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Mario A Ruggero - One of the best experts on this subject based on the ideXlab platform.

  • Timing of cochlear responses inferred from frequency-threshold tuning curves of Auditory-Nerve Fibers
    Hearing research, 2010
    Co-Authors: Andrei N Temchin, Alberto Recio-spinoso, Mario A Ruggero
    Abstract:

    Links between frequency tuning and timing were explored in the responses to sound of Auditory-Nerve Fibers. Synthetic transfer functions were constructed by combining filter functions, derived via minimum-phase computations from average frequency-threshold tuning curves of chinchilla Auditory-Nerve Fibers with high spontaneous activity (Temchin et al., 2008), and signal-front delays specified by the latencies of basilar-membrane and Auditory-Nerve Fiber responses to intense clicks (Temchin et al., 2005). The transfer functions predict several features of the phase-frequency curves of cochlear responses to tones, including their shape transitions in the regions with characteristic frequencies of 1 kHz and 3-4 kHz (Temchin and Ruggero, 2010). The transfer functions also predict the shapes of cochlear impulse responses, including the polarities of their frequency sweeps and their transition at characteristic frequencies around 1 kHz. Predictions are especially accurate for characteristic frequencies

  • mechanical bases of frequency tuning and neural excitation at the base of the cochlea comparison of basilar membrane vibrations and Auditory Nerve Fiber responses in chinchilla
    Proceedings of the National Academy of Sciences of the United States of America, 2000
    Co-Authors: Mario A Ruggero, Shyamla S Narayan, Andrei N Temchin, Alberto Recio
    Abstract:

    Abstract We review the mechanical origin of Auditory-Nerve excitation, focusing on comparisons of the magnitudes and phases of basilar-membrane (BM) vibrations and Auditory-Nerve Fiber responses to tones at a basal site of the chinchilla cochlea with characteristic frequency ≈ 9 kHz located 3.5 mm from the oval window. At this location, characteristic frequency thresholds of Fibers with high spontaneous activity correspond to magnitudes of BM displacement or velocity in the order of 1 nm or 50 μm/s. Over a wide range of stimulus frequencies, neural thresholds are not determined solely by BM displacement but rather by a function of both displacement and velocity. Near-threshold, Auditory-Nerve responses to low-frequency tones are synchronous with peak BM velocity toward scala tympani but at 80–90 dB sound pressure level (in decibels relative to 20 microPascals) and at 100–110 dB sound pressure level responses undergo two large phase shifts approaching 180°. These drastic phase changes have no counterparts in BM vibrations. Thus, although at threshold levels the encoding of BM vibrations into spike trains appears to involve only relatively minor signal transformations, the polarity of Auditory-Nerve responses does not conform with traditional views of how BM vibrations are transmitted to the inner hair cells. The response polarity at threshold levels, as well as the intensity-dependent phase changes, apparently reflect micromechanical interactions between the organ of Corti, the tectorial membrane and the subtectorial fluid, and/or electrical and synaptic processes at the inner hair cells.

  • mechanical bases of frequency tuning and neural excitation at the base of the cochlea comparison of basilar membrane vibrations and Auditory Nerve Fiber responses in chinchilla
    Proceedings of the National Academy of Sciences of the United States of America, 2000
    Co-Authors: Mario A Ruggero, Shyamla S Narayan, Andrei N Temchin, Alberto Recio
    Abstract:

