Transmission of Binaural Cues by Bilateral Cochlear Implants: A Comparison of Spectral Peak-Picking and Interleaved Stimulation Strategies.

Cochlear implants (CIs) effectively restore speech understanding in quiet for many recipients. However, bilateral CI listeners continue to perform poorer than acoustic-hearing listeners on spatial-hearing tasks such as sound localization. One explanation is that stimulation strategies and the lack of coordination across sound processors degrade the fidelity of binaural cues. To provide further insight on this issue, this study compared the binaural cues transmitted by two CI stimulation strategies: a spectral peak-picking stimulation strategy and a constantly stimulating strategy. Two clinical CI sound processors were placed on a binaural manikin centered in a horizontal ring of loudspeakers in an anechoic chamber. Speech and non-speech stimuli were presented from the loudspeakers and the resulting electrical pulse trains were recorded. Envelope interaural time differences and interaural level differences were extracted from the recordings. Binaural cues were compared between the two stimulation strategies and against acoustic cues measured using behind-the-ear microphones. Results showed that, compared to the constantly stimulating strategy, the spectral peak-picking strategy led to more variable and less monotonic binaural cues, which could constrain sound-localization abilities. These findings highlight the need for bilateral coordination of CIs in multiple domains, including electrode selection in peak-picking stimulation strategies and pulse timing. (198/250).