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Julia Englund, Melanie Palomares; The Relationship of Global Form and Coherent Motion Detection to Reading Fluency. Journal of Vision 2011;11(11):433. doi: 10.1167/11.11.433.
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© ARVO (1962-2015); The Authors (2016-present)
Several psychophysical observations suggest that an array of different developmental disabilities share deficits in functions thought to be specific to dorsal stream processing - namely coherent motion detection (Braddick, Atkinson, & Wattam-Bell, 2003). Mechanisms to detect motion coherence have been reported to be abnormal in dyslexics (Eden et al., 1996), suggesting that reading is related to dorsal visual function. We evaluated two questions: (1) Is reading fluency a function of the dorsal visual stream? (2) Is dyslexia characterized by attenuation of or deviation from typical global form and motion detection ability? We measured detection thresholds for coherent motion and coherent form (Glass patterns) using a standard staircase procedure. We found that in typically developing children, reading fluency is significantly correlated with thresholds of global coherent form but not coherent motion when corrected for nonverbal IQ and age. This suggests that reading fluency is a ventral, rather than dorsal, visual function in typically developing children. Additionally, both children and adults performed better at detecting coherent motion than coherent form; performance on both tasks improved between childhood and adulthood. However, we found that dyslexic adults showed a different pattern of performance from both typical adults and children: Dyslexic adults detected coherent form better than coherent motion. They were also worse than typical adults at both tasks. This pattern of results is indicative of deviation from typical development in dyslexia in global visuospatial processing, rather than mere attenuation. Our results show that detecting global form is related to reading fluency in typical development, but that detecting global motion is impaired in dyslexia.
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