Graeme Clark Collection

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    The auditory brainstem response in hearing and deaf cats evoked by intracochlear electrical stimulation
    Black, R. C. ; Clark, Graeme M. ; O'Leary, S. J. ; Walters, C. (Monash University Press, 1983)
    This study was performed to investigate in detail the auditory brainstem response (ABR) for intracochlear electrical stimulation. Brainstem response audiometry is a simple, noninvasive procedure with the responses under many stimulus conditions being readily understood in terms of single auditory nerve discharge properties. The amplitude and latency behaviour of the Nl brainstem response correlates well with that recorded directly from the auditory nerve (Huang & Buchwald, 1978). In addition, the brainstem response can be divided into frequency-specific components corresponding to tonotopical locations in the cochlea, as exhibited in the method of derived responses (e.g. Parker &Thornton, 1978). It is therefore well suited to both physiological and clinical investigation of auditory function and therefore should be useful in evaluating auditory function under conditions of electrical stimulation of the cochlea.
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    Electrical stimulation of the human cochlea: psychophysical and speech studies
    Clark, Graeme M. (Plenum Publishing Corporation, 1981)
    This report describes psychophysical and speech studies conducted on two of our post-lingually deaf patients implanted with the nature of the hearing sensations produced by the individual electrodes, and to investigate the feasibility of the transmission of speech information to higher centres by means of cadences of stimulation using on electrode at a time. Two totally deaf patients (MC1 and MC2) participated in these studies.
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    Cochlear implant research directions
    Clark, Graeme M. (Monduzzi Editore, 1997)
    Frequency Coding: Initial cochlear implant research (Clark, 1969) showed that with electrical stimulation of the auditory nerve there is an electroneural "bottle-neck" limiting the flow of information from sound to the central auditory nervous system. This electroneural "bottle-neck" is due to the difficulty in simulating with electrical stimulation the temporal as well as the place coding of frequency. One of the main aims of our research is to improve cochlear implant performance by widening the "bottle-neck" with better simulation of the temporal and place coding of frequency. Temporal coding is considered to be due to a direct relationship between the intervals between action potentials and the period of the sound wave. Temporal coding is thought to apply to low frequencies, but its importance for high frequencies is still not clear. Place coding is due to excitation of specific sites within the cochlea and the central auditory pathways 'so that a frequency scale is preserved anatomically (i.e. the brain is organized tonotopically).
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    An improved model of electrical stimulation of the auditory nerve
    Bruce, I. ; Irlicht, L. S. ; White, M. ; O'Leary, S. J. ; Dynes, S. ; Javel, E. ; Clark, Graeme M. (Monduzzi Editore, 1997)
    Mathematical models are a useful means of formally describing and investigating pertinent features of complex systems such as the human auditory system. These features may be deduced from physiological and psychophysical experiments utilising animal models or humans, and from engineering studies. Historically, models of the auditory nerve's (AN) response to electrical stimulation have ignored randomness in single-fiber activity which has been recorded in physiological studies. These models, however, have been unable to accurately predict a number of important psychophysical phenomena. In this study, a model that incorporates random activity of the AN is presented, and is shown to predict psychophysical performance. These results indicate that random activity is indeed an important part of the response of the AN to electrical stimulation.