Audiovisual Speech Perception in Aging Cochlear Implant Users and Age-Matched Non-Implanted Adults

Objectives. Older typical-hearing adults without a cochlear-implant (CI) have been found to exhibit greater multisensory benefits when identifying audiovisual speech than younger normal-hearing adults. The greater multisensory benefits demonstrated by older non-CI users can compensate for unisensory auditory and visual speech deficits, allowing them to identify audiovisual speech at a degree of accuracy like that of younger normal-hearing adults. Though most new CI recipients are 65 years of age and older, the reliance of older CI users on such multisensory benefits is unknown. The goal of the current investigation was to evaluate age-related differences in cross-sensory and multisensory benefits in audiovisual speech identification in aging CI users and to examine how they differ from age-matched non-CI users.Design. Twenty middle-aged-to-older CI users (50-83 years of age) and 35 age-matched non-CI controls completed an auditory-visual speech identification task, identifying 288 disyllabic words presented either auditory-alone, visual-alone, or audiovisually. CI users identified speech stimuli streamed directly through their CI device in quiet and in noise (Gaussian) at +10 and +5 dB signal-to-noise ratio (SNR) conditions. Non-CI users identified speech stimuli delivered through earphones in noise at -5, 0, and +5 dB SNR conditions. Different noise conditions were used for CI users and non-CI users to avoid ceiling and floor effects. From visual, auditory, and audiovisual performance, psychometrics for the visual enhancement of audiovisual speech (VE), the auditory enhancement of audiovisual speech (AE), and auditory-visual multisensory enhancement (AVE) were calculated. Group differences (in the overlapping +5 dB SNR condition) and effects of age and noise were tested using linear regression and linear mixed-effects regression models.Results. Both CI users and non-CI users demonstrated canonical differences in visual, auditory, and audiovisual speech identification. VE and AVE were greater for CI users than non-CI users. Critically, AVE increased with the age of older CI users and non-CI users, consistent with age-group differences in AVE we observed in a previous study of non-CI users.Conclusions. The results of the current investigation suggest that CI users, like age-matched non-CI users, rely on multisensory integration more as they age. Older CI users can benefit more from audiovisual input than older non-CI users. These perceptual benefits grant older CI users the capacity to identify audiovisual speech to a degree of accuracy closer to that of older non-CI users, despite deficits in the auditory perception of CI users. As a result, successful use of a CI device may partially depend on the ability of a CI user to integrate information they see with information available from their device, and older CI users may depend on visual input more to successfully use their CI.