Two cues are better than one: Adding interaural time differences improves lateralization for bilateral cochlear-implant listeners

Bilateral cochlear-implant (BI-CI) listeners show limited sensitivity to interaural time differences (ITDs), the dominant localization cue for acoustic-hearing listeners, and mainly rely on interaural level differences (ILDs) for localization. Studies utilizing bilaterally synchronized direct stimulation capable of conveying ITDs have investigated sensitivity to ITDs or ILDs in isolation. It is, however, unclear how these two cues interact in controlled and bilaterally synchronized electrical stimulation. Therefore, this study performed an ITD-ILD cue-weighting lateralization experiment with BI-CI listeners using direct stimulation of single electrodes. Preliminary results show that BI-CI listeners display sensitivity only to ILDs with unsynchronized stimulation and equal sensitivity to both ITDs and ILDs with synchronized stimulation. Additionally, providing ITDs and ILDs together via bilaterally synchronized stimulation resulted in increased lateralization ranges and slopes, thus improved spatial hearing acuity compared to either cue alone. These results suggest providing both ITDs and ILDs via bilaterally synchronized sound processors has the potential to improve spatial hearing in BI-CI listeners. The data have implications for clinical sound processor design and stimulation strategies.