Graeme Clark Collection
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ItemSpeech perception in implanted children: influence of preoperative residual hearing on outcomes [Abstract]( 1998)Since the first child was implanted with the Nucleus 22-channel prosthesis in Melbourne in 1985, several thousand children world-wide have now benefitted from this technology. More effective paediatric assessment and management procedures have now been developed, allowing cochlear implants to be offered to children under the age of 2 years. Improvements in speech processing strategy have also been implemented in the Nucleus implant system, resulting in increased mean speech perception benefits for implanted adults. Although a range of performance on formal measures of hearing, speech or language has been reported for children using implants, results from the first decade of implant experience consistently show that significant benefits are available to children receiving their implant at an early age. Reported speech perception results for implanted children show that a considerable proportion (60%) of paediatric patients in the Melbourne and Sydney clinics are able to understand some open-set speech using electrical stimulation alone. These results, and the upward trend of mean speech perception benefits shown for postlinguistically deafened adults have raised questions as to whether severely, or severely-to-profoundly deaf children currently using hearing aids would in fact benefit more from a cochlear implant. To investigate the potential influence of the degree of preoperative residual hearing on postoperative speech perception, results for all implanted children in the Melbourne and Sydney cochlear implant programs were analysed. Results showed that as a group, children with higher levels of preoperative residual hearing were consistently more likely to achieve open-set speech perception benefits. Potential factors in this finding could be higher levels of ganglion cell survival or greater patterning of the auditory pathways using conventional hearing aids prior to implantation. Conversely, children with the least preoperative residual hearing were less predictable, with some children achieving open-set perception, and others showing more limited closed-set benefits to perception. For these children, it is likely that preoperative residual hearing is of less significance than other factors in outcomes.
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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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ItemSpeech perception for children with different levels of residual hearing using the cochlear 22-channel cochlear prosthesis [Abstract[( 1996)Over the past 10 years, since the implantation of the first children with the Nucleus 22-channel cochlear prosthesis in Melbourne, the number of profoundly deaf children using this implant system has rapidly expanded. Longer-term experience with implanted children has led to improvements in paediatric assessment and management. Speech processing strategies have also been improved, resulting in a series of increases in speech perception benefits. Results of comparative studies of Speak and Multipeak speech processing strategies have shown that open-set word and sentence scores for a group of thirteen children evaluated over a two year period showed an advantage with the Speak speech processing strategy. The increases were noted particularly in speech perception in poor signal-to-noise conditions. Analysis has shown that consonant perception was significantly increased, due to an improved place perception. Given current speech perception scores for implanted children, it has been suggested that severely-to-profoundly deaf children currently using hearing aids could in fact benefit more from a cochlear implant. Preliminary investigation of results for children in the Melbourne and Sydney cochlear implant programs has shown that children with higher levels of preoperative residual hearing as a group do score significantly on open-set word and sentence perception tests using the implant alone. In children with lower levels of residual hearing, results were variable across the group.
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ItemIssues in long-term management of children with cochlear implants and tactile devices [Abstract]( 1994)For many children with severe and profound hearing losses, conventional hearing aids are unable to provide sufficient amplification to ensure good oral communication and/or in the case of very young children, development of speech and language. Traditionally a number of these children have opted for the use of sign language alone or in Total Communication approaches as a primary means of communication. The advent of multiple channel cochlear implants for children and the continuing development of multiple channel speech processing tactile devices provide auditory approaches to resolving communication difficulties for these children. The successful use of such devices depends on a number of factors including the information provided through the aid; the ease of use, convenience and reliability of the aid; the individual communication needs of the child; and the habilitation and management program used with the device. Long-term data has shown that children continue to show increased speech perception benefits from improvements in speech processing and from further experience with these devices. Habilitation and management programs must therefore be geared to meet the changing needs of children as they progress and of families as children mature and face new challenges. Habilitation must address specific individual needs in speech perception and in speech production. For very young children, benefits of improved speech perception should have an impact on the development of speech and language, and habilitation and management must emphasise the need for language growth.
