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Vision Research

Randolph Blake, Rachel Goodman, Andrew Tomarken, Hyun-Woong Kim
Binocular rivalry (BR) and continuous flash suppression (CFS) are compelling psychophysical phenomena involving interocular suppression. Using an individual differences approach we assessed whether interocular suppression induced by CFS is predictable in potency from characteristics of BR that are plausibly governed by interocular inhibition. We found large individual differences in BR dynamics and, in addition, in the strength of CFS as gauged by the incidence and durations of breakthroughs in CFS during an extended viewing periods...
April 16, 2019: Vision Research
Adélaïde Sibeaux, Gemma L Cole, John A Endler
Accurate knowledge of species colour discrimination is fundamental to explain colour based behaviours and the evolution of colour patterns. We tested how the receptor noise limited model, widely used in behavioural ecology, matched actual colour discrimination thresholds obtained using behavioural tests. Guppies (Poecilia reticulata) were first trained to push a target coloured disk placed among eight grey disks of various luminances on a grey plate. Guppies were then tested to find target disks, which varied in colour contrast from the plate...
April 11, 2019: Vision Research
Reuben Rideaux, Andrew E Welchman
Global context can dramatically influence local visual perception. This phenomenon is well-documented for monocular features, e.g., the Kanizsa triangle. It has been demonstrated for binocular matching: the disambiguation of the Wallpaper Illusion via the luminance of the background. For monocular features, there is evidence that global context can influence neuronal responses as early as V1. However, for binocular matching, the activity in this area of the visual cortex is thought to represent local processing, suggesting that the influence of global context may occur at later stages of cortical processing...
April 10, 2019: Vision Research
Avinash J Aher, Mellina M Jacob, Jan Kremers
Electroretinograms (ERGs) elicited by high temporal frequency (26 - 95 Hz) L- and M-cone isolating sine-wave stimuli were investigated in human observers for full-field (FF) and different spatially restricted stimulus sizes (70°, 50°, 30°, and 10° diameter). Responses to L- and M-cone isolating FF stimuli were maximal around 48 Hz and decreased gradually with increasing temporal frequency up to 95 Hz. The response maximum was shifted to about 30 - 32 Hz for both L- and M-cone driven responses obtained with spatially restricted stimuli...
March 26, 2019: Vision Research
Giulio Contemori, Luca Battaglini, Michele Barollo, Ambra Ciavarelli, Clara Casco
The magnocellular deficit theory of dyslexia suggests a selective impairment in contrast detection of stimuli involving pure magnocellular response (e.g. Gabor patches of 0.5 c/deg, 30Hz, low contrast). An alternative hypothesis is that, dyslexia may be associated with a reduction of typical facilitation that normal readers present for stimuli relying on low-level magno-parvo co-activation, relative to stimuli eliciting pure magno activation. According to this hypothesis, any advantage in contrast sensitivity, produced by either decreasing stimuli temporal frequency (from 30 to 10Hz, Experiment 1) or using static stimuli of increasing spatial frequency (from 0...
March 23, 2019: Vision Research
Borja Aguado, Joan López-Moliner
Previous studies have shown that the angle of approach is consistently overestimated for approaching (but passing-by) objects. An explanation based on a slow-motion prior has been proposed in the past to account for this bias. The mechanism relies on the (less reliable) in-depth component of the motion being more attracted towards the slow motion prior than the (more reliable) lateral component. This hypothesis predicts that faster speeds in depth will translate into a greater bias if the perception of velocity in depth follows Weber's law...
March 22, 2019: Vision Research
Emilie Ginestet, Thierry Phénix, Julien Diard, Sylviane Valdois
The word length effect in Lexical Decision (LD) has been studied in many behavioral experiments but no computational models has yet simulated this effect. We use a new Bayesian model of visual word recognition, the BRAID model, that simulates expert readers' performance. BRAID integrates an attentional component modeled by a Gaussian probability distribution, a mechanism of lateral interference between adjacent letters and an acuity gradient, but no phonological component. We explored the role of visual attention on the word length effect using 1,200 French words from 4 to 11 letters...
