Increased cross-modal functional connectivity in cochlear implant users

Stefan Debener,Sebastian Puschmann,Ling-Chia Chen

doi:10.1038/s41598-017-10792-2

Stefan Debener, Sebastian Puschmann + Show 1 more

Open Access

https://doi.org/10.1038/s41598-017-10792-2

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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.

Highlights

Cortical changes induced by sensory deprivation have been robustly reported in blind and deaf individuals[1,2,3]
A recent Functional near-infrared spectroscopy (fNIRS) study reported for the first time decreased resting state functional connectivity between left and right auditory areas in cochlear implant (CI) users compared to normal hearing (NH) controls[28]
With previous evidence pointing towards a negative role of cross-modal activation in auditory cortex and a positive role of cross-modal activation in visual cortex, we predicted speech recognition to have a positive relationship with cross-modal connectivity for auditory stimuli and a negative relationship with cross-modal connectivity for visual stimuli

Summary

Introduction

Cortical changes induced by sensory deprivation have been robustly reported in blind and deaf individuals[1,2,3]. OLSA_n (dB) −2,3 N/A 0,9 −2,6 1,9 −1,9 −2,1 1,7 0 −0,4 0,1 −1,1 3,3 −2,6 0,2 −0,4 1,1 −1,8 3,1 studies in blind and deaf individuals[23,24,25,26,27], little is known about cross-modal connectivity in CI users, despite the significance of such observations in suggesting an increase of information flow between visual and auditory cortices Reasons for this lack of evidence are mostly related to safety concerns with regards to metal implants in a magnetic resonance imaging scanner, which precludes a proper assessment of structural or functional connectivity in CI users. With previous evidence pointing towards a negative role of cross-modal activation in auditory cortex and a positive role of cross-modal activation in visual cortex, we predicted speech recognition to have a positive relationship with cross-modal connectivity for auditory stimuli and a negative relationship with cross-modal connectivity for visual stimuli

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