Vision & Sight Recovery

Presentation of research activities

Over the last years, the CPP-Lab has developed an innovative approach that relies on the respective advantages of a plurality of methods (psychophysics, EEG/MEG, stereotactic EEG, TMS, fMRI) to converge toward a comprehensive understanding of the mechanisms underlying crossmodal perception and plasticity. This work has recently led to significant breakthroughs on at least three major fronts:

1. The multisensory nature of brain networks. We show that sensory systems are not encapsulated but also respond to sensory input from their non-dominant modality. For example, using intracranial electrophysiological recordings in epileptic patients, we showed that sounds can modulate the activity of V1. More recently, relying on advanced multivariate fMRI analyses, we also showed that hMT+/V5 represents the direction of visual and auditory motion in a partially aligned fashion, suggesting that the natural crossmodal tendencies of sensory regions follow the functional organization of brain regions for specific processing. We have now extended this work by showing that face-selective regions (e.g., FFA) can respond to emotional voices and that voice-selective regions can represent facial emotion expressions, again in a co-registered fashion (e.g., ensembles of voxels coding fear in vision also code fear in audition).

2. Functional mapping of regions deprived of their dominant sensory input. Overall, our research is driven by the strong conviction that the study of sensory-deprived individuals represents a unique model system to probe how the brain develops, maintains and changes its functional tuning to adapt its interaction with the environment. Olivier Collignon was among the first to demonstrate that the division of computational labor observed in the occipital cortex of sighted people processing visual inputs is somehow maintained in congenitally blind people processing sounds or touch. For instance, we have shown that category-selective regions in the ventral occipito-temporal stream maintain a certain level of domain organization in the total absence of vision since birth.

3. Interplay between visual deprivation and sight restoration. In addition to a single case study of a patient who recovered sight late in life following the implantation of a Boston keratoprosthesis, we carried out a series of psychophysical and fMRI measurements in adults born with congenital cataracts that were removed within the first two years of life. Our studies suggest that visual deprivation chiefly affects the early stages of information processing while, unexpectedly, leaving the more anterior “higher visual regions” mostly unaffected. These novel results are particularly interesting when contrasted with our finding that early visual regions continue to show increased responses to sounds in cataract-reversal patients, even after more than 20 years of visual experience, and that this enhanced response likely influences multisensory behavior.