ERC Starting Grant: Understanding the nature of face perception: new insights from steady-state visual evoked potentials
Investigator: Bruno Rossion
Start date: 2012-02-01
End date: 2017-01-31
Project Acronym: FACESSVEP
Objective: Face recognition is one of the most complex functions of the human mind/brain, so that no artificial device can surpass human abilities in this function. The goal of this project is to understand a fundamental aspect of face recognition, individual face perception: how, from sensory information, does the human mind/brain build a visual representation of a particular face? To clarify this question, I will introduce the method of steady-state visual evoked potentials (SSVEPs) in the field of face perception. This approach has never been applied to face perception, but we recently started using it and collected strong data demonstrating the feasibility of the approach. It is based on the repetitive stimulation of the visual system at a fixed frequency rate, and the recording on the human scalp of an electrical response (electroencephalogram, EEG) that oscillates at that specific frequency rate. Because of its extremely high signal-to-noise ratio and its non-ambiguity with respect to the measurement of the signal of interest, this method is ideal to assess the human brains sensitivity to facial identity, non-invasively, and with the exact same approach in normal adults, infants and children, as well as clinical populations. SSVEP will also allow tagging different features of a stimulus with different stimulation frequencies (frequency-tagging method), and thus measure the representation and processing of these features independently, as well as their potential integration. Overall, this proposal should shed light on understanding one of the most complex function of the human mind/brain, while its realization will undoubtedly generate relevant data and paradigms useful for understanding other aspects of face processing (e.g., perception of facial expression) and high-level visual perception processes in general.
ERC Starting Grant: Mapping the Deprived Visual System: Cracking function for prediction, MADVIS.
Investigator : Olivier Collignon
Start Date: 2014-04-01
End Date: 2019-03-31
Evolution has endowed the brain with the remarkable ability to reorganize its circuits throughout life in response to experience. 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. From a general point of view, these studies shed new light on the old ‘nature versus nurture’ debate on brain development: while the recruitment of occipital (visual) regions by non-visual inputs in blind individuals highlights the ability of the brain to remodel itself due to experience (nurture influence), the observation of specialized cognitive modules in the occipital cortex of the blinds, similar to those observed in the sighted, highlights the intrinsic constraints imposed to such plasticity (nature influence). Yet, the accumulated corpus of data leaves several essential questions unanswered MADVIS wants to address.
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 will represent the testing ground of MADVIS in order to gain important novel insights on how specific brain regions become, stay and change their functional tuning toward the processing of specific stimuli. The main goal of MADVIS is therefore to make a breakthrough 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) use the fundamental knowledge derived from (1) to test and predict the outcome of sight restoration. Using a pioneering interdisciplinary approach that crosses the boundaries between cognitive neurosciences and ophthalmology, MADVIS will have a large impact on our understanding of how experience at different sensitive periods shapes the response properties of specific brain regions. Finally, MADVIS will eventually pave the way for a new generation of predictive surveys prior to sensory restoration.
L’étude des personnes privées de vision représente une opportunité unique pour comprendre comment l’expérience sensorielle (ou son absence) interagit avec des contraintes biologiques innées afin de façonner l’architecture cérébrale.
Chez une personne voyante, environ 1/3 du cerveau est dédié au traitement de l’information visuelle. Que deviennent ces régions chez une personne aveugle? Est-ce qu’elles disparaissent du au fait qu’elles ne reçoivent pas d’information visuelle? Non, bien au contraire. Ces régions, principalement le cortex occipital traditionnellement considéré comme purement visuel, changent massivement leur rôle afin de soutenir le traitement d’informations non-visuelles comme les sons ou le toucher. D’un point de vue fonctionnel, il est supposé que cette plasticité inter-modale est compensatoire et aide les personnes non-voyantes à mieux entendre ou mieux sentir avec le toucher (imaginez devoir vous rendre à votre travail avec les yeux bandés ou à lire le braille avec vos doigts et vous comprendrez immédiatement à quel point les sens de l’audition et du toucher sont développés chez des personnes non-voyantes).
Cependant, cette plasticité cérébrale soulève inévitablement des défis cruciaux pour les techniques de restauration visuelle. En effet, comment est-ce que les régions visuelles du cerveau, maintenant devenue auditive chez une personne aveugle, peut ré-apprendre à voir? Comprendre les jeux d’interactions entre la plasticité intermodale et la restauration visuelle représente le terrain d’étude du projet MADVIS. Cette recherche permettra notamment d’obtenir des informations cruciales sur la façon dont les régions du cerveau développent, maintiennent et changent leur réglage fonctionnel pour le traitement de stimuli spécifique.
L'objectif principal de MADVIS est donc de faire une percée sur deux fronts principaux: (1) comprendre comment la privation visuelle à différentes périodes sensibles du développement affecte l'organisation fonctionnelle et la connectivité du cortex occipital; et (2) utiliser les connaissances fondamentales qui découlent de l’objectif (1) afin de tester et de prédire l'issue d’une restauration de la vue.
En utilisant une approche interdisciplinaire pionnière qui traverse les frontières entre les neurosciences cognitives et l'ophtalmologie, MADVIS pourrait avoir un grand impact sur notre compréhension de la façon dont l'expérience façonne l’organization du cerveau. Finalement, en tentant de combler le fossé existant entre la réorganisation intermodale et la restauration visuelle, MADVIS pourrait éventuellement ouvrir la voie à une nouvelle génération d’outils diagnostiques avant une restauration sensorielle.