Classification of unit types in the anteroventral cochlear nucleus: PST histograms and regularity analysis

1989 ◽  
Vol 62 (6) ◽  
pp. 1303-1329 ◽  
Author(s):  
C. C. Blackburn ◽  
M. B. Sachs
Keyword(s):  
Cochlear Nucleus ◽  
Interspike Interval ◽  
Discharge Rate ◽  
Low Frequency ◽  
Initial Response ◽  
Instantaneous Rate ◽  
Anteroventral Cochlear Nucleus ◽  
The Mean ◽  
Spike Latency

1. The responses of neurons in the anteroventral cochlear nucleus (AVCN) of barbiturate-anesthetized cats are characterized with regard to features of their responses to short tone bursts (STBs; 25 ms). A "decision tree" is presented to partition AVCN units on the basis of post-stimulus time histogram (PSTH) shape, first spike latency, and discharge rate and regularity calculated as functions of time during responses to STBs. The major classes of AVCN units (primary-like, primary-like-with-notch, chopper, and onset) have been described previously; in this paper, special attention is given to clarifying and systematizing boundaries between classes. Certain types of "unusual" units that may be confused with units in one of the major classes are also examined. 2. When STBs are presented synchronously (constant phase at onset), PSTHs of responses to very-low-frequency (less than 1.0 kHz) tones are difficult if not impossible to resolve into the classes listed above because all unit types phase-lock to low-frequency tones. However, when STBs are presented asynchronously, the responses of units with low best frequencies can be categorized on the basis of PSTH shape and first spike latency. 3. Primary-like, primary-like-with-notch, and onset units are distinguished primarily on the basis of PSTH shape. These three unit types have comparable minimum first spke latencies and synchronization to tones. One type of "unusual" response poses a particular hazard with respect to the generation of uncontaminated primary-like populations. Such "unusual" units have PSTHs that appear primary-like; these units are, however, distinguished by their unusually long first spike latencies. Unlike primary-like units, these "unusual" units show extremely poor synchronization to tones. 4. Chopper units are defined as having an initial response that is highly regular, resulting in the characteristic multimodal PSTH. "Unusual" units with multimodal PSTHs but whose initial responses are not highly regular (measured by the reproducibility of the initial firing pattern in response to multiple repetitions of a STB) are eliminated from the chopper populations. 5. In barbiturate-anesthetized cats, at least three patterns of chopper response can be distinguished on the basis of temporal patterns of rate and regularity adaptation. "Sustained" choppers show no adaptation of instantaneous rate (measured by the inverse of the mean interspike interval), and their discharge remains highly regular throughout the response. "Transiently adapting" choppers undergo a very rapid (less than 10 ms) decrease in instantaneous rate accompanied by a sharp increase in discharge irregularity.(ABSTRACT TRUNCATED AT 400 WORDS)

Regularity and latency of units in ventral cochlear nucleus: implications for unit classification and generation of response properties

1988 ◽  
Vol 60 (1) ◽  
pp. 1-29 ◽  
Author(s):  
E. D. Young ◽  
J. M. Robert ◽  
W. P. Shofner
Keyword(s):  
Standard Deviation ◽  
Cochlear Nucleus ◽  
Interspike Interval ◽  
Rate Adaptation ◽  
Stellate Cells ◽  
Instantaneous Rate ◽  
Ventral Cochlear Nucleus ◽  
Bushy Cell ◽  
Low Pass ◽  
The Mean

1. The responses of neurons in the ventral cochlear nucleus (VCN) of decerebrate cats are described with regard to their regularity of discharge and latency. Regularity is measured by estimating the mean and standard deviation of interspike intervals as a function of time during responses to short tone bursts (25 ms). This method extends the usual interspike-interval analysis based on interval histograms by allowing the study of temporal changes in regularity during transient responses. The coefficient of variation (CV), equal to the ratio of standard deviation to mean interspike interval, is used as a measure of irregularity. Latency is measured as the mean and standard deviation of the latency of the first spike in response to short tone bursts, with 1.6-ms rise times. 2. The regularity and latency properties of the usual PST histogram response types are shown. Five major PST response type classes are used: chopper, primary-like, onset, onset-C, and unusual. The presence of a prepotential in a unit's action potentials is also noted; a prepotential implies that the unit is recorded from a bushy cell. 3. Units with chopper PST histograms give the most regular discharge. Three varieties of choppers are found. Chop-S units (regular choppers) have CVs less than 0.35 that are approximately constant during the response; chop-S units show no adaptation of instantaneous rate, as measured by the inverse of the mean interspike interval. Chop-T units have CVs greater than 0.35, show an increase in irregularity during the response and show substantial rate adaptation. Chop-U units have CVs greater than 0.35, show a decrease in irregularity during the response, and show a variety of rate adaptation behaviors, including negative adaptation (an increase in rate during a short-tone response). Irregular choppers (chop-T and chop-U units) rarely have CVs greater than 0.5. Choppers have the longest latencies of VCN units; all three groups have mean latencies at least 1 ms longer than the shortest auditory nerve (AN) fiber mean latencies. 4. Chopper units are recorded from stellate cells in VCN (35, 42). Our results for chopper units suggest a model for stellate cells in which a regularly firing action potential generator is driven by the summation of the AN inputs to the cell, where the summation is low-pass filtered by the membrane capacitance of the cell.(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.

