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Large-scale preservation and fine-scale reorganization of language and mathematical processing networks in congenital blindness
Poster Session E, Friday, October 2, 11:00 am - 1:00 pm, Wangari Maathai
Manon Pietrantoni1, Antonio Moreno1, Marie Amalric1, Séverine Becuwe1, Ghislaine Dehaene-Lambertz1, Christophe Pallier1, Stanislas Dehaene1,2; 1Cognitive Neuroimaging Unit, INSERM, CEA, CNRS, Université Paris Saclay, NeuroSpin center, 91191 Gif/Yvette, France, 2Collège de France, Université Paris Sciences Lettres (PSL), 11 Place Marcelin Berthelot, 75005 Paris, France
Congenital blindness provides a unique model to investigate how sensory deprivation reshapes cortical organization. Although numerous studies have demonstrated cross-modal recruitment of occipital regions in blind individuals, the fine-grained functional architecture of these reorganized territories remains poorly understood. Moreover, potential alterations outside the occipital cortex have received comparatively little attention. Using 3T fMRI, we compared cortical networks supporting language and mathematical processing in congenitally blind and sighted participants during a True/False task involving 320 sentences. Analyses were conducted at the sentence level by averaging activation maps across 12 congenitally blind participants and approximately 15 sighted participants per sentence. We combined standard univariate contrasts with a sentence-based approach coupled with PCA to characterize functional organization at a finer spatial scale. At the large-scale level, language and mathematical processing recruited highly similar cortical networks in both groups. However, several focal differences emerged in congenitally blind participants. First, language-related activity extended into occipital territories, where distinct regions showed differential sensitivity to semantic and syntactic information. Ventral left occipital regions overlapping V3/V4 showed selective responses to syntactically structured stimuli (grammatical but meaningless sentences versus word lists), whereas dorsal occipital and posterior parietal regions bilaterally showed enhanced responses to semantically meaningful content (meaningful versus meaningless sentences). Second, reduced responses were observed in blind participants within bilateral parahippocampal and parieto-occipital regions for sentences containing geographic place-related information (e.g., countries, cities, landmarks), suggesting altered specialization of spatial-semantic representations. Third, within the occipital cortex of blind individuals, we identified a novel functional topography: mathematical processing preferentially recruited foveal occipital territories, whereas language preferentially engaged more peripheral regions. This eccentricity-based dissociation suggests that intrinsic organizational principles of visual cortex continue to constrain functional specialization despite the absence of visual experience. Finally, whereas sighted participants showed geometry-selective responses in parietal cortex and posterior inferior temporal gyrus, these geometry-specific effects were absent in congenitally blind participants. Instead, these regions responded to mathematical processing more generally, despite comparable behavioral performance across groups. These effects survived whole-brain correction for multiple comparisons. Together, these findings demonstrate that congenital blindness preserves the large-scale architecture of higher cognitive networks while inducing a structured cortical reorganization. Beyond the well-established recruitment of occipital cortex, our results reveal both gains and losses of functional specialization across distributed cortical systems. Overall, these findings highlight the persistence of intrinsic cortical constraints on functional organization independently of visual experience.
Topic Areas: Meaning: Lexical Semantics, Computational Approaches