Increased cross-modal functional connectivity in cochlear implant users

Abstract

Previous studies have reported increased cross-modal auditory and visual cortical activation in cochlear implant (CI) users, suggesting cross-modal reorganization of both visual and auditory cortices in CI users as a consequence of sensory deprivation and restoration. How these processes affect the functional connectivity of the auditory and visual system in CI users is however unknown. We here investigated task-induced intra-modal functional connectivity between hemispheres for both visual and auditory cortices and cross-modal functional connectivity between visual and auditory cortices using functional near infrared spectroscopy in post-lingually deaf CI users and age-matched normal hearing controls. Compared to controls, CI users exhibited decreased intra-modal functional connectivity between hemispheres and increased cross-modal functional connectivity between visual and left auditory cortices for both visual and auditory stimulus processing. Importantly, the difference between cross-modal functional connectivity for visual and for auditory stimuli correlated with speech recognition outcome in CI users. Higher cross-modal connectivity for auditory than for visual stimuli was associated with better speech recognition abilities, pointing to a new pattern of functional reorganization that is related to successful hearing restoration with a CI.