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Séminaire LNC : Manuel Vidal

Manuel Vidal, Institut de Neurosciences de la Timone, Marseille

The interplay between heard voices and seen rivaling lips : an audiovisual study of binocular rivalry

Abstract In binocular rivalry, sensory input remains the same yet subjective experience fluctuates irremediably. With only two mutually exclusive representations competing, it provides an ideal tool to study the selection mechanisms that are involved in the construction of conscious percepts. On the one hand, we investigated the perceptual stabilization effect of an additional sound on the dynamics of binocular rivalry. Previous studies reported conflicting evidence that we attribute to differences in how the sound matched with the visual percepts. Accordingly, we designed speech stimuli for which visual and auditory cortices interact at various levels. We measured how a voice saying /aba/ influences the perceptual alternations when of rivaling faces saying /aba/ and /aga/, either viewing passively or promoting one percept. Real, perceived or irrelevant congruence and incongruence were distinguished comparing McGurk sensitive and insensitive subjects. We found that a congruent sound amplifies considerably attentional control over the selection underlying the perceptual outcome. However, differences in the perceptual stabilization according to the AV congruency suggest there are at least two distinct processes at stake. On the other hand, we are currently investigating whether the suppressed viseme can still interfere with phonemic processing in order to produce the McGurk effect. Preliminary results indicate that under some circumstances, audiovisual speech integration with the unseen talking face does occur. I will start my talk with a brief overview of my past researches, which ranged from spatial cognition to self-motion perception.