THE ROLE OF TOP-DOWN PROCESSES IN NEURAL REORGANIZATION AND SPEECH RECOVERY: A COMPARATIVE EEG AND EYE-TRACKING STUDY IN COCHLEAR IMPLANT CANDIDATES

Recovery of speech perception in Cochlear Implant (CI) users remains difficult to predict, likely influenced by variation in the engagement of "top-down" processes and cross-modal plasticity. This study aims to disentangle the neural impact of sensory deprivation from cognitive aging by characterizing neural speech tracking and reliance on visual information in four groups: CI-candidates (profound deafness), Hearing Aid (HA) users (severe hearing loss), Older normal-hearing controls, and Young controls. High-density EEG and eye-tracking are recorded during listening to continuous speech (Audio-Only vs. Audio-Visual) in a two-speakers paradigm. We utilize Temporal Response Function (TRF) analysis to quantify neural tracking accuracy and latencies to the speech envelope. We expect distinct neural phenotypes across groups along two main dimensions: 1-Aging Effect (Young vs. Older controls): We anticipate a latency shift in early TRF-components reflecting slowed neural transmission independent of hearing loss. 2-Deprivation effect and compensatory strategies: For auditory deficits (tested via Audio-only), CI-candidates are expected to show significantly reduced tracking fidelity and altered EEG-readouts of attention deployment compared to HA-users. Regarding visual dependency, measured by TRF-gain in the Audio-Visual vs. Audio-only conditions, we anticipate a distinct gradient. CI-candidates would show a disproportionately larger TRF-gain,compared to HA-users and controls. Our results, supported by preliminary analyses, highlight a reorganization of top-down strategies towards visual dominance in profound deafness. TRF-analysis could effectively disentangle the neural consequences of aging from sensory deprivation. Identifying a specific "visual dominance" phenotype in CI-candidates could serve as a biomarker to predict and tailor rehabilitation potential.