Graeme Clark Collection
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ItemA training program for use with multichannel speech perception/production tactile devices [Abstract]( 1996)Over the past ten years, there have been remarkable improvements in both conventional hearing aid technology and in the use of multichannel cochlear prostheses. These developments have resulted in improved speech perception for severely and profoundly hearing impaired adults and children. However, a small number of adults and children remain unable to benefit from either of these prosthetic approaches. This may occur as a result of medical/surgical issues, which render implantation unfeasible, or from a decision by the patient or parents that the device is inappropriate for the individual person. In these cases, use of a supplemental speech perception device employing the intact tactile modality has been advocated. A number of single and multichannel devices have been developed, both commercially and in the laboratory. One of these, the Tickle Talker, a multichannel electrotactile speech processor, has been developed and thoroughly evaluated with both adults and children at the University of Melbourne. Benefits to speech perception have been noted on both closed-set phonemic discrimination tests, and on open-set word and sentence scores, where the device was used to supplement lipreading and/or aided residual hearing. Benefits to articulation have also been noted. Recently, improved speech processing and the design of a new electrode handset have been implemented. While these factors are important to device acceptance, the critical factor in improving speech perception and production appears to be the training program which is employed with the device. The program must be based on the information available through the device, but organised to emphasize the integration of tactually-encoded speech information into open-set understanding of words and sentences if communication is to be improved. The important elements of the program will be discussed. At present, no tactile device is able to provide sufficient information for open-set speech understanding using only the tactile input. While this may be an ultimate goal, significant periods of training may be required to achieve this outcome.
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ItemA clinical report on speech production of cochlear implant users( 1995)Objective: The aim was to assess articulation and speech intelligibility over time in a group of cochlear implant users implanted at 8 yr or over. The hypothesis was that the postoperative speech production performance would be greater than the preoperative performance. Design: A test of intelligibility using sentences and an articulation test measuring non-imitative elicited speech were administered to 11 and 10 subjects, respectively, who were implanted with the 22-electrode cochlear implant. Nine subjects received both tests. Age at implantation ranged from 8 yr to 20 yr and implant use ranged from 1 yr to 4 yr 5 mo. Results: For both the intelligibility and articulation tests roughly half of the subjects showed significant improvements over time and group mean postoperative performance significantly exceeded preoperative performance. Improvements occurred for front, middle, and back consonants; for stops, fricatives, and glides and for voiceless and voiced consonants. Conclusions: Despite being deprived of acoustic speech information for many childhood years, roughly half of the patients assessed showed significant gains in speech intelligibility and articulation postimplantation. The lack of a control group of non-implanted patients means that we cannot separate out the influence of the implant on speech production from other influences such as training and tactile-kinaesthetic feedback.
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ItemHabilitation issues in the management of children using the cochlear multiple-channel cochlear prosthesis(Wien, 1994)Since 1985, a significant proportion of patients seen in the Melbourne cochlear implant clinic have been children. The children represent a diverse population, with both congenital and acquired hearing-impairments, a wide-range of hearing levels pre-implant, and an age range from 2 years to 18 years. The habilitation programme developed for the overall group must be flexible enough to be tailored to the individual needs of each child, and to adapt to the changing needs of children as they progress. Long-term data shows that children are continuing to show improvements after 5-7 years of device use, particularly in their perception of open-set words and sentences. Habilitation programs must therefore be geared to the long-term needs of children and their families. Both speech perception and speech production need to be addressed in the specific content of the habilitation program for any individual child. In addition, for young children, the benefits of improved speech perception should have an impact on development of speech and language, and the focus of the programme for this age child will reflect this difference in emphasis. Specific materials and approaches will vary for very young children, school-age and teenage children. In addition, educational setting will have a bearing on the integration of listening and device use into the classroom environment.
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ItemRole of a multichannel electrotactile speech processor in a cochlear implant program for profoundly hearing-impaired adults( 1991)Four profoundly hearing-impaired adults who did not meet current selection criteria for implantation at the University of Melbourne were each fitted with a wearable multichannel electrotactile speech processor (Tickle Talker). The subjects were evaluated with a test battery of speech discrimination tests subsequent to training in use of the device. Thresholds for detection of pure tones were lower for the Tickle Talker than for hearing aids across the frequency range 250 to 4000 Hz. Mean speech detection thresholds for the Ling 5-sound test showed that all sounds were detected by users of the electrotactile device at normal conversational speech intensity levels. Mean speech discrimination scores were significantly higher (p < 0.05) in the tactually aided condition as compared with the tactually unaided for identification of vowels and consonants, on open-set words, open-set sentences, and on connected discourse tracking. Mean scores increased by 20% for vowels, 19% for consonants, 30% for openset words, and 25% for open-set sentences when the Tickle Talker was used in a multimodal combination with lipreading or lipreading and hearing aids. Speechtracking rates for three subjects showed increases of from 18 to 28 wpm when the tactile device was used. Comparison of tactually aided versus unaided tracking rates for two subjects with long-term experience shows continuing improvement with additional experience with the device. These results demonstrate that hearing impaired adults not meeting selection criteria for cochlear implantation may benefit from use of an electrotactile speech processor, and highlight the potential benefits from integration of such devices into cochlear implant programs for profoundly hearing-impaired patients.