    We review the mechanical origin of Auditory-Nerve excitation, focusing on comparisons of the magnitudes and phases of basilar-membrane (BM) vibrations and Auditory-Nerve Fiber responses to tones at a basal site of the chinchilla cochlea with characteristic frequency approximately 9 kHz located 3.5 mm from the oval window. At this location, characteristic frequency thresholds of Fibers with high spontaneous activity correspond to magnitudes of BM displacement or velocity in the order of 1 nm or 50 microm/s. Over a wide range of stimulus frequencies, neural thresholds are not determined solely by BM displacement but rather by a function of both displacement and velocity. Near-threshold, Auditory-Nerve responses to low-frequency tones are synchronous with peak BM velocity toward scala tympani but at 80-90 dB sound pressure level (in decibels relative to 20 microPascals) and at 100-110 dB sound pressure level responses undergo two large phase shifts approaching 180 degrees. These drastic phase changes have no counterparts in BM vibrations. Thus, although at threshold levels the encoding of BM vibrations into spike trains appears to involve only relatively minor signal transformations, the polarity of Auditory-Nerve responses does not conform with traditional views of how BM vibrations are transmitted to the inner hair cells. The response polarity at threshold levels, as well as the intensity-dependent phase changes, apparently reflect micromechanical interactions between the organ of Corti, the tectorial membrane and the subtectorial fluid, and/or electrical and synaptic processes at the inner hair cells.

  • the phases of Auditory Nerve Fiber responses to tones dependence on stimulus frequency and intensity
    Journal of the Acoustical Society of America, 2000
    Co-Authors: Andrei N Temchin, Mario A Ruggero
    Abstract:

    As stimulus intensity increases, the phases of responses to tones of squirrel monkey Auditory‐Nerve Fibers [ANFs; Anderson et al., J. Acoust. Soc. Am. 49, 1131–1139 (1971)] and guinea pig inner hair cells [IHCs; Dallos, Hearing Res. 22, 185–198 (1986)] undergo lags and leads, respectively, at frequencies lower and higher than the characteristic frequency (CF) and remain relatively constant at frequencies near CF. A similar pattern holds for basal sites of the basilar membrane (BM) in several species. In contrast, tectorial‐membrane (TM) vibrations at apical sites of the chinchilla cochlea exhibit phase shifts of opposite polarity [Rhode and Cooper, Aud. Neurosci. 3, 101–121 (1996)]. To explore this inconsistency between neural and mechanical behavior at apical cochlear regions, we investigated the phases of responses to tones of ANFs recorded in deeply anesthetized chinchillas. For stimulus intensities lower than 70 dB SPL, responses of most ANFs (regardless of CF) exhibited phase shifts similar to those observed in squirrel monkey ANFs, guinea pig IHCs, and basal BM sites in several species. Thus, the inconsistency between neural and TM mechanical data cannot be ascribed to species differences or a dependence of phase behavior on CF. [Work supported by NIH Grant DC‐00419.]

Peter Heil - One of the best experts on this subject based on the ideXlab platform.

  • phase locking of Auditory Nerve Fibers the role of lowpass filtering by hair cells
    The Journal of Neuroscience, 2020
    Co-Authors: Adam J Peterson, Peter Heil
    Abstract:

    Phase locking of Auditory-Nerve-Fiber (ANF) responses to the temporal fine structure of acoustic stimuli, a hallmark of the Auditory system's temporal precision, is important for many aspects of hearing. Previous work has shown that phase-locked period histograms are often well described by exponential transfer functions relating instantaneous stimulus pressure to instantaneous spike rate, with no observed clipping of the histograms. The operating points and slopes of these functions change with stimulus level. The mechanism underlying this apparent gain control is unclear but is distinct from mechanical compression, is independent of refractoriness and spike-rate adaptation, and is apparently instantaneous. Here we show that these findings can be accounted for by a model consisting of a static Boltzmann transducer function yielding a clipped output, followed by a lowpass filter and a static exponential transfer function. Using responses to tones of ANFs from cats of both sexes, we show that, for a given ANF, the period histograms obtained at all stimulus levels for a given stimulus frequency can be described using one set of level-independent model parameters. The model also accounts for changes in the maximum and minimum instantaneous spike rates with changes in stimulus level. Notably, the estimated cutoff frequency is lower for low- than for high-spontaneous-rate ANFs, implying a synapse-specific contribution to lowpass filtering. These findings advance our understanding of ANF phase locking by highlighting the role of peripheral filtering mechanisms in shaping responses of individual ANFs.SIGNIFICANCE STATEMENT Phase locking of Auditory-Nerve-Fiber responses to the temporal fine structure of acoustic stimuli is important for many aspects of hearing. Period histograms typically retain an approximately sinusoidal shape across stimulus levels, with the peripheral Auditory system operating as though its overall transfer function is an exponential function whose slope decreases with increasing stimulus level. This apparent gain control can be accounted for by a static saturating transducer function followed by a lowpass filter. In addition to attenuating the AC component, the filter approximately recovers the sinusoidal waveform of the stimulus. The estimated cutoff frequency varies with spontaneous rate, revealing a synaptic contribution to lowpass filtering. These findings highlight the significant impact of peripheral filtering mechanisms on phase locking.

