Effects of Stimulus Spectral Contrast on Receptive Fields of Dorsal Cochlear Nucleus Neurons

2007 ◽  
Vol 98 (4) ◽  
pp. 2133-2143 ◽  
Author(s):  
Lina A. J. Reiss ◽  
Sharba Bandyopadhyay ◽  
Eric D. Young
Keyword(s):  
Cochlear Nucleus ◽  
Discharge Rate ◽  
Receptive Fields ◽  
Poor Performance ◽  
Nerve Fibers ◽  
Dorsal Cochlear Nucleus ◽  
Good Prediction ◽  
Spectral Processing ◽  
Spectral Contrast ◽  
Spectrotemporal Receptive Field

Neurons in the dorsal cochlear nucleus (DCN) exhibit strong nonlinearities in spectral processing. Low-order models that transform the stimulus spectrum into discharge rate using a combination of first- and second-order weighting of the spectrum (quadratic models) usually fail to predict responses to novel stimuli for principal neurons in the DCN, even though they work well in ventral cochlear nucleus. Here we investigate the effects of spectral contrast on the performance of such models. Typically, the models fail for stimuli with natural-sound–like spectral contrasts (∼12 dB), but have good prediction performance at small (3-dB) contrasts. The weights also typically increase substantially in amplitude at smaller spectral contrast. These changes in weight size with contrast are partly inherited from similar effects seen in auditory nerve fibers, but there must be additional effects from inhibitory circuits in the DCN. These results provide insight into the reasons for the poor performance of spectrotemporal receptive field (STRF) models in predicting responses of auditory neurons. Because the general shapes of the weights do not change between low and high contrast, they also suggest that STRFs may capture meaningful properties of neural receptive fields, even though they do not do well at predicting responses.

scholarly journals Nonlinear temporal receptive fields of neurons in the dorsal cochlear nucleus

2013 ◽  
Vol 110 (10) ◽  
pp. 2414-2425 ◽  
Author(s):  
Sharba Bandyopadhyay ◽  
Eric D. Young
Keyword(s):  
Cochlear Nucleus ◽  
Receptive Fields ◽  
Sound Level ◽  
Second Order ◽  
Dorsal Cochlear Nucleus ◽  
Spectral Processing ◽  
Low Contrast ◽  
Response Properties ◽  
First Order ◽  
Order Components

Studies of the dorsal cochlear nucleus (DCN) have focused on spectral processing because of the complex spectral receptive fields of the DCN. However, temporal fluctuations in natural signals convey important information, including information about moving sound sources or movements of the external ear in animals like cats. Here, we investigate the temporal filtering properties of DCN principal neurons through the use of temporal weighting functions that allow flexible analysis of nonlinearities and time variation in temporal response properties. First-order temporal receptive fields derived from the neurons are sufficient to characterize their response properties to low-contrast (3-dB standard deviation) stimuli. Larger contrasts require the second-order terms. Allowing temporal variation of the parameters of the first-order model or adding a component representing refractoriness improves predictions by the model by relatively small amounts. The importance of second-order components of the model is shown through simulations of nonlinear envelope synchronization behavior across sound level. The temporal model can be combined with a spectral model to predict tuning to the speed and direction of moving sounds.

Responses to tones and noise of single cells in dorsal cochlear nucleus of unanesthetized cats

1976 ◽  
Vol 39 (2) ◽  
pp. 282-300 ◽  
Author(s):  
E. D. Young ◽  
W. E. Brownell
Keyword(s):  
Cochlear Nucleus ◽  
Discharge Rate ◽  
Single Cells ◽  
Broad Band ◽  
Inhibitory Response ◽  
Nerve Fibers ◽  
Dorsal Cochlear Nucleus ◽  
Type Ii ◽  
Type Iv ◽  
Band Noise

