The role of onset cues for lateralization of an auditory object in bilateral cochlear implant listeners

Abstract

In bilateral cochlear implant (BiCI) listeners, a common strategy for improving sensitivity to interaural timing differences (ITDs) is to introduce low rate stimulation in some channels. Previous work showed that BiCI listeners can lateralize a single sound with a constant ITD at every pulse of a low rate stimulus. However, in reverberant environments, ITDs for a target sound can change over a short period of time. Previously we have shown that BiCI listeners had difficulty using the ITD in the first pulse of a low-rate pulse train to lateralize a stimulus when the subsequent pulses had ITDs that varied over time. Hence, we hypothesized that a more salient onset is needed in order to restore ITD sensitivity in BiCI listeners when using low rate stimulation. In this study, we measured the number of pulses with a consistent ITD that is needed at the onset in order for BiCI listeners to reliably perceive one sound in the correct location. Results suggest that BiCI listeners need at least five pulses with consistent ITDs in order to report a single auditory object that is correctly lateralized. These results have important implications for low rate strategies aimed at restoring ITD sensitivity to BiCI listeners.