  • phase locking of Auditory Nerve Fibers reveals stereotyped distortions and an exponential transfer function with a level dependent slope
    The Journal of Neuroscience, 2019
    Co-Authors: Adam J Peterson, Peter Heil
    Abstract:

    Phase locking of Auditory-Nerve-Fiber (ANF) responses to the fine structure of acoustic stimuli is a hallmark of the Auditory system9s temporal precision and is important for many aspects of hearing. Period histograms from phase-locked ANF responses to low-frequency tones exhibit spike-rate and temporal asymmetries, but otherwise retain an approximately sinusoidal shape as stimulus level increases, even beyond the level at which the mean spike rate saturates. This is intriguing because apical cochlear mechanical vibrations show little compression, and mechanoelectrical transduction in the receptor cells is thought to obey a static sigmoidal nonlinearity, which might be expected to produce peak clipping at moderate and high stimulus levels. Here we analyze phase-locked responses of ANFs from cats of both sexes. We show that the lack of peak clipping is due neither to ANF refractoriness nor to spike-rate adaptation on time scales longer than the stimulus period. We demonstrate that the relationship between instantaneous pressure and instantaneous rate is well described by an exponential function whose slope decreases with increasing stimulus level. Relatively stereotyped harmonic distortions in the input to the exponential can account for the temporal asymmetry of the period histograms, including peak splitting. We show that the model accounts for published membrane-potential waveforms when assuming a power-of-three, but not a power-of-one, relationship to exocytosis. Finally, we demonstrate the relationship between the exponential transfer functions and the sigmoidal pseudotransducer functions obtained in the literature by plotting the maxima and minima of the voltage responses against the maxima and minima of the stimuli. SIGNIFICANCE STATEMENT Phase locking of Auditory-Nerve-Fiber responses to the temporal fine structure of acoustic stimuli is important for many aspects of hearing, but the mechanisms underlying phase locking are not fully understood. Intriguingly, period histograms retain an approximately sinusoidal shape across sound levels, even when the mean rate has saturated. We find that neither refractoriness nor spike-rate adaptation is responsible for this behavior. Instead, the peripheral Auditory system operates as though it contains an exponential transfer function whose slope changes with stimulus level. The underlying mechanism is distinct from the comparatively weak cochlear mechanical compression in the cochlear apex, and likely resides in the receptor cells.

  • recovery of Auditory Nerve Fiber spike amplitude under natural excitation conditions
    Hearing Research, 2018
    Co-Authors: Adam J Peterson, Antoine Huet, Jerome Bourien, Jeanluc Puel, Peter Heil
    Abstract:

