Graeme Clark Collection
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ItemVowel imitation task: results over time for 28 cochlear implant children under the age of eight years( 1995)With increasing numbers of implanted children under the age of 4 years, numerous researchers have reminded us of the need for valid, sensitive, and reliable tests of developing speech perception.1,2 In addition to studies of the efficacy of implanted prostheses, there is a need to investigate the many variables that influence children's communicative performance, such as changes in speech-coding strategy, updated speech-processing systems, the effects of various training regimens, and the selection of educational and communication modes.
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ItemSpeech perception, production and language results in a group of children using the 22-electrode cochlear implant( 1992)Five children out of a group of nine (aged 5.5 to 19.9 years) implanted with the 22-electrode cochlear implant (Cochlear Ply. Ltd.) have achieved substantial scores on open-set speech tests using hearing without lipreading. Phoneme scores for monosyllabic words ranged from 40% to 72%. Word scores in sentences ranged from 26% to 74%. Four of these five children were implanted during preadolescence. The fifth child, who had a progressive loss and was implanted during adolescence after a short period of very profound deafness, scored highest on all speech perception tests. The remaining four children who did not demonstrate open-set recognition were implanted during adolescence after a long duration of profound deafness. Post-operative performance on closed-set speech perception tests was better than pre-operative performance for all children. Improvements in speech and language assessments were also noted. These improvements tended to be greater for the younger children. The results are discussed with reference to variables which may contribute to successful implant use: such as age at onset, duration of profound hearing loss, age at implantation, aetiology, educational program, and the type of training provided.
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ItemThe effects of auditory feedback from the nucleus cochlear implant on the vowel formant frequencies produced by children and adults( 1993)Cochlear implants provide an auditory signal with which profoundly deaf users may monitor their own speech production. The vowel production of two adults and three children who used the Nucleus multiple-electrode cochlear implant was examined to assess the effect of altered auditory feedback. Productions of words were recorded under conditions where the talkers received auditory feedback (speech processor turned on) and where no auditory feedback was provided (speech processor turned off). Data were collected over 3 days at weekly intervals. First and second formant frequencies were measured and the data were analysed to assess significant differences between auditory feedback conditions, vowel context, and data collection points. Overall, the results varied across talkers, across the data collection days, and depended on the consonant environment of the vowel. However, two effects of auditory feedback were noted. First, there was a generalized shift in first formant frequencies between the processor on and processor off conditions across three of the five subjects, but the shift differed in direction for each subject. Second, for three of the five talkers, the two front vowels /ε/ and /I/ were more neutralised in the absence of auditory feedback. However, this effect was less pronounced than that noted by previous studies.
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ItemCochlear implants in children, adolescents, and prelinguistically deafened adults: speech perception( 1992)A group of 10 children, adolescents, and prelinguistically deafened adults were implanted with the 22-electrode cochlear implant (Cochlear Ply Ltd) at the University of Melbourne Cochlear Implant Clinic and have used the prosthesis for periods from 12 to 65 months. Postoperative performance on the majority of closed-set speech perception tests was significantly greater than chance, and significantly better than preoperative performance for all of the patients. Five of the children have achieved substantial scores on open-set speech tests using hearing without lipreading. Phoneme scores in monosyllabic words ranged from 30% to 72%; word scores in sentences ranged from 26% to 74%. Four of these 5 children were implanted during preadolescence (aged 5:5 to 10:2 years) and the fifth, who had a progressive loss, was implanted during adolescence (aged 14:8 years). The duration of profound deafness before implantation varied from 2 to 8 years. Improvements were also noted over postoperative data collection times for the younger children. The remaining 5 patients who did not demonstrate open-set recognition were implanted after a longer duration of profound deafness (aged 13:11to 20:1 years). The results are discussed with reference to variables that may affect implant performance, such as age at onset of loss, duration of profound loss, age at implantation, and duration of implantation. They are compared with results for similar groups of children using hearing aids and cochlear implants.
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ItemMulti-channel cochlear implants for children: the Melbourne Program( 1991)Although there have been 300 years of deaf education, profoundly-totally deaf children today on average are not able to reach the same level of achievement as their normally hearing peers (Geers & Moog, 1989). This failure of deaf children to develop their true potential is largely due to the difficulty they have in communicating with normally hearing people. During the last 300 years there have been basically two different methods of education used (The New Encyclopaedia Britannica, 1983). Firstly, one which maximises auditory and lip reading cues (auditory/oral), advocated by Juan Pablo Bonet (1620), and one which uses a series of signs to convey meaning (signing), developed by Charles-Michel (1712-89). In addition, there is a method which endeavours to combine both auditory/oral and signing approaches called total communication. In practice, however, children taught by total communication tend to receive speech more predominantly by one or other of these methods.
