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Schematic illustrations of the association field model. The connecting lines show facilitatory connections among neighboring receptive fields, narrowly selective for orientation and spatial frequency , that support contour integration. Adapted, with permission from Elsevier Science, from Field DJ, Hayes A, Hess RF. Contour integration by the human visual system: evidence for a local " association field. " Vision Res. 1993;33:173–193.
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The visual processing of text occurs spontaneously in most readers. Dyslexic persons, however, often report both somatic symptoms and perceptual distortions when trying to read. It is possible that the perceptual distortions experienced by those with dyslexia reflect a disturbance in the basic mechanisms supporting perceptual organization at the ea...
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Citations
... It was found that there is a significant difference between Malay speaking with SLD and typical readers on global visual spatial ability where typical readers performed better on the Block Design subtest as compared to children with SLD. This does not support the hypothesis of the study but is consistent with few previous studies [28][29][30][31][32][33] . ...
Children with Specific Learning Disorder (SLD) faces challenges in academic areas and are often negatively labelled. The learning problems in SLD children were mainly due to poor phonological skill but not much was known about the contribution of visuospatial difficulties. Therefore, this study aims to determine the relationship between phonological awareness skills and global visual-spatial abilities among Malay speaking children with SLD, and to compare children with SLD and typical readers on intellectual functioning, phonological awareness and global visual-spatial ability. An equal number of typical readers (n = 36) and children with SLD were recruited. Data were coded and analysed using Kendall's Tau-b, independent samples t-test and Mann-Whitney U test. Results showed phonological skills have strong negative correlation with global visual-spatial ability (r = .55). The typical readers have significantly higher IQ and better phonological skills and better global visual-spatial skills as compared to the group with SLD. However, there is no conclusive evidence due to specificity of more than one area measured by the assessment tools. Nevertheless, it provides a direction for future research to look into global visual-spatial aspects of SLD to aid in educational instruction in the future, in addition to the long-standing phonology deficit theory.
... Thus, the applicability of the findings to the dyslexic population requires careful interpretation. Simmers and bex (2001), on the contrary, found that people with dyslexia required a longer time to move from one stimulus to the other as they are less sensitive to path stimuli when compared to the group who had no reading disability, indicating that there is no superiority in visual processing in the group with dyslexia. Instead, people with dyslexia tended to have poor perceptual organization and integration skills. ...
... Instead, people with dyslexia tended to have poor perceptual organization and integration skills. using computerized testing is a different and new approach in analysing visual perception and contrary to the assumption that visual-spatial ability is controlled by the left hemisphere, this study found that global processing is caused by a deficit in the right hemisphere (Simmers & bex 2001). Pinto and Peixoto (2011) further supported this finding as they found that the group with dyslexia had decreased ability in performing visual-spatial and visual perceptual tasks. ...
... On the other hand, few studies found no superiority in visual processing in the group with dyslexia. Instead, people with dyslexia tended to have poor perceptual organization, integration skills and had decreased ability in visual-spatial and visual perceptual tasks (Simmers & bex 2001;Sperling et al. 2004;Von Károlyi & Winner 2004;Pinto & Peixoto 2011). This type of deficiency may be age-specific (Rüsseler et al. 2005). ...
... Thus, the applicability of the findings to the dyslexic population requires careful interpretation. Simmers and bex (2001), on the contrary, found that people with dyslexia required a longer time to move from one stimulus to the other as they are less sensitive to path stimuli when compared to the group who had no reading disability, indicating that there is no superiority in visual processing in the group with dyslexia. Instead, people with dyslexia tended to have poor perceptual organization and integration skills. ...
... Instead, people with dyslexia tended to have poor perceptual organization and integration skills. using computerized testing is a different and new approach in analysing visual perception and contrary to the assumption that visual-spatial ability is controlled by the left hemisphere, this study found that global processing is caused by a deficit in the right hemisphere (Simmers & bex 2001). Pinto and Peixoto (2011) further supported this finding as they found that the group with dyslexia had decreased ability in performing visual-spatial and visual perceptual tasks. ...
