Using sentence context and mouth cues to aid speech comprehension: an electroencephalographic study on Cochlear Implant users

The research project presented in the thesis explores the electrophysiological correlates of linguistic prediction and audio-visual speech processing in deaf people with Cochlear Implant (CI) and people with normal hearing, in order to explore possible group differences. We implement an experimental paradigm in which participants observe audio-visual speech stimuli that vary for predictability of the last word of the sentence (i.e. the target) and visibility of mouth articulatory movements. During the procedure, we record the electroencephalographic signal (EEG) in order to compare the different experimental conditions in terms of neural oscillations and Event Related Potential (ERP) response to the target word. We also administrate linguistic tests to participants in order to relate behavioural performance to the electrophysiological results. The thesis presents a theoretical overview on prediction in language comprehension, the neural correlates of prediction and audio-visual speech integration and previous studies exploring these processes in CI users. Then, it presents the methods used in the experiment and preliminary data from a subgroup of participants with CI.