1. Single-unit responses in the dorsal cochlear nucleus of unanesthetized, decerebrate cats have been divided into two categoreis. These have been differentiated on the basis of responses to best-frequency tones. Type IV units responded to best-frequency tones with excitation from threshold to about 20 or 30 dB above threshold; at higher levels, their response was inhibitory. In a few cases, the excitatory area near threshold was not seen and in a few others, the response became excitatory again at high levels. Type IV units could be divided into two groups based on the length of time that inhibition was maintained in response to long tones. Type IV units are not seen in anesthetized cats. 2. Type II/III units responded to best-frequency tones of all levels with excitation. Nonmonotonic rate versus level functions were seen in type II/III units, but they were of much less drastic character; the discharge rate of nonmonotonic type II/III units was still well above spontaneous rate for tones 50 dB above threshold. Type II/III units defined in this way were found to have, on the average, lower rates of spontaneous activity and higher thresholds than type IV units. 3. Type II/III units responded weakly to broad-band noise in comparison to auditory nerve fibers and many of them did not respond at all to noise. Type IV units, with best frequencies above 0.9 kHz, gave excitatory responses to noise. 4. The inhibitory response areas of type IV units could be divided into two areas: a central inhibitory area in the vicinity of best frequency where on- and off-discharges and afterdischarges were seen; and inhibitory side bands at higher and lower frequencies where simple inhibitory responses were seen. In four units, it was possible to show that the central inhibitory area was converted to an excitatory area after administration of an anesthetic dose of pentobarbital. 5. Most type II/III and type IV units could be excited or inhibited by stimuli in the contralateral ear. Broad-band noise was a more effective contralateral stimulus than tones at the ipsilateral best frequency. 6. On the basis of the properties of type II/III and type IV cells, it is suggested that type II/III responses are recorded from interneurons which provide a large share of the inhibitory imput to type IV cells.

Spectral Integration by Type II Interneurons in Dorsal Cochlear Nucleus

1999 ◽  
Vol 82 (2) ◽  
pp. 648-663 ◽  
Author(s):  
George A. Spirou ◽  
Kevin A. Davis ◽  
Israel Nelken ◽  
Eric D. Young
Keyword(s):  
Auditory System ◽  
Cochlear Nucleus ◽  
Discharge Rate ◽  
Inhibitory Interneuron ◽  
Nerve Fibers ◽  
Broadband Noise ◽  
Dorsal Cochlear Nucleus ◽  
Type I ◽  
Type Ii ◽  
Inhibitory Processes

The type II unit is a prominent inhibitory interneuron in the dorsal cochlear nucleus (DCN), most likely recorded from vertical cells. Type II units are characterized by low rates of spontaneous activity, weak responses to broadband noise, and vigorous, narrowly tuned responses to tones. The weak responses of type II units to broadband stimuli are unusual for neurons in the lower auditory system and suggest that these units receive strong inhibitory inputs, most likely from onset-C neurons of the ventral cochlear nucleus. The question of the definition of type II units is considered here; the characteristics listed in the preceding text define a homogeneous type II group, but the boundary between this group and other low spontaneous rate neurons in DCN (type I/III units) is not yet clear. Type II units in decerebrate cats were studied using a two-tone paradigm to map inhibitory responses to tones and using noisebands of varying width to study the inhibitory processes evoked by broadband stimuli. Iontophoresis of bicuculline and strychnine and comparisons of two-tone responses between type II units and auditory nerve fibers were used to differentiate inhibitory processes occurring near the cell from two-tone suppression in the cochlea. For type II units, a significant inhibitory region is always seen with two-tone stimuli; the bandwidth of this region corresponds roughly to the previously reported excitatory bandwidth of onset-C neurons. Bandwidth widening experiments with noisebands show a monotonic decline in response as the bandwidth increases; these data are interpreted as revealing strong inhibitory inputs with properties more like onset-C neurons than any other response type in the lower auditory system. Consistent with these properties, iontophoresis of inhibitory antagonists produces a large increase in discharge rate to broadband noise, making tone and noise responses nearly equal.

