Manuel Vidal

20 février 2012

LPPA, Collège de France, Paris

Investigating the selection mechanisms underlying the construction of conscious percepts

Invité par Frédéric Chavane

Phenomenal experience builds upon the combination of evidence from the outside world collected by our senses and internal expectations. Although various internal representations of the same object are produced, only one will eventually emerge to awareness. In binocular rivalry, sensory input remains the same yet subjective experience fluctuates irremediably. Here only two mutually exclusive representations compete, which provides an ideal tool to study the selection mechanisms underlying the construction of conscious percepts. I will first give you a glimpse of my past researches, which led me to this topic. I will then detail the project in which 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. Thus we used speech stimuli, involving interactions between the visual and auditory cortices 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. I will end discussing ongoing and future projects on the possible processing ways that neural representations of suppressed percepts might follow, on how eye-movements could constrain the perceptual outcome of motion bistable stimuli, and on the link between sensory binding and consciousness.
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