Is There a Deficit of Early Vision in Dyslexia?

Walther-Müller, Peter U

doi:10.1068/p240919

Cited by 71 publications

(21 citation statements)

References 40 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In addition, performance differences between dyslexics and controls have been found for tasks that measure temporal and spatial properties of visual attention (Bouma & Legein, 1977;Brannan & Williams, 1987;Steinman, Steinman, & Garzia, 1998;Facoetti & Molteni, 2001). With some exceptions (Gross-Glenn et al, 1995;Walther-M . u uller, 1995;Hayduk, Bruck, & Cavanagh, 1996;see: Stein, Talcott & Walsh, 2000;Skottun, 2000 for critical reviews), these results have been replicated in a number of psychophysical studies, and have been corroborated to some extent both electrophysiologically and with functional MRI (Livingstone et al, 1991;Lehmkuhle et al, 1993;Eden et al, 1996;Demb, Boynton, & Heeger, 1997).…”

Section: Mechanisms Of Visual Encoding and The Relation To Text Presementioning

confidence: 95%

Visual encoding mechanisms and their relationship to text presentation preference

Pammer¹,

Lavis²,

Cornelissen³

2004

Dyslexia

View full text Add to dashboard Cite

This study was designed to investigate the importance of spatial encoding in reading, with particular emphasis on visuo-spatial encoding mechanisms. Thirty one school children participated in the first study in which they were measured on their ability to solve a centrally presented spatial encoding task, as well as their sensitivity to the frequency doubling illusion across the retina. We found that both spatial frequency doubling sensitivity and performance in the spatial encoding task were correlated with reading, however these tasks were unrelated to each other. Furthermore, frequency doubling sensitivity was correlated with contextual reading, but not single-word reading, while the central spatial encoding task was correlated with both reading tasks. These findings may have functional implications for text presentation preference. Accordingly, in Experiment 2 we demonstrated that children with poor FDT sensitivity read more accurately when words were presented singularly rather than in a whole-text format. In conclusion, we suggest that contextual reading may depend upon two separate and functionally distinct visual encoding mechanisms--one central, important for the spatial discrimination of letters within words, and the other, a spotlighting mechanism important for spatial localization within a body of text. While both mechanisms may constrain reading efficiency, neither mechanism enforces an absolute limit on reading ability.

show abstract

Section: Mechanisms Of Visual Encoding and The Relation To Text Presementioning

confidence: 95%

Visual encoding mechanisms and their relationship to text presentation preference

Pammer¹,

Lavis²,

Cornelissen³

2004

Dyslexia

View full text Add to dashboard Cite

show abstract

“…Negative findings of overall group differences in sensory processing have also been reported (e.g. Gross-Glenn et al, 1995;Walther-M . u uller, 1995;Hill et al, 1999), suggesting that differences in sample selection might mediate some of the different patterns of result found across studies.…”

Section: Caveats: Links Between Sensory Processing and Literacy Skillsmentioning

confidence: 95%

On the relationship between dynamic visual and auditory processing and literacy skills; results from a large primary‐school study

et al. 2002

View full text Add to dashboard Cite

Three hundred and fifty randomly selected primary school children completed a psychometric and psychophysical test battery to ascertain relationships between reading ability and sensitivity to dynamic visual and auditory stimuli. The first analysis examined whether sensitivity to visual coherent motion and auditory frequency resolution differed between groups of children with different literacy and cognitive skills. For both tasks, a main effect of literacy group was found in the absence of a main effect for intelligence or an interaction between these factors. To assess the potential confounding effects of attention, a second analysis of the frequency discrimination data was conducted with performance on catch trials entered as a covariate. Significant effects for both the covariate and literacy skill was found, but again there was no main effect of intelligence, nor was there an interaction between intelligence and literacy skill. Regression analyses were conducted to determine the magnitude of the relationship between sensory and literacy skills in the entire sample. Both visual motion sensitivity and auditory sensitivity to frequency differences were robust predictors of children's literacy skills and their orthographic and phonological skills.

show abstract

“…Sensitivity for these stimulus parameters are usually unimpaired in dyslexics [10,28,31,33,34]. Some psychophysical studies have failed to con®rm that such visual de®cits are associated with dyslexia ( [20,21,61], see also, [17] for review). Nevertheless most experimental evidence is consistent with the hypothesis that the M (or transient) pathway is a locus of their subtle visual impairments (for reviews see [29,30,56]).…”

Section: Introductionmentioning

confidence: 99%

“…However the mechanism by which the putative M-pathway de®cit results in disrupted motion perception is still unclear. For example, Walther-MuÈ ller [61] has suggested that any of a number of possible anomalies in either (or both) the temporal or spatial response functions of cells in the retino-cortical Mpathway could cause a de®cit in dynamic stimulus detection. Dyslexics might also have poor integration of these signals at higher cortical levels.…”

Section: Introductionmentioning

confidence: 99%

Visual motion sensitivity in dyslexia: evidence for temporal and energy integration deficits

et al. 2000

View full text Add to dashboard Cite

In addition to poor literacy skills, developmental dyslexia has been associated with multisensory de®cits for dynamic stimulus detection. In vision these de®cits have been suggested to result from impaired sensitivity of cells within the retino-cortical magnocellular pathway and extrastriate areas in the dorsal stream to which they project. One consequence of such selectively reduced sensitivity is a diculty in extracting motion coherence from dynamic noise, a de®cit associated with both developmental dyslexia and persons with extrastriate, dorsal stream lesions. However the precise nature of the mechanism(s) underlying these perceptual de®cits in dyslexia remain unknown. In this study, we obtained motion detection thresholds for 10 dyslexic and 10 control adults while varying the spatial and temporal parameters of the random dot kinematogram (RDK) stimuli. In Experiment 1 stimulus duration was manipulated to test whether dyslexics are speci®cally impaired for detecting short duration, rather than longer stimuli. Dot density was varied in Experiment 2 to examine whether dyslexics' reduced motion sensitivity was aected by the amount of motion energy present in the RDKs. Dyslexics were consistently less sensitive to coherent motion than controls in both experiments. Increasing stimulus duration did not improve dyslexics' performance, whereas increasing dot density did. Thus increasing motion energy assisted the dyslexics, suggesting that their motion detectors have a lower signal to noise ratio, perhaps due to spatial undersampling. 7

show abstract

Is There a Deficit of Early Vision in Dyslexia?

Cited by 71 publications

References 40 publications

Visual encoding mechanisms and their relationship to text presentation preference

Visual encoding mechanisms and their relationship to text presentation preference

On the relationship between dynamic visual and auditory processing and literacy skills; results from a large primary‐school study

Visual motion sensitivity in dyslexia: evidence for temporal and energy integration deficits

Contact Info

Product

Resources

About