Normal hearing listeners (NH) are known to benefit from several binaural effects which have been well quantified in audiometric tests. Beyond the fact that the better ear may change depending on the position of target and noise sources, and that bimodal fitting allows use of the ear that is best in any given situation, bimodal listening is expected to provide additional binaural benefits.īinaural benefits are especially noticeable in challenging acoustic conditions, for instance when speech recognition is impeded by the presence of background noise. Thus today the bimodal group with electrically aided hearing in one ear and acoustically-aided hearing in the opposite ear represents the largest group of CI users ( Holder et al., 2018). As CI technology and surgical approaches have advanced, many patients with residual hearing in their opposite ear qualify for implantation. Although the grand-averaged difference in N1 amplitude between monaural and binaural listening was similar for NH and the bimodal group, source localization showed group-dependent differences in auditory and speech-relevant cortex, suggesting different processing in the bimodal listeners.Ĭochlear implants (CI) are hearing prostheses that bypass defective sensory hair cells in the cochlea, allowing individuals with severe to profound sensorineural hearing loss to regain much of their hearing. Significant AEP differences between monaural and binaural processing were shown for NH and for bimodal listeners 6 month post-implantation. With CI experience, morphology of the N1 and P2 potentials in the AEP response approximated that of NH, whereas, N2 remained different.
Moreover, a significant negative correlation existed between binaural summation and latency of the P2 potential. Some amount of binaural processing was suggested by a positive binaural summation effect 6 month post-implantation that correlated significantly with symmetry of pure tone thresholds. CI provision resulted in significant improvement of speech recognition with the CI ear, and in taking advantage of the head shadow effect for understanding speech in noise. Data of fifteen participants contributed to the results. Beyond that, bimodal benefit was estimated from the difference in amplitudes and latencies of the N1, P2, and N2 potentials of the brains’ auditory evoked response (AEP) toward speech. The benefit of adding a contralateral hearing aid was calculated in terms of head shadow, binaural summation, binaural squelch, and spatial release from masking from the results of a sentence recognition test. Results of these bimodal listeners were compared to age-matched, normal hearing controls (NH). Patients with bilateral sensorineural hearing loss undergoing implant surgery were tested in their ability to understand speech in quiet and in noise, before and again 3 and 6 months after provision of a CI. It is uncertain, however, whether the brains of bimodal listeners can combine the electrical and acoustical sound information and how much CI experience is needed to achieve an improved performance with bimodal listening. With an extension of implantation candidacy, today many CI listeners use a hearing aid on their contralateral ear, referred to as bimodal listening. Department of Otorhinolaryngology Head and Neck Surgery, Medical Faculty Mannheim, University Medical Center Mannheim, Heidelberg University, Mannheim, GermanyĬochlear implants (CI) improve hearing for the severely hearing impaired.Tobias Balkenhol † Elisabeth Wallhäusser-Franke *† Nicole Rotter Jérôme J.
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