Exploration des mécanismes non conscients de la perception de la parole: approches comportementales et électroencéphalographiques

Sammanfattning: Although a lot of information is available from our environment at every moment, only a small part gives rise to a conscious percept. It is then legitimate to wonder which mechanisms are involved in the perception phenomenon. On the basis of which processes will a sensory stimulation be perceived consciously? What happens to the stimulations that are not consciously perceived?The work presented in this thesis aims to bring some elements of response to these two questions in the auditory modality. Through different behavioral and electroencephalographic studies, we suggest that knowledge could have a top-down facilitatory influence on high-level as well as on low-level (like detection) processing of complex auditory stimulations. The stimulations we have some knowledge about (phonologic or semantic) are more easily detected than the stimulations that contain neither phonologic nor semantic information. We also show that the activation of the knowledge influences the perception of subsequent stimulations, even when the context is not perceived consciously. This is evidenced by a subliminal semantic priming effect and by modifications of the neural oscillations in the beta frequency band associated with lexical processing of stimulations that were not consciously categorized.Hence, auditory perception can be considered as the product of the continuous interaction between the context set by the environment and the knowledge one has about specific stimuli. Such an interaction would lead listeners to preferentially perceive what they already know.