Neural encoding of single-formant stimuli in the cat. II. Responses of anteroventral cochlear nucleus units

1994 ◽  
Vol 71 (1) ◽  
pp. 59-78 ◽  
Author(s):  
X. Wang ◽  
M. B. Sachs
Keyword(s):  
Cochlear Nucleus ◽  
Modulation Depth ◽  
Peak Height ◽  
Nerve Fibers ◽  
Sound Level ◽  
Neural Encoding ◽  
Sound Levels ◽  
Anteroventral Cochlear Nucleus ◽  
Wide Range ◽  
High Sound

1. We have studied responses of anteroventral cochlear nucleus (AVCN) units to single-formant stimuli (SFS), in an effort to make quantitative comparisons with responses observed in auditory-nerve fibers (ANFs) to the same stimuli (Wang and Sachs 1993) and to reveal some of the signal processing mechanisms at the AVCN. Single-unit recordings and subsequent analyses were performed on each type of commonly recorded units, namely primarylike (Pri), primarylike with notch (PN), sustained chopper (ChS), transient chopper (ChT), and onset chopper (OnC), as well as a few onset (On) units, from the AVCN in anesthetized cats. The responses were obtained at a wide range of sound levels and at a frequency range of 1-10 kHz. Modulation in the envelopes of discharge patterns was quantified by a measure called modulation depth. 2. At moderate to high sound levels, most AVCN units were found to have enhanced modulation depth compared with that of ANFs, although the degree of enhancement varies among different types. All AVCN units, except Pri type, showed an enhancement in modulation depth over that of the highest of ANFs at moderate to high sound levels in the order of (from the highest to the lowest) On, OnC, ChT/PN, and ChS. Specifically, 1) modulation depth in Pri units was comparable to that of high spontaneous rate (SR) ANFs at low sound levels and to that of low/medium SR ANFs at high sound levels (in dB SPL). When sound level was normalized by unit threshold, Pri units, on average, exhibited only limited enhancement in envelope modulation at high sound levels (> 80 dB re threshold); 2) PN units showed substantially enhanced modulation depth over that of all SR groups of ANFs at moderate to high sound levels in dB SPL or dB re threshold scales; 3) significant enhancement in modulation depth was seen in both ChS and ChT units, with a slightly higher modulation depth in ChT type across sound levels (in dB SPL or dB re threshold); 4) modulation depth of OnC units was higher than those of primary-like (Pri and PN) and chopper (ChS and ChT) units at a wide range of sound levels; 5) responses from a limited sample of On units showed the highest modulation depth among all types of AVCN units. 3. Detailed analysis revealed that the enhanced modulation depth in the responses of AVCN units is the result of increased envelope peak height and decreased envelope minimum, relative to those of ANFs.(ABSTRACT TRUNCATED AT 400 WORDS)

Coding of envelope modulation in the auditory nerve and anteroventral cochlear nucleus

1992 ◽  
Vol 336 (1278) ◽  
pp. 399-402 ◽  
Keyword(s):  
Cochlear Nucleus ◽  
Auditory Nerve ◽  
Narrow Band ◽  
Modulation Depth ◽  
Sound Level ◽  
Sound Levels ◽  
Anteroventral Cochlear Nucleus ◽  
Threshold Mechanism ◽  
Single Form ◽  
High Sound

We have investigated responses of the auditory nerve fibres (ANFS) and anteroventral cochlear nucleus (AVCN) units to narrow band ‘single-form ant’ stimuli (SFSS). We found that low and medium spontaneous rate (SR) ANFS maintain greater amplitude modulation (AM) in their responses at high sound levels than do high SR units when sound level is considered in dB SPL. However, this partitioning of high and low SR units disappears if sound level is considered in dB relative to unit threshold. Stimuli with carrier frequencies away from unit best frequency (BF) were found to generate higher AM in responses at high sound levels than that observed even in most low and medium sr units for stimuli with carrier frequencies near BF. AVCN units were shown to have increased modulation depth in their responses when compared with high SR ANFS with similar BFS and to have increased or comparable modulation depth when compared with low SR ANFS. At sound levels where AM almost completely disappears in high SR ANFS, most AVCN units we studied still show significant AM in their responses. Using a dendritic model, we investigated possible mechanisms of enhanced AM in AVCN units, including the convergence of inputs from different SR groups of ANFS and a postsynaptic threshold mechanism in the soma.

