Predicting variability in pediatric cochlear implant outcomes through synchronous brain activation patterns: Insights from fNIRS

Objectives: This study examined the relationship between cortical activation and auditory performance in pediatric cochlear implant (CI) users compared to normal-hearing (NH) controls using functional near-infrared spectroscopy (fNIRS). The aim was to identify neural predictors of CI outcome and to investigate post-implantation cortical plasticity. Design: Eighteen pediatric CI users and 17 NH controls performed simultaneously non-speech discrimination and sentence recognition tasks while undergoing fNIRS recording. Cortical activation was assessed in bilateral temporal, frontal, and parietal regions, and correlation and regression analyses examined whether cortical activity predicted auditory performance variability. Results: CI users performed similarly to NH controls on non-speech discrimination (92.6 ± 8.5 % vs. 91.7 ± 7.8 %), but had lower sentence recognition accuracy (76.9 ± 14.1 % vs. 96.1 ± 3.1 %, p < 0.05). Hierarchical regression showed that dual-channel interactions in the CI group explained 68 % of the variance in non-speech discrimination (adjusted R² = 0.68, p = 0.002) and 61 % in sentence recognition (adjusted R² = 0.61, p = 0.001). Right middle temporal gyrus activation was positively correlated with non-speech accuracy (β = 1.20, p = 0.001), while left superior temporal gyrus activation was negatively associated (β = -0.83, p = 0.007). Left inferior frontal gyrus activation was negatively correlated with sentence recognition (β = -0.94, p < 0.001), while left inferior parietal lobule activation was positively associated (β = 0.57, p = 0.007). In contrast, NH participants relied on a more flexible and integrated neural processing network, and no significant cortical predictors were identified, suggesting a less localized, more distributed activation pattern. Conclusions: These findings provide novel insights into neural plasticity and compensatory mechanisms in CI users, emphasizing the crucial role of cortical interactions in non-speech and sentence-level processing. The strong predictive power of hierarchical models highlights the potential of fNIRS in post-implantation cortical assessment. Given the cross-sectional design and sample size limitations, longitudinal research is needed to validate these findings and to further refine auditory rehabilitation strategies to enhance speech perception outcomes in pediatric CI users.