Contrast sensitivity in subgroups of developmental dyslexia

Contrast sensitivity in subgroups of developmental dyslexia It has been proposed that developmental dyslexia is associated with a deficit in the magnocellular pathway of the visual system. Other research focuses upon the heterogeneous nature of developmental dyslexia, and evidence that subgroups of dyslexia may be identified based on selective deficits in specific component reading skills. This study tested the hypothesis that visual processing deficits may be present in different subgroups of developmental dyslexia by comparing the visual contrast sensitivity of three subgroups of dyslexic children (phonological, surface and mixed) and controls. The stimulus designed to measure magnocellular visual function was a low spatial frequency Gaussian blob, flickered sinusoidally at a temporal frequency of 8.33 Hz. The control stimulus, designed to measure parvocellular visual function, was a relatively high spatial frequency Gaussian windowed grating (8 c/deg) slowly ramped on and off. There were no significant differences between the groups of dyslexic and control children in contrast sensitivity to either stimulus. The findings do not support the existence of a magnocellular system deficit in dyslexia. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Vision Research Elsevier

Contrast sensitivity in subgroups of developmental dyslexia

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Publisher
Elsevier
Copyright
Copyright © 2003 Elsevier Science Ltd
ISSN
0042-6989
eISSN
1878-5646
D.O.I.
10.1016/S0042-6989(02)00573-4
Publisher site
See Article on Publisher Site

Abstract

It has been proposed that developmental dyslexia is associated with a deficit in the magnocellular pathway of the visual system. Other research focuses upon the heterogeneous nature of developmental dyslexia, and evidence that subgroups of dyslexia may be identified based on selective deficits in specific component reading skills. This study tested the hypothesis that visual processing deficits may be present in different subgroups of developmental dyslexia by comparing the visual contrast sensitivity of three subgroups of dyslexic children (phonological, surface and mixed) and controls. The stimulus designed to measure magnocellular visual function was a low spatial frequency Gaussian blob, flickered sinusoidally at a temporal frequency of 8.33 Hz. The control stimulus, designed to measure parvocellular visual function, was a relatively high spatial frequency Gaussian windowed grating (8 c/deg) slowly ramped on and off. There were no significant differences between the groups of dyslexic and control children in contrast sensitivity to either stimulus. The findings do not support the existence of a magnocellular system deficit in dyslexia.

Journal

Vision ResearchElsevier

Published: Feb 1, 2003

References

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