    Abstract Knowledge of the refractory properties of Auditory-Nerve Fibers (ANFs) is required for understanding the transduction of the graded membrane potential of the receptor cells into spike trains. The refractory properties inferred when ANFs are excited by electrical stimulation might differ from those present when ANFs are excited naturally by transmitter release from receptor cells. As a proxy for the latter, we investigated the recovery of spike amplitude with time since the previous spike in long extracellular recordings of the activity of individual ANFs from anesthetized Mongolian gerbils. Voltage traces were filtered minimally to avoid distortions of spike amplitude and timing. The amplitude of each spike was defined as the difference between its peak voltage and an extrapolated instantaneous reference voltage at the time of the peak. Spike amplitude was normalized to that of the previous spike to exclude effects of long-term changes in recording conditions. To ensure that the amplitude of the first spike in each pair was fully recovered, each spike pair was used only when preceded by an interspike interval of at least 5 ms. We find that the recovery of spike amplitude is well described by a short dead time followed by a double-exponential recovery function. Total recovery times were short (median: 0.85 ms; interquartile range: 0.74–1.00 ms) and independent of the ANF's characteristic frequency and spontaneous rate, but they increased weakly with increasing mean rate. We emphasize the differences between the recovery of spike amplitude, the recovery of spike probability from postsynaptic refractoriness, and the recovery of spike probability as reflected in the hazard-rate function. Our findings are inconsistent with the long refractory periods assumed in some models, but are consistent with the brief refractoriness assumed in the synapse model of Peterson and Heil (2018), which reproduces the stochastic properties of stationary spontaneous and sound-driven ANF spike trains.

  • a simple model of the inner hair cell ribbon synapse accounts for mammalian Auditory Nerve Fiber spontaneous spike times
    Hearing Research, 2017
    Co-Authors: Adam J Peterson, Peter Heil
    Abstract:

    The initial neural encoding of acoustic information occurs by means of spikes in primary Auditory afferents. Each mammalian primary Auditory afferent (type-I Auditory-Nerve Fiber; ANF) is associated with only one ribbon synapse in one receptor cell (inner hair cell; IHC). The properties of ANF spike trains therefore provide an indirect view of the operation of individual IHC synapses. We showed previously that a point process model of presynaptic vesicle pool depletion and deterministic exponential replenishment, combined with short postsynaptic neural refractoriness, accounts for the interspike interval (ISI) distributions, serial ISI correlations, and spike-count statistics of a population of cat-ANF spontaneous spike trains. Here, we demonstrate that this previous synapse model produces unrealistic properties when spike rates are high and show that this problem can be resolved if the replenishment of each release site is stochastic and independent. We assume that the depletion probability varies between synapses to produce differences in spontaneous rate and that the other model parameters are constant across synapses. We find that this model fits best with only four release sites per IHC synapse, a mean replenishment time of 17 ms, and absolute and mean relative refractory periods of 0.6 ms each. This model accounts for ANF spontaneous spike timing better than two influential, comprehensive models of the Auditory periphery. It also reproduces ISI distributions from spontaneous and steady-state driven activity from other studies and other mammalian species. Adding fractal noise to the rate of depletion of each release site can yield long-range correlations as typically observed in long spike trains. We also examine two model variants having more complex vesicle cycles, but neither variant yields a markedly improved fit or a different estimate of the number of release sites. In addition, we examine a model variant having both short and long relative refractory components and find that it cannot account for all aspects of the data. These model results will be beneficial for understanding ribbon synapses and ANF responses to acoustic stimulation.

Richard Salvi - One of the best experts on this subject based on the ideXlab platform.

  • Auditory Nerve Fiber responses following chronic cochlear de-efferentation.
    The Journal of comparative neurology, 1999
    Co-Authors: Xiang Yang Zheng, Donald Henderson, Sandra L. Mcfadden, Da Lian Ding, Richard Salvi
    Abstract:

    The aim of the present study was to examine the role of the olivocochlear system in Auditory processing by examining the long-term effects of cochlear de-efferentation on Auditory Nerve response properties in adult chinchillas. Spontaneous rates, response thresholds, tuning curves, discharge rate-level functions, and adaptation of single Auditory Nerve Fibers were measured in chinchillas with complete cochlear de-efferentation produced by sectioning the olivocochlear bundle in the internal Auditory meatus. De-efferentation was verified as successful on the basis of acetylcholinesterase staining of surface preparations of the organ of Corti. Following chronic de-efferentation, there was a striking decrease in spontaneous rate, consistent with earlier observations in cats. In addition, the present study shows that complete de-efferentation results in: (1) increased driven discharge rates and decreased dynamic range of discharge rate-level functions, (2) larger onset-to-steady state ratio of discharge rate at moderate intensities, and (3) a hypersensitive tail of the tuning curve. These effects, largely confined to neurons that were most sensitive to frequencies between 2‐8 kHz, indicate that the cochlear efferent system is important in maintaining normal function (e.g., frequency and intensity selectivity) of the Auditory periphery by modulating Auditory Nerve Fiber response properties. J. Comp. Neurol. 406:72‐86, 1999. r 1999 Wiley-Liss, Inc. Indexing terms: inner ear; hearing; central control; efferent innervation