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ItemImproved sound processing for cochlear implants( 2002)Four signal processing schemes currently under development aim to improve the perception of sounds/ especially speech, for children and adults using the Nucleus cochlear implant system. The schemes are (1) fast-acting input-signal compression, (2) Adaptive Dynamic Range Optimisation (ADRO), (3) TESM, a scheme that emphasises transients in signals, and (4) DRSP, a strategy that applies different stimulation rates to selected sets of electrodes.
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ItemApplication of advanced radiographic technology in cochlear implant research( 2001)The effective development of peri-modiolar or other advanced electrode arrays for cochlear implants requires detailed analysis of the insertion procedure and electrode positioning in the cochlea. Routine x-ray techniques cannot provide sufficient detail to meet this need. A new micro-focus x-ray imaging system has been built for our research. The system consists of a x-ray tube with a sub 10-micron focal spot mounted below an adjustable work surface and an image intensifier placed approximately 100 cm above the x-ray aperture. A variety of intracochlear electrode arrays and human temporal bones were studied using this system. The micro-focus x-ray imaging system allows for micro-fluoroscopy to visualise the real time implantation procedure. It also enables capturing of images onto reusable phosphor imaging plates or films for subsequent viewing or analysis. Images are produced at up to 95 times magnification with superior resolution and enhanced contrast. This new radiographic technology plays an important role in development of safe and effective advanced intracochlear electrode arrays.
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ItemInsertion study using new peri-modiolar electrode array designs [Abstract]( 1999)Intracochlear multi-channel cochlear implants have been shown to successfully provide auditory information for profoundly deaf patients by electrically stimulating discrete populations of auditory nerve fibers via a scala tympani (ST) electrode array. Histological and radiological examination of implanted human temporal bones showed that the current straight Nucleus® array is usually positioned against the outer wall of the ST. An electrode array close to the modiolus could be expected to reduce stimulation thresholds and result in a more localized neural excitation pattern.
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ItemBenefits of pre-curved electrode arrays for the Nucleus multichannel cochlear implant [Abstract]( 1998)The purpose of the study was to evaluate whether placement of an electrode closer to the modiolus would provide a more efficient interface with the auditory nerve. A pre-curved, banded 22-electrode array has been developed. Following comprehensive safety studies, the array was inserted in three adult patients. Detailed x-ray analyses have been conducted to specify the positions of the electrode bands. Psychophysical studies have been conducted, within each subject, using electrodes which lie at differing distances from the modiolus. These studies have shown that as the distance from the modiolus decreased, electrode threshold currents decreased and dynamic ranges increased. Thresholds were lower than in a comparison group of standard array users. Forward masking studies showed current spread to be more focused at the electrodes lying closer to the modiolus. Electrode discrimination was also better at electrodes closer to the modiolus. JND for loudness, expressed as a function of dynamic range also decreased in this condition. Thus, a preliminary profile of the parameters of interest, for an improved implant design, suggest that an array which lies closer to the modiolus can result in lower current requirements and a more localised pattern of neural excitation.
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ItemSpeech perception & indirect benefits for severely hearing impaired children using cochlear implants [Abstract]( 1998)The benefits to speech perception, speech production, communication, and quality of life were investigated for severely hearing impaired children using cochlear implants and hearing aids. For the youngest children, assessments of psychological status, and use of a battery of cognitive and language tests were important factors in determining performance benefits prior to the child developing speech. For older children, the effects of increased one-to-one oral habilitation, and systematic encouragement of parental involvement were also investigated. Results suggested that parental support for consistent device use was an important factor in producing outcomes. Children with residual hearing were more likely to achieve open-set perception. Each child was also assessed for changes in quality of life, through use of a standardized health utility instrument. Results from the group were collated, and teamed with a costing assessment for the procedure, which allowed a complete cost-utility analysis to be completed. Results suggested that indirect benefits, such as the effects on speech production, usual activities, lower concentration, and less distress were ranked as more important than changes to hearing in a number of the children. Costs per QALY were consistent with those reported in the literature, and suggested that the cochlear implant is highly cost-effective as a medical technology.
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ItemPerformance benefits and costs for children using cochlear implants and hearing aids [Abstract]( 1998)The value of cochlear implants as an established clinical option for profoundly hearing impaired adults and children has been supported by significant research results over a number of years which has clearly established the benefits available (U.S. National Institutes of Health Consensus Statement 1995). Benefit has traditionally been considered as the direct impact of the cochlear implant procedure on speech perception, or in the case of children, on the use of that auditory information to develop understandable speech and to acquire a knowledge of language. As a consequence of continuing research to improve hardware and speech processing strategies, mean scores on open-set tests of monosyllables or sentence materials for implanted adults using the cochlear implant alone without lipreading have continued to show an upwards trend. In response to the increased mean scores in quiet, perception tests in background noise are now being used as a more accurate direct measure of the potential benefits of cochlear implants to severely-to-profoundly hearing-impaired candidates. Consideration should also be given to indirect benefits, such as reduction in the stress of listening and lipreading, improved performance at work, enhanced opportunity to maintain speech, or in children to develop speech which is understandable to the general community, and the social effects of reducing the isolating effects of profound deafness. Measurement of indirect benefit can be combined with an analysis of the costs of the procedure, enabling evaluation of the implant procedure from a cost-utility standpoint, and a comparison of outcomes using other technologies such as hearing aids. This study will present data on direct and indirect benefits for hearing-impaired children using Nucleus cochlear implant systems, and compare this data with benefits shown for similarly hearing impaired children using hearing aids. The significance of these results to cost-effective delivery of services will be discussed.