Signal quality affects audiovisual speech integration in cochlear implant users and normal-hearing listeners
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Date
2018-03
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Abstract
Human communication often includes the use of visual speech cues to understand an auditory speech signal, with cues from both modalities combined through the process of audiovisual integration. Cochlear implant users, with an impoverished auditory signal, tend to rely more heavily upon visual speech cues and would therefore show stronger weighting of the more reliable visual signal and enhanced suppression of early auditory cortex activity. The current study sought to test these predictions for both cochlear implant (CI) users and normal hearing (NH) listeners to assess the degree of visual influence with vary degrees of auditory and visual reliability. Postlingually deafened CI users and age-matched NH controls participated in an audiovisual phoneme identification task with electroencephalography (EEG) recording. Auditory tokens (/aba/, /aga/, /awa/) were presented at a signal-to-noise ratio (SNR) above or below a participant's predetermined threshold and paired with clear blurred videos of mouth movements that were either congruent or incongruent with the auditory token. Participants identified the consonant they heard with a button press. Behavioral and event-related potential (ERP) results suggest an early influence of reliable visual information on auditory cortex for both groups, though the effect is stronger for NH controls. The NH participants also demonstrated that auditory and visual signal quality interact in the suppression of auditory-evoked potentials, though effects were not observed in CI users. This implies that NH perceivers are more sensitive to differences in acoustic quality, and thus experience more variable effects of visual speech on AV processing than CI users.
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Social and Behavioral Sciences; Social Work; Law: 1st Place (The Ohio State University Edward F. Hayes Graduate Research Forum)
Keywords
speech perception, audiovisual integration, cochlear implants, multisensory perception