| Binaural-bimodal fitting is the hearing aid mode that combining a cochlear implant and a hearing aid in opposite ears. There is a low prototion of hearing-impaired children with binaural-bimodal after cochlear implantion surgery in our country. In the view of clinic, this study focus on the superiority of binaural-bimodal of speech recognition for hearing-impired children as native mandarin Chinese speaker by contrasting with the unilateral cochlear implant, its influencing factors, and try to discuss whether interference exist with binaural-bimodal fitting.Based on a review of domestic and foreign researches, the main body of this study is divided into four parts. Part Ⅰ is the development and tracking study of auditory ability of binaural-bimodal fitting; Part Ⅱ is the contrast study of speech recognition in noise; Part Ⅲ is the contrast study of sound localization; Part Ⅳ is binaural-bimodal study with the method of auditory event-related potential. The Specific methods and results are as follows:Part Ⅰ:Participants was divided into two groups according to hearing aid modes. This experiment contrasted the auditory ability and its development trend of binaural-bimodal group with unilateral cochlear implant group. The results indicated there are significant binaural-bimodal advantages in tone recognition, speech intelligibility in quiet, continuous speech and selective listening ability. It’s suggest to fit hearing aid immediately after surgery and focus on consonant recognition, tone recognition and selective listening ability trainings when6moths after surgery of hearing-impaired children.Part Ⅱ:The speech recognition threshold(SRT) in noise of39participants in different hearing aids mode conditions were tested with closed items and open items speech in noise tests. The result showed that the SRT of binaural-bimodal condition is lower, which has significantly more advantages than unilateral Cl condition. Meanwhile, It should be binaural-bimodal fitting when have available residual hearing in the non-implant ear; the binaural-bimodal wearing experience is an important factor of binaural-bimodal advantage, it suggest to adapt to the binaural-bimodal fitting at least more than6months; and also found a positive correlation between the binaural-bimodal advantage and the length of rehabilitation training period.Part Ⅲ:This part tested sound localization for16participants in different hearing aids mode conditions. The result showed that it’s difficult for Cl children to localize the sound source. The sound localization by minimum IID and ITD in binaural-bimodal condition was better than in unilateral Cl condition, and the advantage decreased with the decrease of the angle. Meanwhile, the wrong position of Cl microphone influences the ability of sound localization, and the hearing aids experiences before Cl surgery may be a factor of binaural-bimodal advantage in sound localization test.Part Ⅳ:This part investigated the characteristic of cortex auditory evoked potential by speech stimulus for normal hearing children and hearing-impaired children in different hearing aids mode condition. The test adopted equiprobable design paradigm and ICA as the artifact correction method. The results show that there were no significant difference in the latency of P1between hearing-impaired children and normal hearing children, it’s indicated that the reconstruction of auditory path by Cl and HA can provide the same process time with the normal auditory system; the amplitude of P1in binaural-bimodal condition was larger than in unilateral Cl condition, it’s indicated the binaural-bimodal advantage by objective test. Moderate correlation was found between the difference of P1amplitude and SRT in noise in different hearing aids mode condition, it’s indicated the two tests can be the subjective and objective assessment index for binaural-bimodal advanteges. And the automatic processing of lexical tones discrimination in preschool-aged children was not mature yet, but consonant discrimination was. The innovations of this study:(1) It’s identified the binaural-bimodal advantages in various aspects of speech recognition for hearing-impired children as native mandarin Chinese speaker and its influencing factors, and suggested some recommendations for clinical practice.(2) In research methods, longitudinal tracing was combined with horizontal comparison, macroscopical trend was combined with microcosmic analysis, subjective auditory behaviour test was combined with objective ERP test. It constructed the assessment mode of speech recognition with binaural-bimodal fitting.(3) It applied the speech stimulus in binaural-bimodal study for the first time and explored the CAEP test for Cl children by applying the new paradigm (equiprobable design) and new signal processing technique (ICA) from recent cognitive neuroscience researches. |
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