Graeme Clark Collection
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ItemSpeech perception as a function of electrical stimulation rate: using the nucleus 24 cochlear implant system( 2000)Objective: To investigate the effect of varying electrical stimulation rate on speech comprehension by cochlear implant users, while keeping the number of stimulated channels constant. Design: Three average rates of electrical stimulation,250, 807, and 1615 pulses per second per channel (pps/ch), were compared using a speech processing strategy that employed an electrode selection technique similar to that used in the Spectral Maxima Sound Processor strategy (McDermott, McKay,& Vandali, 1992; McDermott & Vandali, Reference Note 1; McKay, McDermott, Vandali, & Clark, 1991)and the Spectral Peak strategy (Skinner et al., 1994;Whitford et al., 1995). Speech perception tests with five users of the Nucleus 24 cochlear implant system were conducted over a 21-wk period. Subjects were given take-home experience with each rate condition. A repeated ABC evaluation protocol with alternating order was employed so as to account for learning effects and to minimize order effects. Perception of open-set monosyllabic words in quiet and open-set sentences at signal to noise ratios ranging from +20 to 0 dB, depending on the subject’s ability, were tested. A comparative performance questionnaire was also administered. Results: No statistical differences in group performance between the 250 and 807 pps/ch rates were observed in any of the speech perception tests. However, significantly poorer group performance was observed for the 1615 pps/ch rate for some tests due predominantly to the results of one subject. Analysis of individual scores showed considerable variation across subjects. For some subjects, one or more of the three rate conditions evaluated provided benefits on some speech perception tasks. The results of the comparative performance questionnaire indicated a preference for the 250 and 807pps/ch rates over the 1615 pps/ch rate for most listening situations. Conclusions: For the speech processing strategy, implant system, and subjects evaluated in this study, the group results indicated that the use of electrical stimulation rates higher than 250 pps/ch (up to 1615 pps/ch) generally provided no significant improvement to speech comprehension. However, individual results indicated that perceptual.
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ItemThe development of speech perception in children using cochlear implants: effects of etiologic factors and delayed milestones( 2000)Hypothesis: Speech perception outcomes for cochlear implantation of children vary over a wide range, and it is hypothesized that central pathologic states associated with certain causes of hearing impairment account for a substantial part of the variance. Study Design: A retrospective analysis was carried out to ascertain the relationships between speech perception, etiologic factors, and central pathologic states as indicated by preoperative delayed motor milestones and/or cognitive delays. Setting: Data were obtained from the pre-and postoperative records of patients attending a hospital cochlear implant clinic. Patients: Results for 75 consecutive patients up to age 5 years who underwent implantation were included in the study. Intervention: Patients received a 22-electrode cochlear prosthesis and were seen by the clinic for regular tune-up and assessments. Home-and school-based habilitation was recommended by the clinic. Main Outcome Measures: Speech perception measures were classified on a five-point scale to allow for different evaluation procedures at different ages and developmental stages. Results: The incidence of motor and cognitive delays were fairly evenly spread across etiologic factors, except for cytomegalovirus, which had a much higher than average incidence. Children with motor and/or cognitive delays were significantly slower than other children in the development of speech perception skills after implantation. Etiologic factors did not have a statistically significant effect on speech perception outcome. Conclusions: It is likely that central pathologic states account for a substantial part of the variance among children using cochlear implants. Specific indicators of central pathologic states should be used to assess a child's prognosis in preference to less specific information based on etiologic factors alone.
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ItemThe relationship between speech perception and electrode discrimination in cochlear implantees( 2000)Abstract not available due to copyright.
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ItemGeneralisation of tactile perceptual skills to new context following tactile-alone word recognition training with the Tickle Talker( 2000)Abstract not available due to copyright.
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ItemShort-term auditory memory in children using cochlear implants and its relevance to receptive language [Abstract]( 2000)Current work indicates that many children using cochlear implants are able to hear fine differences between speech sounds but are not progressing as wel1 as expected in receptive language ability. There is anecdotal evidence from teachers that some children using cochlear implants have poor short-term auditory memory ability, which may be impeding their language development. Temporal ordering and short-term memory storage capacity involve higher order processing. Severe auditory deprivation prior to implantation may have caused auditory processing deficits at a cortical level. This study aims to assess short-term, sequential, auditory memory ability in children using cochlear implants and to determine the relationship between this ability and receptive language ability. Short-term auditory memory ability has not been previously investigated in profoundly deaf children using hearing aids and/or cochlear implants. Twenty-four children using the 22-electrode cochlear implant were tested on five short-term sequential memory tasks, three with auditory stimuli and two with visual stimuli. There were 8 children in each of the age groups; 5-6 years, 7-8 years, and 9-11 years. Twenty-four age-matched, normally hearing children served as a control group. Al1 children were also assessed on the receptive subtests of the CELF (Clinical Evaluation of Language Fundamentals) and on the nonverbal scale of the Kaufman Assessment Battery for Children (K-ABC) which measures nonverbal intelligence. This study assessed short-term auditory memory with tasks that required minimal language ability. Prior to the memory tasks, the child had to demonstrate accurate identification of the stimuli with a similar reaction time to the normally hearing controls. As expected there is a significant effect of age on memory performance for the 24 normally hearing children, with older children performing better than the younger children. The memory performance of the children using cochlear implants is therefore described in terms of its deviation from expected performance for a given chronological age. Preliminary results suggest that it is unlikely that auditory deprivation causes a memory deficit specific to the auditory modality. Performance on visual memory tasks is very similar to performance on analogous auditory memory tasks for a group of implant users. The performance of children using cochlear implants on a variety of memory tasks does not appear to be significantly different to that of normally hearing children who are of similar age and nonverbal intel1igence. In contrast their receptive language scores are substantially inferior.
