Graeme Clark Collection
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ItemMeningitis after cochlear implantation: the risk is low, and preventive measures can reduce this further( 2007)Since the 1980s, more than 80 000 people have received cochlear implants worldwide. These implants are designed to enable people who are severely or profoundly deaf to experience sound and speech. Since 1990, implantation has become standard treatment for people who cannot communicate effectively despite well fitted hearing aids. Children who are deaf when they are born can perceive sound and learn to speak if they receive cochlear implants at a young age (ideally under 18 months). The use of cochlear implants has been thought to be safe. But since 2002 the number of patients with meningitis related to cochlear implantation has increased worldwide. Mortality and neurological complications after meningitis are high. We need to investigate the reasons for this and look at measures to reduce them.
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ItemControl strategies for neurons modelled by self-exciting point processes [Abstract]( 1995)Abstract not available due to copyright.
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ItemMultichannel auditory brainstem implants: an Australian case study [Abstract]( 1996)The multichannel Auditory Brainstem Implant (ABI) is an implantable device designed to restore a level of auditory perception in patients with bilateral acoustic neuromas, where the removal of the tumours is expected to result in a total loss of hearing. As with the cochlear implant, the ABI utilises an externally worn speech processor and headset, together with a surgically-placed receiver-stimulator and electrode array. The electrode array, developed through the collaboration of the House Ear Institute in the United States and Cochlear Corporation, consists of eight electrodes on a carrier, which is placed on the surface of the brainstem in the area of the cochlear nucleus.
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ItemCurrent trends in speech perception performance in adult cochlear implant patients [Abstract]( 1996)In 1994, Cochlear Pty. Ltd. (Now Cochlear Limited) released a new speech processor, the Spectra 22, for use with the Nucleus 22-channel cochlear implant. The Spectra 22 speech processor incorporates a new speech processing strategy called SPEAK, which is based upon research conducted by the University of Melbourne. This paper reports post-operative scores on open-set word and sentence materials for adult patients in the Melbourne Cochlear Implant Clinic who have been started up with the Spectra 22 speech processor.
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ItemThe importance of different frequency bands to the speech perception of cochlear implantees [Abstract]( 1996)It is well known that cochlear implantees exhibit a wide range of speech perception ability. Understanding the reason for this variability may lead to improved speech processors. This study investigates whether implantees rely on different areas of the speech spectrum for speech cues, compared to normally hearing listeners, and whether poor performers rely on different spectral areas than better performers. Six subjects with the Mini System 22 implant and using the SPEAK strategy participated in this experiment. Scores for monosyllabic words were obtained using the full speech spectrum and with selected frequency bands removed from the subjects’ speech processor maps. The Articulation Index (AI) is a measure of the proportion of speech information available to a listener, and the relative contribution to AI from different frequency bands is termed the Importance Function. The five frequency bands studied in this experiment were determined to be of equal importance to normally hearing listeners for the speech material used. The scores for each implantee were transformed into AI values, and hence the relative importance of the bands was determined. This relative importance was compared between the implantee group and normally hearing listeners to determine the way in which speech perception by electrical stimulation varies from that by acoustical stimulation. Comparisons were also made between individual implantees to determine whether correlations exist between their speech perception ability and their use of cues in different parts of the spectrum. Further research will determine whether the differences among implantees are correlated with their ability to perceive changes in stimulation place or temporal characteristics.
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ItemCentral auditory processing in schizophrenic patients suffering from auditory hallucinations [Abstract]( 1996)Studies have shown deficits on some specific auditory tasks in schizophrenic patients. Other studies have shown neuroanatomical abnormalities, in the temporal lobes in particular, associated with auditory hallucinations in schizophrenia, although conflicting findings have been reported. The purpose of this study was to comprehensively investigate central auditory processing in schizophrenic patients suffering from auditory, verbal hallucinations. An audiological test battery was performed on a group of 20 schizophrenic patients suffering from verbal hallucinations and a group of 20 normal controls, matched for age, sex educational standard and handedness, in order to determine whether specific central auditory processing deficits are related to the presence of auditory hallucinations. The hallucinators as a group were shown to have essentially normal middle ear, cochlear, VIII nerve and brainstem function as evidenced by normal pure-tone thresholds, speech discrimination in quiet, tympanometry, stapedial reflexes, Rapidly Alternating Speech Perception, binaural fusion and Auditory Brainstem Response results. Staggered Spondaic Word and dichotic consonant-vowel testing revealed significant differences between hallucinators and controls, while Competing Environmental Sounds testing revealed no significant differences between groups. Significant differences emerged between hallucinators and controls for speech in the presence of ipsilateral competition. Tone frequency pattern sequences revealed deficits in verbal responses but not hummed responses in the hallucinatory group. These results suggest specific abnormalities relate to verbal processing in hallucinators. A further comparison with a group of non-hallucinating psychotic patients is in progress to determine whether these findings are specific to hallucinations.
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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 in people with a severe hearing loss: preliminary results [Abstract]( 1996)Recent improvements in multichannel cochlear implants have led to improved speech perception for people with profound hearing impairments. Given this improvement, it has been suggested that some people with severe hearing impairments would be more successful with a cochlear implant than a hearing aid. Unfortunately little research exists to support the suitability of cochlear implants for these individuals. In order to determine this, a detailed investigation of the aided performance of people with severe hearing losses is being conducted at The University of Melbourne (School of Audiology). Severe hearing loss was defined as a pure tone average of greater than 60dBHL, but no worse that 100dBSPL in the better ear. At present, 15 participants have taken part in this study and their results will be discussed. Each participant took part in a standard audiometric assessment which included an audiogram, AB words, tympanometry with acoustic reflexes and an ABR. Each participant’s hearing aids were assessed to make sure that they were optimally aided. Following the hearing aid evaluation the participants took part in a series of traditional speech perception tests which included 24 consonant recognition, 11 vowel recognition, CNC words, CUNY sentences, and the Connected Speech Test (CSTv2). Other tests of speech perception were conducted which looked at the effects of different types of background noise, amounts of reverberation, rates of speech and amount of available context. The aim of this was to better simulate “real-life” listening conditions. Consequently, a range of results for both traditional assessments of speech perception and simulated listening conditions will be presented and compared.
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ItemSpeech perception for hearing aid users versus cochlear implantees [Abstract]( 1996)Abstract not available due to copyright.
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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.