Auditory- and Visual-Speech Evoked Activation of the Superior Temporal Gyrus Contralateral to the Cochlear Implant Predicts Speech Recognition Outcomes

Objectives: Speech recognition outcomes vary widely in cochlear implant recipients, but the reasons for this variability are not well explained by patient history factors alone. Neuroplastic reorganization after both deafness and cochlear implant switch-on can affect how new recipients adapt to electrical hearing. In this study, we evaluate the associations between speech recognition outcomes and stimulus-evoked activation of cortical language processing areas. Design: Forty-three newly implanted post-lingually deaf adult cochlear implant recipients (17 female, mean age at implantation: 58.5 yr, SD: 14.4 yr) were recruited for the longitudinal study. Participants attended two research visits: the first conducted within 1 mo of device switch-on, and the second conducted 1 yr after device switch-on. At each visit, we evaluated speech recognition outcomes in noise and cortical activation using functional near-infrared spectroscopy during a passive listening task, during which a story was told in either an auditory- or visual-speech (lipreading) condition. Results: We found consistent negative correlations between speech understanding outcomes at 1 yr and activation of the superior temporal gyrus at 1 mo in response to both auditory and visual speech. These associations were not observed for activation measured at 1 yr. Subgroup regression analysis revealed that these correlations were most consistently seen in the superior temporal gyrus contralateral to the cochlear implant. Activation in the superior temporal gyrus contralateral to the implant at 1 mo also explained additional variance in speech outcomes at 1 yr beyond clinical factors alone. However, longitudinal analysis showed no association between within-subject changes in activation and changes in speech understanding outcomes within this first year of implant use. Conclusions: Our evidence highlights that neuroplastic changes which occur following adult-onset deafness play an important role in how cochlear implant recipients adapt to their devices after switch-on. The relationship between neuroimaging measures made within 1 mo after device switch-on and speech recognition outcomes at 1 yr can potentially enable triaging of recipients to improve clinical management of implant recipients.