... On the other hand, few studies found no superiority in visual processing in the group with dyslexia. Instead, people with dyslexia tended to have poor perceptual organization, integration skills and had decreased ability in visual-spatial and visual perceptual tasks (Simmers & bex 2001;Sperling et al. 2004;Von Károlyi & Winner 2004;Pinto & Peixoto 2011). This type of deficiency may be age-specific (Rüsseler et al. 2005). ...
This review aims to present an overview of current research findings on the possible relationship between phonological awareness and visual-spatial skills among individuals with dyslexia. Narrative review of the relevant articles were obtained through computerized searches of databases such as PubMed, PubMed Central (PMC) and Google Scholar which included articles from SAGE, Taylor & Francis and Massachusetts Institute of Technology (MIT) Press from the year 2000 to 2014. The key words were explored, both exclusively and in combination with each other, so as to provide a better understanding of the relationship between them among individuals with dyslexia. Although it is evident that there is a phonological deficit in individuals with dyslexia, however, it is inconclusive with regards to the visual-spatial deficit and strength. There is a consensus on the nature of phonological awareness skill deficits but not on the visual spatial abilities in dyslexia. In fact, the relationship between phonological awareness and visual spatial abilities in dyslexia is dependent on the area of visual ability measured.
... Levitt J.B. et al. [4] demonstrate that the responses to a stimulus place within a V1 neuron's receptive field can be either increase or decrease by adding a stimulus in the region surrounding the receptive field. Psychophysical and neurophysiological findings [5][6][7][8] have shown that the cortical cell can be taken as a part of an interactional network rather than an isolated element. Namely, the perception of an oriented stimulus can be influenced by the presence of other such stimuli in its neighborhood. ...
Recently, many image processing applications have taken advantage of a psychophysical and neurophysiological mechanism, called “surround suppression” to extract object contour from a natural scene. However, these traditional methods often adopt a single suppression model and a fixed input parameter called “inhibition level”, which needs to be manually specified. To overcome these drawbacks, we propose a novel model, called “context-adaptive surround suppression”, which can automatically control the effect of surround suppression according to image local contextual features measured by a surface estimator based on a local linear kernel. Moreover, a dynamic suppression method and its stopping mechanism are introduced to avoid manual intervention. The proposed algorithm is demonstrated and validated by a broad range of experimental results.
... Previous studies have shown that people with SCZ are less able to detect and make shape judgments about contours when compared to healthy, psychotic, non-psychotic and non-psychotomimetic substance abusing control groups Silverstein and Keane, 2011). CI impairment has also been observed in aging (Roudaia et al., 2011), dyslexia (Simmers and Bex, 2001), and amblyopia (Polat et al., 1997), and can be affected by psychotomimetic drugs that affect occipital lobe functioning (Uhlhaas et al., 2007;White et al., 2013). To our knowledge, only one prior study has investigated CI in BDD (Rossell et al., 2014). ...
... Studies in psychophysics, electrophysiology, fMRI, and single unit recording have shown that CI and CF are mediated partly via long-range excitatory horizontal connections between orientation-tuned spatial frequency filters in V1/V2 (Hess, Hayes, & Field, 2003). Given that the neurobiological substrate of CI and CF is well explored, tasks probing the processes have proven useful in evaluating visual cortical functioning in the context of aging (Chan, Battista, & McKendrick, 2012;Roudaia, Bennett, & Sekuler, 2008), autism (Del Viva, Igliozzi, Tancredi, & Brizzolara, 2006;Keita, Mottron, Dawson, & Bertone, 2011), development (Kovács, Kozma, Feher, & Benedek, 1999), schizophrenia (Kéri, Kelemen, Benedek, & Janka, 2005;Silverstein, Kovács, Corry, & Valone, 2000), dyslexia (Simmers & Bex, 2001), drug abuse (White, Brown, & Edwards, 2013), and amblyopia (Chandna, Pennefather, Kovács, & Norcia, 2001;Polat, Sagi, & Norcia, 1997), among other cases. In most of these studies, subjects have "normal or corrected-to-normal" vision, which-in its strictest definition -corresponds to a 20/20 cutoff. ...