March 20, 2019: Vision Research
Han-Dong Dan, Fu-Qing Zhou, Xin Huang, Yi-Qiao Xing, Yin Shen
This study investigated changes in intra- and inter-regional functional connectivity (FC) in individuals with retinitis pigmentosa (RP) by using regional homogeneity (ReHo) and FC methods. Sixteen RP individuals and 14 healthy controls (HCs) underwent resting-state functional magnetic resonance imaging scans (fMRI). A combined ReHo and FC method was conducted to evaluate synchronization of brain activity. Compared with HCs, RP individuals had significantly lower ReHo values in the bilateral lingual gyrus/cerebellum posterior lobe (LGG/CPL)...
March 20, 2019: Vision Research
Hitomi Shimakura, Katsuaki Sakata
Adaptation to environmental light allows our visual system to compensate for dynamic changes in the visual environment for avoiding everyday hazards (e.g., misreading traffic lights) and for accurate reaching. We investigated the hypothesis that adaptation to coloured light is achieved not only via photoreceptors in the retina and monocular contrast adaptation, but also by a binocular process that may occur at the level of the cerebral cortex. In the present study, to determine the role of higher-order cortical binocular processes in adaptation to coloured light, participants were adapted to chromatic light such that the duration of adaptation during monocular processing differed from that during binocular processing...
March 20, 2019: Vision Research
Rebecca Ijekah, John Erik Vanston, Michael A Crognale
The shape of the human spectral sensitivity function depends on how it is measured. In the increment threshold (IT) technique, sensitivity is typically measured as the inverse of threshold for detection of increments of monochromatic light presented for relatively long durations on achromatic pedestals. Spectral sensitivity functions derived from IT techniques have long been used to reveal contribution from opponent color channels. Although IT functions have been studied extensively, little attention has been given to functions derived from decrement thresholds (DT), partly due to technical challenges of producing appropriate stimuli...
March 15, 2019: Vision Research
Kier Groulx, Charles Chubb, Jonathan D Victor, Mary M Conte
Visual features such as edges and corners are carried by high-order statistics. Previous analysis of discrimination of "isodipole" textures, which isolate specific high-order statistics, demonstrates visual sensitivity to these statistics but stops short of analyzing the underlying computations. Here we use a new "texture centroid" paradigm to probe these computations. We focus on two canonical isodipole textures, the "even" and "odd" textures: any 2x2 block of even (odd) texture contains an even (odd) number of black (and white) checks...
March 15, 2019: Vision Research
Barbara Piotrowska, Alexandra Willis
Although primarily conceptualized as a disorder of phonological awareness, developmental dyslexia is often associated with broader problems perceiving and attending to transient or rapidly-moving visual stimuli. However, the extent to which such visual deficits represent the cause or the consequence of dyslexia remains contentious, and very little research has examined the relative contributions of phonological, visual, and other variables to reading performance more broadly. We measured visual sensitivity to global motion (GM) and global form (GF), performance on various language and other cognitive tasks believed to be compromised in dyslexia (phonological awareness, processing speed, and working memory), together with a range of social and demographic variables often omitted in previous research, such as age, gender, non-verbal intelligence, and socio-economic status in an unselected sample (n = 132) of children aged 6 - 11...
March 15, 2019: Vision Research
Karin S Pilz, Danai Papadaki
Discrimination performance is better for cardinal motion directions than for oblique ones, a phenomenon known as the oblique effect. In a first experiment of this paper, we tested the oblique effect for coarse motion direction discrimination and compared performance for the two cardinal and two diagonal motion directions. Our results provide evidence for the oblique effect for coarse motion direction discrimination. Interestingly, the oblique effect was larger between horizontal and diagonal than between vertical and diagonal motion directions...
March 13, 2019: Vision Research
Nathan Destler, Manish Singh, Jacob Feldman
We investigated the dimensions defining mental shape space, by measuring shape discrimination thresholds along "morph-spaces" defined by pairs of shapes. Given any two shapes, one can construct a morph-space by taking weighted averages of their boundary vertices (after normalization), creating a continuum of shapes ranging from the first shape to the second. Previous studies of morphs between highly familiar shape categories (e.g. truck and turkey) have shown elevated discrimination at category boundaries, reflecting a kind of "categorical perception" in shape space...
