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.

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)