Contour Interaction Research Articles

Landolt C-Tests With "Fixed" Arcmin Separations Detect Amblyopia But Underestimate Crowding in Moderate-to-Severe Amblyopic Children and Adults.

Crowding is exaggerated in central vision of strabismic amblyopia, impacting on reading ability. Crowding magnitude and interocular differences (IODs) in acuity are indicators for detection, assessment, and monitoring of treatment. Lateral masking (including contour interaction) also affects acuity and can mimic or ameliorate crowding. We investigated lateral masking/contour interaction and crowding impact on crowding magnitude and IOD measures in healthy and amblyopic pediatric and juvenile/adult groups using two Landolt C-tests with "fixed" arcmin separations. Acuity (logMAR) was measured with Landolt C-tests with specified 2.6' ("crowded") and 35' ("uncrowded") separations. Crowding magnitudes (crowded - uncrowded acuities) and IODs were calculated. Participants were 69 subjects with strabismic amblyopia (n = 39 pediatric, i.e. children ≤8years of age), 31 subjects with anisometropic amblyopia (n = 14 pediatric), and 76 healthy controls (n = 36 pediatric). Subjects with amblyopia were subgrouped by acuity as low severity (<0.4 logMAR) or high severity (≥0.4 logMAR) using the 35' separation C-test. Crowding magnitudes were greater in strabismic than in anisometropic amblyopia and control/fellow eyes. They were higher in pediatric control/fellow eyes than in juvenile/adult eyes. In high severity strabismic amblyopia, crowding magnitudes progressively and significantly reduced (slope = -0.17 ± 0.07, P < 0.05) with worsening acuity. IODs for this group were higher on the 2.6' C-test, but lower than expected. In high severity pediatric subjects with anisometropic amblyopia, seven of eight had lower IODs measured with the "crowded" than the "uncrowded" C-tests. These C-tests detect amblyopia but underestimate crowding in children and adults with high severity strabismic amblyopia. Separate isolated optotype acuity and crowding distance tests may better target specific functions, while minimizing the impact of masking.

Distinct Contributions of Alpha and Beta Oscillations to Context-Dependent Visual Size Perception.

Previous studies have proposed two cognitive mechanisms responsible for the Ebbinghaus illusion effect, i.e., contour interaction and size contrast. However, the neural underpinnings of these two mechanisms are largely unexplored. The present study introduced binocular depth to the Ebbinghaus illusion configuration and made the central target appear either in front of or behind the surrounding inducers in order to disturb size contrast instead of contour interaction. The results showed that the illusion effect, though persisted, was significantly reduced under the binocular depth conditions. Notably, the target with a larger perceived size reduced early alpha-band power (8-13Hz, 0-100ms after stimulus onset) at centroparietal sites irrespective of the relative depth of the target and the inducers, with the parietal alpha power negatively correlated with the illusion effect. Moreover, the target with a larger perceived size increased the occipito-parietal beta-band power (14-25Hz, 200-300ms after stimulus onset) under the no-depth condition, and the beta power was positively correlated with the illusion effect when the depth conditions were subtracted from the no-depth condition. The findings provided neurophysiological evidence in favor of the two cognitive mechanisms of the Ebbinghaus illusion by revealing that early alpha power is associated with low-level contour interaction and late beta power is linked to high-level size contrast, supporting the claim that neural oscillations at distinct frequency bands dynamically support different aspects of visual processing.

The curvature effect: Approach-avoidance tendencies in response to interior design stimuli

