Hearing aid gain prescriptions balance restoration of auditory nerve mean-rate and spike-timing representations of speech

2008 ◽  
Author(s):  
Faheem Dinath ◽  
Ian C. Bruce
Keyword(s):  
Auditory Nerve ◽  
Hearing Aid ◽  
Spike Timing

First-Spike Timing of Auditory-Nerve Fibers and Comparison With Auditory Cortex

1997 ◽  
Vol 78 (5) ◽  
pp. 2438-2454 ◽  
Author(s):  
Peter Heil ◽  
Dexter R. F. Irvine
Keyword(s):  
Auditory Cortex ◽  
Auditory Nerve ◽  
Rise Time ◽  
Peak Pressure ◽  
Inverse Function ◽  
Nerve Fibers ◽  
Spike Timing ◽  
Maximum Acceleration ◽  
Minimum Latency ◽  
Auditory Nerve Fibers

Heil, Peter and Dexter R. F. Irvine. First-spike timing of auditory-nerve fibers and comparison with auditory cortex. J. Neurophysiol. 78: 2438–2454, 1997. The timing of the first spike of cat auditory-nerve (AN) fibers in response to onsets of characteristic frequency (CF) tone bursts was studied and compared with that of neurons in primary auditory cortex (AI), reported previously. Tones were shaped with cosine-squared rise functions, and rise time and sound pressure level were parametrically varied. Although measurement of first-spike latency of AN fibers was somewhat compromised by effects of spontaneous activity, latency was an invariant and inverse function of the maximum acceleration of peak pressure (i.e., a feature of the 2nd derivative of the stimulus envelope), as previously found in AI, rather than of tone level or rise time. Latency-acceleration functions of all AN fibers were of very similar shape, similar to that observed in AI. As in AI, latency-acceleration functions of different fibers were displaced along the latency axis, reflecting differences in minimum latency, and along the acceleration axis, reflecting differences in sensitivity to acceleration [neuronal transient sensitivity (S)]. S estimates increased with spontaneous rate (SR), but values of high-SR fibers exceeded those in AI. This suggests that S estimates are biased by SR per se, and that unbiased true S values would be less tightly correlated with response properties covarying with SR, such as firing threshold. S estimates varied with CF in a fashion similar to the cat's audiogram and, for low- and medium-SR fibers, matched those for AI neurons. Minimum latency decreased with increasing SR and CF. As in AI, the standard deviation of first-spike timing (SD) in AN was also an inverse function of maximum acceleration of peak pressure. The characteristics of the increase of SD with latency in a given AN fiber/AI neuron and across AN fibers/AI neurons revealed that the precision of first-spike timing to some stimuli can actually be higher in AI than in AN. The data suggest that the basic characteristics of the latency-acceleration functions of transient onset responses seen in cortex are generated at inner hair cell–AN fiber synapses. Implications for signal processing in the auditory system and for first-spike generation and adaptation in AN are discussed.

scholarly journals The role of cochlear place coding in the perception of frequency modulation

eLife ◽  
2020 ◽  
Vol 9 ◽  
Author(s):  
Kelly L Whiteford ◽  
Heather A Kreft ◽  
Andrew J Oxenham
Keyword(s):  
Frequency Modulation ◽  
Auditory Nerve ◽  
Spike Timing ◽  
Impaired Hearing ◽  
Time Code ◽  
Wide Range ◽  
High Carrier ◽  
Time Coding ◽  
Fast Rates

Natural sounds convey information via frequency and amplitude modulations (FM and AM). Humans are acutely sensitive to the slow rates of FM that are crucial for speech and music. This sensitivity has long been thought to rely on precise stimulus-driven auditory-nerve spike timing (time code), whereas a coarser code, based on variations in the cochlear place of stimulation (place code), represents faster FM rates. We tested this theory in listeners with normal and impaired hearing, spanning a wide range of place-coding fidelity. Contrary to predictions, sensitivity to both slow and fast FM correlated with place-coding fidelity. We also used incoherent AM on two carriers to simulate place coding of FM and observed poorer sensitivity at high carrier frequencies and fast rates, two properties of FM detection previously ascribed to the limits of time coding. The results suggest a unitary place-based neural code for FM across all rates and carrier frequencies.

Comparison of Bandwidths in the Inferior Colliculus and the Auditory Nerve. I. Measurement Using a Spectrally Manipulated Stimulus

2007 ◽  
Vol 98 (5) ◽  
pp. 2566-2579 ◽  
Author(s):  
Myles Mc Laughlin ◽  
Bram Van de Sande ◽  
Marcel van der Heijden ◽  
Philip X. Joris
Keyword(s):  
Inferior Colliculus ◽  
Auditory Nerve ◽  
Spike Timing ◽  
Temporal Coding ◽  
Broadband Noise ◽  
Auditory Periphery ◽  
Interaural Phase ◽  
Interaural Phase Difference ◽  
Frequency Components ◽  
Psychophysical Studies

