Ultrastructural Analysis of Synaptic Endings of Auditory Nerve Fibers in Cats: Correlations with Spontaneous Discharge Rate

1993 ◽  
pp. 65-74 ◽  
Author(s):  
David K. Ryugo ◽  
Debora D. Wright ◽  
Tan Pongstaporn
Keyword(s):  
Auditory Nerve ◽  
Discharge Rate ◽  
Nerve Fibers ◽  
Ultrastructural Analysis ◽  
Spontaneous Discharge ◽  
Auditory Nerve Fibers

Neural mechanisms of tone-on-tone masking: patterns of discharge rate and discharge synchrony related to rates of spontaneous discharge in the chinchilla auditory nerve

1986 ◽  
Vol 56 (6) ◽  
pp. 1763-1780 ◽  
Author(s):  
D. G. Sinex ◽  
D. C. Havey
Keyword(s):  
Auditory Nerve ◽  
Average Rate ◽  
Discharge Rate ◽  
Quantitative Agreement ◽  
Nerve Fibers ◽  
Spontaneous Discharge ◽  
Probe Tone ◽  
Distortion Products ◽  
Auditory Nerve Fibers ◽  
Psychophysical Studies

Responses of chinchilla auditory nerve fibers to brief probe tones in the presence of a fixed tonal masker were obtained. The stimulus conditions were analogous to those that have been used in many psychophysical experiments. The relation between previously described response properties of auditory nerve fibers and features of psychophysical tone-on-tone masking was examined. In psychophysical studies, a fixed narrowband masker produces a characteristic pattern of masked thresholds, which becomes broad and asymmetrical at high masker levels. In the present experiment 1, a 5,000-Hz masker was presented at 30, 50, and 70 dB SPL. Masked thresholds based on the average rate of response to probe tones were estimated for single auditory nerve fibers. The lowest of these masked thresholds formed a pattern similar to the psychophysical masking pattern, becoming broader and more asymmetrical as the masker was increased to 70 dB SPL. The masked thresholds of fibers with low and medium rates of spontaneous discharge (SR) were as low as or lower than the masked thresholds of fibers with high SRs. In certain frequency regions, masked thresholds based on responses to cochlear distortion products were lower than the masked thresholds of any fiber responding to the probe tone; this result is also similar to previous psychophysical observations. In experiment 2, responses of chinchilla auditory nerve fibers to probe tones in the presence of a masker at 1,000 Hz and 50 dB SPL were studied. Probe tone thresholds in the presence of this masker have been measured psychophysically in chinchillas. Thus the relation between behavioral and neural masked thresholds in the same species could be examined. Masked thresholds were estimated from average discharge rate responses and also from discharge synchrony. Good quantitative agreement was observed between the probe tone levels at which changes in average discharge rate were observed and the chinchilla's behavioral masked thresholds. For fibers matched for characteristic frequency, the masked thresholds based on average discharge rate of high-SR fibers tended to be elevated compared with the thresholds of medium-SR fibers. Changes in discharge rate synchronized to the probe tone occurred at levels lower than the chinchilla's behavioral masked thresholds. If discharge synchrony can be used for detection, the code would appear to be based on the relative synchrony to the probe tone and to the masking tone. Low synchrony masked thresholds were obtained from fibers with all SRs.(ABSTRACT TRUNCATED AT 400 WORDS)

Frequency Tuning and Spontaneous Activity in the Auditory Nerve and Cochlear Nucleus Magnocellularis of the Barn Owl Tyto alba

1997 ◽  
Vol 77 (1) ◽  
pp. 364-377 ◽  
Author(s):  
Christine Köppl
Keyword(s):  
Response Latency ◽  
Cochlear Nucleus ◽  
Auditory Nerve ◽  
Frequency Tuning ◽  
Barn Owl ◽  
Nerve Fibers ◽  
Spontaneous Discharge ◽  
Tyto Alba ◽  
Nucleus Magnocellularis ◽  
Auditory Nerve Fibers

