Graeme Clark Collection
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ItemEvoked responses in humans to tones which are sinusoidally amplitude modulated [Abstract]( 1980)Evoked responses have been recorded from the scalp of normal human subjects to continuous sinusoidally-modulated Amplitude-modulated tones. The responses were periodic in nature, and a Fourier transform was used to quantify the amplitude and the phase of the constituent fundamental frequency and harmonic components. The fundamental frequency of the response equalled the frequency of the modulation envelope and the amplitude of the harmonic components was usually less than the fundamental. The responses were also found to be invariant with time for periods exceeding 30 minutes.
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ItemResults in children using the 22 electrode cochlear implant [Abstract]( 1989)Abstract not available due to copyright.
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ItemResults for two children using a multiple-electrode intracochlear implant( 1989)Abstract not available due to copyright.
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ItemSteady-state evoked potentials to amplitude-modulated tones(Butterworths, 1984)This study is an investigation of auditory evoked potentials (AEPs) to amplitude-modulated (AM) tones. The majority of AEP studies describe transient AEPs to pure tones and clicks. These potentials include the brainstem auditory evoked potentials (BAEPs) and the middle- and long-latency cortical potentials. By contrast, the cochlear microphic (CM) and the frequency-following response (FFR) are sustained potentials observed during a pure tone stimulus.
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ItemEvoked responses in humans to continuous amplitude modulated tones [Abstract]( 1982)The clinical use of the slow cortical auditory evoked responses and the auditory brainstem response is now widespread. Both of these responses look at the electrical changes in the brain following the onset of an acoustic stimulus and are known as transient responses. This paper will describe a technique of recording electrical potentials evoked during a continuous sinusoidally-modulated amplitude-modulated tone. This type of response is known as a steady-state response. The responses to this type of sound were found to be periodic, having the same fundamental frequencies as the modulation envelope. A Fourier transform was used to quantify the amplitude and phase of the first two harmonic components of the response. Responses can be recorded for modulation rates from 4Hz to 448Hz, for carrier frequencies from 250Hz to 4KHz and for sound pressure levels (SPLs) from 30dBSPL to 100dBSPPL. In general, the response amplitude increases with SPL. Estimates of latencies of these steady-state potentials can be made by measuring the phase of both harmonics as the modulation frequency is varied. Latencies suggest the auditory cortex as one of the sources of the response. The clinical implication of these results will be discussed.
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ItemThe clinical assessment of cochlear implant patients(Cambridge University Press, 1977)This paper is a discussion of the clinical assessment routine adopted following experience gained over the last three years from evaluating 27 patients with severe sensori-neural deafness to determine whether they are suitable for the cochlear implantation of a multiple-electrode receiving and stimulating device developed jointly in the Departments of Otolaryngology and Electrical Engineering at the University of Melbourne.
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ItemThe effects of muscle relaxants on auditory evoked potentials in humans(Cambridge University Press, 1973)In studies on auditory sensory information processing it is frequently assumed that the average evoked potentials from the scalp are produced by neural generators in the cortex. This may not be the case as there is evidence to suggest that at least one component of the auditory evoked response may be myogenic (Bickford et al., 1964). Therefore, the present study was undertaken to help determine the extent to which auditory evoked responses are myogenic or neurogenic.
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ItemAuditory evoked responses to frequency and amplitude modulated sound( 1973)Auditory evoked responses to pure tone bursts have been described in a number of studies and have been characterized by the P1, N1 and P2 components. The presence of later components, namely N2, P3 and the Contingent Negative Variation, depends largely on the cerebral processing of the stimulus. These evoked responses have been recorded using tone bursts. However, neurophysiological studies have shown that the cortex codes complex sounds. Therefore, we performed a set of acute experiments on the cat, using frequency and amplitude modulated sounds. This was reported in a previous study (Richards and Clark, 1972) which showed that similar onset and later waves could be recorded from the cortex of the cat. In some areas of the cortex the later waves were in synchrony with the modulation envelope.
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ItemCortical evoked response audiometry( 1973)Standard audiometry requires the patient to co-operate and to respond to an auditory stimulus. Thus reliance is placed on the patient's own judgment. There are a few clinical situations where the patient's co-operation cannot be gained or his judgment relied upon. Thus methods of audiometric testing have been derived which rely on observer judgment only. One of these objective methods of audiometry which is being investigated is Evoked Cortical Response Audiometry.
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ItemThe diagnosis and management of communication disorders in children( 1973)Communication disorders are common and may occur if the child has loss of hearing, is mentally retarded, has autism or suffers from higher level language disorders like aphasia and dyslexia.