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ItemElectrode discrimination and speech perception in young children using cochlear implants( 2000)Objective: The aim was to determine the efficacy of a child-appropriate procedure to assess electrode discrimination ability in young children using cochlear implants and to investigate the relationship of electrode discrimination ability and speech perception performance in children implanted at a young age. Design: An adaptation of the play audiometry procedure was used to assess electrode discrimination in seventeen 4- to 10-yr-old children. The children were required to respond with a game-like motor response when a repeating stimulation on a reference electrode “changed” to a different electrode. They were also assessed on a speech feature discrimination test, a closed-set word recognition test and a nonverbal intelligence task. Results: Sixty-five percent of subjects demonstrated ability to discriminate adjacent electrodes in mid and apical regions of the cochlea, whilst the remaining subjects needed electrode separations of between two and nine electrodes for successful discrimination. In a forward stepwise regression analysis electrode discrimination ability was found to be the strongest factor in accounting for variance in the speech perception scores. Subject variables such as duration of deafness, nonverbal intelligence and implant experience did not significantly account for further variance in the speech perception scores for this group of children. Conclusions: Electrode discrimination ability was the strongest factor in predicting performance on speech perception measures in a group of children using cochlear implants.
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ItemWhat factors contribute to successful outcomes for children using cochlear implants( 2000)Long term speech perception data has been collected for 100 children using the Nucleus multichannel cochlear prosthesis in Melbourne. Scores on a number of different assessments are available at approximately six month intervals following implantation for these children. The group represents an unselected sample of cochlear implant users, as all children were included if they had sufficient developmental skills to perform formal speech perception tests. Information was also collected on each child regarding type of hearing loss, age of onset of profound hearing loss, duration of profound hearing loss, age at implantation, pre and post-implant communication mode, developmental delay, speech processing strategy and length of experience with implant use.
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ItemLatest results for adults & children using cochlear implants & future implications( 2000)The overall success of a cochlear implant procedure is most often quantified by assessing how well implantees can understand speech. This is because a primary aim of the application of cochlear implants is to improve communication, and it is relatively straightforward to obtain accurate measures of speech recognition. The quality of cochlear implant hearing is not well described by measuring an audiogram, as the detection of sound is similar across all implantees if the device is functioning correctly. A commonly used measure of speech understanding is the CID everyday sentence test where the number of correctly identified words within sentences is assessed. In the early days of cochlear implants, subjects could only recognize a few words without lipreading but the most recent results show average scores of 80% without lipreading for this sentence test, after 6 months of experience with the device.
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ItemHearing levels and speech perception prior to cochlear implantation - are they predictive of outcomes for adult implant users?( 2000)As the speech perception results obtained for adults using multichannel cochlear implants have improved, people with a wider range of hearing losses are now considering implantation. In the mid-1980s, most adults undergoing cochlear implantation had little or no residual hearing. This made selection and counselling relatively straightforward as any level of hearing obtained through use of the cochlear implant could be considered as a benefit in such cases. Most patients evaluated for implantation today have some degree of useful residual hearing, and may be reliant on this hearing to varying degrees in their everyday life. In essence, they have something to lose if their postoperative performance is poor. In counselling these patients, it would be most helpful to have reliable predictors of postoperative performance. A number of factors such as duration of profound hearing loss, congenital profound hearing loss, and certain aetiologies (eg, head injury) have shown significant links with outcomes in previous studies.
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ItemApplication of the cochlear implant to profoundly hearing impaired adolescents: re-visiting the inclusion criterion for older children( 2000)Objective: The purpose of this study is to examine the range of outcomes for older children receiving the multi-channel cochlear implant. Recent improvements in the speech perception performance for profoundly hearing impaired children and adults have lead to expanded selection criterion for cochlear implant inclusion. That is, the efficacy of cochlear implants for adults with acquired hearing loss is well documented. In addition, the application of the cochlear implant to young children has lead to improvements in open set speech perception, speech production and language acquisition. In contrast, congenitally deaf and prelingually deafened children who are implanted after the age of 8 years have performed poorer than children implanted at a younger age on speech perception, speech production and psychophysical performance measures.