Level dependence of cochlear nucleus onset unit responses and facilitation by second tones or broadband noise

1995 ◽  
Vol 73 (1) ◽  
pp. 141-159 ◽  
Author(s):  
I. M. Winter ◽  
A. R. Palmer
Keyword(s):  
Cochlear Nucleus ◽  
Discharge Rate ◽  
Nerve Fibers ◽  
Sound Level ◽  
Spike Timing ◽  
Broadband Noise ◽  
Sound System ◽  
Rate Level ◽  
Sound Levels ◽  
Level Function

1. The responses of onset units in the cochlear nucleus of the anesthetized guinea pig have been measured to single tones, two-tone complexes, and broadband noise (BBN; 20-kHz bandwidth). The onset units were subdivided into three groups, onset-I (OnI), onset-L (OnL), and onset-C (OnC), on the basis of a decision tree using their peristimulus time histogram (PSTH) shape and discharge rate in response to suprathreshold best-frequency (BF) tone bursts. 2. PSTHs were constructed from responses either to single tones at a unit's BF or to BBN as a function of level. When sufficient sustained activity could be elicited from the unit, arbitrarily defined as > 100 spikes/s, a coefficient of variation (CV) was calculated; the majority were characterized by a CV that was similar to transient chopper units (0.35 < CV < 0.5). First spike latency decreased monotonically with increasing sound level. For the majority of onset units, the first spike timing was very precise. 3. BF rate-level functions recorded from OnL and OnC units did not show any signs of discharge rate saturation at the highest sound levels we have used (100-115 dB SPL). No systematic relationship was observed between the threshold at BF and the shape of the rate-level function. BBN rate-level functions were typically characterized by higher discharge rates than in response to BF tones. However, for OnI units and a minority of other onset units, there was little difference in the shape of their rate-level functions in response to BF tones or BBN. 4. The threshold of most onset units to BBN was similar to the threshold to a BF tone that had similar overall root-mean-square (RMS) energy. The BBN threshold was, on average, 5.5 dB greater than the BF threshold. This result contrasts with that found in auditory-nerve fibers recorded in the same species, with the use of an identical sound system, where the threshold to BBN was, on average, 19.4 dB higher. The mean threshold difference between BBN and BF tones for a population of chopper units recorded in the same series of experiments was 17.7 dB. The relative thresholds to BBN and BF tones indicated that the bandwidths near the onset units' BF threshold were broader than could be estimated with the use of single tones. Ten units were characterized by bimodal response areas.(ABSTRACT TRUNCATED AT 400 WORDS)

Neural encoding of single-formant stimuli in the cat. I. Responses of auditory nerve fibers

1993 ◽  
Vol 70 (3) ◽  
pp. 1054-1075 ◽  
Author(s):  
X. Wang ◽  
M. B. Sachs
Keyword(s):  
Direct Current ◽  
Auditory Nerve ◽  
Nerve Fibers ◽  
Fundamental Component ◽  
Sound Levels ◽  
Wide Range ◽  
Spectral Components ◽  
Auditory Nerve Fibers ◽  
High Sound ◽  
Envelope Modulation

