A systematic review of altered resting‐state networks in early deafness and implications for cochlear implantation outcomes

Abstract Auditory deprivation following congenital/pre‐lingual deafness (C/PD) can drastically affect brain development and its functional organisation. This systematic review intends to extend current knowledge of the impact of C/PD and deafness duration on brain resting‐state networks (RSNs), review changes in RSNs and spoken language outcomes post‐cochlear implant (CI) and draw conclusions for future research. The systematic literature search followed the PRISMA guideline. Two independent reviewers searched four electronic databases using combined keywords: ‘auditory deprivation’, ‘congenital/prelingual deafness’, ‘resting‐state functional connectivity’ (RSFC), ‘resting‐state fMRI’ and ‘cochlear implant’. Seventeen studies (16 cross‐sectional and one longitudinal) met the inclusion criteria. Using the Crowe Critical Appraisal Tool, the publications' quality was rated between 65.0% and 92.5% (mean: 84.10%), ≥80% in 13 out of 17 studies. A few studies were deficient in sampling and/or ethical considerations. According to the findings, early auditory deprivation results in enhanced RSFC between the auditory network and brain networks involved in non‐verbal communication, and high levels of spontaneous neural activity in the auditory cortex before CI are evidence of occupied auditory cortical areas with other sensory modalities (cross‐modal plasticity) and sub‐optimal CI outcomes. Overall, current evidence supports the idea that moreover intramodal and cross‐modal plasticity, the entire brain adaptation following auditory deprivation contributes to spoken language development and compensatory behaviours.