Köppl, Christine. Frequency tuning and spontaneous activity in the auditory nerve and cochlear nucleus magnocellularis of the barn owl Tyto alba. J. Neurophysiol. 77: 364–377, 1997. Single-unit recordings were obtained from the brain stem of the barn owl at the level of entrance of the auditory nerve. Auditory nerve and nucleus magnocellularis units were distinguished by physiological criteria, with the use of the response latency to clicks, the spontaneous discharge rate, and the pattern of characteristic frequencies encountered along an electrode track. The response latency to click stimulation decreased in a logarithmic fashion with increasing characteristic frequency for both auditory nerve and nucleus magnocellularis units. The average difference between these populations was 0.4–0.55 ms. The most sensitive thresholds were ∼0 dB SPL and varied little between 0.5 and 9 kHz. Frequency-threshold curves showed the simple V shape that is typical for birds, with no indication of a low-frequency tail. Frequency selectivity increased in a gradual, power-law fashion with increasing characteristic frequency. There was no reflection of the unusual and greatly expanded mapping of higher frequencies on the basilar papilla of the owl. This observation is contrary to the equal-distance hypothesis that relates frequency selectivity to the spatial respresentation in the cochlea. On the basis of spontaneous rates and/or sensitivity there was no evidence for distinct subpopulations of auditory nerve fibers, such as the well-known type I afferent response classes in mammals. On the whole, barn owl auditory nerve physiology conformed entirely to the typical patterns seen in other bird species. The only exception was a remarkably small spread of thresholds at any one frequency, this being only 10–15 dB in individual owls. Average spontaneous rate was 72.2 spikes/s in the auditory nerve and 219.4 spikes/s for nucleus magnocellularis. This large difference, together with the known properties of endbulb-of-Held synapses, suggests a convergence of ∼2–4 auditory nerve fibers onto one nucleus magnocellularis neuron. Some auditory nerve fibers as well as nucleus magnocellularis units showed a quasiperiodic spontaneous discharge with preferred intervals in the time-interval histogram. This phenomenon was observed at frequencies as high as 4.7 kHz.

Effect of electrical stimulation of the crossed olivocochlear bundle on auditory nerve response to tones in noise

1987 ◽  
Vol 57 (4) ◽  
pp. 1002-1021 ◽  
Author(s):  
R. L. Winslow ◽  
M. B. Sachs
Keyword(s):  
Auditory Nerve ◽  
Noise Level ◽  
Dynamic Range ◽  
Response Rate ◽  
Discharge Rate ◽  
Nerve Fibers ◽  
Range Shift ◽  
Auditory Nerve Fiber ◽  
Auditory Nerve Fibers ◽  
Rate Suppression

The discharge rates of single auditory-nerve fibers responding to best-frequency (BF) tones of varying level presented simultaneously with fixed level broadband noise were recorded with and without electrical stimulation of the crossed olivocochlear bundle (COCB). In the absence of COCB stimulation, monotonic increases in noise level produce monotonic increases in the low-level noise-driven response rate of auditory nerve fibers. As a result of adaptation, these increases in noise-driven response rate produce monotonic decreases in saturation discharge rate. At high noise levels, these compressive effects may eliminate the differential rate response of auditory nerve fibers to BF tones. COCB stimulation can restore this differential rate response by producing large decreases in noise-driven response rate and large increases in saturation discharge rate. In backgrounds of quiet, COCB stimulation is known to shift the dynamic range of single auditory nerve fiber BF tone responses to higher stimulus levels. In the presence of background noise, COCB stimulation produces upward shift of dynamic range, which decreases with increasing noise level. At high noise levels, COCB-induced decompression of rate-level functions may occur with little or no dynamic range shift. This enables auditory nerve fibers to signal changes in tone level with changes in discharge rate at lower signal-to-noise ratios than would be possible otherwise. Broadband noise also produces upward shift of the dynamic range of single auditory nerve fiber BF tone response. Noise-induced dynamic range shift of BF tone response was measured as a function of noise level with and without COCB stimulation. COCB stimulation elevates the threshold of noise-induced dynamic range shift. This shift is thought to result from two-tone rate suppression. Increases in the threshold of noise-induced shift due to COCB stimulation therefore suggests an interaction between the mechanism of two-tone rate suppression and the mechanism by which COCB stimulation produces dynamic range shift. These interactions were further investigated by recording auditory nerve fiber rate responses to fixed-level BF excitor tones presented simultaneously with fixed-frequency variable level suppressor tones. Rate responses were recorded with and without COCB stimulation. Experimental results were quantified using a phenomenological model of two-tone rate suppression presented by Sachs and Abbas.

