Quantitative model for the effects of stimulus frequency upon synchronization of auditory nerve discharges

1973 ◽  
Vol 54 (2) ◽  
pp. 361-364 ◽  
Author(s):  
David I. Anderson
Keyword(s):  
Auditory Nerve ◽  
Stimulus Frequency ◽  
Quantitative Model

scholarly journals Basilar membrane responses to two-tone and broadband stimuli

1992 ◽  
Vol 336 (1278) ◽  
pp. 307-315 ◽  
Keyword(s):  
Auditory Nerve ◽  
Basilar Membrane ◽  
Stimulus Frequency ◽  
Cell Receptor ◽  
Outer Hair Cells ◽  
Intermodulation Distortion ◽  
Mechanical Responses ◽  
Distortion Products ◽  
Cochlear Neurons ◽  
Rate Suppression

The responses to sound of mammalian cochlear neurons exhibit many nonlinearities, some of which (such as two-tone rate suppression and intermodulation distortion) are highly frequency specific, being strongly tuned to the characteristic frequency (CF) of the neuron. With the goal of establishing the cochlear origin of these auditory-nerve nonlinearities, mechanical responses to clicks and to pairs of tones were studied in relatively healthy chinchilla cochleae at a basal site of the basilar membrane with CF of 8-10 kHz. Responses were also obtained in cochleae in which hair cell receptor potentials were reduced by systemic furosemide injection. Vibrations were recorded using either the Mossbauer technique or laser Doppler-shift velocimetry. Responses to tone pairs contained intermodulation distortion products whose magnitudes as a function of stimulus frequency and intensity were com parable to those of distortion products in cochlear afferent responses. Responses to CF tones could be selectively suppressed by tones with frequency either higher or lower than CF; in most respects, mechanical two-tone suppression resembled rate suppression in cochlear afferents. Responses to clicks displayed a CF-specific compressive nonlinearity, similar to that present in responses to single tones, which could be profoundly and selectively reduced by furosemide. The present findings firmly support the hypothesis that all CF-specific nonlinearities present in the auditory nerve originate in analogous phenomena of basilar membrane vibration. However, because of their lability, it is almost certain that the mechanical nonlinearities themselves originate in outer hair cells.

scholarly journals No Effect of Interstimulus Interval on Acoustic Reflex Thresholds

2019 ◽  
Vol 23 ◽  
pp. 233121651987416
Author(s):  
Hannah Guest ◽  
Kevin J. Munro ◽  
Samuel Couth ◽  
Rebecca E. Millman ◽  
Garreth Prendergast ◽  
...  
Keyword(s):  
Young People ◽  
Hair Cells ◽  
Auditory Nerve ◽  
Interstimulus Interval ◽  
Stimulus Frequency ◽  
Nerve Fibers ◽  
Acoustic Reflex ◽  
Clinically Normal ◽  
High Stimulus ◽  
Temporal Aspect

The acoustic reflex (AR), a longstanding component of the audiological test battery, has received renewed attention in the context of noise-induced cochlear synaptopathy—the destruction of synapses between inner hair cells and auditory nerve fibers. Noninvasive proxy measures of synaptopathy are widely sought, and AR thresholds (ARTs) correlate closely with synaptic survival in rodents. However, measurement in humans at high stimulus frequencies—likely important when testing for noise-induced pathology—can be challenging; reflexes at 4 kHz are frequently absent or occur only at high stimulus levels, even in young people with clinically normal audiograms. This phenomenon may partly reflect differences across stimulus frequency in the temporal characteristics of the response; later onset of the response, earlier onset of adaptation, and higher rate of adaptation have been observed at 4 kHz than at 1 kHz. One temporal aspect of the response that has received little attention is the interstimulus interval (ISI); inadequate duration of ISI might lead to incomplete recovery of the response between successive presentations and consequent response fatigue. This research aimed to test for effects of ISI on ARTs in normally hearing young humans, measured at 1 and 4 kHz. Contrary to our hypotheses, increasing ISIs from 2.5 to 8.5 s did not reduce ART level, nor raise ART reliability. Results confirm that clinically measured ARTs—including those at 4 kHz—can exhibit excellent reliability and that relatively short (2.5 s) ISIs are adequate for the measurement of sensitive and reliable ARTs.

