Department of Special Education and Communication Disorders


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Interaural asymmetry decreases sensitivity to binaural cues such as interaural time differences (ITD) for bilateral cochlear implant users. However, the effects of interaural asymmetry may be mitigated for this population by the broad current spread typical of electrical stimulation. Current spread can be estimated using spread of excitation (SOE) functions. These measure the extent to which electrodes stimulate overlapping neural populations. This is done by measuring electrically evoked compound action potentials (eCAPs) in response to stimulating different masker electrodes. The goal of this study was to determine if SOE functions can predict the effect of interaural asymmetry on cochlear implant users’ ITD thresholds. SOE functions were measured for multiple probe electrodes across the array. Participants also completed an ITD detection task that measured the ITD thresholds for different interaural electrode pairs. The preliminary results suggest that eCAPs may not be directly predictive of the effect of asymmetry on ITD sensitivity, but they may offer insight into the minimum interaural asymmetry that will affect ITD sensitivity. Future studies will investigate the relationship between SOE and other binaural cues, such as interaural level differences.