The impact of blindness onset on the connectivity profile of the occipital cortex

Rezk, Mohamed [UCL] Pelland, Maxime Atilgan, Hicret Collignon, Olivier [UCL]

Resting state functional connectivity (rs-FC) has been widely used to investigate the functional (re)organization of the “visual” cortex in blind people. However, discrepant results have emerged with some studies pointing to massive changes in the connectivity profile of occipital regions in blind individuals while other studies showing similar pattern of occipital connectivity in the blind and the sighted. Moreover, the impact of the onset of blindness on these measures remains poorly understood. This question is however crucial to understand if there is a sensitive period in development for reorganizing occipital networks. In this study we investigated the functional connectivity changes between occipital regions and the rest of the brain in early blind (EB), late blind (LB), and their matched controls using fMRI data acquired at rest. We relied on a bootstrap Analysis of Stable Clusters (BASC) to subdivide the brain into meaningful functional parcels. Whereas both blind groups showed reorganization of the connectivity profile of the occipital cortex, these connectivity changes were more much more extended in early blind individuals. We demonstrate that certain connectivity changes occur regardless of the blindness onset, while others being specific to early or late blindness. These results were further supported by using multivariate pattern classification showing highly significant classification rate of individuals to their respective groups based on the connectivity fingerprint of their occipital regions. However, we also observed certain sub-regions within the ventral occipital cortex (e.g. PPA) that show a similar connectivity profile across all groups. Altogether, our data suggests regions-specific impacts of blindness onset on the connectivity architecture of the occipital cortex.