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ItemDesign fundamentals for a tactile speech processor: i) encoding of speech information, and ii) biomedical safety considerations [Abstract]( 1992)Approaches to providing speech information through the tactual modality have varied in: number and spatial location of transducers; method of interfacing with the skin's sensory apparatus; and content of speech information presented. Use of a multiple speech feature encoding approach to design of a tactile device was implemented in the wearable multichannel electrotactile speech processor or Tickle Talker developed at the University of Melbourne. Psychophysical studies established that subjects could discriminate salient electrical parameters in the tactual display, and that this information could be used to discriminate acoustic speech feature contrasts. Results with normally-hearing and hearing-impaired adults and children using an FOF2 encoding strategy showed improved discrimination scores for closed-set speech feature discrimination batteries, closed-set vowel and consonant identification tasks, as well as for open-set word and sentence comprehension. Based on analyses of tactual encoding of speech features, alternative speech processing strategies designed to increase the quality of speech information available were evaluated. Results for two hearing-impaired adults showed improved feature discrimination with the addition of a voicing signal to the FOF2 strategy. Biomedical safety investigations conducted concurrently have established that the electrical parameters of the stimulus waveform, electrode handset design, and electrical circuitry of the device are free from potential risks. Longer-term physiological assessments included measures of possible effects of electrical stimulation on tactual sensitivity, finger temperature, finger and hand blood flow, electrical thresholds and maximum comfortable levels, and on central nervous system, function as measured by EEG. Results of the kinesthetic, vascular and neurological assessments showed no significant contraindications which might limit application or long-term use of the device.
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ItemThe Tickle Talker: a speech perception aid for profoundly hearing impaired children [Abstract]( 1990)Fifteen prelingually profoundly hearing-impaired children participated in speech perception training and evaluation, to assess potential benefits from use of the Tickle Talker. This device, a multichannel electrotactile speech processor, developed by Cochlear Pty. Ltd. and the University of Melbourne, presents speech as a pattern of electrical sensations felt on the fingers. The eight small electrodes are located over the digital nerve bundles, on both sides of the four fingers of the non-dominant hand. Speech processing hardware is similar to that used in the 22-channel cochlear implant. In the encoding strategy, second formant frequency (F2) is presented as electrode position, speech waveform amplitude as stimulus strength, and fundamental frequency (FO) as rate of stimulation. Each child participated in an ongoing training program involving clinicians, teachers and parents. The evaluation program included measures of sound and speech detection thresholds, and discrimination of speech features, words and open-set sentences. Both individual and mean scores for all the children demonstrate significant improvements in speech perception scores when input from the Tickle Talker is combined with either aided-residual hearing, or aided residual hearing and lipreading. These results are consistent with those previously reported for profoundly hearing-impaired adults using the Tickle Talker, and indicate that children are able to integrate speech information provided through the tactual modality with information from vision or residual hearing.
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ItemStudies in tactile speech perception using the University of Melbourne Tickle Talker [Abstract]( 1998)During the past four years, a series of studies have been undertaken investigating the perception of speech presented through the tactile modality. These studies formed part of a project to develop an effective and safe electro tactile speech perception device for those children and adults requiring additional communication assistance to that provided by hearing aids, but unable to benefit from cochlear implants.
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ItemSpeech perception in children following habilitation with background noise [Abstract]( 1996)Recent evaluation of open-set work and sentence perception results for a group of children evaluated over a two year period showed that improvements to speech perception scores in poor signal-to-noise conditions were possible with use of the Speak speech processing strategy. The increases were noted particularly in speech perception in poor signal-to-noise conditions. However, overall scores were still lower that for hearing in quiet. As children are often in noisy environments, it was of interest to assess whether specific habilitation involving perception in controlled background noise could improve perception. A preliminary study evaluating perception of open-set words and sentences in background noise for four children has been completed. Each of the children was assessed over a six month period, using repeated assessments of connected discourse tracking, and word and sentence perception scores. At each assessment, measures were made both in quiet and in background noise. The specific signal-to-noise ration varied with each child, but was kept constant through the evaluation. During the six month period, children had weekly habilitation sessions, which included specific perceptual training in controlled background noise. Preliminary results indicate that training in ‘controlled noise’ can significantly improve speech perception results for this group of children.