Previous research suggests that curved vs. angular interior environments trigger affective (e.g., preference) and behavioural (e.g., approach-avoidance) responses. Yet, behavioural responses have mainly been assessed through explicit evaluations, such as self-reports. We aimed to investigate this phenomenon more ‘implicitly’ using a battery of reaction time (RT) paradigms, particularly focusing on approach-avoidance tendencies.Online participants (initial N = 219) undertook four randomized tasks involving 20 photo-realistic living room images matched for contours (angular vs. curved) and styles (modern vs. classic). We intended to capture attentional (Dot Probe Task [DPT]), motoric (Approach Avoidance Task [AAT]), as well as associative-semantic (Implicit Association Task [IAT]) and -motoric (Stimulus Response Compatibility Task [SRCT]) biases towards contours.The DPT and AAT showed no significant effects. However, we observed a significant congruency effect in the IAT (F(1,192) = 97.51, p < .001, ƞ2 = 0.074), whereby images were assigned faster into categories when those were curved-approach and angular-avoid (instead of curved-avoid, angular-approach). Additionally, we found a significant direction x contour interaction (F(1,179) = 7.08, p = .009, ƞ2 = 0.004) in the SRCT, attributable to within-curvature differences (faster approach compared to avoidance). Moreover, within-directions comparisons revealed a faster avoidance of angular than curved conditions.Our findings confirmed an effect of contours on approach-avoidance tendencies using RT paradigms. We identified semantic associations between curvature and approach and angularity and avoidance behaviour. Furthermore, we demonstrated differential approach (faster) – avoidance (slower) representations in relation to curvature rather than an avoidance of angularity. These findings may hint towards (partially) automatic responses to contours in interior design, which in addition to self-reports, should be further researched concerning criterion validity, such as in correlation with physiological and psychological reactions to built spaces.

Cortical distance unifies the extent of parafoveal contour interactions.

It is well known that crowding, the disruptive influence of flanking items on identification of targets, is the primary limiting factor to object identification in the periphery, while limits in the fovea are more determined by the ability to resolve individual items. Whether this is a dichotomous or merely a quantitative difference, and the transition between these two regimes, has remained unexplained. Here, using an adaptive optics system for optimal control of optical and stimulus factors, we measured threshold acuity for identification of Tumbling Es flanked by bars at a variety of flanker spacings and eight eccentricities in the parafovea. Thresholds at each eccentricity were influenced by resolution, contour interaction, and a saturating pedestal effect. When target-flanker spacing was plotted in terms of cortical distance, a single canonical clipped-line fit unified the resultant curves. The critical spacing for letters flanked by bars was found to be 1.3 to 1.5 cortical millimeters, corresponding to approximately 0.1*E outside the fovea.

Number of flankers influences foveal crowding and contour interaction differently

Nearby flanking objects degrade visual resolution. If the flankers are similar to the acuity target, this influence is called crowding (CW), whereas if the flanking stimuli are simple bars then the phenomenon is known as contour interaction (CI). The aim of this study was to compare the influence of the number and position of flankers on foveal CW and CI to investigate possible differences in mechanism of these two effects. Five normal observers viewed single, foveally presented Sloan letters surrounded by 1, 2 or 4 flankers (either a Sloan letter or one-stroke-width bars), presented at several edge-to-edge separations. Single flankers were presented in the right, left, top or bottom position, 2 flankers were placed equally to the right and left or top and bottom of the central target, and 4 flankers were equally spaced in all four directions. Percent correct letter identification was determined for each type, number, position and separation of flankers and confusion matrices were constructed for separations equal to 20% and 100% letter width. Increasing the number of flankers caused an increase in the magnitude of both phenomena. CW showed a greater magnitude than CI for higher numbers of flankers. Analysis of confusion matrices suggests that in addition to the edge-to-edge interaction that appears to mediate CI, letter substitution and feature pooling contribute significantly to CW when higher numbers of flankers are presented. Foveal CW is more strongly influenced by an increase in the number of flankers than CI, which can be explained by the presence of additional interaction effects.

Low-spatial-frequency priming potentiates the high-level mechanisms of contextual influence

The context sensitivity of visual size perception can be enhanced by prior exposure to low-spatial-frequency (LSF) relative to high-spatial-frequency information. Whether LSF priming affects low- or high-level mechanisms of contextual influence remains to be clarified. By using the Ebbinghaus illusion, which is a classic example of context-dependent size perception, we reduced the lightness contrast of surrounding inducers relative to the background and the shape similarity of the central target and surrounding inducers to diminish or eliminate low-level contour interaction and high-level size contrast, respectively. The results showed that LSF-related enhancement of context influence was unaffected by a change to the surround elements’ contrast but not by a change to the shape similarity between the target and surround. The findings provide evidence that LSF priming primarily affects high-level rather than low-level mechanisms of contextual influence, possibly by weakening the suppressive function of feedback connections from higher visual regions to the early visual cortex.