Responses of ventral cochlear nucleus onset and chopper units as a function of signal bandwidth

1996 ◽  
Vol 75 (2) ◽  
pp. 780-794 ◽  
Author(s):  
A. R. Palmer ◽  
D. Jiang ◽  
D. H. Marshall
Keyword(s):  
Spectral Density ◽  
Cochlear Nucleus ◽  
Narrow Range ◽  
Discharge Rate ◽  
Nerve Fibers ◽  
Low Noise ◽  
Dorsal Cochlear Nucleus ◽  
Ventral Cochlear Nucleus ◽  
Wide Range ◽  
Response Area

1. The responses of units in the ventral cochlear nucleus in anesthetized guinea pigs have been measured to best-frequency tones, noise bands geometrically centered around the unit best frequency, and noise bands asymmetrically positioned around the best frequency. 2. Each unit isolated was characterized using peristimulus time histograms (PSTHs) to best-frequency tones at 20 and 50 dB suprathreshold, frequency-intensity response areas and rate-versus-level functions in response to best-frequency tones and wideband noise. The data reported here are derived from full analyses of 5 chopper units and 17 onset units. The onsets were divided into onset-I (OnI), onset-L (OnL), and onset-C (OnC) by the criteria described by Winter and Palmer: the PSTHs of OnI units show only an onset response, OnL units respond with a single spike at onset followed by a low level of sustained activity, and OnC units have PSTHs with one to four onset peaks and low levels of sustained discharge. 3. In response to geometrically centered noise bands of constant spectral density, the discharge of chopper units and one OnI unit increased over a relatively narrow range of bandwidths, corresponding to the equivalent rectangular bandwidth calculated from their response area, and then became constant. In contrast, OnL and OnC units showed increases in discharge rate with noise bandwidth over very wide ranges of bandwidth. The growth of the discharge rate with noise bandwidth was approximately linear on double logarithmic axes and therefore could be described by a power function with an exponent of 0.37. This relation held even for noise levels near threshold. 4. When noise bands with constant spectral density (at the input to the earphone) were presented with one edge fixed at the unit's best frequency, the discharge rate of most chopper units and the one OnI unit increased over a narrow range of bandwidths and then became constant. This pattern was observed irrespective of whether the second edge of the noise was progressively increased above, or decreased below, the best frequency. For two of the chopper units, in which lateral inhibitory sidebands could be demonstrated, increasing the noise bandwidth led first to increases and then to decreases in the discharge rate as the noise energy impinged upon the sideband. The chopper units act like energy detectors with a filter corresponding to their single tone response area, but, for some units, with the addition of inhibitory sidebands. 5. For the OnL and OnC units, increasing the noise bandwidth above or below best frequency caused progressive increases in the discharge rate over wide ranges of bandwidth. These increases occurred even for low noise spectral densities. The growth in discharge rate for these onset units was well fitted at all spectral density levels by power functions: one above best frequency and one below. At levels of the noise 40 dB above the unit threshold, the point at which the discharge rate reached 90% of its maximum was, on average, about 2 octaves below best frequency and 1 octave above. For some onset units, changes in the discharge rate were seen as the noise bandwidth was varied over about 14 kHz, which is about one-third of the total frequency hearing range of the guinea pig. 6. The data for onset units is consistent with the hypothesis that onset units in the ventral cochlear nucleus achieve their precision in the temporal domain by integration of the inputs from auditory nerve fibers with a wide range of best frequencies. The range of frequency over which onset units integrate frequency matches that of the inhibitory input to dorsal cochlear nucleus neurons, suggesting a possible role as an inhibitory interneuron.

