Neural responses to reflection symmetry for shapes defined by binocular disparity, and for shapes perceived as regions of background.

Human perception of symmetry is associated with activation in an extended network of extrastriate visual areas. This activation generates an ERP called the Sustained Posterior Negativity (SPN). In most studies so far, the stimuli have been defined by luminance. We tested whether the SPN is present when stimuli are defined by stereoscopic disparity using random dot stereograms (RDS). In Experiment 1, we compared the SPN signal for contours specified by binocular disparity and contours specified by monocular cues. The SPN was equivalent, suggesting that the type of contour does not alter the SPN signal. In Experiment 2 we exploited the unique property of RDS to provide unambiguous figure-ground arrangements. Psychophysical work has shown that symmetry is more easily detected when it is a property of a single object (i.e., within a figure), compared to a property of a gap between two objects (i.e., the ground). Therefore, the target regions in this experiment could either be foreground or background. The SPN onset was delayed when the symmetry was in a ground region. This may be because object formation interferes with the processing of shape information in the ground region.

Interobserver variability in quality assessment of magnetic resonance images.

BACKGROUND: The perceptual quality of magnetic resonance (MR) images influences diagnosis and may compromise the treatment. The purpose of this study was to evaluate how the image quality changes influence the interobserver variability of their assessment. METHODS: For the variability evaluation, a dataset containing distorted MRI images was prepared and then assessed by 31 experienced medical professionals (radiologists). Differences between observers were analyzed using the Fleiss' kappa. However, since the kappa evaluates the agreement among radiologists taking into account aggregated decisions, a typically employed criterion of the image quality assessment (IQA) performance was used to provide a more thorough analysis. The IQA performance of radiologists was evaluated by comparing the Spearman correlation coefficients, ρ, between individual scores with the mean opinion scores (MOS) composed of the subjective opinions of the remaining professionals. RESULTS: The experiments show that there is a significant agreement among radiologists (κ=0.12; 95% confidence interval [CI]: 0.118, 0.121; P<0.001) on the quality of the assessed images. The resulted κ is strongly affected by the subjectivity of the assigned scores, separately presenting close scores. Therefore, the ρ was used to identify poor performance cases and to confirm the consistency of the majority of collected scores (ρmean = 0.5706). The results for interns (ρmean = 0.6868) supports the finding that the quality assessment of MR images can be successfully taught. CONCLUSIONS: The agreement observed among radiologists from different imaging centers confirms the subjectivity of the perception of MR images. It was shown that the image content and severity of distortions affect the IQA. Furthermore, the study highlights the importance of the psychosomatic condition of the observers and their attitude.

Impairment of cyclopean surface processing by disparity-defined masking stimuli.

Binocular disparity signals allow for the estimation of three-dimensional shape, even in the absence of monocular depth cues. The perception of such disparity-defined form depends, however, on the linkage of multiple disparity measurements over space. Performance limitations in cyclopean tasks thus inform us about errors arising in disparity measurement and difficulties in the linkage of such measurements. We used a cyclopean orientation discrimination task to examine the perception of disparity-defined form. Participants were presented with random-dot sinusoidal modulations in depth and asked to report whether they were clockwise or counter-clockwise rotated. To assess the effect of different noise structures on measurement and linkage processes, task performance was measured in the presence of binocular, random-dot masks, structured as either antiphase depth sinusoids, or as random distributions of dots in depth. For a fixed number of surface dots, the ratio of mask-to-surface dots was varied to obtain thresholds for orientation discrimination. Antiphase masks were found to be more effective than random depth masks, requiring a lower mask-to-surface dot ratio to inhibit performance. For antiphase masks, performance improved with decreased cyclopean frequency, increased disparity amplitude, and/or an increase in the total number of stimulus dots. Although a cross-correlation model of disparity measurement could account for antiphase mask performance, random depth masking effects were consistent with limitations in relative disparity processing. This suggests that performance is noise-limited for antiphase masks and complexity-limited for random masks. We propose that use of differing mask types may prove effective in understanding these distinct forms of impairment.