1. We have studied auditory responses to a set of speech-related narrowband sounds, single-formant stimuli (SFSs), in populations of auditory nerve fibers (ANFs). An analytic method was developed to extract the envelope of temporal discharge patterns of the ANF responses to nonsinusoidally modulated stimuli, whose spectra have multiple clusters of components. Such responses are often encountered in the auditory system when complex stimuli are used and have traditionally been studied by analyzing the fundamental component of the responses. 2. The envelope modulation in the SFSs is shown to be represented by the response patterns of ANFs. When the whole ANF population is considered, the information on modulation in stimulus envelope does not disappear at the highest sound level tested at all best frequencies (BFs) we studied (1-10 kHz). The representation is the best at medium sound levels and degrades at high sound levels. Low/medium-spontaneous rate (SR) ANFs showed greater envelope modulation in their responses at high sound levels than do high-SR ANFs. The quality of the representation at high sound levels is, on average, proportional to BF threshold of an ANF. On the basis of populations of ANFs with all SRs, the envelope modulation in the SFSs is represented over a wide range of sound levels. 3. We found that low-BF ANFs differ from high-BF ANFs in representing envelope modulation in the SFSs. For ANFs with BFs less than approximately 6 kHz, information on stimulus envelope is not only contained in spectral components near direct current but also in components at the vicinities of frequencies equal to BF and its multiples. In fact, for ANFs with BFs < 3 kHz, the contribution from spectral components centered at BF to overall response modulation is greater than that from spectral components near direct current. These findings indicate that, by using measures solely based on the fundamental component, the amount of modulation in the responses to narrowband stimuli is underestimated for low-BF ANFs. 4. Off-BF stimulation of ANFs with SFSs was found to result in increased envelope modulation in responses at high sound levels. The further away the stimulus is centered relative to unit BF, the greater the modulation it induces, provided that the stimulus is capable of exciting the unit. An SFS centered as close as 15% off unit BF can produce a significant increase in the modulation of responses at very high sound levels.(ABSTRACT TRUNCATED AT 400 WORDS)

Differential Expression of Three Distinct Potassium Currents in the Ventral Cochlear Nucleus

2003 ◽  
Vol 89 (6) ◽  
pp. 3070-3082 ◽  
Author(s):  
Jason S. Rothman ◽  
Paul B. Manis
Keyword(s):  
Differential Expression ◽  
Cochlear Nucleus ◽  
Nerve Fibers ◽  
Delayed Rectifier ◽  
High Threshold ◽  
Type I ◽  
Acoustic Environment ◽  
Ventral Cochlear Nucleus ◽  
Wide Range ◽  
Slope Factor

In the ventral cochlear nucleus (VCN), neurons transform information from auditory nerve fibers into a set of parallel ascending pathways, each emphasizing different aspects of the acoustic environment. Previous studies have shown that VCN neurons differ in their intrinsic electrical properties, including the K+ currents they express. In this study, we examine these K+ currents in more detail using whole cell voltage-clamp techniques on isolated VCN cells from adult guinea pigs at 22°C. Our results show a differential expression of three distinct K+ currents. Whereas some VCN cells express only a high-threshold delayed-rectifier-like current ( IHT), others express IHT in combination with a fast inactivating current ( IA) and/or a slow-inactivating low-threshold current ( ILT). IHT, ILT, and IA, were partially blocked by 1 mM 4-aminopyridine. In contrast, only ILT was blocked by 10–100 nM dendrotoxin-I. A surprising finding was the wide range of levels of ILT, suggesting ILT is expressed as a continuum across cell types rather than modally in a particular cell type. IA, on the other hand, appears to be expressed only in cells that show little or no ILT, the Type I cells. Boltzmann analysis shows IHT activates with 164 ± 12 (SE) nS peak conductance, -14.3 ± 0.7 mV half-activation, and 7.0 ± 0.5 mV slope factor. Similar analysis shows ILT activates with 171 ± 22 nS peak conductance, -47.4 ± 1.0 mV half-activation, and 5.8 ± 0.3 mV slope factor.

scholarly journals Ephrin-A3 Is Required for Tonotopic Map Precision and Auditory Function in the Mouse Auditory Brainstem

2021 ◽  
Author(s):  
Natalia Hoshino ◽  
Yazan Altarshan ◽  
Ahmad Alzein ◽  
Amali Fernando ◽  
Hieu Nguyen ◽  
...  
Keyword(s):  
Axon Guidance ◽  
Cochlear Nucleus ◽  
Auditory Brainstem ◽  
Nerve Fibers ◽  
Auditory Brainstem Responses ◽  
Dependent Manner ◽  
Anteroventral Cochlear Nucleus ◽  
Sound Discrimination ◽  
Frequency Changes ◽  
Second Wave

