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Eva Dundas, Yafit Gabay, David Plaut, Marlene Behrmann; Altered hemispheric specialization for faces and word in developmental dyslexia. Journal of Vision 2014;14(10):1438. doi: https://doi.org/10.1167/14.10.1438.
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Extensive evidence gleaned from investigations with adults reveals the existence of highly specialized and seemingly independent neural mechanisms for visual word recognition in the left hemisphere, and for visual face recognition in the right hemisphere (for review, see Toga & Thompson, 2003). Emerging evidence suggests, however, that these two domains are not independent and that word lateralization is driving the emergence of face lateralization (Dundas, Plaut, & Behrmann, 2013; Dehaene et al., 2011) On this account, participants with disrupted organization of word processing should also exhibit altered organization of face processing. The current study examines the hemispheric superiority for faces and words in adults who have been diagnosed with developmental dyslexia, and demonstrate persistent reading difficulties. Using behavioral and neurophysiological measures, we replicate the standard finding of greater accuracy and stronger N170 in the left over the right hemisphere for words, and conversely, greater accuracy and stronger N170 in the right over the left hemisphere for faces in adults without reading difficulty. In adults with developmental dyslexia, however, we did not observe a hemispheric difference in accuracy for words or for faces. Despite showing a stronger N170 in the left over the right hemisphere for words, the N170 for words had longer latency and was more drawn out than it was for adults without reading difficulties. In turn, the adults with developmental dyslexia showed no difference in the strength of the N170 for faces between hemispheres. These findings suggest that the hemispheric organization of face and word processing do not develop independently, and that when there is a failure to develop coherent word processing in the left hemisphere, face processing does not become instantiated in the right hemisphere. A theoretical account in which competition for visual representations unfolds over the course of development is proposed to account for the findings.
Meeting abstract presented at VSS 2014
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