Hole superiority effect with 3D figures formed by binocular disparity.

The global-first theory of topological perception claims that topological perception is prior to the perception of local features (e.g., Chen, 1982, 2005). Our previous studies demonstrated a hole superiority effect (HSE): Figures with holes are more detectable than figures without holes. Such an HSE was shown with figures formed by either orientation-defined texture (Zhang, 2009) or a black-and-white contrast (Meng, Cui, Zhou, Chen, & Ma, 2012). The present study used binocular disparity as one more organizing factor for testing the abstract nature of the HSE, indicating holes, as a typical kind of topological invariance, are represented in vision independent of the features that were forming the holes. The disparity-forming figures were well controlled for luminance, spatial frequency, subjective contours, and other nontopological factors, which are commonly considered as counter explanations against the topological theory.

Shape from Contour: Computation and Representation.

The human visual system reliably extracts shape information from complex natural scenes in spite of noise and fragmentation caused by clutter and occlusions. A fast, feedforward sweep through ventral stream involving mechanisms tuned for orientation, curvature, and local Gestalt principles produces partial shape representations sufficient for simpler discriminative tasks. More complete shape representations may involve recurrent processes that integrate local and global cues. While feedforward discriminative deep neural network models currently produce the best predictions of object selectivity in higher areas of the object pathway, a generative model may be required to account for all aspects of shape perception. Research suggests that a successful model will account for our acute sensitivity to four key perceptual dimensions of shape: topology, symmetry, composition, and deformation.

Costs of Selective Attention: When Children Notice What Adults Miss.

One of the lawlike regularities of psychological science is that of developmental progression-an increase in sensorimotor, cognitive, and social functioning from childhood to adulthood. Here, we report a rare violation of this law, a developmental reversal in attention. In Experiment 1, 4- to 5-year-olds ( n = 34) and adults ( n = 35) performed a change-detection task that included externally cued and uncued shapes. Whereas the adults outperformed the children on the cued shapes, the children outperformed the adults on the uncued shapes. In Experiment 2, the same participants completed a visual search task, and their memory for search-relevant and search-irrelevant information was tested. The young children outperformed the adults with respect to search-irrelevant features. This demonstration of a paradoxical property of early attention deepens current understanding of the development of attention. It also has implications for understanding early learning and cognitive development more broadly.

Gradients of relative disparity underlie the perceived slant of stereoscopic surfaces.

Perceived stereoscopic slant around a vertical axis is strongly underestimated for isolated surfaces, suggesting that neither uniocular image compression nor linear gradients of absolute disparity are very effective cues. However, slant increases to a level close to geometric prediction if gradients of relative disparity are introduced, for example by placing flanking frontal-parallel surfaces at the horizontal boundaries of the slanted surface. Here we examine the mechanisms underlying this slant enhancement by manipulating properties of the slanted surface or the flanking surfaces. Perceived slant was measured using a probe bias method. In Experiment 1, an outlined surface and a randomly textured surface showed similar slant underestimation when presented in isolation, but the enhancement in slant produced by flankers was significantly greater for the textured surface. In Experiment 2, we degraded the relative disparity gradient by (a) reducing overall texture density, (b) reducing flanker width, or (c) adding disparity noise to the flankers. Density had no effect while adding noise to the flankers, or reducing their width significantly decreased perceived slant of the central surface. These results support the view that the enhancement of slant produced by adding flanking surfaces is attributable to the presence of a relative disparity gradient and that the flanker effect can spread to regions of the surface not directly above or below the gradient.

Economic irrationality is optimal during noisy decision making.