Perceptual grouping leads to objecthood effects in the Ebbinghaus illusion.

The Ebbinghaus illusion is argued to be a product of low-level contour interactions or a higher cognitive comparison process. We examined the effect of grouping on the illusion by manipulating objecthood, i.e., the degree to which an object is a cohesive perceptual entity. We hypothesized that reduced objecthood would decrease the illusion magnitude, because the objects become less efficient in the comparison process. To test this hypothesis, we used a version of the illusion where the target and flanking objects were squares that were composed from their corners or sides. Degree of objecthood was manipulated by changing the gap size or rotation angle of the elements constructing the objects, so that larger gaps and angles produced less cohesive objects than smaller. Participants performed an adjustment procedure on the test target to match a control target in size. In addition, subjective reports of the objects’ shape were collected as a measure of perceived shape. Our results show decreased illusion magnitude with increasing gap size and rotation angle. Surprisingly, the perceived shape of the objects did not correlate with illusion magnitude. These results provide novel evidence of the role of mid-level processes in the Ebbinghaus illusion and point to a dissociation between subjective and objective measures of objecthood.

Error-controlled adaptive LR B-splines XIGA for assessment of fracture parameters in through-cracked Mindlin-Reissner plates

This paper presents an error-controlled adaptive extended isogeometric analysis (XIGA) for assessment of fracture behavior for through-cracked Mindlin-Reissner plates. The locally refined (LR) B-splines that facilitate the local refinement are used as the basis functions for the approximations, while the kinematics of plates are described in terms of the Mindlin-Reissner plate theory. Appropriate enrichment functions for cracked plates are incorporated into the formulation to represent geometrically displacement discontinuities across the crack faces and singularity of the stress in the vicinity at the crack tips, thus cracks are modeled topologically independent of the computational mesh. Here we extend the Zienkiewicz-Zhu method-based error estimation to the XIGA formulation for cracks in Mindlin-Reissner plates such that non-smoothnesses and stress singularity are reflected accurately. We conduct the error-controlled adaptivity for local mesh refinement to enhance the accuracy and performance. Fracture parameters (i.e., mixed-mode intensity factors) are calculated through the contour interaction integral method in the context of Mindlin-Reissner plate theory. Several numerical examples for through-cracked plates are studied to show the accuracy and effectiveness of the proposed formulation in modeling fracture of cracked moderately thick plates.

ДВУХКОНТУРНАЯ ВАЛЮТНО-ФИНАНСОВАЯ СИСТЕМА КАК ИНСТРУМЕНТ РАЗВИТИЯ НАЦИОНАЛЬНОЙ ЭКОНОМИКИ РОССИЙСКОЙ ФЕДЕРАЦИИ И ОБЕСПЕЧЕНИЯ ЕЕ СУВЕРЕНИТЕТА

The article is devoted to the ensuring the sovereignty of the national economy of the Russian Federation. The authors believe that the basis for achieving this goal is the creation of an investment circuit in the structure of the Russian financial system. The article presents an analysis of the structural levels of the modern international monetary and financial system and identifies the features of the functioning of countries belonging to different levels. The authors propose to expand the gold and foreign exchange reserves at the expense of a group of dual goods and create commodity and currency reserves, by help of which will then launch the internal investment circuit. The interaction of contours is proposed to be carried out using a new financial instrument “calculated gold”, which is formed according to the author’s algorithm.

Upturn of the contour-interaction function at small flanking bar-to-target separations

Nearby flanking bars degrade letter identification and resolution, a phenomenon known as contour interaction. However, many previous studies found that the relationship between foveal letter identification and flanker separation is non-monotonic, with an upturn in performance at very small target-to-flanker separations. Here, we replicate this observation and show that a similar upturn occurs also for targets presented at 5 deg in the inferior field, if the target-to-flanker separation is sufficiently small. The presence and magnitude of the observed performance upturn depends on the flanking-bar width, being more evident for narrower compared to wider flanking bars. We interpret our results to indicate that neural interactions between nearby contours reduce performance when the target and flanking bars form discrete neural images. At sufficiently small separations, the images of the target and flanking bars can not be distinguished and performance is governed by the contrast of the target in the blended neural image.