Abstract Tonotopy is a prominent feature of the vertebrate auditory system and forms the basis for sound discrimination, but the molecular mechanism underlying its formation remain largely elusive. Ephrin/Eph signaling is known to play important roles in axon guidance during topographic mapping in other sensory systems. Here, we determined that ephrin-A3 molecules are expressed in a ventral to dorsal descending gradient along the tonotopic axis in developing mouse cochlear nucleus. During cochlear nucleus innervation by auditory nerve fibers, ephrin-A3 forward signaling can repel these fibers in a stage-dependent manner. In ephrin-A3 mutant animals, the tonotopic map is degraded and isofrequency bands of neuronal activation become imprecise in the anteroventral cochlear nucleus. Ephrin-A3 mutants also exhibit a delayed second wave in auditory brainstem responses and impaired detection sound frequency changes. Our findings establish an essential role for ephrin-A3 in forming precise tonotopy in the auditory brainstem to ensure accurate sound discrimination.

Frequency extent of two-tone facilitation in onset units in the ventral cochlear nucleus

1996 ◽  
Vol 75 (1) ◽  
pp. 380-395 ◽  
Author(s):  
D. Jiang ◽  
A. R. Palmer ◽  
I. M. Winter
Keyword(s):  
Cochlear Nucleus ◽  
Auditory Nerve ◽  
Low Frequency ◽  
Nerve Fibers ◽  
Inhibitory Input ◽  
Ventral Cochlear Nucleus ◽  
Narrow Region ◽  
Morphological Studies ◽  
Wide Range ◽  
Auditory Nerve Fibers

1. The frequency threshold curves (FTCs) of 91 single units in the cochlear nucleus of the anesthetized guinea pig were measured using a conventional single-tone paradigm and a two-tone paradigm designed to elucidate the frequency extent of two-tone facilitation in onset units (On). Units were classified according to existing classification schemes into primary-like (n = 3), chopper (n = 23), and three onset groups: OnI (n = 12), OnC (n = 29), and OnL (n = 24). Histological reconstructions show onset units to be widely distributed within the ventral cochlear nucleus in a manner generally consistent with its tonotopic organization. 2. The FTCs of onset units differed in their minimum thresholds, the steepness of their high- and low-frequency cutoffs, and their sharpness of tuning as quantified by the quality factor at 10 dB (Q10dB) above best frequency (BF) threshold values. There was considerable overlap in the sharpness of tuning between onset units and auditory nerve fibers, as indicated by the distribution of Q10dB values in the octave around 10 kHz: onset units had Q10dB values of 3.56 +/- 1.38 (SD), compared with 6.3 +/- 2.48 for auditory nerve fibers. The tuning of chopper units was similar to that of auditory nerve fibers (5.52 +/- 1.46). 3. Seventy-five percent of onset units showed some degree of facilitation (a threshold reduction) when their FTCs were measured in the presence of BF tones 4 dB below BF threshold. The frequency extent of such facilitation was variable, with a maximum of 6 octaves around the BF. In extreme cases facilitation could be measured when the BF tone was as low as 30 dB below BF threshold. 4. In 17% of onset units, suppressive effects were evident, as shown by noncontiguous frequency regions of facilitation. These suppressive effects might be a reflection either of suppression in the auditory nerve input or of a direct inhibitory input to the onset units. The strength of this effect suggests that inhibition is a likely explanation, consistent with the finding in previous morphological studies of profuse synapses with pleomorphic vesicles on multipolar cells. 5. FTCs of chopper and primary-like units measured in the presence of BF tones showed little facilitation. The facilitation that was observed in chopper units was confined to a narrow region around BF and disappeared when the facilitatory tone was lowered to 4 dB below BF threshold. 6. These data support the hypothesis that onset units, but not chopper or primary-like units, receive excitatory inputs from auditory nerve fibers with a wide range of BFs. However, the frequency range of facilitation and the magnitude of the threshold facilitation varied from unit to unit, suggesting that the off-BF inputs from auditory nerve fibers are not evenly distributed or equally effective in all units.

