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Neuroplastic mechanisms underlying the emergence of VWFA over reading acquisition
Poster Session D, Saturday, September 13, 5:00 - 6:30 pm, Field House
Jibiao Han1, Ted K. Turesky2, Megan Yf Loh2, Xiaoxia Feng1, Nadine Gaab2, Xi Yu1; 1Beijing Normal University, 2Harvard University
Introduction. The ventral temporal cortex (VTC) supports high-order visual processes through topologically organized, category-selective functional parcel, such as the fusiform face area (FFA) and the visual word form area (VWFA). These parcels exhibit distinct developmental trajectories, offering a window into neuroplasticity in the VTC. For example, the face-selective responses in FFA are present in infancy and continue to develop throughout childhood, whereas the neighboring VWFA with word-selectivity emerges only after reading instruction. The relationship between these two regions remains elusive. Competing theories of VTC neuroplasticity propose that the VWFA may emerge from previously face-selective cortex (i.e., “strong competition”), constrain continued FFA development (i.e., “blocking” model), or develop independently of the FFA (i.e., “no competition”). Methods and Results. To investigate these hypotheses, we collected functional MRI from 69 children performing an audiovisual matching task involving faces, words, letter and colors. Participants were scanned at reading onset (T1, 65.8 ± 6.0 months, n=35) and/or after at least one year of reading experiences (T2, 93.7±14.1 months, n=56), with 22 children participating at both time points (i.e., longitudinal sample). For each participant, FFA and VWFA regions were defined based on face-selective (faces > [words + colors]) and word-selective (words > [faces + colors]) contrasts. We first characterized group-level category-selectivity in VTC over development. In both longitudinal and full samples, bilateral FFA was evident at both time points (all p <0.025), whereas word-selective activation appeared only in the left-hemispheric (LH) VWFA at T2 (all p <0.05), and not at T1 or in the right hemisphere (RH, all p > 0.09). Crucially, the left VWFA defined at T2 showed no category selectivity at T1 in the longitudinal sample. Next, we examined the individualized topological lateralization for both categories. In both samples, FFA showed consistent right topological lateralization (i.e., more face-selective voxels in RH than LH) at both timepoints (all p <0.002), while VWFA exhibited left lateralization only at T2 (T1: all p >0.07; T2: all p <0.015). Notably, FFA right-lateralization (i.e., voxel number in RH versus LH) correlated significantly with VWFA left-lateralization at T2 (longitudinal sample: r = 0.75, p < 0.001; full sample: r = 0.49, p < 0.001), but not at T1 (both p > 0.09). Finally, we analyzed topological changes in the left FFA relative to VWFA emergence in the longitudinal sample. We observed that voxels selectively responsive to faces at T1 but not T2 (i.e., “disappearing FFA”) were spatially closer to the emerging VWFA at T2, compared to voxels with consistent face selectivity at both time points (i.e., “stable FFA”; t20 =-2.34, p = 0.03). Conclusion. Our results show that face selectivity in both hemispheres proceeds the reading-associated development of word selectivity in the left hemisphere. However, the VWFA does not arise from previously face-selective cortex, challenging the strong competition theory. Instead, the emergence of the left VWFA is associated with a topological shift of the left FFA away from the developing VWFA and increased right-hemispheric lateralization of the FFA, supporting the "blocking” model over the “no competition” account of VTC neuroplasticity.
Topic Areas: Reading,