An ERP Study on the Combined-stimulation Advantage in Vocoder Simulations

Electric hearing is presently the only treatment solution for patients with profound-to-severe hearing loss. For those patients also preserving low-frequency residual hearing on the ipsilateral ear, combined electric-and-acoustic stimulation (EAS) could notably improve their speech understanding abilities relative to those aided with electric-only (E-only) hearing. Early behavioral studies have consistently shown the advantage of combined stimulation. The aim of this work was to objectively examine the advantage of combined stimulation over electric-only hearing using an oddballparadigm based event-related potential (ERP) experiment. The vowel stimulus was processed by vocoding processes simulating the E-only and EAS conditions, and the generated stimuli were presented to normal-hearing listeners in the ERP experiment. Experiment results showed that the mismatch negativity (MMN) response elicited in the combined-stimulation condition featured a smaller peak amplitude and a more delayed peak latency than that in the E-only condition. The MMN results in this work demonstrated that compared with the ERP response elicited in the E-only condition, the response in the combinedstimulation condition was much closer to that elicited by the full-spectrum stimulus, yielding neurophysiological evidence on the combined-stimulation advantage.