According to normative theories, reward-maximizing agents should have consistent preferences. Thus, when faced with alternatives A, B, and C, an individual preferring A to B and B to C should prefer A to C. However, it has been widely argued that humans can incur losses by violating this axiom of transitivity, despite strong evolutionary pressure for reward-maximizing choices. Here, adopting a biologically plausible computational framework, we show that intransitive (and thus economically irrational) choices paradoxically improve accuracy (and subsequent economic rewards) when decision formation is corrupted by internal neural noise. Over three experiments, we show that humans accumulate evidence over time using a "selective integration" policy that discards information about alternatives with momentarily lower value. This policy predicts violations of the axiom of transitivity when three equally valued alternatives differ circularly in their number of winning samples. We confirm this prediction in a fourth experiment reporting significant violations of weak stochastic transitivity in human observers. Crucially, we show that relying on selective integration protects choices against "late" noise that otherwise corrupts decision formation beyond the sensory stage. Indeed, we report that individuals with higher late noise relied more strongly on selective integration. These findings suggest that violations of rational choice theory reflect adaptive computations that have evolved in response to irreducible noise during neural information processing.

Disparate bilingual experiences modulate task-switching advantages: A diffusion-model analysis of the effects of interactional context on switch costs.

Drawing on the adaptive control hypothesis (Green & Abutalebi, 2013), we investigated whether bilinguals' disparate interactional contexts modulate task-switching performance. Fifty-eight bilinguals within the single-language context (SLC) and 75 bilinguals within the dual-language context (DLC) were compared in a typical task-switching paradigm. Given that DLC bilinguals switch between languages within the same context, while SLC bilinguals speak only one language in one environment and therefore rarely switch languages, we hypothesized that the two groups' stark difference in their interactional contexts of conversational exchanges would lead to differences in switch costs. As predicted, DLC bilinguals showed smaller switch costs than SLC bilinguals. Our diffusion-model analyses suggest that DLC bilinguals' benefits in switch costs are more likely driven by task-set reconfiguration than by proactive interference. Our findings underscore the modulating role of the interactional context of conversational exchanges in task switching.

[Taylor Complex Figure test: administration and correction according to a normalization and standardization process in Spanish population]. / Test de la figura compleja de Taylor: administración y corrección según un proceso de normalización y estandarización en población española.

INTRODUCTION: The Taylor Complex Figure (TCF) was created as an alternate form for the Rey-Osterrieth Complex Figure. Although both figures are widely used, to date, it has not been carried out the normalization of the TCF for Spanish population. AIM: To normalize and standardize the TCF taking into account the sociodemographic characteristics of the Spanish population. SUBJECTS AND METHODS: The present study is part of the Normacog Project. Seven hundred participants were recruited (18-90 years old), assessing the visuo-constructive ability and immediate visual memory by TCF. The effect of age, level of education and gender was analyzed on the performance of TCF and percentiles and scalar score for eight ranges of age and scalar score adjusted by the level of education. RESULTS: Results showed a significant effect of age and level of education on the performance in copy and memory of TCF, whereas gender was not significant. Age and education explained from 25.3% to 35.7% of the variance of TCF performance. The older and less educated, the worse performance shown in TCF. Percentiles, scalar score for each range of age and scalar score adjusted by the level of education were obtained. CONCLUSION: Administration instructions, scoring and the normative data of the TCF are provided taking into account the Spanish sociodemographic characteristics for adults in our country.

TITLE: Test de la figura compleja de Taylor: administracion y correccion segun un proceso de normalizacion y estandarizacion en poblacion española.Introduccion. La figura compleja de Taylor (FCT) fue creada como alternativa a la figura compleja de Rey-Osterrieth. Aunque ambas figuras son instrumentos ampliamente utilizados, no se ha realizado hasta la fecha la normalizacion de la FCT para poblacion española. Objetivo. Normalizar y estandarizar la FCT, considerando las caracteristicas sociodemograficas de la poblacion española. Sujetos y metodos. El presente estudio se enmarca dentro del proyecto Normacog. Se seleccionaron 700 participantes (rango: 18-90 años), y se evaluaron la capacidad visuoconstructiva y la memoria visual inmediata mediante la FCT. Se analizaron el efecto de la edad, el nivel educativo y el sexo sobre el rendimiento de la FCT, y se crearon los percentiles, las puntuaciones escalares para ocho rangos de edad y la puntuacion escalar ajustada por el nivel educativo. Resultados. Los resultados muestran un efecto significativo de la edad y el nivel educativo sobre el rendimiento en copia y memoria de la FCT, mientras que el sexo no influyo significativamente. La edad y la educacion explicaban el 25,3-35,7% de la varianza en la FCT. A mayor edad y menor nivel educativo, peor era el rendimiento obtenido en la FCT. Se obtienen los percentiles, las puntuaciones escalares para cada rango de edad y la puntuacion escalar individual ajustada por el nivel educativo. Conclusion. Se aportan los materiales para la administracion y correccion del test de FCT, asi como los datos normativos de la FCT teniendo en cuenta las caracteristicas sociodemograficas españolas para todo el rango adulto en nuestro pais.