Contour integration (CI) combines appropriately aligned and oriented elements into continuous boundaries. Collinear facilitation (CF) occurs when a low-contrast oriented element becomes more visible when flanked by collinear high-contrast elements. Both processes rely at least partly on long-range horizontal connections in early visual cortex, and thus both have been extensively studied to understand visual cortical functioning in aging, development, and clinical disorders. Here, we ask: Can acuity differences within the normal range predict CI or CF? To consider this question, we measured binocular visual acuity and compared subjects with 20/20 vision to those with better-than-20/20 vision (SharpPerceivers) on two tasks. In the CI task, subjects located an integrated shape embedded in varying amounts of noise; in the CF task, subjects detected a low-contrast element flanked by collinear or orthogonal high-contrast elements. In each case, displays were scaled in size to modulate element visibility and spatial frequency (4-12 cycles/deg). SharpPerceivers could integrate contours under noisier conditions than the 20/20 group (p = .0002), especially for high spatial frequency displays. Moreover, although the two groups exhibited similar collinear facilitation, SharpPerceivers could detect the central target with lower contrast at high spatial frequencies (p <. 05). These results suggest that small acuity differences within the normal range-corresponding to about a one line difference on a vision chart-strongly predict element detection and integration. Furthermore, simply ensuring that subjects have normal or corrected-to-normal vision is not sufficient when comparing groups on contour tasks; visual acuity confounds also need to be ruled out.
... For example, studies show an overlap between schizophrenia and both verbal and nonverbal learning disabilities in terms of cognitive impairments and their anatomical correlates. [27][28][29][30][31][32][33][34] At the same time, schizophrenia and autism appear to represent opposite extremes on some dimensions, [35][36][37][38] and thus investigation of the pattern of similarities and differences between these disorder classes may be quite revealing. Schizophrenia is also associated with an elevated rate of conduct disorder and antisocial personality disorder diagnoses, 39 and these may share biological abnormalities, such as reduced functional connectivity involving the frontal cortex 40 and cortical thinning. ...
What kind of a thing is schizophrenia? What causes it? Can it be cured or prevented? These questions have challenged researchers for over 100 years. However, despite thousands of new studies every year, and major technological advances, schizophrenia research is not leading to consistent improvements in the lives of people with the disorder.1 What might make a difference? One possibility is that a shift in the way that schizophrenia is conceptualized and approached may lead to improvements in our understanding of the condition, which could then translate into more effective methods of prevention and promotion of recovery. But, what would these changes look like, and what is necessary to make them happen? Addressing these key questions was the goal of the Ernst Struungmann Forum, “Schizophrenia: Evolution and Synthesis,” a meeting held at the Frankfurt Institute for Advanced Studies, in July 2012. For 5 intense days of discussion and debate (there were no paper presentations), an invited group of expert and experienced researchers with diverse scientific backgrounds from around the world (see Appendix for list of participants) explored novel ways of conceptualizing schizophrenia and integrating data across levels of analysis with the goal of accelerating advances in treatment development and prevention. As with all Struungmann Forums, the topic was divided into four, more tractable, themes, each with an associated set of questions. Participants were assigned to 1 of 4 groups to consider background papers (written just prior to the Forum by selected Forum attendees). Summaries of each group’s conclusions on the novel approaches to advance the field were ultimately presented to the whole group for discussion and debate.