Nonlinear Modeling of Auditory-Nerve Rate Responses to Wideband Stimuli

2005 ◽  
Vol 94 (6) ◽  
pp. 4441-4454 ◽  
Author(s):  
Eric D. Young ◽  
Barbara M. Calhoun
Keyword(s):  
Auditory Nerve ◽  
Transfer Functions ◽  
Discharge Rate ◽  
Nonlinear Modeling ◽  
Nerve Fibers ◽  
Second Order ◽  
Spectral Processing ◽  
Spectrum Shape ◽  
Level Function ◽  
Auditory Nerve Fibers

The spectral selectivity of auditory nerve fibers was characterized by a method based on responses to random-spectrum-shape stimuli. The method models the average discharge rate of fibers for steady stimuli and is based on responses to ≈100 noise-like stimuli with pseudorandom spectral levels in 1/8- or 1/16-octave frequency bins. The model assumes that rate is determined by a linear weighting of the spectrum plus a second-order weighting of all pairs of spectrum values within a certain frequency range of best frequency. The method allows prediction of rate responses to stimuli with arbitrary wideband spectral shapes, thus providing a direct test of the degree of linearity of spectral processing Auditory-nerve fibers are shown to rely mainly on linear weighting of the stimulus spectrum; however, significant second-order terms are present and are important in predicting responses to random-spectrum shape stimuli, although not for predicting responses to noise filtered with cat head-related transfer functions. The second-order terms weight the products of levels at identical frequencies positively and the products of different frequencies negatively. As such, they model both curvature in the rate versus level function and suppressive interactions between different frequency components. The first- and second-order characterizations derived in this method provide a measure of higher-order nonlinearities in neurons, albeit without providing information about temporal characteristics.

Sensitivity of auditory nerve fibers to spectral notches

1993 ◽  
Vol 70 (2) ◽  
pp. 655-666 ◽  
Author(s):  
P. W. Poon ◽  
J. F. Brugge
Keyword(s):  
Transfer Function ◽  
Auditory Nerve ◽  
Discharge Rate ◽  
Free Field ◽  
Nerve Fibers ◽  
Broadband Noise ◽  
Dependent Manner ◽  
Repeated Presentation ◽  
Spontaneous Rate ◽  
Auditory Nerve Fibers

1. Listeners use direction-dependent spectral cues introduced by the torso, head, and pinnae to localize the source of a sound in space. Among the prominent direction-dependent spectral features in the free field-to-eardrum transfer function are narrow regions of low acoustic energy referred to as spectral notches. In this paper, we studied the sensitivity of single auditory nerve fibers in the barbiturate-anesthetized cat to broadband noise that had been filtered by a function whose shape approximated natural notches in the free field-to-eardrum transfer function. 2. Two experimental paradigms were employed. The first was the repeated presentation of a burst of broadband noise filtered by the simulated-notch function. Center frequency of the notch was held constant at or around the fiber characteristic frequency (CF). We refer to this as a "stationary" notch stimulus. The second paradigm was the repeated presentation of a broadband noise that was constructed from noise segments, each filtered by the simulated notch, whose CF was incremented and then decremented in a systematic way. We refer to this as a "moving" notch stimulus. Results from these two paradigms were compared with respect to notch detection. 3. Data were obtained from 161 single auditory nerve fibers having CFs ranging from 0.4 to 40 kHz. Most fibers studied had CFs > 5 kHz, and they detected the presence of the spectral notch in an intensity- and frequency-dependent manner. Each fiber responded vigorously to the presence of broadband noise. When the CF of the notch encroached on the response area of the fiber, there was a demonstrable reduction in discharge rate. The greatest reduction in discharge rate occurred when the notch was centered at the fiber's CF and when the level of the notch signal was some 15-55 dB above the fiber's noise threshold. There was close association in the frequency-intensity plane between the position of the most effective notch and the fiber's threshold tuning curve. 4. For high-spontaneous rate fibers, a moving-notch stimulus, but not a stationary one, reduced the discharge below the spontaneous rate at and in the immediate vicinity of the most effective notch frequency. This increases sensitivity to a spectral notch and suggests a mechanism by which localization ability is enhanced when there is relative motion between a sound source and the head.(ABSTRACT TRUNCATED AT 400 WORDS)

scholarly journals Probing adaptation and spontaneous firing in human auditory-nerve fibers with far-field peri-stimulus time responses

2021 ◽  
Author(s):  
Antoine Huet ◽  
Charlène Batrel ◽  
Xavier Dubernard ◽  
Jean-Charles Kleiber ◽  
Gilles Desmadryl ◽  
...  
Keyword(s):  
Auditory Nerve ◽  
Round Window ◽  
Nerve Fibers ◽  
Electrical Signal ◽  
Cochlear Nerve ◽  
Spontaneous Discharge ◽  
Rapid Adaptation ◽  
Discharge Rates ◽  
Auditory Nerve Fibers ◽  
Stimulus Time