Perceptual grouping via binocular disparity: The impact of stereoscopic good continuation.

Stereoscopic contextual effects are widely reported but are generally discussed in terms of 2-D Gestalt grouping principles, e.g., good continuation or closure. We propose that there are disparity-based grouping operations that are separable from 2-D grouping and instead depend on the distribution of binocular disparity information. Two experiments assess the impact of perceptual grouping via good disparity continuation. First, perceived depth magnitude is reduced for a multidot contour with a smooth disparity gradient compared to the end points in isolation. This reduction is eliminated when disparity jitter is introduced to the intermediate dots. Second, observers showed more efficient visual search for the continuous contour versus the discontinuous version. Therefore, when there is spatial support for interpretation of a slanted object, quantitative depth is reduced, but is rapidly detected in visual search. These results reflect the operation of disparity-based grouping, extending the 2-D principle of good continuation into the third dimension.

Costs of storing colour and complex shape in visual working memory: Insights from pupil size and slow waves.

We investigated the impact of perceptual processing demands on visual working memory of coloured complex random polygons during change detection. Processing load was assessed by pupil size (Exp. 1) and additionally slow wave potentials (Exp. 2). Task difficulty was manipulated by presenting different set sizes (1, 2, 4 items) and by making different features (colour, shape, or both) task-relevant. Memory performance in the colour condition was better than in the shape and both condition which did not differ. Pupil dilation and the posterior N1 increased with set size independent of type of feature. In contrast, slow waves and a posterior P2 component showed set size effects but only if shape was task-relevant. In the colour condition slow waves did not vary with set size. We suggest that pupil size and N1 indicates different states of attentional effort corresponding to the number of presented items. In contrast, slow waves reflect processes related to encoding and maintenance strategies. The observation that their potentials vary with the type of feature (simple colour versus complex shape) indicates that perceptual complexity already influences encoding and storage and not only comparison of targets with memory entries at the moment of testing.

Vulnerabilidade de famílias de idosos assistidos pela Estratégia Saúde da Família / Vulnerabilidad de las familias de adultos mayores asistidas por la Estrategia Salud de la Familia / Vulnerability of families of elderly citizens cared for by the Family Health Strategy

RESUMO Objetivo: estudo descritivo, exploratório, de corte transversal, cujo objetivo foi identificar a vulnerabilidade de famílias de idosos assistidos pela Estratégia Saúde da Família (ESF). Método: foi desenvolvido por meio de entrevistas domiciliárias realizadas com uma amostra de 500 famílias de idosos assistidas por 32 equipes da ESF da cidade de Dourados, MS. O Índice de Desenvolvimento da Família (IDF) foi adaptado para classificá-las em função da situação de vulnerabilidade. Resultados: os resultados revelaram a presença de famílias multigeracionais, com baixa escolaridade entre os indivíduos com idade superior a 20 anos e alta taxa de analfabetismo entre os idosos. Identificaram-se 403 famílias em situação de vulnerabilidade aceitável, 95 em vulnerabilidade grave e duas famílias em situação de vulnerabilidade muito grave. As dimensões mais críticas do IDF foram os acessos ao conhecimento e ao trabalho. Conclusão: conclui-se que há necessidade de mais investimentos no cuidado a esses idosos e suas famílias na Atenção Básica. .