  • effects of selective inner hair cell loss on Auditory Nerve Fiber threshold tuning and spontaneous and driven discharge rate
    Hearing Research, 1997
    Co-Authors: Jian Wang, Dalian Ding, Nicholas Powers, Philip Hofstetter, Patricia G Trautwein, Richard Salvi
    Abstract:

    Current theories assume that the outer hair cells (OHC) are responsible for the sharp tuning and exquisite sensitivity of the ear whereas inner hair cells (IHC) are mainly responsible for transmitting acoustic information to the central nervous system. To further evaluate this model, we used a single (38 mg/kg) or double dose (38 mg/kg, 2 times) of carboplatin to produce a moderate (20-28%) or severe (60-95%) IHC loss while sparing a large proportion of the OHCs. The surviving OHCs were functionally intact as indicated by normal cochlear microphonic (CM) potentials and distortion product otoacoustic emissions (DPOAE). Single-unit responses were recorded from Auditory Nerve Fibers to determine the effects of the moderate or severe IHC loss on the output of the surviving IHCs. Most neurons that responded to sound in the single-dose group had normal or near-normal thresholds and normal tuning. Relatively few neurons in the double-dose group responded to sound because of the severe IHC loss. The neurons that did respond to sound had narrow tuning curves. Some neurons in the double-dose group also had thresholds that were within the normal range, but most had thresholds that were elevated a mild-to-moderate degree. These results indicate that intact IHCs can retain relatively normal sensitivity and tuning despite massive IHC loss in surrounding regions of the cochlea. However, the spontaneous and driven discharge rates of neurons in the carboplatin-treated animals were significantly lower than normal. These changes could conceivably be due to sublethal damage to surviving IHCs or to postsynaptic dysfunction in the Auditory Nerve.

Shyamla S Narayan - One of the best experts on this subject based on the ideXlab platform.

  • mechanical bases of frequency tuning and neural excitation at the base of the cochlea comparison of basilar membrane vibrations and Auditory Nerve Fiber responses in chinchilla
    Proceedings of the National Academy of Sciences of the United States of America, 2000
    Co-Authors: Mario A Ruggero, Shyamla S Narayan, Andrei N Temchin, Alberto Recio
    Abstract:

    Abstract We review the mechanical origin of Auditory-Nerve excitation, focusing on comparisons of the magnitudes and phases of basilar-membrane (BM) vibrations and Auditory-Nerve Fiber responses to tones at a basal site of the chinchilla cochlea with characteristic frequency ≈ 9 kHz located 3.5 mm from the oval window. At this location, characteristic frequency thresholds of Fibers with high spontaneous activity correspond to magnitudes of BM displacement or velocity in the order of 1 nm or 50 μm/s. Over a wide range of stimulus frequencies, neural thresholds are not determined solely by BM displacement but rather by a function of both displacement and velocity. Near-threshold, Auditory-Nerve responses to low-frequency tones are synchronous with peak BM velocity toward scala tympani but at 80–90 dB sound pressure level (in decibels relative to 20 microPascals) and at 100–110 dB sound pressure level responses undergo two large phase shifts approaching 180°. These drastic phase changes have no counterparts in BM vibrations. Thus, although at threshold levels the encoding of BM vibrations into spike trains appears to involve only relatively minor signal transformations, the polarity of Auditory-Nerve responses does not conform with traditional views of how BM vibrations are transmitted to the inner hair cells. The response polarity at threshold levels, as well as the intensity-dependent phase changes, apparently reflect micromechanical interactions between the organ of Corti, the tectorial membrane and the subtectorial fluid, and/or electrical and synaptic processes at the inner hair cells.

