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Sung Jun Joo, Patrick Donnelly, Jason Yeatman; Learning to read does not affect motion processing in dyslexia. Journal of Vision 2017;17(10):642. doi: https://doi.org/10.1167/17.10.642.
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Visual sensitivity to motion is correlated with reading skills. Yet, the causal relationship between motion sensitivity and reading skills has been debated for more than thirty years. One hypothesis posits that dyslexia is caused by a deficit in the magnocellular pathway, indicated by deficits in motion processing. An alternative hypothesis maintains that the process of learning to read causes an enhancement in motion sensitivity and, therefore, the motion processing deficit observed in dyslexia is the consequence of a lack of, or poor quality, reading experience. Here we used an intensive reading intervention program to test the causal relationship between learning to read and motion processing. Children (n = 20) received 160 hours of training and practice with phonological and reading skills, and we measured behavioral sensitivity on a motion direction-discrimination task using random dot motion stimuli before (session 1), during (session 2 and 3), and after (Session 4) the intervention to assess how reading intervention affects motion sensitivity. Reading intervention resulted in a substantial increase (~ one grade level) in standardized measures of reading abilities; however, learning to read did not affect motion sensitivity. In each individual, motion sensitivity increased during the first session (before intervention) as children learned to perform the task at threshold, and then sensitivity remained stable over the course of the intervention program. Furthermore, the motion sensitivity deficit did not negatively impact the learning process: children with the most severe motion sensitivity deficits showed the same improvement in reading skills as children with typical motion sensitivity. To conclude, our findings call into question the causal relationship between motion sensitivity and dyslexia, and suggest that the correlation between the two might be caused by other common mechanisms, or that motion processing is just one of many factors that contribute to the multifaceted impairments in developmental dyslexia.
Meeting abstract presented at VSS 2017
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