The Functional Role of Excitatory and Inhibitory Interactions in Chopper Cells of the Anteroventral Cochlear Nucleus

1994 ◽  
Vol 6 (6) ◽  
pp. 1127-1140 ◽  
Author(s):  
Ying-Cheng Lai ◽  
Raimond L. Winslow ◽  
Murray B. Sachs
Keyword(s):  
Cochlear Nucleus ◽  
Auditory Nerve ◽  
Dendritic Tree ◽  
Nerve Fibers ◽  
High Threshold ◽  
Spontaneous Rate ◽  
Anteroventral Cochlear Nucleus ◽  
Rate Versus ◽  
High Stimulus ◽  
Auditory Nerve Fibers

Chopper cells in the anteroventral cochlear nucleus of the cat maintain a robust rate-place representation of vowel spectra over a broad range of stimulus levels. This representation resembles that of low threshold, high spontaneous rate primary auditory nerve fibers at low stimulus levels, and that of high threshold, low spontaneous rate auditory-nerve fibers at high stimulus levels. This has led to the hypothesis that chopper cells in the anteroventral cochlear nucleus selectively process inputs from different spontaneous rate populations of primary auditory-nerve fibers at different stimulus levels. We present a computational model, making use of shunting inhibition, for how this level dependent processing may be performed within the chopper cell dendritic tree. We show that this model (1) implements level-dependent selective processing, (2) reproduces detailed features of real chopper cell post-stimulus-time histograms, and (3) reproduces nonmonotonic rate versus level functions in response to single tones measured.

scholarly journals How Wildlife Respond to Natural Noise

2021 ◽  
Author(s):  
Dylan G.E. Gomes
Keyword(s):  
Sound Level ◽  
Anthropogenic Sources ◽  
Anthropogenic Noise ◽  
Frequency Noise ◽  
Spider Webs ◽  
Predator Prey ◽  
Sound Levels ◽  
Natural Noise ◽  
Acoustic Environments ◽  
High Sound

Animal sensory systems have evolved in a natural din of noise since the evolution of sensory organs. Anthropogenic noise is a recent addition to the environment, which has had demonstrable, largely negative, effects on wildlife. Yet, we know relatively little about how animals respond to natural sources of noise, which can differ substantially in acoustic characteristics from human-caused noise. Here we review the noise literature and suggest an evolutionary approach for framing the study of novel, anthropogenic sources of noise. We also push for a more quantitative approach to acoustic ecology research. To build a better foundation around the effects of natural noise on wildlife, we experimentally and continuously broadcast whitewater river noise across a landscape for three summers. Additionally, we use spectrally-altered river noise to explicitly test the effects of masking as a mechanism driving patterns. We then monitored bird, bat, and arthropod abundance and activity and assessed predator-prey relationships with bird and bat foraging assays and by counting prey in spider webs. Birds and bats largely avoided high sound levels in noisy environments. Bats also avoided acoustic environments dominated by high frequency noise while birds avoided noise that overlapped with their song, the latter trend suggesting that communication is impaired. Yet, when sound levels were high overlapping noise was not any more disruptive than non-overlapping noise, which suggests that intense noise interferes with more than communication. Avoidance of noise that overlapped in frequency with song was stronger for low-frequency singers. Bats that employ higher frequency echolocation were more likely to avoid high sound level noise; we explore potential explanations for this pattern. Most arthropod Orders responded to noise, yet the directions of effects were not consistent across taxa. Some arthropods increased in abundance in high sound level areas - perhaps in response to the absence of bird and bat predators. Reinforcing this possibility, visually foraging birds and passively listening bats decreased foraging effort beyond what was expected based on declines in abundance and activity. Orb-weaving spiders increased dramatically in high sound level areas, which could be due to a release from predation, an increase in prey capture, or direct attraction to high sound level river noise. Overall, we demonstrated significant changes to many vertebrate and invertebrate taxa during playback of whitewater river noise. We were able to parse out the effects of sound pressure level and background frequency on these individual taxa and predator-prey behaviors. Our results reveal that animals have likely long been affected by particular characteristics of noise, which may help explain contemporary responses to anthropogenic noise. As the spatial and temporal footprint of anthropogenic noise is orders of magnitude greater than intense natural acoustic environments, the insights provided by our data increase the importance of mitigating noise pollution impacts on animals and their habitats. It is clear that natural noise has the power to alter animal abundances and behavior in a way that likely reverberates through entire communities and food webs. Future work should focus on strengthening the relationships between these potential predators and prey and highlight how the structure of the system changes under such noise treatments.

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