Perception of temporal cues in word segments under bimodal divided attention in simulated cochlear implant listening

Abstract

Auditory temporal processing is important for cochlear-implant (CI) users to understand speech. Speech processing often unfolds along with sensory inputs from other modalities. This study examined whether dividing attention across modalities affects temporal processing of word segments in simulated CI listening. Adults with normal hearing performed categorization tasks on unprocessed and 8-channel vocoded versions of a Dish-Ditch contrast with varying silent intervals preceding the word-final fricative. The categorization performance was measured concurrently with a visual working memory task on meaningless images. This divided attention (AV-div) condition was compared with an audiovisual selective attention (AV-sel) condition in which participants focused on the categorization task and ignored the visual stimuli, and with an auditory-only (AO) condition in which participants performed the categorization task without the visual stimuli. Preliminary results (N = 5) revealed that participants tended to report more “Dish” responses for words with longer silence intervals under the two AV conditions than the AO condition, especially for the AV-div condition. The AV-related effects on the categorization performance appear to be reduced for vocoded than unprocessed words. These results suggest that concurrent visual information affects auditory temporal processing, which might lead to speech understanding difficulties of CI users in multisensory contexts.