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Nov 1980

Volume 68, Issue S1, pp. S1-S116

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back to top Session JJ. Physiological Acoustics V: Neural Mechanisms
Contributed Papers
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Introcellular responses of hair cells in the alligator lizard: Dependence on tone frequency and level (A)

Thomas Holton and Thomas F. Weiss

J. Acoust. Soc. Am. Volume 68, Issue S1, pp. S65-S65 (1980); (1 page)

Online Publication Date: 11 Aug 2005

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Receptor potentials of hair cells in the basal region of the basilar papilla of anesthetized alligator lizards were recorded with micropipettes. The steady‐state tone response consists of a dc component and ac components at multiples of the tone frequency. The isopotential contour (“tuning curve”) of the dc or the fundamental ac component has a sharply tuned “tip” on a more broadly tuned region. The dependence of receptor potential components on sound‐pressure level (“level functions”) was measured at different tone frequencies. These functions saturate at high sound‐pressure levels; the maximum value of the dc component is independent of frequency, while the maximum value of the fundamental ac component decreases with increasing tone frequency. Shapes of level functions at tone frequencies in the tuning curve “tip” differ from those at other frequencies, suggesting the presence of a frequency dependent non‐linearity in hair cell transduction. (Research supported by NIH.)
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Nonlinear behavior of neural responses from lateral line hair cells (A)

David Strelioff, W. Gary Sokolich, and Vicente Honrubia

J. Acoust. Soc. Am. Volume 68, Issue S1, pp. S65-S65 (1980); (1 page)

Online Publication Date: 11 Aug 2005

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The characteristics of neural responses to combinations of sinusoidal electrical (E) and mechanical (M) stimuli were studied in the lateral line hair cell system of the African clawed toad, Xenopus laevis. The effect of a 4‐Hz E or M stimulus on the neural response to a 40‐Hz E or M stimulus was a 4‐Hz modulation of the mean firing rate and of the response to the 40‐Hz stimulus. Discrete Fourier transforms of PST histograms of the neural responses to various combinations of E and M stimuli yielded components at the fundamental and second harmonic frequencies of the applied stimuli and at their sum and difference frequencies. When both stimuli are electric the amplitudes and phases of the observed components are similar to those produced by a quadratic nonlinearity. The most important finding in this study is that the responses to electrical stimuli are nonlinear. This finding implies that nonlinearities observed in the neural responses from hair cell systems are due to nonlinearities in the electrical properties of the hair cells in addition to those in the mechano‐electrical transduction process.
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Vibration sensitivity in the bullfrog inner ear (A)

Ra. A. Baird and E. R. Lewis

J. Acoust. Soc. Am. Volume 68, Issue S1, pp. S65-S66 (1980); (2 pages)

Online Publication Date: 11 Aug 2005

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Eighth‐nerve studies with dye‐filled electrodes reveal the peripheral origins of vibration‐sensitive units and extend previous physiological observations of such units by L. Cazin and J. Lannou [C. R. Soc. Biol. (Paris) 169, 1067–1071 (19751]. We find that these units are distinguished from auditory units by high sensitivity to substrate‐borne vibration (thresholds between 0.001 and 0.01 g) and low sensitivity to airborne sound (thresholds over 80 dB SPLI, with C. F.s from 20 Hz to more than 100 Hz for both stimulus modes. Auditory units originate in the amphibian or basilar papilla; vibratory units originate in the saccule or lagena. Vibratory units from either organ exhibit resting discharge frequencies from 0 to 80 spikes/s and exhibit phase‐locking of individual spikes to sinusoidal vibratory stimuli up to 150 Hz. For stimulus frequencies below resting discharge frequency, most units respond with two or more spikes per stimulus cycle, thereby maintaining average discharge frequency at or above resting frequency. Occasionally a unit responds with one spike per cycle to stimulus frequencies below resting frequency. At low stimulus intensity, phase‐locking is incomplete. Some lagenar (not saccular) vibratory units are sensitive as well to head position. [Research supposed by NSF Grant BNS‐8005834.]
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Anatomo‐physiological correlation in vestibular afferent neurons of frogs (rana catesbiana) (A)