Neuronal circuits associated with the output of the dorsal cochlear nucleus through fusiform cells

1994 ◽  
Vol 71 (3) ◽  
pp. 914-930 ◽  
Author(s):  
S. Zhang ◽  
D. Oertel
Keyword(s):  
Cochlear Nucleus ◽  
Auditory Nerve ◽  
Nerve Fibers ◽  
Dorsal Cochlear Nucleus ◽  
Resting Potential ◽  
Temporal Association ◽  
Common Source ◽  
Excitatory Postsynaptic Potential ◽  
Current Voltage ◽  
Synaptic Responses

1. Intracellular recordings were made from 21 anatomically identified fusiform cells in the dorsal cochlear nucleus (DCN) of mice in slices. The aim of the experiments was to dissect the synaptic responses to shocks of the auditory nerve to correlate functional characteristics with the different classes of synaptic inputs. 2. When depolarized from rest (-57 +/- 5 mV) with current pulses, fusiform cells fired regular, overshooting action potentials that were followed by two undershoots. The frequency of firing increased with the strength of injected current by between 100 and 300 spikes/s/nA. The current-voltage relationship rectified between 10 and 15 mV below the resting potential. The slopes of current-voltage relationships of fusiform cells in the range between the resting potential and 10 mV hyperpolarization indicated an average input resistance of 86 +/- 37 M omega. 3. In each of the labeled fusiform cells frequent, spontaneous inhibitory postsynaptic potentials (IPSPs) were recorded singly or in bursts. Some, but not all, IPSPs were preceded by a slowly rising excitatory postsynaptic potential (EPSP). The temporal association of spontaneous EPSPs and IPSPs suggests that they are driven by a common source, possibly granule cells. 4. Shocks to the auditory nerve evoked synaptic responses consisting of early (1 to approximately 10 ms) and late (approximately 10 to 100 ms) components. 6,7-Dinitroquinoxaline-2,3-dione (DNQX) at 20 to 40 microM eliminated all detectable excitation and all late IPSPs. Late bursts of IPSPs, therefore, are mediated through a polysynaptic pathway that includes a DNQX-sensitive stage. Strong shocks to the nerve root elicited single monosynaptic IPSPs, indicating that inhibitory interneurons have processes close to the auditory nerve. Strychnine at 0.5 microM eliminated all detectable inhibition. 6. Cuts through the posteroventral cochlear nucleus (PVCN), which severed the descending branches of auditory nerve fibers, eliminated early EPSPs and IPSPs leaving late, slowly rising EPSPs and bursts of IPSPs in responses to shocks of the auditory nerve. Late, slowly rising EPSPs and bursts of IPSPs, as well as monosynaptic IPSPs, could also be evoked by stimulating the anteroventral cochlear nucleus (AVCN). 7. Focal applications of glutamate evoked excitation and inhibition from many parts of a slice, with patterns varying among cells, indicating that fusiform cells receive inputs through several groups of interneurons.(ABSTRACT TRUNCATED AT 400 WORDS)

scholarly journals Receptive Field for Dorsal Cochlear Nucleus Neurons at Multiple Sound Levels

2007 ◽  
Vol 98 (6) ◽  
pp. 3505-3515 ◽  
Author(s):  
Sharba Bandyopadhyay ◽  
Lina A. J. Reiss ◽  
Eric D. Young
Keyword(s):  
Receptive Field ◽  
Cochlear Nucleus ◽  
Weighting Function ◽  
Sound Level ◽  
Second Order ◽  
Dorsal Cochlear Nucleus ◽  
Low Contrast ◽  
Spectral Contrast ◽  
Natural Stimuli ◽  
Frequency Components

Neurons in the dorsal cochlear nucleus (DCN) exhibit nonlinearities in spectral processing, which make it difficult to predict the neurons’ responses to stimuli. Here, we consider two possible sources of nonlinearity: nonmonotonic responses as sound level increases due to inhibition and interactions between frequency components. A spectral weighting function model of rate responses is used; the model approximates the neuron's rate response as a weighted sum of the frequency components of the stimulus plus a second-order sum that captures interactions between frequencies. Such models approximate DCN neurons well at low spectral contrast, i.e., when the SD (contrast) of the stimulus spectrum is limited to 3 dB. This model is compared with a first-order sum with weights that are explicit functions of sound level, so that the low-contrast model is extended to spectral contrasts of 12 dB, the range of natural stimuli. The sound-level–dependent weights improve prediction performance at large spectral contrast. However, the interactions between frequencies, represented as second-order terms, are more important at low spectral contrast. The level-dependent model is shown to predict previously described patterns of responses to spectral edges, showing that small changes in the inhibitory components of the receptive field can produce large changes in the responses of the neuron to features of natural stimuli. These results provide an effective way of characterizing nonlinear auditory neurons incorporating stimulus-dependent sensitivity changes. Such models could be used for neurons in other sensory systems that show similar effects.

