Graeme Clark Collection
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ItemLong-term speech perception in children with cochlear implants [Abstract]( 1997)Multichannel cochlear implants have been in use with children for over ten years with an acceleration, in recent years, in the number of young children being implanted. Analysis of speech perception results provides one way of measuring the success of implants in children. The desired outcomes in terms of overall benefit may be better assessed by speech production and language measures. However, in terms of the main aim of cochlear implants, it is useful to look at speech perception initially. This represents a measure of auditory ability which can be compared to normal performance and it is auditory ability that cochlear implants attempt to restore. Language and speech production depend on other factors in addition to auditory ability but it is probably a reasonable assumption that good speech perception is a prerequisite for good speech production and oral language. At the University of Melbourne, we have been able to follow the speech perception of implanted children over the long term. Analysis of results has shown that approximately 80% of implanted children of all ages achieve some understanding of openset speech in sentences (BKB sentences) with a mean score of 32% (n=38).
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ItemThe auditory cortex and auditory deprivation: experience with cochlear implants in the congenitally deaf [Abstract]( 1995)The primary auditory cortex (AI) exhibits a topographic representation of the organ of Corti in normal hearing animals. Plasticity studies have shown that this orderly representation of frequency can be modified following a restricted hearing loss or by behavioural trainingl,2. Little is known, however, of the effects of a profound hearing loss on AI, although a number of early studies have suggested an enhancement of activity from other modalities3. Knowledge of the functional status of the central auditory pathway in the profoundly deaf, and the ability of these structures to undergo reorganization particularly following long periods of auditory deprivation - are important issues for the clinical management of cochlear implant patients. In this paper we review our recent clinical and experimental experience with cochlear implants in the congenitally deaf.
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ItemResults of multichannel cochlear implantation in very young children [Abstract]( 1995)Most researchers and clinicians working in the cochlear implant field have assumed that profoundly deaf children will have a better prognosis in terms of speech perception, speech production and language development, implanted at as young an age as possible. However, it has been difficult to gather direct evidence for this hypothesis due to the problems in assessing children under the age of five years with formal tests.
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ItemSpeech perception results for implanted children with different levels of preoperative residual hearing [Abstract]( 1996)Many reports have established that hearing-impaired children using the Nucleus 22-channel cochlear implant may show both significant benefits to lipreading, and significant scores on open-set words and sentences using electrical stimulation only. These findings have raised suggestions that severely or severely-to-profoundly deaf children might benefit more from a cochlear implant than conventional amplification.
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ItemSpeech perception results for the nucleus multiple channel cochlear implant in children and adults with residual hearing [Abstract]( 1996)Speech perception results for profoundly deaf children and adults using advanced speech processing strategies for the Nucleus multiple-channel cochlear implant have continued to improve, and are now better than those reported in research with severely-to-profoundly hearing-impaired people using aided residual hearing.
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ItemSpeech perception benefits for implanted children with preoperative residual hearing [Abstract]( 1995)Since the implantation of the first children with the Nucleus 22-channel cochlear prosthesis in Melbourne in 1985, there has been rapid expansion in the number of implanted children world-wide. Improved surgical technique and experience in paediatric assessment and management have contributed to a trend to implant very young children. At the same time there has also been continuing development of improved speech processing strategies resulting in greater speech perception benefits.
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ItemLatest results and future directions in speech processing for the Nucleus multichannel cochlear prosthesis [Abstract]( 1995)The past two years has seen the introduction of the Speak speech encoding scheme for most patients using the Nucleus 22-channel cochlear prosthesis. This scheme, based on the Spectral Maxima Speech Processor (SMSP) developed at the University of Melbourne, uses a bank of 20 band-pass filters to present detailed spectral information to the intracochlear electrode array. Clinical trials of this speech processor have shown highly significant improvements over the previous Multipeak scheme in English, German, French and Japanese speaking patients. The largest improvements were evident for open-set testing in background noise, which represents a more realistic measure of everyday benefit than testing in quiet. The latest results for adults who have changed from Multipeak to Speak will be presented, along with results over time for newly-implanted patients using the Speak scheme. New research aimed at improving the speech processing in both the spectral and temporal domains will also be discussed.
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ItemMultichannel cochlear implants in children: an overview of experimental and clinical results [Abstract]( 1991)During the last decade there has been great progress in the clinical management of profound, postlinguistically deafened adults through the use of multichannel cochlear implants. The device developed by Cochlear Pty. Ltd. in association with the University of Melbourne, electrically stimulates selective regions of the residual auditory nerve using an array of 22 Pt electrodes located within the scala tympani. A speech processing strategy has been developed to provide patients with both voice pitch, and first and second formant information. Following experimental safety studies and successful clinical trials, this device was approved for use in adults by the United States FDA in 1985. In 1990, following further miniaturization of the implant, the FDA approved the device for use in profoundly deafened children above the age of two years. The present paper presents an overview of our recent biological safety studies and clinical experience with cochlear implants in children, and discusses the likely future development of these devices. Our biological safety studies were designed to evaluate the safety and design requirements of cochlear implantation in children, and more recently has focussed on issues for implantation in very young children (< 2 years old). These studies included the measurement of growth in the human temporal bone and the development of lead wires that can accommodate such growth, the development of an electrode fixation technique close to the cochlea, the effect of cochlear implantation on skull growth, the effect of long-term electrical stimulation on the maturing auditory system and the stimulating electrodes, and the effect of middle ear infection on cochlear implantation. Our clinical experience is based on twenty-five children that have now been implanted in our clinic. They include (i) postlinguistically deafened children; (ii) congenitally or early-deafened young children; and (iii) congenitally or early deafened adolescents. Clinical testing has shown improvements in speech perception, speech production and language in all three groups. Postlinguistically deafened children show similar speech perception results to postlinguistically deafened adults. For the congenitally deaf, younger children tend to show better results than the adolescents. Significantly, these clinical results are consistent with results from 142 children obtained from clinics throughout the world. These experimental and clinical results support the use of cochlear implants in young children. Further clinical improvements can be expected in the future with advances in both hardware and speech processing strategies.