General: All data will be acquired at the Centre for Cognitive Neuroscience (CCNS). MEG (Study 1 and Study 2) will be recorded with a 306-channel Elekta Neuromag Triux device. EEG activity (Study 1 and Study 2) will be recorded using a 64-channel system, which is already being used for CI studies. The electrooculogram will be recorded concurrently with additional horizontal and vertical electrodes. Continuous tracking of the head location via five indicator coils will allow correcting of head movements. MEG data will be preprocessed and analysed offline using Fieldtrip (Oostenveld, Fries, Maris, & Schoffelen, 2011), an open source toolbox for MATLAB (Mathworks), and custom-written functions. Data will be off-line filtered, noisy channels and segments rejected, and independent component analysis will be used to clean the data from artifacts. Binocular eye movements will be additionally recorded via an eye tracker (EyeLink 1000, SR Research), to ensure that participants maintain fixation during the recording. MEG data with eye blinks and segments in which the mouth was not fixated will be rejected on the basis of eye-tracking.
A core hypothesis of this proposal is that lip movements that accompany speech can be exploited to calibrate relevant neural processes in auditory processing regions. This will become especially expressed in increased cortical entrainment, marking the behaviourally relevant alignment of neural rhythms to important information in the speech stream. While this mechanism is of general utility it could be of crucial importance for speech rehabilitation of deaf individuals following CI. For this project, building up on our previous work, we have devised a simple experimental paradigm, that allows us to address the following outstanding research questions:
1) How do parametric modulations of auditory and visual speech information affect cortical entrainment in normal-hearing individuals?
2) How is visual entrainment to speech-related lip movements altered in deaf individuals as compared to normal hearing controls and what is the influence of onset of deafness?
3) How does pre-operative visual entrainment (including aforementioned 'unheard speech') to lip movements in deaf individuals correlate with speech rehabilitation following CI?
4) How does entrainment to auditory and visual speech information change across CI rehabilitation and how are these changes related to rehabilitation success?