Graeme Clark Collection
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ItemPreoperative residual hearing as a predictor of postoperative speech scores for adult cochlear implant users [Abstract]( 1994)The development of multiple channel cochlear implants has been a significant advance in the rehabilitation of profound hearing loss. Speech perception benefits have been particularly evident for postlinguistically deafened adults, who as a group have shown not only supplementation of lipreading scores but also significant comprehension of words and sentences using an implant alone, without the aid of lipreading. In many cases, patients are able to use their implant for telephone conversation. Speech perception benefits for adult users have increased with advances in speech processing and improved means of habilitation. These improvements in open-set speech benefits for adult users have resulted in a steady increase in group mean scores and a reevaluation of selection criteria for cochlear implantation. In the initial development of cochlear implants, only those with little or no residual hearing were considered as candidates. Current selection criteria now include those with substantial residual hearing, who may score up to 40% in the best-aided condition on word and sentence speech perception tests. In order to provide realistic expectations for prospective cochlear implant patients, it is important to establish the relationship of many preimplant factors to postimplant speech perception benefits. For severely hearing impaired adults, the relationship between preoperative residual hearing, as measured by aided word and sentence speech perception test scores, and postoperative speech perception benefits is of significant interest. Analysis of data collected over a 15 year period for adult patients is presented. The rationale for conducting full speech perception assessments for all potential cochlear implant patients is stressed.
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ItemThe perception of electrodes by cochlear implant patients who became deaf early in life [Abstract]( 1994)Two separate studies measuring the perception of differences in site of electrode stimulation were conducted with cochlear implant patients who became deaf early in life. The multiple-electrode prosthesis manufactured by Cochlear Pty. Limited was used. Two of the possible mechanisms for the discrimination of different electrodes are pitch and loudness. The first study measured the discrimination of different electrodes using two procedures which minimised the influences of loudness cues on performance. In the first procedure, the stimulation patterns were symmetric sweeps across electrodes. The reference stimuli were apical-basal trajectories and the comparison stimuli were basal-apical trajectories. The electric stimulation levels were the same in the reference and comparison stimuli because the same electrodes were used in the trajectories. In the second procedure, the stimulation patterns used randomised variations in electric stimulation levels on the different electrodes. By randomly varying the loudness of the stimuli in a discrimination task, the patient is required to listen for more salient cues such as pitch. Both procedures gave comparable results. The second study was concerned with the estimation of order in percepts for stimulation on the different electrodes along the array which was related to the tonotopic order of the cochlea. Approximately half of the early-deafened patients tested revealed a tonotopic order in percepts which was comparable to that obtained from postlinguistically deafened adults.
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ItemPreliminary evaluation of a wearable multichannel electrotactile speech processor [Abstract]( 1988)Speech discrimination testing, using both open-and closed-set materials was carried out with four severely-to-profoundly hearing impaired adults. and seven normally hearing subjects, to assess performance of a wearable eight-channel electrotactile aid (Tickle Talker). The device consisted of a handset composed of nine electrodes, a stimulator-unit, and a speech processor and input microphone. Eight small electrodes were located over the digital nerve bundles on each side of the four fingers of one hand, and a larger common electrode was placed on the wrist. Subjects perceived eight separate channels of information, each corresponding to a stimulus on one side of one finger. The speech processor provided estimates of second formant frequency, fundamental frequency and amplitude of the speech waveform. These features were coded as electrode position, pulse rate and pulse width respectively. This processing strategy (FOF2AO) is similar to that used in an earlier model of the Cochlear Pty. Ltd. cochlear implant.