Throughout our deliberations, we kept in mind our goal of clinical impact. This strategy is consistent with that of the recent Rand Europe Mental Health Retrosight Report on Schizophrenia.2 That report included the following conclusions: (1) global mental health research over the past 20 years has led to a diverse and beneficial range of academic, health, social, and economic impacts; (2) clinical research has had a larger impact on patient care than basic research although there is much variability regarding this outcome in the basic research area; and (3) where scientists bear in mind clinical relevance, there is more likely to be impact. In addition, our strategy of choosing experts from across a wide spectrum of research topics and methods is supported by Retrosight’s conclusion that those involved in mental health research who work across boundaries produce findings that are associated with wider health and social benefits. What follows is a summary of our deliberations over the Forum week and considerable follow-up email discussion. We have distilled these conversations into this short text, and, as the meeting organizers, we take responsibility for any omissions. We also have updated some of the recommendations with reference to recent research. A full-length description of the questions and issues that motivated the Forum can be found in chapter 1 of a recently published book,3 with the remainder of that volume comprising the background papers that stimulated the discussions and the final summaries of the group discussions addressing the issues.
... A previous study found a visual deficit in contour integration in English readers with dyslexia (Simmers & Bex, 2001). Visual contour integration may play an even more significant role in Chinese handwriting particularly due to its logographic presentation (Lam, Au, Leung, & Li-Tsang, 2011). ...
... In the last decade, many research studies have examined the relationship between visual perceptual skills and reading. Studies have found that people with dyslexia have impaired abilities in performing higher-order, global visual tasks, such as visual contour integration, implying that higher-order cortical areas are involved, and/or abnormal cooperative associations between distant cortical loci exist in dyslexia (Simmers & Bex, 2001;Sireteanu et al., 2008).Visual contour integration skill (VC skill) is defined as the ability to integrate local spatial inputs across the visual field to form a global percept of a contour or path. This ability can be measured psychophysically in a test that requires the detection of a path defined by aligned, spatially narrow-band elements on a dense field of otherwise similar elements that are randomly oriented and positioned (Simmers & Bex, 2001) (see Fig. 2). ...
... Studies have found that people with dyslexia have impaired abilities in performing higher-order, global visual tasks, such as visual contour integration, implying that higher-order cortical areas are involved, and/or abnormal cooperative associations between distant cortical loci exist in dyslexia (Simmers & Bex, 2001;Sireteanu et al., 2008).Visual contour integration skill (VC skill) is defined as the ability to integrate local spatial inputs across the visual field to form a global percept of a contour or path. This ability can be measured psychophysically in a test that requires the detection of a path defined by aligned, spatially narrow-band elements on a dense field of otherwise similar elements that are randomly oriented and positioned (Simmers & Bex, 2001) (see Fig. 2). As mentioned earlier, Chinese characters involve complex geometric figurations and stroke arrangements (Lam et al., 2011). ...
A previous study found a visual deficit in contour integration in English readers with dyslexia (Simmers & Bex, 2001). Visual contour integration may play an even more significant role in Chinese handwriting particularly due to its logographic presentation (Lam, Au, Leung, & Li-Tsang, 2011). The current study examined the relationship between children's performance in visual contour (VC) integration and Chinese handwriting. Twenty students from grade 3 to grade 6 were recruited (M=9.51, SD=1.02) from a mainstream primary school using the convenience sampling method. Ten students were identified by teachers as having handwriting problems, and the other 10 were typical students. Participants performed the VC tasks and their handwriting performance was assessed by a Chinese Handwriting Assessment Tool (CHAT) in a classroom setting. Correlation analyses revealed that VC accuracy was significantly and negatively correlated with on paper time and total writing duration. t-Test analyses revealed statistically significant differences in VC accuracy between students with typical and poor handwriting, with consistently better VC accuracy performance in all conditions in the typical handwriting group. The results may have important implications for interventions aiming at improving children's handwriting.
... Our results might also bring a new argument into the ongoing debate on dyslexia and whether its causes are visuospatial or phonological (Ahissar, Lubin, Putter-Katz & Banai, 2006;Di Filippo, Zoccolotti & Ziegler, 2008;Valdois, Bosse & Tainturier, 2004;Vidyasagar & Pammer, 2010;Ziegler & Goswami, 2005;Ziegler, Pech-Georgel, Dufau & Grainger, 2010;Bosse, Tainturier & Valdois 2007;Lallier, Donnadieu, Berger & Valdois, 2010;Peyrin, Demonet, N'Guyen-Morel, Le Bas & Valdois, 2011). Previous research has found that among several visuospatial deficits, dyslexic subjects have inferior contour integration abilities (Simmers & Bex, 2001). Our results raise the possibility that this deficit, rather than being a cause of dyslexia, could be in fact its consequence. ...