March 13, 2019: Vision Research
Barton L Anderson, Kairen Tan, Phillip J Marlow
The mechanisms responsible for generating illusory contours are thought to fulfil an adaptive role in providing estimates of missing contour fragments generated by partial camouflage. One striking apparent counter-example to this view was described in Current Biology 21 (2011) 492-496, which showed that illusory contours could arise in motion displays depicting visible occluding discs occluding and disoccluding thin contours. These motion sequences generate illusory contours even though they play no necessary role in accounting for occlusion and disocclusion of the thin contours...
March 12, 2019: Vision Research
Mirella Telles Salgueiro Barboni, Einat Hauzman, Balázs Vince Nagy, Cristiane Maria Gomes Martins, Avinash J Aher, Tina I Tsai, Daniela Maria Oliveria Bonci, Dora Fix Ventura, Jan Kremers
Retinal and cortical signals initiated by a single cone type can be recorded using the spectral compensation (or silent substitution) paradigm. Moreover, responses to instantaneous excitation increments combined with gradual excitation decreases are dominated by the response to the excitation increment. Similarly, the response to a sudden excitation decrement dominates the overall response when combined with a gradual excitation increase. Here ERGs and VEPs were recorded from 34 volunteers [25.9 ± 10.4 years old (mean ± 1 SD); 25 males, 9 females] to sawtooth flicker (4 Hz) stimuli that elicited L- or M-cone responses using triple silent substitution...
March 4, 2019: Vision Research
Arii Watanabe, Maiko Fujimoto, Keita Hirai, Tomokazu Ushitani
The use of topological features in visual recognition has been demonstrated only in species with global-cue precedence. We investigated whether pigeons, with local-cue precedence, use topological features as cues for discriminating different shapes. The subjects in the topology group were required to discriminate stimuli based on whether the shapes contained one or no holes, whereas the subjects in the pseudocategory group were required to discriminate stimuli based on arbitrary categories. In contrast to the pseudocategory group, which showed little improvement in stimuli discrimination over the sessions, the topology group showed rapid improvement, indicating that the latter group performed better than what was expected from rote learning...
March 1, 2019: Vision Research
Heida Maria Sigurdardottir, Kristjan Helgi Hjartarson, Gudbjorn Larus Gudmundsson, Árni Kristjánsson
Both intact and deficient neural processing of faces has been found in dyslexic readers. Similarly, behavioral studies have shown both normal and abnormal face processing in developmental dyslexia. We tested whether dyslexic adults are impaired in tests of own-race and other-race face recognition. As both face and word recognition rely considerably on visual expertise, we wished to investigate whether face recognition problems of dyslexic readers might stem from difficulties with experience-driven expert visual processing...
March 1, 2019: Vision Research
Guido Barbieri Bittencourt, Einat Hauzman, Daniela Maria Oliveira Bonci, Dora Fix Ventura
Snakes inhabit a great variety of habitats, whose spectral quality of light may vary a lot and influence specific adaptations of their visual system. In this study, we investigated the genetics of the visual opsins and the morphology of retinal photoreceptors, of two nocturnal snakes from the Viperidae family, Bothrops jararaca and Crotalus durissus terrificus, which inhabit preferentially the Atlantic Rain Forest and the Brazilian Savannah, respectively. Total RNA was extracted from homogenized retinas and converted to cDNA...
February 28, 2019: Vision Research
Adélaïde Sibeaux, Madison L Keser, Gemma L Cole, Alexandrea M Kranz, John A Endler
Visual pigments can vary across the retina in many vertebrates, but the behavioural consequences of this retinal heterogeneity are unknown. Guppies (Poecilia reticulata) vary dorsoventrally in visual pigments and forage both on the ground and at the water surface, exposing different retinal regions to two very different visual environments. We tested guppy behaviour towards a moving stimulus presented below or above the guppy. We used 12 different narrow-band wavelength stimuli matching each of the opsin peak sensitivities presented either at the top or the bottom of our experimental apparatus...
February 28, 2019: Vision Research
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