Audiovisual speech perception at various presentation levels in Mandarin-speaking adults with cochlear implants

Objectives: (1) To evaluate the recognition of words, phonemes and lexical tones in audiovisual (AV) and auditory-only (AO) modes in Mandarin-speaking adults with cochlear implants (CIs); (2) to understand the effect of presentation levels on AV speech perception; (3) to learn the effect of hearing experience on AV speech perception. Methods: Thirteen deaf adults (age = 29.1±13.5 years; 8 male, 5 female) who had used CIs for >6 months and 10 normal-hearing (NH) adults participated in this study. Seven of them were prelingually deaf, and 6 postlingually deaf. The Mandarin Monosyllablic Word Recognition Test was used to assess recognition of words, phonemes and lexical tones in AV and AO conditions at 3 presentation levels: speech detection threshold (SDT), speech recognition threshold (SRT) and 10 dB SL (re:SRT). Results: The prelingual group had better phoneme recognition in the AV mode than in the AO mode at SDT and SRT (both p = 0.016), and so did the NH group at SDT (p = 0.004). Mode difference was not noted in the postlingual group. None of the groups had significantly different tone recognition in the 2 modes. The prelingual and postlingual groups had significantly better phoneme and tone recognition than the NH one at SDT in the AO mode (p = 0.016 and p = 0.002 for phonemes; p = 0.001 and p<0.001 for tones) but were outperformed by the NH group at 10 dB SL (re:SRT) in both modes (both p<0.001 for phonemes; p<0.001 and p = 0.002 for tones). The recognition scores had a significant correlation with group with age and sex controlled (p<0.001). Conclusions: Visual input may help prelingually deaf implantees to recognize phonemes but may not augment Mandarin tone recognition. The effect of presentation level seems minimal on CI users' AV perception. This indicates special considerations in developing audiological assessment protocols and rehabilitation strategies for implantees who speak tonal languages.