The acquisition of reading has an extensive impact on the developing brain and leads to enhanced abilities in phonological processing and visual letter perception. Could this expertise also extend to early visual abilities outside the reading domain? Here we studied the performance of illiterate, ex-illiterate and literate adults closely matched in age, socioeconomic and cultural characteristics, on a contour integration task known to depend on early visual processing. Stimuli consisted of a closed egg-shaped contour made of disconnected Gabor patches, within a background of randomly oriented Gabor stimuli. Subjects had to decide whether the egg was pointing left or right. Difficulty was varied by jittering the orientation of the Gabor patches forming the contour. Contour integration performance was lower in illiterates than in both ex-illiterate and literate controls. We argue that this difference in contour perception must reflect a genuine difference in visual function. According to this view, the intensive perceptual training that accompanies reading acquisition also improves early visual abilities, suggesting that the impact of literacy on the visual system is more widespread than originally proposed.
... Instead there is increasing evidence that a global distortion of the visual space both in the temporal and spatial domains takes place in dyslexic subjects. Such finding would rely on the impairment of psychophysical tasks such as motion perception (Cornelissen et al., 1995;Eden et al., 1996;Demb et al., 1998;Slaghuis and Ryan, 1999;Talcott et al., 2000;Hansen et al., 2001;Wilmer et al., 2004), contour integration (Simmers and Bex, 2001), spatial localization (Stein, 1989;Stein et al., 1989) and spatial relations representation (Pontius, 1981). ...
... In the spatial domain, Simmers and Bex (2001) measured the threshold in detecting contours of paths made of Gabor patterns within a field of randomly oriented distracter elements. They found sensibility to be reduced in dyslexic subjects by a factor of two or three compared to normal readers, thence suggesting that some deficit in global processing takes place. ...
... Actually, different and apparently heterogeneous alterations involving the global visual perception in both the temporal and spatial domain are found to affect dyslexic readers. In particular impaired motion perception (Cornelissen et al., 1995;Eden et al., 1996;Demb et al., 1998;Slaghuis and Ryan, 1999;Talcott et al., 2000;Hansen et al., 2001;Wilmer et al., 2004), contour integration (Simmers and Bex, 2001), spatial localization (Stein, 1989;Stein et al., 1989) and spatial relations representation (Pontius, 1981). Nevertheless, such anomalies per se do not seem able to account for the clinical patterns. ...
According to wide literature, a global impairment in the temporal and spatial domains as well as an increased crowding effect is common of dyslexics. The aim of the study was to evaluate if such subjects suffer from a more general impairment of spatial relationship perception (SRP) and in particular from anomalous spatial relationship anisotropy (SRA) thus accounting both for their global perceptual distortions and abnormal crowding. SRP of 39 young disabled readers and 23 normal subjects were measured by a specifically designed psychophysical technique based on circular and elliptical target recognitions. A general impairment of SRP characterized by increased horizontal/vertical anisotropy was found in the dyslexic sample compared to the controls. In the second part of the experiment, reading efficiency and reading time were measured by MNREAD(©) reading cards in standard conditions and after increasing horizontal spatial extension of the sentence by different values. We suppose this modification could well compensate the abnormal anisotropy found in dyslexics. Data obtained in the two groups were compared. A strong correlation between reading efficiency (a parameter we have specifically devised) and horizontal spatial text relationship values were present in the patients (r=.87, p<.01), but not in the controls. The same was found taking into consideration mean reading time (r=-.82, p<.01). We therefore gather that an alteration of SRP, characterized by an increased anisotropy may be involved in developmental dyslexia.
