Increases resting-state PET activity after cochlear implantation in adult deafened cats

For the hearing rehabilitation of patients with profound sensorineural hearing loss, cochlear implants (CIs) are widely used. However, the result of CI is variable, and the central neural plasticity is considered to be a reason for this variability. We hypothesize that the resting-state cortical networks play a role in the condition of profound hearing loss and are affected by CI. To investigate the resting-state neuronal networks after cochlear implantation, we acquired 18F-fluorodeoxyglucose (FDG)-positron emission tomography (PET) images in experimental animals.Eight domestic adult cats were enrolled in this study. The hearing threshold of the enrolled animals was within the normal range, as measured by auditory evoked potential. They were divided into two groups: control (n=4) and hearing loss (n=4) groups. Hearing loss was induced by co-administration of ethacrynate and kanamycin. FDG-PET was performed at normal hearing state and at 4 and 11 months after the deafening procedure. Cochlear implantation was performed in the right ear and electrical cochlear stimulation was performed for 7 months (from 4 to 11 months after the deafening procedure). Acquired PET images were analyzed and compared between the two groups and among the three time points.At 4 months after hearing loss, the auditory cortical area's activity decreased, and the associated visual area activity increased. After 7 months of cochlear stimulation, the superior marginal gyrus and cingulate gyrus showed hypermetabolism, and these areas were components of the default mode network. The inferior colliculi showed hypometabolism.Resting-state cortical activity was elevated after cochlear stimulation in the default mode network component. This suggests that the awareness level was elevated after hearing restoration by the CI.