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)

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.

scholarly journals Intrinsic and synaptic properties of vertical cells of the mouse dorsal cochlear nucleus

2012 ◽  
Vol 108 (4) ◽  
pp. 1186-1198 ◽  
Author(s):  
Sidney P. Kuo ◽  
Hsin-Wei Lu ◽  
Laurence O. Trussell
Keyword(s):  
Cochlear Nucleus ◽  
Action Potentials ◽  
Fluorescent Protein ◽  
Nerve Fibers ◽  
Dorsal Cochlear Nucleus ◽  
Mammalian Brain ◽  
Fusiform Cell ◽  
Whole Cell Patch Clamp ◽  
Green Fluorescent ◽  
Vertical Cell

Multiple classes of inhibitory interneurons shape the activity of principal neurons of the dorsal cochlear nucleus (DCN), a primary target of auditory nerve fibers in the mammalian brain stem. Feedforward inhibition mediated by glycinergic vertical cells (also termed tuberculoventral or corn cells) is thought to contribute importantly to the sound-evoked response properties of principal neurons, but the cellular and synaptic properties that determine how vertical cells function are unclear. We used transgenic mice in which glycinergic neurons express green fluorescent protein (GFP) to target vertical cells for whole cell patch-clamp recordings in acute slices of DCN. We found that vertical cells express diverse intrinsic spiking properties and could fire action potentials at high, sustained spiking rates. Using paired recordings, we directly examined synapses made by vertical cells onto fusiform cells, a primary DCN principal cell type. Vertical cell synapses produced unexpectedly small-amplitude unitary currents in fusiform cells, and additional experiments indicated that multiple vertical cells must be simultaneously active to inhibit fusiform cell spike output. Paired recordings also revealed that a major source of inhibition to vertical cells comes from other vertical cells.

Nonlinear Modeling of Auditory-Nerve Rate Responses to Wideband Stimuli

2005 ◽  
Vol 94 (6) ◽  
pp. 4441-4454 ◽  
Author(s):  
Eric D. Young ◽  
Barbara M. Calhoun
Keyword(s):  
Auditory Nerve ◽  
Transfer Functions ◽  
Discharge Rate ◽  
Nonlinear Modeling ◽  
Nerve Fibers ◽  
Second Order ◽  
Spectral Processing ◽  
Spectrum Shape ◽  
Level Function ◽  
Auditory Nerve Fibers

The spectral selectivity of auditory nerve fibers was characterized by a method based on responses to random-spectrum-shape stimuli. The method models the average discharge rate of fibers for steady stimuli and is based on responses to ≈100 noise-like stimuli with pseudorandom spectral levels in 1/8- or 1/16-octave frequency bins. The model assumes that rate is determined by a linear weighting of the spectrum plus a second-order weighting of all pairs of spectrum values within a certain frequency range of best frequency. The method allows prediction of rate responses to stimuli with arbitrary wideband spectral shapes, thus providing a direct test of the degree of linearity of spectral processing Auditory-nerve fibers are shown to rely mainly on linear weighting of the stimulus spectrum; however, significant second-order terms are present and are important in predicting responses to random-spectrum shape stimuli, although not for predicting responses to noise filtered with cat head-related transfer functions. The second-order terms weight the products of levels at identical frequencies positively and the products of different frequencies negatively. As such, they model both curvature in the rate versus level function and suppressive interactions between different frequency components. The first- and second-order characterizations derived in this method provide a measure of higher-order nonlinearities in neurons, albeit without providing information about temporal characteristics.

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