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Anita J. Simmers, Peter J. Bex; Deficit of Visual Contour Integration in Dyslexia. Invest. Ophthalmol. Vis. Sci. 2001;42(11):2737-2742. doi: https://doi.org/.
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purpose. 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 early stages of visual processing. Integration of information
over extended areas of visual space can be measured psychophysically in
a task 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. In the present
study a contour integration task was used to investigate such
perceptual organization in dyslexia.
methods. The detection of contours or paths composed of Gabor micropatterns was
performed within a field of randomly oriented distracter elements in a
2-alternate forced choice (AFC) task. The stimuli were
manipulated by randomly varying both the density of the background
noise elements and the number of elements that defined a path of
results. In all observers, sensitivity to the paths increased with the number of
target elements comprising the path, and subjects in both groups
exhibited similar trends in relative density of the stimuli. However,
in all conditions, dyslexic observers were two to three times less
sensitive to path stimuli than the control group.
conclusions. In the present study the authors have described a visual deficit in a
global integration task in dyslexia. The pattern of deficits reported
suggest that abnormal cooperative associations may be present in
dyslexia that are indicative of poor perceptual
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