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Gross potentials recorded from the cochlea of the skinkTiliqua rugosa

I. Characterization of evoked responses with regard to morphology

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Summary

Compound action potentials (CAP), summating potentials (SP) and both fundamental and second harmonic components of the cochlear microphonic (CM) were recorded from the round window and scala tympani in response to gated and continuous pure tones. The high-pass characteristics of the round-window tissues distorted the evoked d.c. response and the superimposed CAP (Fig. 2) and there was some cancellation of the resulting SP and first negative component of the CAP (Fig. 3). SP sensitivity estimates derived from the scala tympani were more sensitive than those of the round window; a.c. potentials were unaffected (Fig. 4). The SP intensity curves were found to be the most reproducible of the gross response components (Figs. 5, 6, 7). Although there was considerable variation in the group CM data, there were reproducible idiosyncrasies in the intensity curves of individuals which were attributed to unique asymmetries in the basilar papilla causing an asymmetrical stimulation of oppositely polarized hair cells. Multiple maxima in lizard CM intensity curves described by other authors are explained by different mechanisms. The general shapes of the CM and SP sensitivity curves were in agreement with those reported in previous studies (Fig. 8).

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Abbreviations

CAP :

compound action potential

CM :

cochlear microphonic

CMF :

cochlear microphonic fundamental

CMH :

cochlear microphonic second harmonic

SP :

summating potential

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Authors and Affiliations

  1. Department of Physiology, University of Western Australia, 6009, Nedlands, Western Australia

    Robert M. Holmes & Brian M. Johnstone

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  1. Robert M. Holmes
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  2. Brian M. Johnstone
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Additional information

Cogger (1979) has suggested the inclusion of the speciesrugosa in the genusTiliqua, which has been the convention in recent publications and has the support of serological studies (Hutchinson 1980). Synonyms used in auditory studies includeTrachysaurus rugosus (Johnstone and Johnstone 1969a, b; Miller 1966),Tiliqua rugosus (Gutgesell 1975) andTrachydosaurus r. rugosus (Wever 1978). Common names include bobtail, stump-tailed, sleepy and shingleback lizard

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Holmes, R.M., Johnstone, B.M. Gross potentials recorded from the cochlea of the skinkTiliqua rugosa . J. Comp. Physiol. 154, 719–727 (1984). https://doi.org/10.1007/BF01350225

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  • DOI: https://doi.org/10.1007/BF01350225

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