Impact of visual experience on the functional organization and the connectivity of the occipital cortex

Abstract

How specific brain regions attain, maintain and modify their functional tuning regarding the processing of specific stimuli has long fascinated researchers in neurosciences. Contrasting the impact of congenitally versus lately acquired blindness provides a unique model to probe how experience at different developmental periods shapes the functional organization of the occipital cortex (classically considered as visual). I will demonstrate that visual deprivation, acquired early or late in life, induces massive recruitment of occipital regions for auditory processing. Importantly, right dorsal occipital regions, which are known to be preferentially involved in the processing of the spatial relations among visual objects in sighted individuals, are preferentially involved during tasks involving the spatial processing of non-visual inputs in congenitally blind individuals. However such functional specialization in reorganized occipital regions was not observed in the late blind, suggesting that vision has to be lost during an early sensitive period in order to transfer its functional specialization for space processing toward a non-visual modality. By using a combination of functional (psychophysiological interactions) and effective (dynamic causal modeling with Bayesian model selection) connectivity techniques, we also demonstrate that the developmental period of visual deprivation not only influence the functional architecture, but also the connectivity of the occipital cortex. I will finally illustrate how such findings are clinically important now that a growing number of medical interventions may restore vision after a period of visual deprivation.