Study of the Role of Top-down Processes in Neuronal Reorganization and Recovery From Sensory Loss: an Exploratory Behavioral and Electroencephalographic Study in Cochlear-supported Deaf Patients

Profound bilateral deafness leads to sensory deprivation and neuronal reorganization ( visual recruitment of the auditory cortex). Although cochlear implants restore hearing, comprehension performance varies considerably. Peripheral factors explain only 40% of this variance. This study posits that central top-down processes (attention, inhibition), marked by alpha oscillations in EEG, play a key role. Understanding the evolution of these neuronal signatures and their link to pre-implantation visual dependence could allow the identification of biomarkers predictive of the success of auditory rehabilitation.

• neurophysiological assessment (Other): Electroencephalography and eye tracking
• Cognitive, behavioral and quality of life assessment (Behavioral): Cognitive anfd behavioral assessment : Speech recognition test in silence (MBAA) and in noise, verbal working memory task with distractors, Trail Making Test and MoCA test. Quality of lige assessment : This questionnaire is a set of scales concerning patients' hearing abilities, experience, and listening skills in different situations. For each question, the patient must answer by choosing a number between 1 (not at all) and 10 (perfectly).

Primary outcomes

• Evolution of oscillatory signatures [6 months]: Composite criterion :the modulation of alpha oscillations, measured through frequency analysis, amplitude variations and temporal synchronization via EEG, in response to a word recognition task in silence.

Secondary outcomes

• EEG (alpha) signatures and eye-tracking [6 months]: Descriptive evaluation : Evolution of EEG (alpha) signatures and eye-tracking trajectories (composite criterion)
• Speech recognition performance [6 months]: Speech recognition performance (MBAA, accuracy, response time) in silence and noise : Composite criterion
• alpha modulation and memory/auditory [6 months]: Correlations between alpha modulation and memory/auditory performance : Descriptive evaluation
• audiovisual, visual and auditory comparison [6 months]: The comparison between audiovisual, visual and auditory modalitie (descriptive evaluation)
• SSQ [6 months]: This questionnaire is a set of scales concerning patients' hearing abilities, experience, and listening skills in different situations. For each question, the patient must answer by choosing a number between 1 (not at all) and 10 (perfectly).

Sex: All, ages: 18 Years to any, accepts healthy volunteers

Inclusion Criteria:

For cochlear implant patients:

* Adult patients
* Profound bilateral hearing loss requiring a first cochlear implant
* Normal cochlear anatomy (confirmed by preoperative imaging)
* Full insertion of the cochlear electrode array planned
* Acceptance of the protocol and signing of the informed consent form
* Enrollment in a social security or equivalent plan

For young patients with normal hearing:

* Adult patients aged 18 to 40
* Normal and symmetrical hearing
* Acceptance of the protocol and signature of the informed consent form
* Affiliation with a social security scheme or equivalent

For older patients with normal hearing:

* Patients over 50 years of age, matched by gender and age (+/- 2 years) with the cochlear implant patient group
* Normal and symmetrical hearing, with hearing thresholds < 20 dB HL at 2 kHz and < 40 dB HL at 4 kHz
* Acceptance of the protocol and signature of the informed consent form
* Affiliation with a social security scheme or equivalent

For experienced cochlear implant recipients:

* Adult patients.
* Unilateral cochlear implant activated for 1 year or more.
* Disyllabic word recognition score at 60 dB in free field of 70% or higher.
* Acceptance of the protocol and signature of the informed consent form.
* Affiliation with a social security plan or equivalent.

For severely deaf patients fitted with hearing aids:

* Adult patients.
* Severe bilateral hearing loss.
* Rehabilitation with one or two optimally fitted hearing aids.
* Acceptance of the protocol and signing of the informed consent form.
* Enrollment in a social security or equivalent health insurance plan.

Exclusion Criteria:

* History of associated neurological pathology
* Etiologies with unfavorable prognoses, such as recurrent chronic otitis media: These conditions are associated with a poor prognosis due to chronic inflammation that can affect the cochlea
* Duration of profound bilateral deafness exceeding 5 years (worse prognosis)
* Contraindications to EEG or other neurophysiological examinations within the study (for all groups)
* Cognitive impairment confirmed by the MOCA test for the cochlear implant patient group and the group of elderly subjects with normal hearing
* Use of psychotropic medications that may interfere with the results of cognitive or neurological tests
* History of epilepsy or other major neurological disorders
* Pregnancy or breastfeeding
* Participation in another interventional research protocol or one that impacts the criteria studied in this project
* Individuals under legal guardianship (guardianship, tutorship, curatorship, institutionalized, or under a future protection mandate)

• Mathieu MARX, PU-PH, Principal investigator, University Hospital, Toulouse