Zexi Chen¹ (), Marianna Elisa Schmidt^2,3, Shahin Nasr^4,5, Cherlyn Joan Ng^1,6, Daniel Ts’o⁷; ¹University of California, Irvine, Irvine, CA, USA, ²Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany, ³Max Planck School of Cognition, Leipzig, Germany, ⁴Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA, USA, ⁵Harvard Medical School, Boston, MA, USA, ⁶Brunson Center for Translational Vision Research, University of California, Irvine, CA, USA, ⁷SUNY Upstate Medical University, Syracuse, NY, USA

Introduction: Intra-areal functional connections (FCs) within V1 are thought to support coherent visual perception across the visual field. These connections, however, are not uniform; rather, they exhibit systematic heterogeneity that may help explain known perceptual asymmetries. In this study, we tested whether intra-V1 FC varies between foveal and peripheral regions as suggested based on foveal confluence—the dense clustering of foveal representations in V1. We then asked whether this organizational principle is altered in amblyopia, a developmental disorder that disproportionately affects foveal vision. Methods: In Experiment 1, 33 adults (aged 22-43) with neurotypical vision were scanned during resting state (eyes closed) in a 3T MRI (3mm isotropic); 20 of these participants also completed a separate 7T session (1mm isotropic). Experiment 2 included 4 neurotypical controls (aged 24-47) and 7 individuals with amblyopia (aged 27-60; 4 with strabismus and 3 with anisometropia) scanned at 7T. For all participants, the V1 surface representing the central 10° was segmented into 16 equal-area subregions. Intra-V1 FC was quantified using partial correlations between vertices across these subregions (Schmidt et al., 2025). Results: In Experiment 1, regions representing more foveal visual field locations showed significantly stronger FC with one another than with regions representing equivalent eccentricities in the periphery (p<10-4). This pattern was robust across both field strengths and detectable across deep, middle, and superficial layers at 7T. Our preliminary results in Experiment 2 showed that, compared to controls, strabismic amblyopia showed both reduced foveal bias and a global reduction in intra-V1 FC, whereas anisometropic amblyopia preserved overall FC magnitude but showed reduced foveal specificity. In both amblyopia subtypes, the weakened foveal bias was more apparent in superficial layers. Conclusion: These findings reveal a pronounced foveal-centric organization of V1 FC and demonstrate its vulnerability to disruptions in balanced binocular vision early in life.

Acknowledgements: This work was supported by NIH NEI (R01 EY030434), and by the MGH/HST Athinoula A. Martinos Center for Biomedical Imaging. Crucial resources were made available by a NIH Shared Instrumentation Grant S10-RR019371.