  • mechanical bases of frequency tuning and neural excitation at the base of the cochlea comparison of basilar membrane vibrations and Auditory Nerve Fiber responses in chinchilla
    Proceedings of the National Academy of Sciences of the United States of America, 2000
    Co-Authors: Mario A Ruggero, Shyamla S Narayan, Andrei N Temchin, Alberto Recio
    Abstract:

    We review the mechanical origin of Auditory-Nerve excitation, focusing on comparisons of the magnitudes and phases of basilar-membrane (BM) vibrations and Auditory-Nerve Fiber responses to tones at a basal site of the chinchilla cochlea with characteristic frequency approximately 9 kHz located 3.5 mm from the oval window. At this location, characteristic frequency thresholds of Fibers with high spontaneous activity correspond to magnitudes of BM displacement or velocity in the order of 1 nm or 50 microm/s. Over a wide range of stimulus frequencies, neural thresholds are not determined solely by BM displacement but rather by a function of both displacement and velocity. Near-threshold, Auditory-Nerve responses to low-frequency tones are synchronous with peak BM velocity toward scala tympani but at 80-90 dB sound pressure level (in decibels relative to 20 microPascals) and at 100-110 dB sound pressure level responses undergo two large phase shifts approaching 180 degrees. These drastic phase changes have no counterparts in BM vibrations. Thus, although at threshold levels the encoding of BM vibrations into spike trains appears to involve only relatively minor signal transformations, the polarity of Auditory-Nerve responses does not conform with traditional views of how BM vibrations are transmitted to the inner hair cells. The response polarity at threshold levels, as well as the intensity-dependent phase changes, apparently reflect micromechanical interactions between the organ of Corti, the tectorial membrane and the subtectorial fluid, and/or electrical and synaptic processes at the inner hair cells.

  • Auditory Nerve Fiber representation of temporal cues to voicing in word medial stop consonants
    Journal of the Acoustical Society of America, 1994
    Co-Authors: Donal G. Sinex, Shyamla S Narayan
    Abstract:

    The length of the interval between the onset of consonant closure and the onset of voicing in a following vowel is a temporal cue that may distinguish between consonants /d/ and /t/ in word‐medial environments; this interval has been called the ‘‘consonant duration’’ [V. W. Zue and M. Laferriere, J. Acoust. Soc. Am. 66, 1039–1050 (1979); S. Davis and W. V. Summers, J. Phon. 17, 339–353 (1989)]. The representation of this cue in the discharge patterns of chinchilla Auditory‐Nerve Fibers was measured. The two‐syllable utterances /ida/, /ita/, /uda/, and /uta/ were recorded by one male and one female talker. The onset of consonant closure produced discharge rate decreases in nearly all neurons. Either the release of closure or the onset of voicing for the second vowel could elicit an increase in discharge rate. The latencies of these discharge rate changes varied across populations of neurons. A neural measure of consonant duration was extracted from the pattern of latencies. The ‘‘encoded duration’’ was longer for utterances with a medial /t/ than for utterances with a medial /d/. For each utterance the encoded duration increased with increases in characteristic frequency. The variability of the encoded duration measure was small enough to preserve the distinction between utterances with different word‐medial consonants. The variability of the encoded duration was large, relative to the acoustic differences between utterances that included the same medial consonant. This pattern of variability could contribute to the formation of perceptual categories by reducing the audibility of within‐category acoustic differences.

Hiroyuki Mino - One of the best experts on this subject based on the ideXlab platform.

