Instructive and reorganizing effects of experience on development of human visual cortices.

Visual behavior and visual cortex function in adulthood are affected by early visual experience. In humans, the developmental origins of these differences amongst adults are not known. It is often assumed that differences reflect reorganizing effects of blindness on cortical function. Whether vision also plays an instructive role is not known. Here we compare newly available resting state (functional connectivity) data from two large cohorts of sighted infants (Developing Human Connectome Project (dHCP), second release: n=327, third release: n=475) to data from sighted adults (blindfolded, n=50) and blind adults (n=30). By comparing the "starting state" of infants to that of blind and sighted adults, we dissociate the instructive contributions of visual experience from the reorganizing effects of blindness on functional connectivity of visual cortices. As previously reported, we find that in sighted adults, visual networks show stronger functional connectivity with other sensory-motor networks (i.e., auditory, somatosensory) than with higher-cognitive prefrontal networks. Adults born blind show the opposite pattern: stronger functional connectivity between visual and prefrontal than visual and other non-visual sensory-motor networks. The resting state patterns of infants resemble those of blind adults in secondary visual cortices, revealing an instructive role of vision in establishing the sighted adult connectivity pattern. In primary visual cortex (V1), the sighted infants show an intermediate pattern between that of sighted and blind adults, suggesting both instructive effects of vision and reorganizing effects of blindness in V1. Relative to both adult groups, when comparing connectivity across different sub-regions of visual and prefrontal cortex, infants show less specialization relative to both adult groups. Finally, lateralization of connectivity in infants resembles that of sighted adults, consistent with reorganizing effects of blindness. These results dissociate instructive and reorganizing effect of experience on visual cortex functional connectivity, providing insight into developmental mechanisms.