RESUMEN Objetivo: estudio descriptivo, exploratorio, transversal, con el objetivo de identificar la vulnerabilidad de familias adultos mayores asistidas por la Estrategia Salud de la Familia (ESF). Método: fue desarrollado mediante entrevistas a una muestra de 500 familias de adultos mayores bajo la responsabilidad de 32 equipos de ESF en la ciudad de Dourados, MS, Brasil. El Índice de Desarrollo de la Familia (IDF) fue adaptado para clasificar las familias de acuerdo a la situación de vulnerabilidad. Resultados: los resultados revelaron la presencia de familias multigeneracionales con bajo nivel de educación entre las personas mayores de 20 años y las altas tasas de analfabetismo entre los adultos mayores. Se identificaron 403 familias en situación de vulnerabilidad aceptable, 95 con vulnerabilidad grave y dos familias en situación de vulnerabilidad muy grave. Las dimensiones más críticas en el IDF fueron el acceso al conocimiento y al trabajo. Conclusión: se concluye que existe la necesidad de una mayor inversión, con un enfoque en la atención primaria, con el fin de atender a las personas mayores y sus familias. .

ABSTRACT Objective: the present descriptive, exploratory, cross-sectional study aimed to identify the vulnerability of families of elderly citizens cared for by the Family Health Strategy (FHS). Method: the research employed home interviews and was developed with a sample of 500 families of aged people cared for by 32 FHS teams in the city of Dourados, MS, Brazil. The Family Development Index (FDI) was adapted in order to classify the families according to their degree of vulnerability. Results: the results revealed the presence of multigenerational families with low educational levels among individuals over the age of 20 and high illiteracy rates among elderly citizens. There were 403 families whose vulnerability was acceptable, 95 in severe vulnerability, and two families in a condition of very severe vulnerability. The most critical dimensions of the FDI were the access to knowledge and to work. Conclusion: the study identifi ed that there is still a need for further investments that can assist these aged people and their families in the Primary Health Care. .

Brightness masking is modulated by disparity structure.

The luminance contrast at the borders of a surface strongly influences surface's apparent brightness, as demonstrated by a number of classic visual illusions. Such phenomena are compatible with a propagation mechanism believed to spread contrast information from borders to the interior. This process is disrupted by masking, where the perceived brightness of a target is reduced by the brief presentation of a mask (Paradiso & Nakayama, 1991), but the exact visual stage that this happens remains unclear. In the present study, we examined whether brightness masking occurs at a monocular-, or a binocular-level of the visual hierarchy. We used backward masking, whereby a briefly presented target stimulus is disrupted by a mask coming soon afterwards, to show that brightness masking is affected by binocular stages of the visual processing. We manipulated the 3-D configurations (slant direction) of the target and mask and measured the differential disruption that masking causes on brightness estimation. We found that the masking effect was weaker when stimuli had a different slant. We suggest that brightness masking is partly mediated by mid-level neuronal mechanisms, at a stage where binocular disparity edge structure has been extracted.

Solving stereo transparency with an extended coarse-to-fine disparity energy model.

Modeling stereo transparency with physiologically plausible mechanisms is challenging because in such frameworks, large receptive fields mix up overlapping disparities, whereas small receptive fields can reliably compute only small disparities. It seems necessary to combine information across scales. A coarse-to-fine disparity energy model, with both position- and phase-shift receptive fields, has already been proposed. However, because each scale decodes only one disparity for each location and uses the decoded disparity to select cells at the next scale, this model cannot represent overlapping surfaces at different depths. We have extended the model to solve stereo transparency. First, we introduce multiplicative connections from cells at one scale to the next to implement coarse-to-fine computation. The connection is the strongest when the presynaptic cell's preferred disparity matches the postsynaptic cell's position-shift parameter, encouraging the next scale to encode residual disparities with the more reliable phase-shift mechanism. This modification not only eliminates the artificial decoding and selection steps of the original model but also enables maintenance of complete population responses throughout the coarse-to-fine process. Second, because of this modification, explicit decoding is no longer necessary but rather is for visualization only. We use a simple threshold criterion to decode multiple disparities from population energy responses instead of a single disparity in the original model. We demonstrate our model using simulations on a variety of transparent and nontransparent stereograms. The model also reproduces psychophysically observed disparity interactions (averaging, thickening, attraction, and repulsion) as the depth separation between two overlapping planes varies.

