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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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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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.