Modelling the sensitivity of cells in the anteroventral cochlear nucleus to spatiotemporal discharge patterns

1992 ◽  
Vol 336 (1278) ◽  
pp. 403-406 ◽  
Keyword(s):  
Cochlear Nucleus ◽  
Auditory Nerve ◽  
Cross Correlation ◽  
Low Frequency ◽  
Phase Spectrum ◽  
Coincidence Detection ◽  
Potential Mechanism ◽  
Complex Sounds ◽  
Anteroventral Cochlear Nucleus ◽  
Discharge Patterns

This study investigates a potential mechanism for the processing of acoustic information that is encoded in the spatiotemporal discharge patterns of auditory nerve (AN) fibres. Recent physiological evidence has demonstrated that some low-frequency cells in the anteroventral cochlear nucleus (AVCN) are sensitive to manipulations of the phase spectrum of complex sounds (Carney 1990 b ). These manipulations result in systematic changes in the spatiotemporal discharge patterns across groups of low-frequency an fibres having different characteristic frequencies (CFS). One interpretation of these results is that these neurons in the AVCN receive convergent inputs from AN fibres with different CFS, and that the cells perform a coincidence detection or cross-correlation upon their inputs. This report presents a model that was developed to test this interpretation.

Sensitivities of cells in anteroventral cochlear nucleus of cat to spatiotemporal discharge patterns across primary afferents

1990 ◽  
Vol 64 (2) ◽  
pp. 437-456 ◽  
Author(s):  
L. H. Carney
Keyword(s):  
Phase Shift ◽  
Cochlear Nucleus ◽  
Low Frequency ◽  
Phase Spectrum ◽  
Posterior Region ◽  
Anteroventral Cochlear Nucleus ◽  
Complex Stimuli ◽  
A Cell ◽  
Discharge Patterns ◽  
Phase Spectra

1. This study tested the hypothesis that a cell in the anteroventral cochlear nucleus (AVCN) that receives convergent input from auditory nerve (AN) fibers can be sensitive to the temporal pattern of discharges on the set of AN fibers providing its input. 2. The temporal discharge pattern across the population of low-frequency AN fibers was manipulated by varying the phase spectra of complex stimuli that had fixed, flat magnitude spectra. By introducing a phase shift with variable slope at a particular frequency, the relative times of discharge of phase-locked neurons with different characteristic frequencies (CFs) could be varied. In this manner the overall spatiotemporal discharge pattern across the array of AN fibers was systematically manipulated. 3. Some low-frequency cells in the AVCN were sensitive to changes in the slope of the phase transition of the complex stimulus. The cells that were sensitive came from several different cell types in the AVCN. Their responses were consistent with the hypothesis that these cells were sensitive to the temporal relationships between discharges on their primary inputs and that they received inputs with different CFs, because the phase shifts introduced relative time differences between different frequencies. 4. Other cells were not sensitive to the degree of phase shift of the stimulus. This insensitivity implied either that these cells received inputs of the same, or nearly the same, CF, or that they were not sensitive to the time differences introduced by these changes in the phase spectra, or both. 5. The cells that were sensitive to the manipulations of the phase spectrum were located in the posterior region of anterior AVCN and in the posterior region of AVCN and thus were presumably either globular bushy, small spherical bushy, or stellate cells. No sensitive cells were located in the most anterior region of the AVCN, where large spherical bushy cells are located. 6. Temporal discharge patterns across the AN population in response to complex stimuli change as a function of level. Accordingly, the sensitivity of neurons to changes in the phase transitions of the complex stimuli used in this study was often affected by the level of the stimulus. 7. The sensitivity to changes in the phase spectrum was a frequency-specific effect. That is, a cell was most sensitive to changes made in phase that were centered near its CF and less sensitive to changes in phase that were introduced at frequencies below or above CF.(ABSTRACT TRUNCATED AT 400 WORDS)

Signs of functional maturation of peripheral auditory system in discharge patterns of neurons in anteroventral cochlear nucleus of kitten

1978 ◽  
Vol 41 (6) ◽  
pp. 1557-1559 ◽  
Author(s):  
J. F. Brugge ◽  
E. Javel ◽  
L. M. Kitzes
Keyword(s):  
Cochlear Nucleus ◽  
Auditory Nerve ◽  
Discharge Rate ◽  
Phase Locking ◽  
Low Frequency ◽  
Second Phase ◽  
Extended Phase ◽  
Anteroventral Cochlear Nucleus ◽  
Peripheral Auditory System ◽  
Different Response

1. Responses to pure tones were recorded from single neurons in the anteroventral cochlear nucleus (AVCN) in kittens ranging in age from 4 to 45 days. Different response properties mature at different times after birth. 2. The shapes of response areas of AVCN neurons after the 1st postnatal week resemble those recorded in the AVCN and auditory nerve of the adult. During the 1st wk after birth the high-frequency portion of the response area is extended. Phase-locked responses to stimulus frequencies below about 600 Hz occur at this time. Phase vs. frequency measurements and shapes of response areas indicate that by the end of the 1st postnatal week the cochlear partition may be capable of supporting a traveling wave along most of its length. 3. Functional development proceeds through a second phase which lasts until the end of the 2nd or the beginning of the 3rd wk of life. During that time threshold, maximal discharge rate, and average first-spike latency achieve adult values. 4. Phase-locking to low-frequency tones, to the extent displayed by phase-sensitive neurons in the adult AVCN or auditory nerve, is achieved last, after the 3rd or 4th wk postpartum.

