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Michal Ben-Shachar, Robert F. Dougherty, Gayle K. Deutsch, Polina V. Potanina, Brian A. Wandell; The development of visual sensitivity to words in ventral occipito-temporal sulcus. Journal of Vision 2005;5(8):1054. doi: 10.1167/5.8.1054.
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© ARVO (1962-2015); The Authors (2016-present)
INTRO Left ventral Occipito-Temporal Sulcus (OTS) responds more powerfully to visual words than to checkerboards (Cohen et al., 2003). We have shown that BOLD response to words in this region decreases with increasing amounts of noise. In this study, we ask how early this sensitivity develops.
METHODS We measured BOLD signals while 7–12y children with varying reading skills viewed word stimuli in an implicit reading task. Subjects judged the color of a fixation cross in the center of each word. Word visibility was parametrically manipulated by forming a convex sum of the word with a phase scrambled version of itself. Stimuli were presented in 12s (6 items) blocks, alternating with fixation blocks. Twenty-six 2.5×2.5×3 mm axial slices were acquired (3T GE Signa, spiral acquisition) covering occipito-temporal cortex. To assess the spatial distribution of noise sensitivity, we computed a GLM and created contrast maps for the high visibility vs. low visibility conditions in each brain. We measured the size of the BOLD response to words as a function of noise level within left OTS, defined anatomically and functionally by contrasting word conditions vs. fixation.
RESULTS We found robust activation in left OTS in 20 out of 22 children (some as young as 7y) for high vs. low visibility words. ROI analysis revealed that individual response functions in this region decreased with increasing amounts of noise, but the shape of this function varied between subjects. Response decrease to added noise was not found in early visual areas (V1/2/3).
CONCLUSIONS Sensitivity for words in visual noise develops as early as age 7, and manifests in similar brain regions as in the adult reader. This is in agreement with behavioral data showing a ‘viewing position effect’ for words in children at the end of the first grade (Aghababian and Nazir, 2000). Correlating individual response functions with behavioral reading measures will further elucidate the functional significance of this early perceptual sensitivity for words.
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