V. Honrubia, S. Sitko, W. Betts, J. Kimm, and I. Schwartz

J. Acoust. Soc. Am. Volume 68, Issue S1, pp. S66-S66 (1980); (1 page)

Online Publication Date: 11 Aug 2005

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The morphological characteristics of physiologically identified neurons innervating the horizontal and vertical semicircular canals of rana catesbiana were investigated following intra‐axonal horseradish peroxidase injections. Two distinct types of neurons were found. “Regular neurons” had spontaneous firing rates with a low (0.12 to 0.5) coefficient of variation (CV) while “irregular neurons” had CV > 0.5. Morphologically, the cell bodies of regular neurons had smaller diameters than irregular neurons: 7.1 ± 2.0 μm vs 12.7 ± 3.0 μm longitudinally and 4.9 ± 1.4 μm vs 7.6 ± 1.3 μm transversely. Small neurons were located in the antero‐ventral and large neurons in the dorso‐posterior portion of the anterior vestibular nerve. Differences were also found in the characteristics of response to physiological stimuli. During 0.5‐Hz rotation, gain and phase of regular and irregular neurons were 0.98 ± 0.87 spikes × s−1/deg × s−1 and 2.7 ± 18.6 degrees relative to head velocity and 3.02 ± 0.7 spikes × s−1/deg × s−1 and 29.7 ± 9.6 deg, respectively. The time constant of the response decay to an impulse of acceleration was 6.77 ± 5.1 and 4.4 ± 1.05 s for regular and irregular, respectively. In conclusion, although frogs have only type II hair cells, they have two types of vestibular afferents with characteristics similar to those found in mammals.
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Experimental and analytic studies of synchronized responses in the chinchilla auditory nerve (A)

E. M. Relkin and D. M. Harris

J. Acoust. Soc. Am. Volume 68, Issue S1, pp. S66-S66 (1980); (1 page)

Online Publication Date: 11 Aug 2005

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The current interest in the coding of sounds by the temporal aspects of spike trains in the auditory nerve suggested a parametric study of synchrony of firing to low frequency sounds and the various indices used to quantify synchronization. Index of synchrony and preferred phase were measured as a function of sound pressure and frequency for single units in the auditory nerve of the chinchilla. Results from several previous studies in other laboratories agree well with the current data which are, however, more complete. It was found that synchrony is a function of frequency and level relative to threshold but otherwise independent of fiber characteristic frequency (CF). Preferred phase, however, depended on the relation between frequency and CF as well as level. The maximum value of synchrony obtained for all fibers formed a low‐pass function of frequency with a high frequency rolloff of approximately 6 dB/octave. A simple model consisting of a half‐wave rectifier followed by a low‐pass filter could predict the period histograms remarkably well. Analysis of the indices of synchrony has shown them to be relatively insensitive to the scatter of firing over one half‐cycle, explaining, in part, the steepness of synchrony‐versus‐level functions. [Supported by NINCDS.]
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Differences in the CF dependence of response phase of gerbil and guinea pig auditory nerve fibers (A)

W. G. Sokolich, W. Ohima, and D. Strelioff

J. Acoust. Soc. Am. Volume 68, Issue S1, pp. S66-S66 (1980); (1 page)

Online Publication Date: 11 Aug 2005

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Time‐locked responses of auditory nerve fibers to acoustic sinusoids having frequencies between 100 and 400 Hz were studied in gerbils and guinea pigs. With the exception of the responses of gerbil fibers with CFs above 10 kHz, which produce double‐peaked histograms, the responses of most fibers in both species produce single‐peaked histograms when the modulation of spontaneous activity is less than 100%. Within this restricted modulation range, the preferred phase of response is relatively independent of stimulus amplitude. Nonetheless, the variation of the response phase with CF is fundamentally different in the two species. Whereas gerbil fibers show an abrupt 180° phase transition in the CF range between 2 and 4 kHz, the response phase of guinea pig fibers is CF‐independent for stimulus frequencies that are at least ½ octave below fiber CF. The finding of different phase functions in the two species indicates that caution should be exercised in basing models of the neural excitation process in the cochlea solely on data obtained from one mammalian species.
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Relationships between trapezoidal EP variations and auditory nerve fiber responses in gerbils and guinea pigs (A)