A defining feature of auditory systems across animal divisions is the ability to sort different frequency components of a sound into separate neural frequency channels. Narrowband filtering in the auditory periphery is of obvious advantage for the representation of sound spectrum and manifests itself pervasively in human psychophysical studies as the critical band. Peripheral filtering also alters coding of the temporal waveform, so that temporal responses in the auditory periphery reflect both the stimulus waveform and peripheral filtering. Temporal coding is essential for the measurement of the time delay between waveforms at the two ears—a critical component of sound localization. A number of human psychophysical studies have shown a wider effective critical bandwidth with binaural stimuli than with monaural stimuli, although other studies found no difference. Here we directly compare binaural and monaural bandwidths (BWs) in the anesthetized cat. We measure monaural BW in the auditory nerve (AN) and binaural BW in the inferior colliculus (IC) using spectrally manipulated broadband noise and response metrics that reflect spike timing. The stimulus was a pair of noise tokens that were interaurally in phase for all frequencies below a certain flip frequency (fflip) and that had an interaural phase difference of π above fflip. The response was measured as a function of fflip and, using a separate stimulus protocol, as a function of interaural correlation. We find that both AN and IC filter BW depend on characteristic frequency, but that there is no difference in mean BW between the AN and IC.

scholarly journals Adaptation Reduces Spike-Count Reliability, But Not Spike-Timing Precision, of Auditory Nerve Responses

2007 ◽  
Vol 27 (24) ◽  
pp. 6461-6472 ◽  
Author(s):  
M. Avissar ◽  
A. C. Furman ◽  
J. C. Saunders ◽  
T. D. Parsons
Keyword(s):  
Auditory Nerve ◽  
Spike Timing ◽  
Spike Count ◽  
Timing Precision ◽  
Spike Timing Precision

scholarly journals Perception of frequency modulation is mediated by cochlear place coding

2018 ◽  
Author(s):  
Kelly L. Whiteford ◽  
Heather A. Kreft ◽  
Andrew J. Oxenham
Keyword(s):  
Frequency Modulation ◽  
Auditory Nerve ◽  
Additional Data ◽  
Spike Timing ◽  
Impaired Hearing ◽  
Time Code ◽  
Detection Thresholds ◽  
High Modulation ◽  
Highly Correlated ◽  
Fast Rates

AbstractNatural sounds convey information via frequency and amplitude modulations (FM and AM). Humans are acutely sensitive to the slow rates of FM that are crucial for speech and music. This sensitivity has been thought to rely on precise stimulus-driven auditory-nerve spike timing (time code), whereas a coarser code, based on variations in the cochlear place of stimulation (place code), represents faster FM. Here we test this longstanding theory in listeners with normal and impaired hearing, resulting in widely varying place-coding fidelity. Contrary to predictions, FM detection thresholds at slow and fast rates are highly correlated and closely related to the fidelity of cochlear place coding. We support this conclusion with additional data showing that place-based coding degrades at high modulation rates and in high spectral regions in ways that were previously interpreted as reflecting the limits of fine neural timing. The results suggest a unitary place-based neural code for FM.

scholarly journals FM velocity selectivity in the inferior colliculus is inherited from velocity-selective inputs and enhanced by spike threshold

2011 ◽  
Vol 106 (5) ◽  
pp. 2399-2414 ◽  
Author(s):  
Joshua X. Gittelman ◽  
Na Li
Keyword(s):  
Inferior Colliculus ◽  
Auditory Nerve ◽  
Nerve Fibers ◽  
Spike Timing ◽  
Directional Selectivity ◽  
Extracellular Recordings ◽  
Spike Threshold ◽  
Velocity Selectivity ◽  
Whole Cell Recordings ◽  
Synaptic Mechanisms

Frequency modulation (FM) is computed from the temporal sequence of activated auditory nerve fibers representing different frequencies. Most studies in the inferior colliculus (IC) have inferred from extracellular recordings that the precise timing of nonselective inputs creates selectivity for FM direction and velocity (Andoni S, Li N, Pollak GD. J Neurosci 27: 4882–4893, 2007; Fuzessery ZM, Richardson MD, Coburn MS. J Neurophysiol 96: 1320–1336, 2006; Gordon M, O'Neill WE. Hear Res 122: 97–108, 1998). We recently reported that two additional mechanisms were more important than input timing for directional selectivity in some IC cells: spike threshold and inputs that were already selective (Gittelman JX, Li N, Pollak GD. J Neurosci 29: 13030–13041, 2009). Here, we show that these same mechanisms, selective inputs and spike threshold, underlie selectivity for FM velocity and intensity. From whole cell recordings in awake bats, we recorded spikes and postsynaptic potentials (PSPs) evoked by downward and upward FMs that swept identical frequencies at different velocities and intensities. To determine the synaptic mechanisms underlying PSP selectivity (relative PSP height), we derived sweep-evoked synaptic conductances. Changing FM velocity or intensity changed conductance timing and size. Modeling indicated that excitatory conductance size contributed more to PSP selectivity than conductance timing, indicating that the number of afferent spikes carried more FM information to the IC than precise spike timing. However, excitation alone produced mostly suprathreshold PSPs. Inhibition reduced absolute PSP heights, without necessarily altering PSP selectivity, thereby rendering some PSPs subthreshold. Spike threshold then sharpened selectivity in the spikes by rectifying the smaller PSPs. This indicates the importance of spike threshold, and that inhibition enhances selectivity via a different mechanism than previously proposed.

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