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Visual Cortex Recruitment in Blindness Emerges Before Word Meaning: Evidence from Brain-Constrained Neural Network Simulations
Poster Session A, Wednesday, September 30, 11:00 am - 1:00 pm, Wangari Maathai
Maxime Carriere1, Rosario Tomasello1,2,3; 1Freie Universität, 2University of Potsdam, 3Cluster of Excellence
Visual cortex recruitment for language and cognition is a striking expression of neuroplasticity in congenital blindness, but its developmental origin remains unclear. Does occipital recruitment emerge only after word meanings are acquired, or can it arise earlier from pre-symbolic motor and phonological learning? We addressed this question using a biologically constrained spiking neural network model of 12 frontotemporal and occipital cortical areas, simulated under sighted and visually deprived conditions. Networks underwent a two-phase learning protocol. In Phase 1, motor-action circuits and phonological word-form circuits were learned separately, mimicking early action execution and babbling-like activity before word–meaning mapping. In Phase 2, these pre-established circuits were associated through symbolic learning, linking auditory word forms to action referents during simulated action-word learning. After each phase, we tested neural reactivation during action execution and auditory word recognition, and quantified both area-specific spiking dynamics and inter-areal synaptic connectivity. Blind networks showed significantly stronger recruitment of visual areas, including primary visual and temporo-occipital cortex, already after Phase 1 during action reactivation, indicating that occipital recruitment can arise before semantic word–referent associations are established. After symbolic learning, auditory word recognition elicited broader activation of visual cortices in blind than sighted networks, accompanied by longer extrasylvian reverberation times, a putative correlate of verbal working memory. Connectivity analyses showed that symbolic learning strengthened coupling between perisylvian language areas and extrasylvian motor-semantic regions in both sighted and blind networks, reflecting the formation of links between auditory word-form and action-referent circuits. In blind networks, this associative reorganization was accompanied by stronger visual-stream and fronto-visual coupling, indicating deprivation-driven synaptic recruitment of occipital cortex for action-words. These findings suggest that visual cortex recruitment in blindness does not require fully established semantic representations, but emerges progressively from early motor and phonological learning and is further amplified during word–meaning acquisition.
Topic Areas: Computational Approaches, Language Development/Acquisition