THE INTERPLAY BETWEEN ORTHOGRAPHY AND PHONOLOGY PROCESSING IN THE LEFT VENTRAL OCCIPITO-TEMPORAL CORTEX: RELATION TO READING ACQUISITION AND DYSLEXIA

Learning to read requires integrating orthographic and phonological representations, a process supported by the left ventral occipitotemporal cortex (lvOT). While cross-sectional studies suggest a developmental posterior–anterior shift in lvOT engagement, longitudinal evidence in atypical reading development remains limited.

To address this gap, we conducted a longitudinal fMRI study in Polish-speaking children. Sixty-one participants (20 with dyslexia, 41 typically developing controls) were followed from the onset of formal literacy instruction (TP1; 6.02–7.36 years) to third grade, approximately three years later (TP2; 9.10–10.34 years). During fMRI, children completed auditory phonological tasks targeting different grain sizes: alliteration (small-grain), rhyme (large-grain), and word matching (control). An orthographic visual localizer (words > false font) was used to define individual anterior and posterior lvOT regions of interest (ROI).

ROI analyses revealed a significant increase in lvOT activation from TP1 to TP2 during small-grain phonological processing (alliteration), observed in both anterior and posterior lvOT (all p ≤ .01). No comparable developmental changes were found for large-grain or control conditions. Mixed-effects analyses provided no evidence for a posterior–anterior redistribution of lvOT activity over time. At the whole-brain level, children with dyslexia showed greater recruitment of posterior parietal and domain-general regions relative to controls (cluster-level FWE-corrected p < .05).

These findings indicate that, in transparent orthography, reading development entails increased lvOT involvement in small-grain phonological processing rather than a spatial shift along the posterior–anterior lvOT axis. In dyslexia, altered engagement of domain-general networks may reflect compensatory mechanisms supporting phonological processing during reading acquisition.