The long-term objective of the proposed research is to obtain a better understanding of the effectiveness of cochlear implants ad tactile aids in promoting improved development of speech in totally deaf children. Existing data suggest that these devices do promote speech development in the children who use them, but knowledge is still limited with respect to: (1) the range of speech production skills developed, (2) the time course over which improvement occurs, and (3) the highest level of speech production that is possible with current devices. Five longitudinal experiments are proposed that will provide a comprehensive set of data on the acquisition of physiological, phonetic, and phonological skills in three experimental groups of children: single-channel cochlear implant (3M/House device) users, multichannel cochlear implant (Nucleus 22-Channel Cochlear Implant System) users, and multichannel vibrotactile aid (Tactaid 7) users. Experiment I will examine changes in physiological speech production with aerodynamic speech measures. Experiment II is designed to quantify changes in phonetic speech production skills. Acquisition of English phonology will be examined in Experiment III. The relationship between speech perception and production skills is examined in Experiment IV. In Experiment V, selected speech production measures will be obtained with the subjects' devices turned OFF, and compared to the same measures obtained with their devices turned ON. The ON/OFF paradigm will identify those aspects of speech production that require ongoing auditory (or vibrotactile) feedback to be maintained. Speech development within- groups will be examined over time to quantify the rate of learning and extent of speech development that occurs with each type of device. Comparison between-groups will provide data on the relative effectiveness of the different devices in promoting speech development. The influence of age at onset of deafness and other demographic variables on speech development also will be examined. Speech development in the experimental groups will be compared to that in two groups of subjects who use conventional hearing aids. One group will have substantial residual hearing in the profound range of impairment. Their performance will be used to establish the upper limit of speech development hypothesized to be possible with an implant or tactile aid. The other group will have limited residual hearing, especially in the high frequencies. If their performance is poorer than that of the experimental subjects, then this would indicate that cochlear implants or tactile aids are more effective in promoting speech development in children with some residual hearing than are conventional hearing aids.
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