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Heida Sigurdardottir, Eysteinn Ivarsson, Kristjana Kristinsdóttir, Arni Kristjansson; Is dyslexia due to deficits in high-level visual processing? Face and object recognition problems in dyslexia. Journal of Vision 2016;16(12):1315. doi: 10.1167/16.12.1315.
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© ARVO (1962-2015); The Authors (2016-present)
Previous research has consistenly shown that the left fusiform gyrus, a part of the ventral visual stream, is hypoactive in dyslexic children and adults. The region is involved in the perception of words, faces, and other homogeneous or complex objects. We therefore investigated whether dyslexics show abnormal facial recognition and within-category recognition of other visual objects. We tested 20 dyslexic adults and 20 typical readers (matched for age, gender, and education) on several tasks that rely on high level ventral stream regions: The Cambridge Face Memory Test (CFMT; upright/inverted faces), the Vanderbilt Holistic Face Processing Test (VHFPT), and the Vanderbilt Expertise Test (VET). All tests call for fine shape discriminations of objects within a category. We also included a control test involving color recognition. For dyslexic participants, but not typical readers, performance was significantly poorer than previously reported average performance on the CFMT (upright faces). Compared to their matched typical readers, dyslexics also found it harder to recognize faces (CFMT). While dyslexics had facial recognition problems, they did not show atypical holistic processing of faces, one of the hallmarks of face processing (as measured by the face inversion effect and the VHFPT).This is consistent with their left fusiform hypoactivation; the right hemisphere is generally considered to be more involved in holistic processing. Additionally, dyslexics' within-category recognition of non-face objects (VET) was impaired, compared to typical readers. Conversely, no consistent differences were found on the color recognition control test that shares many important components with both the CFMT and the VET. The results support the intriquing proposal that difficulties in reading in dyslexia might be the most salient manifestation of a more general high-level visual deficit.
Meeting abstract presented at VSS 2016
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