scholarly journals Representation of the spectral dominance region of pitch in the steady-state temporal discharge patterns of cochlear nucleus units

2008 ◽  
Vol 124 (5) ◽  
pp. 3038-3052 ◽  
Author(s):  
William P. Shofner
Keyword(s):  
Steady State ◽  
Cochlear Nucleus ◽  
Cochlear Nucleus Units ◽  
Discharge Patterns

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)

The representations of the steady-state vowel sound /e/ in the discharge patterns of cat anteroventral cochlear nucleus neurons

1990 ◽  
Vol 63 (5) ◽  
pp. 1191-1212 ◽  
Author(s):  
C. C. Blackburn ◽  
M. B. Sachs
Keyword(s):  
Steady State ◽  
Cochlear Nucleus ◽  
Nerve Fibers ◽  
Stimulus Level ◽  
Complex Stimulus ◽  
Vowel Sound ◽  
Stimulus Representation ◽  
Anteroventral Cochlear Nucleus ◽  
Discharge Patterns ◽  
Bushy Cells

1. We have recorded the responses of neurons in the anteroventral cochlear nucleus (AVCN) of barbiturate-anesthetized cats to the synthetic, steady-state-vowel sound /e/, presented over a range of stimulus intensities. 2. The responses of (putative) spherical bushy cells [primary-like (Pri) units] to the vowel resemble those of auditory-nerve fibers (ANFs) in terms of both rate and temporal encoding at low and moderate stimulus levels. It was not possible to study the responses of most Pri units at the highest stimulus level because of the large neurophonic component present in recordings from most primarylike units at higher stimulus levels. 3. The responses of many (putative) globular bushy cells [primarylike with notch (PN) units] to the vowel resemble those of ANFs; however, there appears to be greater heterogeneity in the responses of units in the PN population than in the Pri population in terms of both temporal and rate encoding. 4. Populations of stellate cells (chopper units) have degraded representations of the temporal information in ANF population discharge patterns in response to the vowel; this is consistent with the responses of these units to pure tones. Both regular (ChS) and irregular (ChT) chopper subpopulations, however, maintain better rate-place representations of the vowel spectrum than does the population of ANFs as a whole. The rate-place representations of the vowel spectrum by both chopper populations closely resemble those of low and medium spontaneous rate ANFs at most stimulus levels. 5. The data presented in this paper suggest that a functional partition of the AVCN chopper population could yield two distinct rate representations in response to a complex stimulus: one that is graded with stimulus level (over a 30 to 40 dB range) and that, even at rate saturation, maintains a "low contrast" stimulus representation; and a second that maintains a robust, "high contrast" stimulus representation at all levels but that confers less information about stimulus level.

Responses of Cochlear Nucleus Units in the Chinchilla to Iterated Rippled Noises: Analysis of Neural Autocorrelograms

1999 ◽  
Vol 81 (6) ◽  
pp. 2662-2674 ◽  
Author(s):  
William P. Shofner
Keyword(s):  
Cochlear Nucleus ◽  
Time Lag ◽  
Time Lags ◽  
Complex Sounds ◽  
Related Information ◽  
Complex Stimuli ◽  
Temporal Encoding ◽  
Cochlear Nucleus Units ◽  
Stimulus Features ◽  
Discharge Patterns

Responses of cochlear nucleus units in the chinchilla to iterated rippled noises: analysis of neural autocorrelograms. Temporal encoding of stimulus features related to the pitch of iterated rippled noises was studied for single units in the chinchilla cochlear nucleus. Unlike other periodic complex sounds that produce pitch, iterated rippled noises have neither periodic waveforms nor highly modulated envelopes. Infinitely iterated rippled noise (IIRN) is generated when wideband noise (WBN) is delayed (τ), attenuated, and then added to (+) or subtracted from (−) the undelayed WBN through positive feedback. The pitch of IIRN[+, τ, −1 dB] is at 1/τ, whereas the pitch of IIRN[−, τ, −1 dB] is at 1/2τ. Temporal responses of cochlear nucleus units were measured using neural autocorrelograms. Synchronous responses as shown by peaks in neural autocorrelograms that occur at time lags corresponding to the IIRN τ can be observed for both primarylike and chopper unit types. Comparison of the neural autocorrelograms in response to IIRN[+, τ, −1 dB] and IIRN[−, τ, −1 dB] indicates that the temporal discharge of primarylike units reflects the stimulus waveform fine structure, whereas the temporal discharge patterns of chopper units reflect the stimulus envelope. The pitch of IIRN[±, τ, −1 dB] can be accounted for by the temporal discharge patterns of primarylike units but not by the temporal discharge of chopper units. To quantify the temporal responses, the height of the peak in the neural autocorrelogram at a given time lag was measured as normalized rate. Although it is well documented that chopper units give larger synchronous responses than primarylike units to the fundamental frequency of periodic complex stimuli, the largest normalized rates in response to IIRN[+, τ, −1 dB] were obtained for primarylike units, not chopper units. The results suggest that if temporal encoding is important in pitch processing, then primarylike units are likely to be an important cochlear nucleus subsystem that carries the pitch-related information to higher auditory centers.

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.

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.

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