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ItemThe histopathology of the human temporal bone and auditory central nervous system following cochlear implantation in a patient: correlation with psychophysics and speech perception results( 1988)Cochlear implantation has become a recognised surgical procedure for the management of a profound-total hearing loss, especially in patients who have previously had hearing before going deaf (postlingual deafness). Nevertheless, it is important for progress in the field that patients who have had a cochlear implant, bequeath their temporal bones for research. This will then make it possible to further assess the safety of the procedure, and the factors that are important for its effectiveness. Biological safety has been assessed in a number of studies on animals, in particular, the biocompatibility of the materials used (1,2), the histopathological effects of long-term implantation on the cochlea (3, 4, 5, 6, 7, 8), and the effects of chronic electrical stimulation on the viability of spiral ganglion cells (9, 10, 11, 12). In studying the temporal bones of deceased cochlear implant patients it is possible to help establish that the animal experimental results are applicable to Man. Surgical trauma has been most frequently evaluated by inserting electrodes into cadaver temporal bones. It is important, however, to examine bones that have been previously implanted surgically to ensure that the cadaver findings are applicable to operations on patients. The effectiveness of cochlear implantation can be studied by correlating the histopathological findings, the dendrite and spiral ganglion cell densities, in particular, with the psychophysical and speech perception results. Other benefits also accrue, for example, establishing the accuracy of preoperative X-rays and electrical stimulation of the promontory in predicting cochlear pathology and spiral ganglion cell numbers. For the above reasons it has been especially interesting to examine both the temporal bones and central nervous system from one of our patients (patient 13) who participated in the initial clinical trial of the Cochlear Proprietary Limited (a member of the Nucleus group) multiple-electrode cochlear prosthesis, and who died due to a myocardial infarction following coronary bypass surgery.
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ItemThe University of Melbourne/Nucleus cochlear prosthesis( 1988)This is a review of research to develop the University of Melbourne/Nucleus cochlear prosthesis for patients with a profound-total hearing loss. A more complete review can be obtained in Clark et al. A prototype receiver-stimulator and multiple-electrode array developed at the University of Melbourne was first implanted in a postlingually deaf adult patient with a profound-total hearing loss on 1 August 1978. A speech processing strategy which could help this patient understand running speech, especially when combined with lipreading was developed in 1978 following initial psychophysical studies. A prototype wearable speech processor was fabricated in 1979, that could provide significant help for the first two patients in understanding running speech when used in combination with lipreading compared with lipreading alone, and it also enabled them to understand some running speech when using electrical stimulation alone. An implantable receiver-stimulator and wearable speech processor embodying the principles of the prototype devices were then produced for clinical trial by the Australian biomedical firm, Nucleus Ltd, and its subsidiaries, Cochlear Pty Ltd and Cochlear Corporation. This cochlear implant was initially clinically trialled on six patients at The Royal Victorian Eye & Ear Hospital in 1982, and shown to give similar results to those obtained with the prototype device. In view of these findings a clinical trial was carried out for a Premarket Approval Application to the US Food and Drug Administration (FDA), and extended to a number of centres in the US, Canada, and West Germany. This clinical trial confirmed that patients could understand running speech when electrical stimulation was combined with lipreading, and that some patients could also understand running speech when using electrical stimulation alone. Today, more than 600 patients world-wide are using cochlear implants developed from the research described in this paper.
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ItemEvaluation of a two-formant speech-processing strategy for a multichannel cochlear prosthesis( 1987)Initial results with the two-formant speech-processing strategy (F0FIF2) confirm the advantage of a multichannel cochlear prosthesis capable of stimulating at different sites within the cochlea. The successful presentation of two spectral components by varying the place of stimulation leads to the possibility of presenting further spectral information in this manner. Because virtually all multichannel implant patients demonstrate good "place" (electrode site) discrimination, these more refined coding strategies should lead to benefits for the majority of implantees. Already, with the F0FIF2 strategy, we have a system that appears to provide some effective auditory-alone communication ability for the average patient.
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ItemA multiple-electrode intracochlear implant for children( 1987)A multiple-electrode intracochlear implant that provides 21 stimulus channels has been designed for use in young children. It is smaller than the adult version and has magnets to facilitate the attachment of the headset. It has been implanted in two children aged 5 and 10 years. The two children both lost hearing in their third year, when they were still learning language. Following implantation, it was possible to determine threshold and comfortable listening levels for each electrode pair. This was facilitated in the younger child by prior training in scaling visual and electrotactile stimuli. Both children are regular users of the implant, and a training and assessment program has been commenced.
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ItemAcoustic parameters measured by a formant-estimating speech processor for a multiple-channel cochlear implant( 1987)Abstract not available due to copyright.