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MADVIS Report Summary

Project ID: 337573
Funded under: FP7-IDEAS-ERC
Country: Belgium

Periodic Report Summary 2 - MADVIS (Mapping the Deprived Visual System: Cracking function for prediction)

One of the most striking demonstrations of experience-dependent plasticity comes from studies of blind individuals showing that the occipital cortex (traditionally considered as purely visual) massively changes its functional tuning to support the processing of non-visual inputs. These mechanisms of crossmodal plasticity, classically considered compensatory, inevitably raise crucial challenges for sight- restoration. How will the non-visual inputs interfere, coexist or disappear following the re-acquisition of vision? Addressing this issue is particularly timely now, given the recent advent of sight-restoration techniques. The neglected relation between crossmodal plasticity and sight-recovery represents the testing ground for MADVIS in order to gain important novel insights on how specific brain regions become, stay and change their functional tuning towards processing specific stimuli.
In the first project phase, MADVIS made breakthroughs on two fronts: (1) understanding how visual deprivation at different sensitive periods in development affects the functional organization and connectivity of the occipital cortex; and (2) using the fundamental knowledge derived from (1) to test and predict the outcome of sight restoration. We were able to show that while the recruitment of occipital (visual) regions by non-visual inputs in blind individuals highlights the ability of the brain to remodel itself on the basis of experience (nurture influence); the observation of specialized processing units in the reorganized occipital cortex of the blindsimilar to those observed in the sighted-, highlights the intrinsic constraints imposed on such plasticity (nature influence). However, in contrast to the idea that the participation of the occipital regions of blind people during non-visual processing simply reflects an “extension” of the multisensory nature of these regions, we showed that early, and to a lesser extent late blind deprivation, is accompanied by a large-scale crossmodal reorganization of brain networks. The overarching goal of MADVIS was to relate the knowledge gathered from blind people to sight-restoration. We have been already able to demonstrate that visual deprivation, if appearing early in life, leads to long-lasting crossmodal involvement of occipital regions for sound processing that remains for years after sight-recovery. Somehow surprisingly, these brain and behavioral reorganizations can also be found if the period of deprivation is very short (e.g. few months) but early in life. The results from these studies provide support for the existence of multifaceted interplay between the neuroplastic mechanisms linked to sight deprivation and restoration. Apart from these novel scientific insights, we have also prepared the methodological foundation for the next project period, including the assessment of the functional significance of crossmodal plasticity with Transcranial Magnetic Stimulation or the evaluation of whether change in functional connectivity of the occipital cortex is also linked to changes in structural connectivity between distant brain regions. The methodological developments that have been at the core of this first phase of the MADVIS project have profound potentials far beyond the scope of our project.

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