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)

Inhibitory inputs modulate discharge rate within frequency receptive fields of anteroventral cochlear nucleus neurons

1994 ◽  
Vol 72 (5) ◽  
pp. 2124-2133 ◽  
Author(s):  
D. M. Caspary ◽  
P. M. Backoff ◽  
P. G. Finlayson ◽  
P. S. Palombi
Keyword(s):  
Cochlear Nucleus ◽  
Discharge Rate ◽  
Cell Types ◽  
Dorsal Cochlear Nucleus ◽  
Superior Olivary Complex ◽  
Gamma Aminobutyric Acid ◽  
Excitatory Response ◽  
Morphological Studies ◽  
Anteroventral Cochlear Nucleus ◽  
Response Area

1. The amino acid neurotransmitters gamma-aminobutyric acid (GABA) and glycine function as inhibitory neurotransmitters associated with nonprimary inputs onto spherical bushy and stellate cells, two principal cell types located in the anteroventral cochlear nucleus (AVCN). These neurons are characterized by primary-like (including phase-locked) and chopper temporal response patterns, respectively. 2. Inhibition directly adjacent to the excitatory response area has been hypothesized to sharpen or limit the breadth of the tonal frequency receptive field. This study was undertaken to test whether GABA and glycine circuits function primarily to sharpen the lateral edges of the tonal excitatory response area or to modulate discharge rate within central portions of the excitatory response area of AVCN neurons. 3. To test this, iontophoretic application of the glycineI antagonist, strychnine, or the GABAA antagonist, bicuculline, was used to block inhibitory inputs after obtaining control families of isointensity contours (response areas) from extracellularly recorded AVCN neurons. 4. Blockade of GABA and/or glycine inputs was found to increase discharge rate primarily within the excitatory response area of neurons displaying chopper and primary-like temporal responses with little or no change in bandwidth or in off-characteristic frequency (CF) discharge rate. 5. The principal sources of inhibitory inputs onto AVCN neurons are cells located in the dorsal cochlear nucleus and superior olivary complex, which appear to be tonotopically matched to their targets. In agreement with these morphological studies, the data presented in this paper suggest that most GABA and/or glycine inhibition is tonotopically aligned with excitatory inputs. 6. These findings support models that suggest that GABA and/or glycine inputs onto AVCN neurons are involved in circuits that adjust gain to enable the detection of signals in noise by enhancing signal relative to background.

Enhancement of neural synchronization in the anteroventral cochlear nucleus. II. Responses in the tuning curve tail

1994 ◽  
Vol 71 (3) ◽  
pp. 1037-1051 ◽  
Author(s):  
P. X. Joris ◽  
P. H. Smith ◽  
T. C. Yin
Keyword(s):  
Cochlear Nucleus ◽  
Tuning Curve ◽  
Phase Locking ◽  
Low Frequency ◽  
Companion Paper ◽  
Acoustic Stimuli ◽  
Anteroventral Cochlear Nucleus ◽  
Temporal Features ◽  
Peripheral Auditory System ◽  
Trapezoid Body

1. Discharges of neurons in the peripheral auditory system contain information about the temporal features of acoustic stimuli. Phase-locking of neurons in the anteroventral cochlear nucleus (AVCN) is usually reported to be less robust than in auditory nerve (AN) fibers, which provide their major input. In a companion paper we reported that some cells in AVCN of the cat show enhanced phase-locking compared with the AN when stimulated at the frequency to which they are most sensitive [characteristic frequency (CF)]. We called neurons "high-sync" when they showed vector strengths (R, a measure of phase-locking) > or = 0.9. Here we report phase-locking properties to stimuli at frequencies below CF. 2. Horseradish peroxidase-filled glass micropipettes or metal microelectrodes were inserted into the trapezoid body (TB), which is the large output tract of the AVCN. Acoustically driven fibers were classified on the basis of the shape of the poststimulus time (PST) histograms to short tone bursts at CF. We then presented low-frequency tones of increasing SPL and determined the maximum R value at 500 Hz (R500) for each fiber. Using the same experimental protocol we studied phase-locking in the ANs of two animals because maximal R values at the tuning curve tail have not been reported for AN fibers. 3. Although phase-locking in AN fibers is usually assumed to be independent of CF, we found that fibers with CF > 2 kHz tended to have higher R500 values than fibers with CF < or = 2 kHz. Moreover, R500 was > or = 0.9 in 20% (42 of 196) of the fibers studied and could be as high as 0.95. This population of fibers was defined as having "high-sync tails" and consisted almost entirely of fibers with low or medium spontaneous rate. 4. High-CF TB fibers stimulated at 500 Hz showed very high phase-locking. High-sync tails (R500 > or = 0.9) were found in 41 of 70 TB fibers. For a subset of these fibers (1/3 in total: 23 of 70) phase-locking was higher than is ever observed in the AN (R500 > or = 0.95); these fibers were defined as showing synchronization "enhancement." Virtually all fibers showing synchronization enhancement had primary-like-with-notch (PLN) PST histograms. Chopper and primary-like fibers showed high-sync tails for CFs > 3 kHz. 5. Synchronization filter functions were obtained for high-CF AN fibers by determining maximum synchronization for a range of stimuli below CF.(ABSTRACT TRUNCATED AT 400 WORDS)

