Table of Contents Author Guidelines Submit a Manuscript
Neural Plasticity
Volume 2016 (2016), Article ID 4382656, 13 pages
http://dx.doi.org/10.1155/2016/4382656
Research Article

Cross-Modal Functional Reorganization of Visual and Auditory Cortex in Adult Cochlear Implant Users Identified with fNIRS

1Neuropsychology Lab, Department of Psychology, European Medical School, Carl-von-Ossietzky University Oldenburg, 26129 Oldenburg, Germany
2Department of Neurology, Hannover Medical School, 30625 Hannover, Germany
3Cluster of Excellence Hearing4all, 26129 Oldenburg, Germany
4Research Center Neurosensory Science, University of Oldenburg, 26129 Oldenburg, Germany

Received 5 June 2015; Accepted 20 August 2015

Academic Editor: Aage R. Møller

Copyright © 2016 Ling-Chia Chen et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Cochlear implant (CI) users show higher auditory-evoked activations in visual cortex and higher visual-evoked activation in auditory cortex compared to normal hearing (NH) controls, reflecting functional reorganization of both visual and auditory modalities. Visual-evoked activation in auditory cortex is a maladaptive functional reorganization whereas auditory-evoked activation in visual cortex is beneficial for speech recognition in CI users. We investigated their joint influence on CI users’ speech recognition, by testing 20 postlingually deafened CI users and 20 NH controls with functional near-infrared spectroscopy (fNIRS). Optodes were placed over occipital and temporal areas to measure visual and auditory responses when presenting visual checkerboard and auditory word stimuli. Higher cross-modal activations were confirmed in both auditory and visual cortex for CI users compared to NH controls, demonstrating that functional reorganization of both auditory and visual cortex can be identified with fNIRS. Additionally, the combined reorganization of auditory and visual cortex was found to be associated with speech recognition performance. Speech performance was good as long as the beneficial auditory-evoked activation in visual cortex was higher than the visual-evoked activation in the auditory cortex. These results indicate the importance of considering cross-modal activations in both visual and auditory cortex for potential clinical outcome estimation.