Graeme Clark Collection

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1992 - 1996 5
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Author: Clark, Graeme × End date: 2009 × Subject: auditory nerve × Subject: cochlear implant × Subject: cochlear%20implant × Subject: electrical stimulation ×

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Now showing 1 - 5 of 5
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    Discharge rate-level functions from dorsal cochlear nucleus single units in response to acoustic and electrical stimulation of the auditory nerve
    O'Leary, S. J. ; Clark, Graeme M. ; Tong, Y. C. ( 1995)
    Discharge rate-level (I/O) functions possessed by dorsal cochlear nucleus (DCN) units were examined, in response to bipolar electrical stimulation of the cochlea of the barbiturate-anesthetized cat. Spontaneously active units usually possessed nonmonotonic functions with a minimum, and spontaneously inactive units usually possessed monotonic functions or nonmonotonic functions with a maximum (NM+). In response to acoustic high-pass filtered noise, the function relating discharge rate and cut off frequency resembled the same unit's I/O function to electrical stimulation. The I/O functions to acoustic characteristic tones were usually monotonic or NM+. These results suggest that in the DCN, a prerequisite for the generation of acoustic-like responses with an electrical stimulus may be the matching of the cochlear place and spatial extent activated by each stimulus.
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    Chronic electrical stimulation of the auditory nerve at high stimulus rates: preliminary results
    Shepherd, R. K. ; Xu, J. ; Millard, R. E. ; Clark, Graeme M. ( 1994)
    The present preliminary report describes the electrophysiological response of the cochlea during long-term stimulation. The data indicate that electrical stimulation at a rate of 1000 pulses per second does not appear to adversely affect the implanted cochlea.
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    The development of speech processing strategies for the University of Melbourne/cochlear multiple channel implantable hearing prosthesis.
    Clark, Graeme M. ( 1992)
    The speech processing strategies that have been used with the University of Melbourne/Cochlear multiple channel implantable hearing prosthesis have been developed systematically from the inaugural one that extracted the second formant and presented this on a place coding basis and the voicing frequency which determined the rate of stimulation. Speech processing has also depended heavily on biological research to ensure that the stimulus parameters used or the operative approach did not damage the spiral ganglion cells it was hoped to stimulate. The advances in speech processing from Melbourne primarily have been to extract more features and spectral information and present this on a place coding basis. This has led to a progressive improvement in speech perception, and a small number of patients can achieve nearly 100% correct scores for open sets of phonetically-balanced words using electrical stimulation alone.
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    Effects of chronic electrical stimulation on cochlear nuclear neuron size in deaf kittens [Abstract]
    Kawano, Atsushi ; Seldon, H. Lee ; Clark, Graeme M. ; Kakuhisa, Eiji ; Funasaka, Sotaro ( 1996)
    It is now well recognized that normal afferent innervation is necessary for the development. This study investigated the effect of chronic electrical stimulation of the auditory nerve on the maturation of cochlear nucleus soma area of the neonatally deafened kittens. Eight kittens were deafened using kanamycin and ethacrynic acid, received a stimulated intracochlear implant in the left side and a dummy implant in right side, and classified two groups - the stimulated and the control group.
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    Decrement in auditory nerve function following acute high rate stimulation in guinea pigs [Abstract]
    Tykocinski, M. ; Shepherd, R. K. ; Clark, Graeme M. ( 1995)
    Cochlear implants have been shown to successfully provide profoundly deaf patients with auditory cues for speech discrimination. Psychophysical studies suggested that speech processing strategies based on stimulus rates of up to 1000 pulses per second (pps) may lead to an improvement in speech perception, due to a better representation of the rapid variations in the amplitude of speech. However, "neural fatigue" has been known to occur following brief periods of electrical stimulation at rates high enough to ensure that stimuli occur within the neurons relative refractory period, and has been shown to depend on stimulus duration and rate of the evoked neural activity. Prolonged electrical stimulation at these high stimulus rates could, therefore, have an adverse effect on the neurons metabolism and result in cellular energy depletion.