  • effects of the rates of pseudo spontaneous spikes generated by electric stimuli on information transmission in an Auditory Nerve Fiber model
    International Conference of the IEEE Engineering in Medicine and Biology Society, 2013
    Co-Authors: Parichat Kumsa, Hiroyuki Mino
    Abstract:

    In this study, the effects of the rate of pseudo-spontaneous spikes on information transmission of the spike trains in response to the electric pulsatile stimulus currents in an Auditory Nerve Fiber (ANF) model is investigated through computer simulation. The pseudo-spontaneous spikes can be generated by high rate pulsatile electric stimuli, making it possible to efficiently encode sound stimuli into the spike trains of the ANF in cochlear prostheses. In this investigation, the information rate of the spike trains in response to sinusoidally modulated pulsatile electric stimuli was estimated as the amplitude of the pulsatile electric stimuli (the rate of pseudo-spontaneous spikes) was varied. The results show that the information rates increased, reached a maximum, and then decreased, in several different values of modulation depth, as the rate of pseudo-spontaneous spikes increased. This may imply a resonance phenomenon dependent on the rate of pseudo-spontaneous spikes generated by electric stimuli in the ANF model. These findings may play a key role in the design of better cochlear prostheses.

  • effects of rates of spontaneous synaptic vesicle secretions in inner hair cells on information transmission in an Auditory Nerve Fiber model
    International Conference of the IEEE Engineering in Medicine and Biology Society, 2012
    Co-Authors: Parichat Kumsa, Hiroyuki Mino
    Abstract:

    In this article, we investigate how the rates of spontaneous synaptic vesicle secretions affect information transmission of the spike trains in response to the inner hair cell (IHC) synaptic currents in an Auditory Nerve Fiber (ANF) model through computer simulations. The IHC synaptic currents were modeled by a filtered inhomogeneous Poisson process modulated with sinusoidal functions, while the stochastic ion channel model was incorporated into each node of Ranvier in the ANF model with spiral ganglion. The information rates were estimated from the entropies of the inter-spike intervals of the spike trains to evaluate information transmission in the ANF model. The results show that the information rates increased, reached a maximum, and then decreased as the rate of spontaneous secretion increased, implying a resonance phenomenon dependent on the rate of spontaneous IHC synaptic secretions. In conclusion, this phenomenon similar to the regular stochastic resonance may be observed due to that spontaneous IHC synaptic secretions may act as an origin of fluctuation or noise, and these findings may play a key role in the design of better Auditory prostheses.

  • encoding of information into neural spike trains in an Auditory Nerve Fiber model with electric stimuli in the presence of a pseudospontaneous activity
    IEEE Transactions on Biomedical Engineering, 2007
    Co-Authors: Hiroyuki Mino
    Abstract:

    This paper presents an information-theoretic analysis of neural spike trains in an Auditory Nerve Fiber (ANF) model stimulated extracellularly with Gaussian or sinusoidal waveforms in the presence of a pseudospontaneous activity of spike firings. In the computer simulation, stimulus current waveforms were applied repeatedly to a stimulating electrode located 1 mm above the 26th node of Ranvier, in an ANF axon model having 50 nodes of Ranvier, each consisting of stochastic sodium and potassium channels. From spike firing times recorded at the 36th node of Ranvier, a post-stimulus time histogram (PSTH) was generated, and raster plots were depicted for 30 stimulus presentations, in order to investigate the temporal precision and reliability of the spike firing times. Also, inter spike intervals were generated and then "total" and "noise" entropies were estimated to obtain the mutual information and the information rate of the spike trains. It was shown in the case of Gaussian electric stimuli that the temporal precision of spike firing times and the reliability of spike firings were found to increase as the standard deviation (SD) of the Gaussian electric stimuli increased. It was also shown in the case of sinusoidal electric stimuli where there was a specific amplitude of sinusoidal waveforms, the information rate being maximized. It was implied that setting the parameters of electric stimuli to the specific values which maximize the information rate might contribute to efficiently encoding information into the spike trains in the presence of a pseudospontaneous activity of spike firings