scholarly journals Small dendritic synapses enhance temporal coding in a model of cochlear nucleus bushy cells

2021 ◽  
Author(s):  
Elisabeth Koert ◽  
Thomas Kuenzel
Keyword(s):  
Membrane Potential ◽  
Cochlear Nucleus ◽  
Auditory Nerve ◽  
Stimulus Frequency ◽  
Dendritic Tree ◽  
Temporal Coding ◽  
Functional Explanation ◽  
Model Parameters ◽  
Temporal Precision ◽  
Bushy Cells

Spherical bushy cells (SBCs) in the the anteroventral cochlear nucleus receive a single or very few powerful axosomatic inputs from the auditory nerve. However, SBCs are also contacted by small regular bouton synapses of the auditory nerve, located in their dendritic tree. The function of these small inputs is unknown. It was speculated that the interaction of axosomatic inputs with small dendritic inputs improved temporal precision, but direct evidence for this is missing. In a compartment model of spherical bushy cells with a stylized or realistic 3D-representation of the bushy dendrite we thus explored this proposal. Phase-locked dendritic inputs caused both tonic depolarization and a modulation of the model SBC membrane potential at the frequency of the stimulus. For plausible model parameters dendritic inputs were subthreshold. Instead, the tonic depolarization increased the excitability of the SBC model and the modulation of the membrane potential caused a phase-dependent increase in the efficacy of the main axosomatic input. This improved rate, entrainment and temporal precision of output action potentials. However, these effects showed differential dependency on the stimulus frequency. A careful exploration of morphological and biophysical parameters of the bushy dendrite suggested a functional explanation for the peculiar shape of the bushy dendrite. Our model for the first time directly implied a role for the small excitatory dendritic inputs in auditory processing: they modulate the efficacy of the main input and are thus a plausible mechanism for the improvement of temporal precision and fidelity in these central auditory neurons.

scholarly journals Mechanics of the Mammalian Cochlea

2001 ◽  
Vol 81 (3) ◽  
pp. 1305-1352 ◽  
Author(s):  
Luis Robles ◽  
Mario A. Ruggero
Keyword(s):  
Hair Cell ◽  
Auditory Nerve ◽  
Basilar Membrane ◽  
Frequency Tuning ◽  
Stimulus Frequency ◽  
Nerve Fibers ◽  
Outer Hair Cells ◽  
Cochlear Amplifier ◽  
Ear Ossicles ◽  
Auditory Nerve Fibers

In mammals, environmental sounds stimulate the auditory receptor, the cochlea, via vibrations of the stapes, the innermost of the middle ear ossicles. These vibrations produce displacement waves that travel on the elongated and spirally wound basilar membrane (BM). As they travel, waves grow in amplitude, reaching a maximum and then dying out. The location of maximum BM motion is a function of stimulus frequency, with high-frequency waves being localized to the “base” of the cochlea (near the stapes) and low-frequency waves approaching the “apex” of the cochlea. Thus each cochlear site has a characteristic frequency (CF), to which it responds maximally. BM vibrations produce motion of hair cell stereocilia, which gates stereociliar transduction channels leading to the generation of hair cell receptor potentials and the excitation of afferent auditory nerve fibers. At the base of the cochlea, BM motion exhibits a CF-specific and level-dependent compressive nonlinearity such that responses to low-level, near-CF stimuli are sensitive and sharply frequency-tuned and responses to intense stimuli are insensitive and poorly tuned. The high sensitivity and sharp-frequency tuning, as well as compression and other nonlinearities (two-tone suppression and intermodulation distortion), are highly labile, indicating the presence in normal cochleae of a positive feedback from the organ of Corti, the “cochlear amplifier.” This mechanism involves forces generated by the outer hair cells and controlled, directly or indirectly, by their transduction currents. At the apex of the cochlea, nonlinearities appear to be less prominent than at the base, perhaps implying that the cochlear amplifier plays a lesser role in determining apical mechanical responses to sound. Whether at the base or the apex, the properties of BM vibration adequately account for most frequency-specific properties of the responses to sound of auditory nerve fibers.

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