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Rosemary Le, Brian Wandell, Michal Ben-Shachar, Nathan Witthoft; The field of view of word-responsive regions in visual cortex. Journal of Vision 2016;16(12):1426. doi: 10.1167/16.12.1426.
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© 2017 Association for Research in Vision and Ophthalmology.
Introduction Skilled reading involves rapid recognition of foveally-presented word forms. fMRI measurements have shown that regions in ventral occipito-temporal cortex are trained to rapidly recognize word forms, but the spatial sensitivity of these regions is not well understood. Here we measure its field of view – the portion of the visual world that reliably evokes a response in these regions. We examine how the field of view is modulated by stimulus type. Methods We used population receptive field (pRF) methods to measure the field of view in word-responsive cortex. Two types of stimuli – words and checkerboards – were used as the contrast pattern in bars that swept through the visual field (16° radius). The responses were modeled using the compressive summation model (Kay 2013). Separate pRF models were fit to each stimulus type. The visual word form area (VWFA) and its right-hemisphere homolog (rVWFA) were functionally localized in each subject (n = 21). Results When measured with word stimuli, the field of view of the VWFA is elliptical and extends from the fovea to 5-7° along the horizontal meridian. More than 90% of the pRF centers within the VWFA are within 5° eccentricity. The same trend can be seen in rVWFA. The field of view of word-responsive regions shows a bias for the right lower visual field. When the pRFs are measured with checkerboard stimuli, the same regions show noisier and less consistent field of view across subjects. In contrast, the field of view in V1 is highly consistent for all stimuli. Discussion In response to word stimuli, the field of view of word-responsive regions is foveally-biased. The field of view of word-responsive cortex, but not V1, is stimulus dependent. These findings provide a new paradigm for studying cortical responses in relation to individual reading performance.
Meeting abstract presented at VSS 2016
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