AbstractInformation in sound stimuli is conveyed from sensory hair cells to the cochlear nuclei by the firing of auditory nerve fibers (ANFs). For obvious ethical reasons, single unit recordings from the cochlear nerve have never been performed in human, thus functional hallmarks of ANFs are unknown. By filtering and rectifying the electrical signal recorded at the round window of gerbil cochleae, we reconstructed a peri-stimulus time response (PSTR), with a waveform similar to the peri-stimulus time histograms (PSTHs) recorded from single ANFs. Pair-by-pair analysis of simultaneous PSTR and PSTH recordings in gerbil provided a model to predict the rapid adaptation and spontaneous discharge rates (SR) in a population of ANFs according to their location in the cochlea. We then probed the model in the mouse, in which the SR-based distribution of ANFs differs from the gerbil. We show that the PSTR-based predictions of the rapid adaptation time constant and mean SR across frequency again matched those obtained by recordings from single ANFs. Using PSTR recorded from the human cochlear nerve in 8 normal-hearing patients who underwent cerebellopontine angle surgeries for a functional cranial-nerve disorders (trigeminal neuralgia or hemifacial spasm), we predicted a rapid adaptation of about 3 milliseconds and a mean SR of 23 spikes/s in the 4 kHz frequency range in human ANFs. Together, our results support the use of PSTR as a promising diagnostic tool to map the auditory nerve in humans, thus opening new avenues to better understanding neuropathies, tinnitus, and hyperacusis.

Tinnitus and Neural Activity

1983 ◽  
Vol 26 (4) ◽  
pp. 629-632 ◽  
Author(s):  
Richard J. Salvi ◽  
William A. Ahroon
Keyword(s):  
Hearing Loss ◽  
Neural Activity ◽  
Auditory Nerve ◽  
High Frequency ◽  
Discharge Rate ◽  
Nerve Fibers ◽  
Spontaneous Discharge ◽  
Frequency Noise ◽  
High Frequency Noise ◽  
Discharge Rates

The spontaneous discharge rates of auditory nerve fibers were measured in a group of normal chinchillas and in a group of chinchillas with high-frequency, noise-induced hearing loss. In contrast to normal units, the high-frequency units in the noise-exposed animals tended to have elevated spontaneous discharge rates, high thresholds, and a lack of two-tone inhibition. The change in spontaneous discharge rate across the distribution of nerve fibers is related to models of tinnitus and to human psychophysical data.

Effects of continuous noise backgrounds on rate response of auditory nerve fibers in cat

1984 ◽  
Vol 51 (6) ◽  
pp. 1326-1344 ◽  
Author(s):  
J. A. Costalupes ◽  
E. D. Young ◽  
D. J. Gibson
Keyword(s):  
Auditory Nerve ◽  
Noise Level ◽  
Background Noise ◽  
Dynamic Range ◽  
Discharge Rate ◽  
Nerve Fibers ◽  
Noise Levels ◽  
High Noise ◽  
Continuous Noise ◽  
Auditory Nerve Fibers

This study describes the effects of broadband background noise on the average discharge rate to best-frequency (BF) tones of auditory nerve fibers in the cat. The effects of exposure to long-term continuous noise are compared to the effects of noise gated on and off simultaneously with test tones. Addition of background noise causes a shift of the dynamic portion of tone-evoked rate versus level functions to higher tone intensities. The shift occurs at a mean rate of 0.61 dB of shift for each 1-dB increment in noise level. The rate of shift is independent of best frequency and spontaneous discharge rate. The noise level at which the shift begins is frequency dependent and is consistent with the frequency-dependent bandwidths of auditory nerve fiber tuning curves. The adjustment of the dynamic range shows many similarities to two-tone suppression. Therefore, it is most likely that it is caused by suppression of the response to the BF test tone by energy present in the noise at surrounding frequencies. At high noise levels, the ability of auditory nerve fibers to respond to test tones is limited by the rate response to the noise. As noise level increases, the discharge rate it evokes approaches a fiber's saturation rate and ultimately eliminates the fiber's ability to respond to test tones. Low spontaneous rate fibers, which have been shown to have higher thresholds and wider dynamic range (17,29), are significantly more resistant to saturation by high noise levels. Exposure to broadband noise prior to onset of test tones produces an overall decrement in response rate. This phenomenon is similar to the effects of short-term adaptation (32) and seems to develop independently of the shift of dynamic range. At high noise levels, previous exposure to the noise produces a small dynamic range shift. This effect is similar to that produced by suppression but is smaller. The effect is occluded in continuous noise backgrounds by the adjustment of sensitivity produced by suppression.

Sign in / Sign up

Export Citation Format

Share Document