Contrast Energy and Contour Interaction.

Contour interaction describes an impairment of visual acuity produced by nearby flanking features, which exerts a significant impact in many clinical tests of visual acuity. Our results indicate that the magnitude of interaction depends either on the flanker contrast energy (i.e., the product of flanker contrast and width) or the flanker contrast alone, depending on the contrast energy of the flankers. The discrimination of acuity targets is impaired by the presence of nearby flanking contours, a phenomenon known as contour interaction. In this study, we measured percent correct identification for threshold size, high-contrast Sloan letters at the fovea and at 5° in the inferior visual field for different combinations of flanking-bar width, and Weber contrast corresponding to specific fixed values of contrast energy (width × contrast, in %-min arc). For flanking bars with low-contrast energy, contour interaction exhibited no systematic dependence on the flanking-bar width. However, when the flanking bars had higher contrast energy, narrower high-contrast bars produced significantly greater contour interaction than wider bars of lower contrast. The results are consistent with the interpretation that contour interaction depends primarily on the contrast energy of flanking contours when their contrast energy is low. As the contrast energy of the flanking contours increases, the magnitude of contour interaction depends on the flanker contrast. For high-contrast flanking contours, the magnitude of contour interaction saturates when the width of the flanking contours is approximately 20% of letter size.

Adaptive orthotropic XIGA for fracture analysis of composites

This paper is concerned with the numerical investigation of fracture mechanics parameters for cracked orthotropic composite structures by using an efficient computational approach. The adaptive extended isogeometric analysis (XIGA) based on locally refined (LR) B-splines is thus developed. This adaptive XIGA is enhanced by both signed-distance and orthotropic crack-tip enrichment functions to represent strong discontinuity and singularity induced by crack, respectively. In addition, to improve the integration accuracy, the ‘sub-triangle’ and ‘almost polar’ techniques are adopted for the cut and crack tip elements, respectively. For adaptivity, the smoothed stress field is achieved to develop the posteriori error estimator based local refinement, according to the Zienkiewicz–Zhu estimation. Such posteriori error estimator is then used to determine refinement domains, where the local refinement takes place. The proposed approach is applied for fracture analyses of orthotropic composites, in which the stress intensity factors (SIFs) are evaluated using the contour interaction integral technique. The accuracy of the proposed adaptive orthotropic XIGA is validated through a comparison of SIFs obtained from the proposed method and the available reference solutions. Furthermore, numerical results show that the convergence rate of the adaptive local refinement is faster than that of the global refinement approach.

Fracture modeling with the adaptive XIGA based on locally refined B-splines

This paper aims at investigating fracture behavior of single and multiple cracks in two-dimensional solids by an adaptive extended isogeometric analysis (XIGA) based on locally refined (LR) B-splines. The adaptive XIGA is capable of modeling cracks without considering the location of crack faces due to the local enrichment technique based on partition-of-unity concept. The XIGA approximation is locally enriched by Heaviside function and crack tip enrichment functions to capture the discontinuity across crack faces and singularity in the vicinity of crack tips. The LR B-splines, which are generalized by B-splines and NURBS, not only inherent desirable properties of the B-splines and NURBS but also can be locally refined, ideally suitable for adaptive analysis. Structured mesh refinement strategy is applied to perform local refinement for LR B-splines based on a posteriori error estimator. According to the recovery technique proposed by Zienkiewicz and Zhu, the smoothed strain field is obtained to construct the posteriori error estimation based local refinement. The stress intensity factors (SIFs) are evaluated using the contour interaction integral technique. Several benchmark numerical examples are illustrated in comparison to analytical or reference solutions to verify the accuracy and efficiency of the developed approach. The proposed adaptive XIGA method is also applied to a curved crack, multiple cracks and complicated structure with a crack, which sufficiently presents the applicability of the proposed method in crack modeling. In addition, the convergence rate of the adaptive local refinement strategy is numerically studied and compared with that of the global refinement approach. The convergence rate of the adaptive local refinement is shown to be faster than that of the global refinement.

