Resting-state Functional Connectivity Predicts Cochlear-Implant Speech Outcomes

Background Cochlear implants (CIs) have revolutionized hearing restoration for individuals with severe or profound hearing loss. However, a substantial and unexplained variability persists in CI outcomes, even when considering subject-specific factors such as age and the duration of deafness. In this study, we explore the utility of resting-state functional near-infrared spectroscopy (fNIRS) recordings to predict speech understanding outcomes before and after CI implantation. Our hypothesis revolves around resting-state functional connectivity (FC) as a reflection of brain plasticity post-hearing loss and implantation. Specifically, we hypothesized that the average clustering coefficient in resting FC networks can capture this variation among CI users. Methods Twenty-two cochlear implant candidates participated in this study. Resting-state fNIRS data were collected pre-implantation and at one month, three months, and one year post-implantation. Speech understanding performance was assessed using CNC words in quiet and BKB sentences in noise one year post-implantation. Resting-state functional connectivity networks were constructed using regularized partial correlation, and the average clustering coefficient was measured in the signed weighted networks as a predictive measure for implantation outcomes. Results Our findings demonstrate a significant correlation between the average clustering coefficient in resting-state functional networks and speech understanding outcomes. Importantly, our analysis reveals that this measure provides unique information not accounted for by subject-specific factors such as age and duration of deafness. Conclusion This approach utilizes an easily deployable resting-state functional brain imaging metric to predict speech understanding outcomes in implant recipients. The results indicate that the average clustering coefficient, both pre and post implantation, correlates with speech understanding outcomes. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement This study was supported by a grant from the Passe and Williams Foundation to Colette M. McKay. Tommy Peng was supported by a Junior Fellowship from the Passe and Williams Foundation. Jamal Esmaelpoor was supported by the University of Melbourne Research Scholarship. The Bionics Institute acknowledges the support it receives from the Victorian Government through its Operational Infrastructure Support Program. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: The Human Research Ethics Committee of the Royal Victorian Eye and Ear Hospital approved this study (ethics approval number 16.1262H), and all participants provided written informed consent. I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes All data produced in the present study are available upon reasonable request to the authors