Directional motion contrast sensitivity in developmental dyslexia
Slaghuis, Walter and Ryan, John F. (2006) Directional motion contrast sensitivity in developmental dyslexia. Vision Research, 46 (20). pp. 3291-3303. ISSN 0042-6989 | PDF - Full text restricted - Requires a PDF viewer 340Kb | |
Official URL: http://dx.doi.org/10.1016/j.visres.2006.05.009 AbstractAbstract
The present study compared the perception of visual motion in two dyslexia classification schemes; the Boder (1973) dyseidetic, dysphonetic and mixed subgroups and Williams, Stuart, Castles and McAnally (2003) surface, phonological and mixed subgroups by measuring the contrast sensitivity for drifting gratings at three spatial frequencies (1.0, 4.0 and 8.0 c/deg) and five drift velocities (0.75, 3.0, 6.0, 12.0 and 18.0 cyc/s) in a sample of 32 children with dyslexia and 32 matched normal readers. The findings show that there were no differences in motion direction perception between normal readers and the group with dyslexia when dyslexia was taken as a homogeneous group. Motion direction perception was found to be intact in the dyseidetic and surface dyslexia subgroups and significantly lowered in both mixed dyslexia subgroups. The one inconsistency in the findings was that motion sensitivity was significantly lowered in the Boder (1973) dysphonetic subgroup and intact in the Williams et al. (2003) phonological subgroup. The findings also provide evidence for the presence of a disorder in sequential and temporal order processing that appears to reflect a difficulty in retaining sequences of non-meaningful auditory and visual stimuli in short-term working memory in children with dyslexia.
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