Graeme Clark Collection
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ItemHearing restoration with the multichannel auditory brainstem implant( 1997)Restoration of useful hearing is now possible in patients with bilateral acoustic neuromas by direct electrical stimulation of the cochlear nucleus. Our first experience with the Multichannel Auditory Brainstem Implant is reported. A forty four year old female with bilateral acoustic neuromas and a strong family history of Neurofibromatosis Type II presented with profound bilateral hearing impairment. Translabyrinthine removal of the right tumour was performed with placement of the Nucleus eight electrode Auditory Brainstem Implant. Intraoperative electrically evoked auditory brainstem response monitoring successfully confirmed placement over the cochlear nucleus. Postoperatively, auditory responses were obtained on stimulation of all electrodes with minimal non-auditory sensations. The patient now receives useful auditory sensations using the "SPEAK" speech processing strategy. Auditory brainstem Implantation should be considered for patients with Neurofibromatosis Type II in whom hearing preservation tumour removal is not possible.
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ItemPsychophysical studies with two binaural cochlear implant subjects( 1997)Abstract not available due to copyright.
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ItemEngineering(Singular Publishing, 1997)The last two decades have seen major advances in cochlear implants for profoundly deaf people. Implants are now used by severely to profoundly deaf adults and children in almost every phase of daily life. They have become an established treatment, and today's expectations for all aspects of the cochlear implant system are much greater than they were for the experimental devices of the early 1980s. Hardware designs have improved to meet clinical and research demands, technological developments have made the devices smaller and more reliable, and speech processing research has yielded a series of improvements in patient benefit.
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ItemThe Melbourne Cochlear Implant Clinic program(Singular Publishing, 1997)The Melbourne Cochlear Implant Clinic program involves a multidisciplinary clinical team, collaborating with those engaged in more fundamental research, and with the biomedical company Cochlear Limited. This chapter reflects the contributions of many professionals to managing children with cochlear implants.
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ItemElectrical stimulation of the auditory nerve with a cochlear implant and the temporal coding of sound frequencies: a brief review( 1997)There is considerable evidence that the brain translates (encodes) the frequency of a sound into both place of excitation (place encoding), and the pattern of intervals between action potentials (temporal encoding). Furthermore, temporal encoding is now thought to be due to a temporal as well as spatial pattern of action potentials in a small group of neurons. This pattern needs to be reproduced with a cochlear implant for improved speech processing. Our recent research has also demonstrated that the timing of excitatory postsynaptic potentials seen with intracellular recordings from brain cells, rather than extracellularly recorded action potentials, correlates better with the frequency of sound. These excitatory postsynaptic potentials are likely to be the link between the patterns of action potentials arriving at nerve cells and the biomolecular activity in the cell. This response also needs to be replicated with improved speech processing strategies.
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ItemCochlear implants in adults and children: comment( 1997)This is a well-written review of the NIH Consensus report on cochlear implants for adults and children.
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ItemPitch and loudness estimation for single and multiple pulse per period electric pulse rates by cochlear implant patients( 1997)Abstract not available due to copyright.
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ItemVariability of amplitude and area of the auditory nerve compound action potential( 1997)The strength of neural response to sensory stimuli is often estimated by measurement of the amplitude of gross neural potentials. These gross potentials reflect the summed activity of a population of neurons. The amplitude of these potentials is dependent upon the synchrony of the contributing neural responses. We compared the variability of the peak-to-peak amplitude of the auditory nerve compound-action potential (CAP) with that of the area under the peaks. The area under the peaks was significantly less variable than the amplitude for responses to low frequency stimuli. Responses to other stimuli showed differences in the same direction, but these were not significant. We conclude that the area under these peaks is a more precise measure of neural response than measurement of waveform amplitude, at least for responses to low frequency stimuli.
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ItemThe Bionic ear towards 2000 and beyond: The William Carey Lecture 20th August 1998( 1999)I consider it a great honour to have been invited to give the William Carey Lecture, especially when one considers how much Carey contributed to the welfare of people in India. He was an outstanding man with many gifts and wide-ranging interests and influence --in fields as diverse as botany, economics, medicine, print and communications technology, libraries, engineering, conservation, agriculture, social reform, astronomy and Indian religions. All his work was done in the name of God, and his Christian belief. My address is entitled The Bionic Ear: Towards 2000 and beyond. I want to emphasise from the start that research directions beyond the year 2000 are built upon the achievements of the past and the present. Furthermore, although we have made great progress with the Bionic Ear, we have some distance to go before we can give most people near normal hearing.
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ItemSpeech results with a bilateral multi-channel cochlear implant subject for spatially separated signal and noise( 1999)Speech tests in noise were administered to a bilaterally implanted cochlear implant subject. Performance for simultaneous use of two identical implants, with the same speech processing strategy on two independent standard clinical processors, was compared with that of the better performing monaural side alone. Speech was presented at an angle of 45 degrees toward one ear, with noise at 45 degrees toward the contralateral side. Tests were also administered for speech and noise reversed in location. When the speech signal was on the same side as the subject's better performing ear, monaural and binaural tests resulted in similar scores. When the speech was on the opposite side, however, the binaural condition showed significantly better speech scores. The results indicate that binaural implants can provide improved performance in noise when speech and noise arc spatially separated.