Graeme Clark Collection
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ItemElectrical network properties and distribution of potentials in the cat cochlea [Abstract](Australian Physiological and Pharmacological Society, 1978)The-patterns of electrical resistance and capacitance in the cochlea formed by the anatomical organisation of the tissue structures and fluids are important in determining the distribution of electrical potentials which arise during normal acoustic stimulation (von Bekesy,1951). Cochlear potential distributions have in the past been measured by recording from the scalar fluids both the spread of cochlear microphonics and also potentials due to electrical stimulation. However, similar distributions in the hair cell-nerve ending region of the organ of Corti may not necessarily occur because of current shunting effects due to the electrical network patterns. To examine these current shunting effects, a three dimensional mathematical model of the electrical properties of the cat cochlea was constructed. This was formed from a two dimensional cochlear cross-section model similar to that proposed by Johnstone et al., (1966) for the guinea pig. Sixteen such sections were resistively coupled to form the three dimensional model. Results derived from this model predict that during electrical stimulation of the cochlea, the current in the organ of Corti region attenuates quite differently to the scalar voltage by a degree which depends on the stimulus electrode configuration.
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ItemAuditory evoked potentials and auditory sequential memory [Abstract]( 1974)The evaluation of intelligence in infants and young children is important in assessing their prognosis and institutional placement, and is difficult with present clinical methods. Therefore, the recent studies which show a correlation between visual evoked responses and intelligence are of value. It is also of importance to determine if auditory evoked potentials may be used in assessing children with communication disorders, as their defect frequently involves the auditory system, and they will often require evoked response audiometry to exclude loss of hearing from the diagnosis.
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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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ItemThe design of an ear bar system for auditory neruophysiological research( 1972)Absolute sound intensity measurements at the ear drum are important in auditory research. Previous attempts to measure sound intensity using a small bore probe tube coupled to a microphone have proved unsatisfactory. In the present investigation an alternative system employing two condenser microphones coupled to the input end of the ear bar was used to estimate the sound intensity at the ear drum. Consideration was also given to minimizing harmonic distortion and resonance in the system.