The Roles Potassium Currents Play in Regulating the Electrical Activity of Ventral Cochlear Nucleus Neurons

2003 ◽  
Vol 89 (6) ◽  
pp. 3097-3113 ◽  
Author(s):  
Jason S. Rothman ◽  
Paul B. Manis
Keyword(s):  
Cochlear Nucleus ◽  
Auditory Nerve ◽  
Threshold Current ◽  
Repetitive Firing ◽  
Resting Membrane Potential ◽  
Type I ◽  
Type Ii Cells ◽  
Type Ii ◽  
Ventral Cochlear Nucleus ◽  
Discharge Patterns

Using kinetic data from three different K+ currents in acutely isolated neurons, a single electrical compartment representing the soma of a ventral cochlear nucleus (VCN) neuron was created. The K+ currents include a fast transient current ( IA), a slow-inactivating low-threshold current ( ILT), and a noninactivating high-threshold current ( IHT). The model also includes a fast-inactivating Na+ current, a hyperpolarization-activated cation current ( Ih), and 1–50 auditory nerve synapses. With this model, the role IA, ILT, and IHT play in shaping the discharge patterns of VCN cells is explored. Simulation results indicate that IHT mainly functions to repolarize the membrane during an action potential, and IA functions to modulate the rate of repetitive firing. ILT is found to be responsible for the phasic discharge pattern observed in Type II cells (bushy cells). However, by adjusting the strength of ILT, both phasic and regular discharge patterns are observed, demonstrating that a critical level of ILT is necessary to produce the Type II response. Simulated Type II cells have a significantly faster membrane time constant in comparison to Type I cells (stellate cells) and are therefore better suited to preserve temporal information in their auditory nerve inputs by acting as precise coincidence detectors and having a short refractory period. Finally, we demonstrate that modulation of Ih, which changes the resting membrane potential, is a more effective means of modulating the activation level of ILT than simply modulating ILT itself. This result may explain why ILT and Ih are often coexpressed throughout the nervous system.

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.

Excitatory/inhibitory response types in the cochlear nucleus: relationships to discharge patterns and responses to electrical stimulation of the auditory nerve

1985 ◽  
Vol 54 (4) ◽  
pp. 917-939 ◽  
Author(s):  
W. P. Shofner ◽  
E. D. Young
Keyword(s):  
Receptive Field ◽  
Cochlear Nucleus ◽  
Auditory Nerve ◽  
Type I ◽  
Type Ii ◽  
Type Iii ◽  
Rate Level ◽  
Cochlear Nucleus Units ◽  
Excitatory Responses ◽  
Discharge Patterns

We have studied the response properties of single units in the cochlear nucleus of unanesthetized decerebrate cats. The purpose of the study was to compare the properties of cochlear nucleus units as described in two commonly used classification schemes. Units were first classified according to their receptive-field properties based on the relative prominence of excitatory and inhibitory responses to tones and noise. Units were then classified on the basis of their discharge patterns to short tone bursts at their best frequencies (BFs). Our results show that systematic relationships exist between the receptive-field properties and discharge patterns of cochlear nucleus units. Type I units give only excitatory responses to tones and noise. They are characterized by primary-like and chopper discharge patterns. Some units in the anteroventral cochlear nucleus have prepotentials in their spike waveforms. Prepotential units most often show primary-like discharge patterns, but prepotential units characterized by nonprimary-like discharge patterns are also found. Most prepotential units lack detectable inhibitory sidebands (type I), but two of the nonprimary-like prepotential units encountered in this study had inhibitory sidebands (type III). Type III units also give excitatory responses to BF tones, but they have inhibitory sidebands. Most type III units give chopper discharge patterns, and these units can be recorded throughout the cochlear nucleus. Some type III units in the dorsal cochlear nucleus give complex discharge patterns that can be described as a composite of the pauser pattern and other patterns. The complexity of these responses seems to increase as the amount of inhibition at BF increases. Type I/III units give excitatory responses to tones and noise, but have little or no spontaneous activity so they cannot be tested directly for inhibitory responses. Type I/III units typically show chopper discharge patterns. One group of type I/III units have rate-level functions with sloping saturation, suggesting that these may receive a predominance of input from low spontaneous rate auditory nerve fibers. Type II units are nonspontaneous and give excitatory responses to tones, but give weak or no responses to noise. While type II units are homogeneous as a group in terms of their response maps. BF rate-level functions, and responses to noise, they show a variety of discharge patterns in response to short tone bursts at BF.(ABSTRACT TRUNCATED AT 400 WORDS)

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