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How Arabic Letter Allography Reshapes Neural Representations from V1 to Frontal Cortex
Poster Session A, Wednesday, September 30, 11:00 am - 1:00 pm, Wangari Maathai
Sami Boudelaa1, Adem Yacizi2, Ahmet Cihan Uzun2, Mohamed Lamine Seghier3, Milos Ljubisavljevic1, Osama Abdullah4, Ausaf Ahmed Farooqui2; 1UAE University, 2Bilkent University, Turkey, 3Khalifa University, UAE, 44New York Abu Dhabi University, UAE
Current theories of reading posit modality-specific representations of (a) letter forms, (b) motor plans and (c) abstract representations that serve to unify these modality-specific formats. In support of this, previous research strongly suggest that letters are encoded through multiple interacting neural representations including the left mid-fusiform gyrus along with ventral temporal and dorsal parietal areas. However, this theorising and the empirical research supporting it are exclusively based on English and languages like it. Here we take this line of research a significant step forward by focussing on Arabic, a language with a unique orthographic feature: allography, the change in shape letters undergo according to their position within a word. We directly test quantitative models of the similarity/dissimilarity structure of distributed neural representations of letters using Representational Similarity Analysis (RSA) to analyze the BOLD response recorded from single letter viewing in 20 skilled Arabic readers. Our analyses reveal two dissociable neural patterns. In left‑lateralized occipital regions (V1 and extrastriate regions), we found selective tuning to allographic form: the isolated letter “ع” was representationally closer to the isolated form of the distinct letter “غ” than to its own medial variant “ــعــ”. By contrast, frontotemporal language regions, especially inferior frontal regions, supported abstract letter identity, such that allographic variants of the same letter (e.g., isolated “ع” and medial “ــعــ”) clustered together regardless of their visual form. These findings suggest that while the earliest cortical stages of reading can be shaped by language‑specific orthographic structure, later language regions represent the abstract letter identity, demonstrating that a truly general theory of reading must accommodate writing systems where the mapping between form and identity is systematically context‑dependent.
Topic Areas: Reading, Writing and Spelling