Assessment of trypophobia and an analysis of its visual precipitation.

We developed and validated a symptom scale that can be used to identify "trypophobia", in which individuals experience aversion induced by images of clusters of circular objects. The trypophobia questionnaire (TQ) was based on reports of various symptom types, but it nevertheless demonstrated a single construct, with high internal consistency and test-retest reliability. The TQ scores predicted discomfort from trypophobic images, but not neutral or unpleasant images, and did not correlate with anxiety. Using image filtering, we also reduced the excess energy at midrange spatial frequencies associated with both trypophobic and uncomfortable images. Relative to unfiltered trypophobic images, the discomfort from filtered images experienced by observers with high TQ scores was less than that experienced with control images and by observers with low TQ scores. Furthermore, we found that clusters of concave objects (holes) did not induce significantly more discomfort than clusters of convex objects (bumps), suggesting that trypophobia involves images with particular spectral profile rather than clusters of holes per se.

Effect of disparity on the perception of motion-defined contours

We present three experiments that explored the effect of binocular disparity on the perception of contours defined by motion in a Spatiotemporal Boundary Formation. Depending on the disparity, the stimulus is perceived as an object that moves behind a holed surface (occluded configuration) or as a luminous transparency that moves over a surface that contains dots (occluding configuration). In all of the experiments, we used a Vernier task to assess the strength of contour perception. In the first experiment, we measured acuity as a function of disparity for a range of speeds and dot densities. The results showed that, despite the difference in the percepts, acuity was similar in both situations, replicating the dependence on speed and dot density demonstrated in previous studies. In the second experiment, the results showed that the dynamics of contour integration were identical for both occluded and occluding configurations. In the third experiment, we tested whether the mechanism of contour integration works independently from the interpretation of the scene. In this experiment, we inverted the disparity during stimulus presentation so that the stimulus switched between occluded and occluding configurations. The results showed that the switch of the depth order increased the threshold to the value obtained with a shorter presentation time. This might be produced by a resetting of the integration process driven by the change of depth order. The results are discussed within a conceptual model that places the process of contour integration in the context of the perception of objects in a Spatiotemporal Boundary Formation...

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.

Some views are better than others: evidence for a visual bias in object views self-generated by toddlers.

How objects are held determines how they are seen, and may thereby play an important developmental role in building visual object representations. Previous research suggests that toddlers, like adults, show themselves a disproportionate number of planar object views - that is, views in which the objects' axes of elongation are perpendicular or parallel to the line of sight. Here, three experiments address three explanations of this bias: (1) that the locations of interesting features of objects determine how they are held and thus how they are viewed; (2) that ease of holding determines object views; and (3) that there is a visual bias for planar views that exists independently of holding and of interesting surface properties. Children 18 to 24 months of age manually and visually explored novel objects (1) with interesting features centered in planar or ¾ views; (2) positioned inside Plexiglas boxes so that holding biased either planar or non-planar views; and (3) positioned inside Plexiglas spheres, so that no object properties directly influenced holding. Results indicate a visual bias for planar views that is influenced by interesting surface properties and ease of holding, but that continues to exist even when these factors push for alternative views.

Enhancing scene structure in prosthetic vision using iso-disparity contour perturbance maps.

We present a novel approach for enhancing structurally significant features in a scene to facilitate safe mobility with prosthetic vision. Previous approaches rely on visually salient features (e.g., intensity gradients, size, texture), or surface fitting (e.g., ground plane extraction), to determine and convey regions of structural change in the scene. Such approaches can be costly to compute, and/or are not guaranteed to detect all features relevant to the needs of safe mobility (e.g., small, low-contrast trip hazards). Assuming a dense disparity image, we propose a novel feature using iso-disparity contours. Regions of significant structural change are detected via a cost function based on local comparisons of iso-disparity contour orientations. Through this, structurally interesting features such as surface boundaries and general clutter are extracted and emphasised in the output visual representation. Our approach is real-time, and requires no surface fitting. Experimental results quantitatively and qualitatively validate our approach.