Visual evoked potentials in postlingually deafened adult cochlear implant users
Viola, F. C.1,2, Hine, J.2, Thorne, J.1,2, Barks, A.2, Eyles, J.3, Bleeck, S.3, Schneider, T. R.4, and Debener, S.1,2
1Biomagnetic Center, Dept. of Neurology, University Hospital Jena; 2MRC Institute of Hearing Research, Southampton, UK; 3Institute of Sound and Vibration Research, University of Southampton, UK; 4Department of Neurophysiology, University Medical Center Hamburg-Eppendorf, Hamburg
During deafness, the visual system takes control of auditory cortex capacity, a phenomenon known as visual take-over. However, how deafness-related compensatory plasticity relates to clinical outcome after cochlear implantation (CI) is not well understood. In an ongoing study, we compared visual evoked potential (VEP) topographies from 12 post-lingually deafened adults using a CI with a sample of 18 normal hearing controls. Visual stimuli were taken from the Multimodal Stimulus Series (cf. www.debener.de) and presented in an audio-visual semantic priming paradigm while EEG was recorded from 68 scalp sites. Inspection of VEP P2 amplitudes at midline electrodes revealed a Group x SITE interaction (p<.05) that remained significant after vector normalisation. As predicted, CI users showed a more anterior distribution in the P2 latency range. A source-based analysis of the visual take-over phenomenon will be presented and the results will be discussed with regard to the clinical performance of CI users.