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G K Yates

Publications and source records attributed to G K Yates.

9 recordsLinked to original sources
PubMed1992

Mechanical preprocessing in the mammalian cochlea.

The mammalian cochlea responds with exquisite sensitivity to the small fluctuations in air pressure that make up the stimulus of sound. Moreover, it responds to pressure fluctuations that occur extremely rapidly and that vary over a wide range of intensities--in both cases, to an extent outside the capabilities of unaided nerve fibres. Research performed during the past decade has shown that these properties are dependent on a physiological source of mechanical energy that operates probably within the outer hair cells of the organ of Corti. These cells, which are anatomically and functionally similar to the primary receptor cells, the inner hair cells, are believed to function as a source of mechanical power to assist the mechanical sensitivity of the cochlea, by mechanisms that currently are not understood. Several possible mechanisms have been proposed, but each has limitations that may make it an unsuitable candidate. Recent work has also demonstrated the likely role of mechanoelectrical transduction in outer hair cells in controlling the power source and thereby influencing the sensitivity and amplitude range of the cochlea.

Animals↗
PubMed1991

Auditory-nerve spontaneous rates vary predictably with threshold.

The variation of spontaneous rate with auditory nerve thresholds is compared with predictions from a simple assumption: that spontaneous and driven activity are basically similar, both being evoked by inner hair cell transmembrane potential. Under this view, spontaneous activity is seen as a response to a standing current within the hair cell and should therefore vary with threshold in a manner predictable from measured rate-intensity functions. A method for comparing spontaneous rates of fibres with differing thresholds is developed and applied to previously-collected data. The results show that spontaneous rates are quite consistent with the hypothesis, indicating no need for more complicated theories of spontaneous activity.

Action Potentials↗
PubMed1991

Rate-versus-level functions of primary auditory nerve fibres: evidence for square law behaviour of all fibre categories in the guinea pig.

Detailed measurements of rate-versus-level (RI) functions close to threshold were made from single primary auditory nerve fibres in the guinea pig cochlea. For all fibres, a simple square law provided the best statistical fit to the data near threshold, regardless of spontaneous fibrin rate of the fibre. In no case was a better fit obtained with an exponent greater than 2. We conclude that a simple square law is an accurate description of the underlying synaptic drive to all primary auditory nerve fibres. For fibres with very low spontaneous firing rates the best square law fit near threshold frequently led to the formal mathematical estimate of a negative firing rate as the asymptotic value of the spontaneous firing rate. The 'negative spontaneous rate' of low spontaneous rate fibres derived from curve fitting can be conceptualized by postulating that for sound pressures well below threshold in these fibres the underlying synaptic drive lies below a threshold value at a site determining action potential generation.

Acoustic Stimulation↗
PubMed1990

Basilar membrane nonlinearity and its influence on auditory nerve rate-intensity functions.

Previous papers have shown that the shapes of rate-intensity functions of auditory nerve fibres vary with spontaneous rate (Sachs and Abbas 1974; Sachs et al. 1989; Winter et al. 1990; Yates et al. 1990), and that the variation is due to the nonlinear properties of the basilar membrane. This paper examines the basilar membrane nonlinearity and provides a semi-quantitative explanation for it in terms of previous models (Zwicker 1979; Patuzzi et al. 1989) and an analogue model. It thereby provides explanations for the shapes of the basilar membrane input-output curves and for the way in which they vary with trauma. The shapes of the neural rate-intensity functions are quantified and shown to be consistent with the low-threshold data of Geisler et al. (1985). Several nonlinear properties of the cochlea, such as recruitment, are also interpreted.

Animals↗
PubMed1979

Bone conduction mechanisms: Mössbauer measurements on the role of ossicular inertia.

The Mössbauer technique was used to measure displacements of the stapes footplate and adjacent temporal bone during bone conduction stimulation at frequencies from 250 to 400 Hz in anaesthetized guinea pigs. The stapes was found not to be driven at amplitudes or phases that differed significantly from those of the temporal bone. Measurement of stapes displacements during air conduction stimulation, and of temporal bone displacements during bone conduction stimulation producing matching cochlear microphonic amplitude, enabled calculation of limiting values of amplitude and phase difference necessary to produce the required relative displacement. The obtained values (less than 1 dB for amplitude and 1--4 degrees for phase) were beyond the resolution of the measurement system employed for reasonable nuclear counting times. The results provide quantitative estimates of the magnitude of inertial effects, but do not establish whether ossicular inertia is an important factor in bone conduction stimulation.

Acoustic Stimulation↗
PubMed1979

Cochlear action potential threshold and single unit thresholds.

There is a close correlation between the sound pressure of tone burst required to affect a primary auditory neuron at its characteristic frequency and that which will produce a detectable N1 response at the same frequency. Units with thresholds from 80--0 db SPL (recorded from damaged and undamaged cochleas) were 0--20 dB , respectively, more sensitive than the action potential response.

Action Potentials↗