Method for preliminary crossing, niveling of flowering caisson type pneumo-structure and pressure of the Earth basis

The prediction of the cutting force of the knives of contouring hydraulic structures of the sinking type (caisson) is not solved unambiguously in hydrotechnical science, and its pre-fixation is impossible without additional, costly bottom processing, which leads to limited use of contemporary and economical conversions such as large-diameter pilots, floating bottomless moorings and other gravitational hydraulic constructions with contour interactions with the bottom. The essence of the problem is to create a method of designing the basic contour of a new type of floating caisson, leveling a gear made up of one or more caissons, a continuous consolidation of the earth's foundation under the main caisson contour, pre-stressing of the ground foundation the main caisson contour with loads greater than operational in case of necessity of subsequent filling with another contractor by raising a water column above the average water level in the caissons working chambers after laying on the bottom, keeping the raised water volume above the average water level to the project elevation, redistributing the weight of the raised and retained water volume as a gravity fill in operating conditions.

THE OBJECTIVES AND MECHANISMS OF THE AGENCIES OF THE CLUSTER MANAGEMENT TO ENSURE ITS EFFICIENT OPERATION

Purpose:justification of structure of elements and structure of a control system of sectoral-territorial innovative clusters.Methods:article is based on the analysis of the international and domestic experience of creation of control systems of innovative clusters. By her preparation methods of the theoretical, functional and structural analysis and also business simulation are used.Results:following the results of the conducted research it is proved that at creation of a control system of sectoral and territorial innovative clusters (STIC) it is necessary to be guided by three main imperatives. The first consists that if we form a control system of a cluster, then it is necessary and to operate with categories of the theory of management when determining her functions, but not activities of this or that body as it is accepted in domestic practice today. The second consists in need of formal addition of the functions which are carried out by consultative governing body (supervisory board), the providing activity of quick and administrative body of a cluster (management company). And the third in use of design and functional approach to creation of a control system adequate to problems of a cluster.Conclusions and Relevance:STIC control system besides the functions having to management of a cluster direct reference is designed to solve a problem of ensuring interaction of external and internal contours of his business model. For this purpose the recommended structure of a control system, according to results of a research, has to include: The Ministry of Economic Development of the subject of Federation in which the cluster is located; specialized department of Minpromtorg of Russia; this or that state corporation (in case anchor residents of a cluster are its part); general meeting of participants of a cluster; supervisory board and management company. Realization of policy, the strategy and projects directed to formation and strengthening of network interaction of its participants will act as the main form of rendering impact of a control system of a cluster on his development.

THE OBJECTIVES AND MECHANISMS OF THE AGENCIES OF THE CLUSTER MANAGEMENT TO ENSURE ITS EFFICIENT OPERATION

Purpose: justification of structure of elements and structure of a control system of sectoral-territorial innovative clusters. Methods: article is based on the analysis of the international and domestic experience of creation of control systems of innovative clusters. By her preparation methods of the theoretical, functional and structural analysis and also business simulation are used. Results: following the results of the conducted research it is proved that at creation of a control system of sectoral and territorial innovative clusters (STIC) it is necessary to be guided by three main imperatives. The first consists that if we form a control system of a cluster, then it is necessary and to operate with categories of the theory of management when determining her functions, but not activities of this or that body as it is accepted in domestic practice today. The second consists in need of formal addition of the functions which are carried out by consultative governing body (supervisory board), the providing activity of quick and administrative body of a cluster (management company). And the third in use of design and functional approach to creation of a control system adequate to problems of a cluster. Conclusions and Relevance: STIC control system besides the functions having to management of a cluster direct reference is designed to solve a problem of ensuring interaction of external and internal contours of his business model. For this purpose the recommended structure of a control system, according to results of a research, has to include: The Ministry of Economic Development of the subject of Federation in which the cluster is located; specialized department of Minpromtorg of Russia; this or that state corporation (in case anchor residents of a cluster are its part); general meeting of participants of a cluster; supervisory board and management company. Realization of policy, the strategy and projects directed to formation and strengthening of network interaction of its participants will act as the main form of rendering impact of a control system of a cluster on his development.