W. G. Sokolich, W. Oshima, and D. Strelioff

J. Acoust. Soc. Am. Volume 68, Issue S1, pp. S66-S66 (1980); (1 page)

Online Publication Date: 11 Aug 2005

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It has been shown [Sokolich et al., J. Acoust. Soc. Am., 59, 963–974 (1976)] that most gerbil auditory nerve fibers show one of three time patterns of response to acoustically‐evoked trapezoidal time patterns of EP change. Pattern “A” is characteristic of fibers with CFs below 2 kHz, pattern “B”, of fibers with CFs between 3 and 6 kHz, and pattern “C”, of fibers with CFs above 8 kHz. Although all three patterns contain four distinct response components reflecting both static and dynamic aspects of trapezoidal EP change, the patterns differ in that the sign of one or more components depends on fiber CF. The present comparative study reveals that pattern “A” is exhibited by all guinea pig fibers with CFs below and by many fibers with CFs above 7 kHz. Nonetheless, some guinea pig fibers with CFs above 7 kHz show pattern “B”. In spite of the difference in the dependence of response pattern on CF, all patterns observed in both species support the conclusion that neither excitation nor inhibition of auditory nerve fibers is uniquely related to specific aspects of either static or dynamic changes in EP or to associated aspects of basilar membrane motion.
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Measurements on phase in primary units in cat (A)

Jont B. Allen

J. Acoust. Soc. Am. Volume 68, Issue S1, pp. S66-S66 (1980); (1 page)

Online Publication Date: 11 Aug 2005

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The following procedure was used to measure the neural phase in cat: first tuning curves were made using the procedures of Kiang, Moxon, and Liberman. Then sweeps of given amplitude and frequency were made through the neural super‐threshold response region. At each frequency, a histogram to the pure tone was generated phase locked to the tonal stimulus, and based on either two seconds of stimulus or 200 spikes. The phase was then estimated from the Fourier coefficient of the histogram at the stimulus frequency. Below 2 kHz, good correlation was observed in most units as a function of frequency. After removing the phase shift associated with a fixed delay, which was CF dependent, we found a π phase shift below the CF indicating a spectral zero in the transfer function between neural response and ear canal pressure. The bandwidth and frequency of the zero appeared to be quite signal dependent. In other frequency regions the phase was much less signal level dependent.
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Coding of stimulus intensity by neurons in the anteroventral cochlear nucleus of kittens (A)

J. F. Brugge, L. M. Kitzes, and E. Jayel

J. Acoust. Soc. Am. Volume 68, Issue S1, pp. S67-S67 (1980); (1 page)

Online Publication Date: 11 Aug 2005

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The effects of stimulus intensity on the number of spikes evoked in AVCN neurons was studied in kittens 4 to 45 days old. For neurons whose spike‐count functions saturated, the number of dB required to raise that count from 10% to 90% of maximum (DRI) was determined at various frequencies within the response area. For kittens younger than 14 days the shapes and slopes of the curves are remarkably similar over a wide frequency range within the response area. The functions rise sharply to a maximum and commonly in young animals decrease abruptly. The mean DRI increases with age. At 4‐5 days the DRI at CF ranges between 10 and 18 dB; during the second week these values vary from 6 to 27 dB. Between 14 and 20 days the functions achieve the shapes and slopes of those seen in older kittens and those described for the cochlear nuclei and auditory nerve of adult cat. At 20 days the DRI varies between 13 and 56 dB. As thresholds diminish over the first 2 weeks, tuning curves change from being initially shallow to increasingly “V” shaped.
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