GABAA receptor antagonist bicuculline alters response properties of posteroventral cochlear nucleus neurons

1992 ◽  
Vol 67 (3) ◽  
pp. 738-746 ◽  
Author(s):  
P. S. Palombi ◽  
D. M. Caspary
Keyword(s):  
Receptor Antagonist ◽  
Gabaa Receptor ◽  
Cochlear Nucleus ◽  
Discharge Rate ◽  
Response Patterns ◽  
Excitatory Response ◽  
Gabaa Receptor Antagonist ◽  
Intensity Functions ◽  
Spike Latency ◽  
Post Onset

1. The role of GABAergic inhibitory inputs onto posteroventral cochlear nucleus (PVCN) neurons in the anesthetized chinchilla was investigated through iontophoretic application of the GABAA receptor agonist muscimol and the GABAA receptor antagonist bicuculline. The majority of the neurons studied displayed phasic temporal response patterns. 2. All the neurons were sensitive to bicuculline and displayed an increase in discharge rate, which was greatest during the post-onset portion of the response. Most of the tested neurons were also sensitive to muscimol, which appeared to mimic the putative effect of endogenous GABA. 3. Bicuculline reduced the average first-spike latency and the average variability of the first-spike latency. Muscimol had the opposite effect. 4. Bicuculline did not significantly alter the threshold but rather increased discharge rate at suprathreshold intensities. 5. The width of the excitatory response area was not significantly increased by application of bicuculline. The increase in discharge rate occurred within the units' excitatory response areas. 6. The shape of the rate-intensity functions was not altered by bicuculline application. 7. We conclude that GABAergic inhibitory inputs control the post-onset discharge rate of some PVCN neurons. They may suppress tonic activity, resulting in more phasic discharge patterns.

scholarly journals Temporal Measures and Neural Strategies for Detection of Tones in Noise Based on Responses in Anteroventral Cochlear Nucleus

2006 ◽  
Vol 96 (5) ◽  
pp. 2451-2464 ◽  
Author(s):  
Yan Gai ◽  
Laurel H. Carney
Keyword(s):  
Cochlear Nucleus ◽  
Dynamic Range ◽  
Discharge Rate ◽  
Broadband Noise ◽  
Auditory Neuron ◽  
Tone Frequency ◽  
Detection Thresholds ◽  
Anteroventral Cochlear Nucleus ◽  
Temporal Measures ◽  
Tone Level

To examine possible neural strategies for the detection of tones in broadband noise, single-neuron extracellular recordings were obtained from the anteroventral cochlear nucleus (AVCN) in anesthetized gerbils. Detection thresholds determined by average discharge rate and several temporal metrics were compared with previously reported psychophysical detection thresholds in cats ( Costalupes 1985 ). Because of their limited dynamic range, the average discharge rates of single neurons failed to predict psychophysical detection thresholds for relatively high-level noise at all measured characteristic frequencies (CFs). However, temporal responses changed significantly when a tone was added to a noise, even for neurons with flat masked rate-level functions. Three specific temporal analyses were applied to neural responses to tones in noise. First, temporal reliability, a measure of discharge time consistency across stimulus repetitions, decreased with increasing tone level for most AVCN neurons at all measured CFs. Second, synchronization to the tone frequency, a measure of phase-locking to the tone, increased with tone level for low-CF neurons. Third, rapid fluctuations in the poststimulus time histograms (PSTHs) decreased with tone level for a number of neurons at all CFs. For each of the three temporal measures, some neurons had detection thresholds at or below psychophysical thresholds. A physiological model of a higher-stage auditory neuron that received simple excitatory and inhibitory inputs from AVCN neurons was able to extract the PSTH fluctuation information in a form of decreased rate with tone level.

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