscopically defined features.

Three Grades of Grammatical Involvement: Syntax from a Minimalist Perspective

AbstractThis article presents a Whig history of Minimalism, suggesting that it is the natural next step in the generative program initiated in the mid 1950s. The program so conceived has two prongs: (i) unifying the disparate modules by demonstrating that they are generated by the same basic operations and respect the same general conditions and (ii) assessing which of these basic operations and conditions are parochial to the faculty of language (FL) and which are reflect more general features of cognitive computation. What makes Minimalism ‘minimal’ is the conviction that the bulk of the operations and principles inFLare proprietary to that cognitive module. The article illustrates the aims of the project by discussing some ways of reducing Binding Theory to the theory of Movement.

Synchronized Audio-Visual Transients Drive Efficient Visual Search for Motion-in-Depth

In natural audio-visual environments, a change in depth is usually correlated with a change in loudness. In the present study, we investigated whether correlating changes in disparity and loudness would provide a functional advantage in binding disparity and sound amplitude in a visual search paradigm. To test this hypothesis, we used a method similar to that used by van der Burg et al. to show that non-spatial transient (square-wave) modulations of loudness can drastically improve spatial visual search for a correlated luminance modulation. We used dynamic random-dot stereogram displays to produce pure disparity modulations. Target and distractors were small disparity-defined squares (either 6 or 10 in total). Each square moved back and forth in depth in front of the background plane at different phases. The target’s depth modulation was synchronized with an amplitude-modulated auditory tone. Visual and auditory modulations were always congruent (both sine-wave or square-wave). In a speeded search task, five observers were asked to identify the target as quickly as possible. Results show a significant improvement in visual search times in the square-wave condition compared to the sine condition, suggesting that transient auditory information can efficiently drive visual search in the disparity domain. In a second experiment, participants performed the same task in the absence of sound and showed a clear set-size effect in both modulation conditions. In a third experiment, we correlated the sound with a distractor instead of the target. This produced longer search times, indicating that the correlation is not easily ignored.

Synchronized audio-visual transients drive efficient visual search for motion-in-depth

In natural audio-visual environments, a change in depth is usually correlated with a change in loudness. In the present study, we investigated whether correlating disparity and loudness provides a functional advantage in binding disparity and sound amplitude in a visual search paradigm. To test this assumption, we used a method similar to that used by Van der Burg et al. (2008) to show that non-spatial modulations of loudness can drastically improve spatial visual search for a correlated luminance modulation. Subsequently (2010), they varied the shape of temporal modulation and demonstrated that transient events (square modulations) are required for this search efficiency, and that sinusoidal audiovisual modulations do not support efficient search. We used dynamic random-dot stereogram displays to produce pure disparity modulations. Target and distractors were 0.35 × 0.35 degrees disparity-defined squares (either 6 or 10 in total) presented on a ring at 2.5 deg eccentricity. Each square moved back and forth in depth from zero to +12 arcmin (crossed) disparity at different phases. The target's depth modulation was synchronized with an amplitude-modulated 500 Hz tone. Visual and auditory modulations were always congruent (both sinewave or squarewave). Four observers were asked to give speeded responses in a discrimination task on the target. Because binocular matching processes are known to favor smooth over abrupt changes of disparity across space and time, we expected the sine modulation condition to be at least as efficient as the square modulation in supporting efficient search. However, results show a significant improvement in visual search in the square condition compared to the sine condition, suggesting that transient auditory information can efficiently drive visual search in the disparity domain. In a second experiment, correlating sound with a distractor led to longer search times, indicating that the correlation is not easily ignored.

Multiple channels for horizontal, but only one for vertical corrugations? A new look at the stereo anisotropy

Stereo vision displays a well-known anisotropy: disparity-defined slant is easier to detect for rotations about a horizontal axis than about a vertical axis, and low-frequency sinusoidal depth corrugations are easier to detect when the corrugations are horizontal than when they are vertical. Here, we determined disparity thresholds for vertically and horizontally oriented depth corrugations with both sinusoidal and square-wave profiles. We found that the orientation anisotropy for square waves is much weaker than for sine waves and is almost independent of frequency. This weaker anisotropy for square waves can be explained by considering the Fourier harmonics present in the stimulus. Using linear models imported from the luminance and texture perception domain, the disparity thresholds for square waves can be very well predicted from those for sine waves, for both horizontally and vertically oriented corrugations. For horizontally oriented corrugations, models based on the root mean square of the output of a single linear channel or the output of multiple linear channels worked equally well. This is consistent with previous evidence suggesting that stereo vision has multiple channels tuned to different spatial frequencies of horizontally oriented disparity modulations. However, for vertically oriented corrugations, only the root mean squared output of a single linear channel explained the data. We suggest that the stereo anisotropy may arise because the stereo system possesses multiple spatial frequency channels for detecting horizontally oriented modulations in horizontal disparity, but only one for vertically oriented modulations.

A Self in the Mirror: Mirror Neurons, Self-Referential Processing, and Substance Use Disorders

Mirror neurons in the Rhesus monkey and the mirror neuron system (MNS) in the human brain respond to actions that are executed by self and observed in another animal or person (i.e., imitated). The status of the MNS in humans is unclear, with some positive and some negative findings using electroencephalography and functional neuroimaging. We suggest that the fronto-parietal MNS may be disparate nodes or modules of a (poorly understood) self-referential processing system that is important in drug abuse and addiction. We then discuss some theories of the etiology of these disorders that emphasize the self. A modular approach to human brain organization and function (as opposed to strict localizationist or extreme globalist models) may resolve some issues surrounding the MNS and drug abuse.