Peri-saccadic spatial compression in dyslexia F Maij, J Atsma, P Medendorp |
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Donders Institute, Radboud University Nijmegen, Netherlands
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| When reading, the eyes jump from word to word. Each saccadic eye movement causes a shift in the retinal image, which must be compensated for by the brain in order to create a stable percept of the text. Could an insufficient compensation explain deficits that are seen in dyslexic readers? A typical paradigm to test this compensatory mechanism examines the localization of flashes presented near the time of saccades. Non-impaired participants mislocalize flashes, as if visual space is compressed toward the saccade endpoint. The size of this compression depends on various factors, including saccade kinematics. Interestingly, recent studies have suggested that peri-saccadic compression in dyslectic participants is attenuated compared to non-impaired controls. However, because saccadic characteristics differ also in dyslexics, the question arises whether this difference in compression is simply due to differences in eye movement behavior. In this study, we tested peri-saccadic compression as a function of saccade kinematics in both dyslexics and controls, by manipulating saccade amplitude between 10 and 14 degrees. We found a clear effect of saccade amplitude on peri-saccadic compression in controls. Preliminary findings suggest that compression effects differ between dyslexics and controls. More experiments and analyses are currently under way to validate this notion. |
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