Abstract
SIGNIFICANCE: Cochlear implants (CIs) are a proven intervention for severe hearing loss; however, outcomes vary widely among CI recipients. Emerging evidence suggests that cortical adaptation to the electric hearing provided by CIs play a crucial role. AIM: We investigate cortical brain activation differences in CI users, comparing individuals with good speech understanding (good performers, GP) to those with poor outcomes (poor performers, PP) alongside a control group with normal hearing (NH). APPROACH: We recruited 46 CI users and 26 NH participants to perform a clinically adapted audiovisual speech comprehension task while we measured their brain activity using functional near-infrared spectroscopy (fNIRS). We corroborated our findings with objective and behavioral data. RESULTS: Our findings showed distinct brain activation patterns associated with speech understanding. GP showed comparable brain activation patterns to NH in audio-only conditions, indicative of successful hearing rehabilitation. Further, both GP and PP participants showed an adaptive mechanism during visual speech processing. However, compared with GP, PP relied heavily on visual cues and showed altered neural resource allocation during audio-only conditions, potentially limiting their overall rehabilitation success. CONCLUSIONS: fNIRS revealed significant differences in brain activation between GP and PP, highlighting the role of cortical factors in CI rehabilitation. Understanding these neural mechanisms has the potential to lead to better patient counseling, optimized postoperative management, and personalized therapeutic strategies to improve outcomes for CI users.