id_813. LONGITUDINAL CHANGES IN PHONOLOGICAL PROCESSING IN THE LEFT VENTRAL OCCIPITOTEMPORAL CORTEX: FMRI EVIDENCE FROM TYPICAL READERS AND CHILDREN WITH DYSLEXIA
Agnieszka Mankiewicz1, Agnieszka Dębska2
1 University of Warsaw, College of Inter-Faculty Individual Studies in Mathematics and Natural Sciences, Warsaw, Poland
2 Laboratory of Language Neurobiology, Nencki Institute of Experimental Biology, Polish Academy of Sciences, Warsaw, Poland
INTRODUCTION: Reading acquisition is a complex process that relies on the systematic mapping of orthographic symbols onto phonological representations. It fundamentally reshapes phonological processing, leading to the automatic co-activation of orthographic information even during purely auditory tasks. This developmental pattern is disrupted in dyslexia, where degraded phonological processing results in failure to establish the integrated system.
AIM(S): This study investigated how the left ventral occipitotemporal cortex (lvOT) supports the development of orthography–phonology coupling in typical and atypical reading, focusing on the posterior–anterior gradient proposed to reflect a trajectory from small- to large-grain processing.
METHOD(S): We conducted a longitudinal fMRI study with 61 Polish‑speaking children (20 with dyslexia, 41 controls). Participants were scanned twice: at the onset of formal reading instruction (TP1) and roughly three years later (TP2). Children completed three auditory phonological tasks probing different grain sizes: an alliteration task (small‑grain), a rhyme task (large‑grain), and a word‑matching control. An orthographic visual‑localizer contrast delineated individual posterior and anterior lvOT regions of interest (ROIs). Activation within both ROIs was analysed using mixed‑effects models.
RESULTS: ROI analyses revealed increased activation from TP1 to TP2 during the alliteration condition in both anterior and posterior lvOT (all p ≤ .01). No longitudinal changes were observed for rhyme or control conditions, and no posterior–anterior shift in activation was found. This pattern was similar in both groups.
CONCLUSIONS: These findings indicate increasing lvOT involvement in small-grain phonological processing during reading acquisition, without evidence of posterior–anterior reorganisation. Comparable developmental trajectories across groups provide no evidence for delayed specialisation along the lvOT posterior–anterior axis in dyslexia, suggesting its core deficits may lie elsewhere.
FINANCIAL SUPPORT: This study was supported by the National Science Centre (Narodowe Centrum Nauki) grant number 2024/54/E/HS6/00242.