Contour interaction under photopic and scotopic conditions.

In the present study, we asked whether contour interaction undergoes significant changes for different luminance levels in the central and peripheral visual field. This study included nine normal observers at two laboratories (five at Palacky University Olomouc, Czech Republic and four at the University of Houston, USA). Observers viewed a randomly selected Sloan letter surrounded by four equally spaced bars for several separations measured edge-to-edge in min arc. Stimuli were viewed foveally under photopic and mesopic luminances and between 5° and 12° peripherally for four different background luminances of the display monitors, corresponding to photopic, mesopic, scotopic, and dim scotopic levels. The extent of the contour interaction in the fovea is approximately 20 times smaller than in the periphery. Whereas the magnitude of foveal contour interaction markedly decreases with decreasing luminance, no consistent luminance-induced change occurs in peripheral contour interaction. The extent of contour interaction does not scale with the size of the target letter, either in the fovea or peripherally. The results support a neural origin of contour interaction consistent with the properties of center-surround antagonism.

Foveal Crowding Resolved

Crowding is the substantial interference of neighboring items on target identification. Crowding with letter stimuli has been studied primarily in the visual periphery, with conflicting results for foveal stimuli. While a cortical locus for peripheral crowding is well established (with a large spatial extent up to half of the target eccentricity), disentangling the contributing factors in the fovea is more challenging due to optical limitations. Here, we used adaptive optics (AO) to overcome ocular aberrations and employed high-resolution stimuli to precisely characterize foveal lateral interactions with high-contrast letters flanked by letters. Crowding was present, with a maximal edge-to-edge interference zone of 0.75-1.3 minutes at typical unflanked performance levels. In agreement with earlier foveal contour interaction studies, performance was non-monotonic, revealing a recovery effect with proximal flankers. Modeling revealed that the deleterious effects of flankers can be described by a single function across stimulus sizes when the degradation is expressed as a reduction in sensitivity (expressed in Z-score units). The recovery, however, did not follow this pattern, likely reflecting a separate mechanism. Additional analysis reconciles multiple results from the literature, including the observed scale invariance of center-to-center spacing, as well as the size independence of edge-to-edge spacing.

Is the Ebbinghaus illusion a size contrast illusion?

The Ebbinghaus illusion, in which a central target surrounded by larger context figures looks smaller than when surrounded by smaller context figures, is usually classified as a size contrast illusion. Thus “size contrast” is the dominant account of this effect. However, according to an alternative “contour interaction” account this phenomenon has little to do with size contrast but is rather caused by distance-dependent attractive and repulsive interactions between neural representation of contours. Here evidence is presented against the size contrast account and consistent with the contour interaction account. Experiment 1 was a control study confirming that the illusion can be obtained using displays consisting only of squares, which are more convenient to manipulate than the standardly used circles. In Experiment 2, the standard configuration involving small context figures surrounding the target was compared to a novel configuration, which involved many “spread” small context figures. The illusory effect of the standard context was stronger than the illusory effect of the spread context, in accord with the prediction of the contour interaction account, and contrary to the prediction of the size contrast account. In Experiment 3 two novel configurations were used, based on standard and spread contexts. The results were in accord with the prediction of the contour interaction account, whereas the size contrast account had no prediction because the stimuli did not involve conventional size contrast. Additional aspects of the stimuli and an account of the illusion based on a perspective interpretation are also discussed.

A closer look at four-dot masking of a foveated target.

Four-dot masking with a common onset mask was recently demonstrated in a fully attended and foveated target (Filmer, Mattingley & Dux, 2015). Here, we replicate and extend this finding by directly comparing a four-dot mask with an annulus mask while probing masking as a function of mask duration, and target-mask separation. Our results suggest that while an annulus mask operates via spatially local contour interactions, a four-dot mask operates through spatially global mechanisms. We also measure how the visual system’s representation of an oriented bar is impacted by a four-dot mask, and find that masking here does not degrade the precision of perceived targets, but instead appears to be driven exclusively by rendering the target completely invisible.