Interaction Between Electric and Acoustic Cues in Diotic Condition for Speech Perception in Quiet and Noise by Cochlear Implantees *†Ce ´line Richard, *‡Evelyne Ferrary, *Ste ´phanie Borel, *‡Olivier Sterkers, and *‡Alexis Bozorg Grayeli *Otolaryngology Department, APHP, Ho ˆ pital Beaujon, Clichy; ÞOtolaryngology Department, Ho ˆpital Nord, CHU de Saint Etienne, St-Etienne; and þUMRS-867, Inserm, Universite ´ Paris 7 Denis Diderot, Paris, France Objective: This study aimed to evaluate the interaction of electric and acoustic cues in diotic condition in cochlear implantees. Materials and Methods: Five adult cochlear implantees with residual contralateral hearing were prospectively evaluated in hearing aid only (HA), cochlear implant only (CI), and HA + CI modes by audiometry (pure tone, dissyllabic words, and sen- tences), and sound quality questionnaires. CI electrodes corre- sponding to preserved frequencies in the contralateral ear (free- field aided thresholds, G50 dB) were then deactivated, and patients were retested after 20 to 30 days. Results: Sentences in silence showed a benefit of CI and the additive effect of HA + CI. As expected, performances with CI alone decreased after apical electrode deactivation. In contrast, speech performances (Marginal Benefit from Acoustic Ampli- fication sentences) in HA + CI mode were not altered by elec- trode deactivation in silence (90 T 5.9% before versus 81 T 10.1% after deactivation, not significant, 2-way analysis of variance) or in noise (78 T 4.8% before versus 66 T 11.9% after deactivation, not significant, 2-way analysis of variance). Per- formances for dissyllabic words confirmed these results. Ques- tionnaires showed a significant compensation of partial electrode deactivation by the contralateral hearing. Moreover, the human voice was reported to be significantly less metallic. Conclusion: These results suggested a significant comple- mentarity of acoustic and electric diotic cues but also some redundancy affecting the sound quality. Key Words: Cochlear apex stimulationVCochlear implantVDiotic listeningVHearing aidVSound quality. Otol Neurotol 33:30Y37, 2012. It is now established that patients using a cochlear implant (CI) on one side and a hearing aid (HA) on the opposite ear obtain benefits from binaural hearing (1). However, the extent to which this binaural advantage is due to a redundancy of information in the 2 different modes or to other factors is not clear (2,3). In normal hearing, benefits of binaural condition may be attributed to the head shadow, the binaural squelch, and the sum- mation effects (3). The head shadow effect accounts for a different signal-to-noise ratio (SNR) between ears. This effect is primarily seen in frequencies higher than 1,500 Hz and ranges from 7 dB in the speech range up to 20 dB in high frequencies. It explains the difficulties encountered by individuals with unilateral hearing loss when their interlocutor is placed on the deaf side and their need to direct their functional ear toward the signal source (3). The binaural summation effect refers to the improve- ment of signal detection in the binaural versus the mon- aural presentation. A binaural presentation improves the SNR approximately 2 dB in bilaterally aided or normal hearing (3,4). When a signal is presented binaurally, its detection is improved by the phase lags between the left and the right ears for the signal or the noise. This reduction of the noise impact on speech intelligibility is defined as the binaural squelch effect, which reflects the ability of the auditory system to combine information from both ears and to provide an enhanced central representation in comparison to monaural hearing. This effect takes ad- vantage of the spatial separation between the signal and the noise sources and the differences in time and intensity between these sources in each ear. Other cues accounting for speech perception benefit and the natural quality of the sound in bimodal hearing are conveyed by the voice fundamental frequency and the fine structure (5,6). These physiological observations explain that unilateral cochlear implantees with no contralateral hearing often have great difficulty understanding speech in noisy and acoustically cluttered environments, whereas individuals with binaural Address correspondence and reprint requests to Alexis Bozorg Grayeli, M.D., Ph.D., Otolaryngology Department, Ho ˆpital Beaujon, 100 Boulevard du Ge ´ne ´ral Lerclerc, 92118 Clichy Cedex, France; E-mail: alexis.bozorg- grayeli@bjn.aphp.fr The authors disclose no conflicts of interest. Otology & Neurotology 33:30Y37 Ó 2011, Otology & Neurotology, Inc. 30 Copyright © 2011 Otology & Neurotology, Inc. Unauthorized reproduction of this article is prohibited.