Spectral and temporal response patterns of single units in the chinchilla dorsal cochlear nucleus

1987 ◽  
Vol 96 (2) ◽  
pp. 406-419 ◽  
Author(s):  
James A. Kaltenbach ◽  
James C. Saunders
Keyword(s):  
Cochlear Nucleus ◽  
Dorsal Cochlear Nucleus ◽  
Single Units ◽  
Response Patterns ◽  
Temporal Response

Temporal and mean rate discharge patterns of single units in the dorsal cochlear nucleus of the anesthetized guinea pig

1996 ◽  
Vol 76 (3) ◽  
pp. 1667-1688 ◽  
Author(s):  
S. E. Stabler ◽  
A. R. Palmer ◽  
I. M. Winter
Keyword(s):  
Steady State ◽  
Cochlear Nucleus ◽  
Interspike Interval ◽  
Discharge Rate ◽  
Sound Level ◽  
Dorsal Cochlear Nucleus ◽  
Single Units ◽  
Type I ◽  
Rate Level ◽  
Type Iv

1. We examined the temporal and mean rate discharge characteristics of 514 single units recorded extracellularly from the dorsal cochlear nucleus (DCN) of anesthetized guinea pigs. A mean rate response area (receptive field) was measured for the majority of units in this study. Each response area was placed in one of seven categories (type I to type V and the intermediate types I/III and IV-T) as defined by previous workers. The shape of the best frequency (BF) rate-level function has been used to aid in the distinction between type IV and type IV-T units, and the classification of type II units is based on their relative response to noise and tone bursts. 2. The threshold of single units was normalized to the cochlear action potential (CAP) threshold (a negative relative threshold indicates that the unit's threshold was more sensitive than the corresponding CAP threshold). There were significant differences (P < 0.05; 1-way analysis of variance--Duncan test) between the mean relative thresholds of type IV units (-12 dB) and those of type I (-6.52 dB), type II (-3 dB), and type I/III units (-4.25 dB). There were also significant differences between the relative thresholds of types III and IV-T and those of types I/III and II. 3. Rate-level functions at a unit's BF were divided into groups according to shape and degree of nonmonotonicity. Six units responded with a decrease in firing rate at all suprathreshold sound levels. However, most units increased their discharge rate over approximately the first 20 dB above BF threshold. Units were further subdivided by the change in slope 20 dB above BF threshold. The majority of units (60%) showed monotonic increases in discharge rate with sound level: some rate-level functions clearly resembled the sloping saturation rate-level functions observed in intermediate-threshold auditory nerve fibers. An unexpected finding was the relatively large number of nonmonotonic rate-level functions (40%). Among a relatively homogenous group of projection neurons (predominantly type IV and pause/build units) with nonmonotonic rate-level functions, the range of "best intensities" (the sound level evoking the highest discharge rate) was < 50 dB. This range of best intensities is narrower than found in higher auditory nuclei. 4. Units were also classified by their temporal activity pattern in response to suprathreshold BF tones. The most common pattern identified is the pause/build pattern (n = 294). This temporal activity pattern has been associated with the principal output neuron of the DCN, the fusiform cell. Our definition of pause/build units includes units with an almost constant steady-state discharge rate. Nonmonotonic rate-level functions were observed in 42% (99 of 233) of pause/build units. A measure of discharge regularity (the SD of the interspike interval/mean interspike interval: coefficient of variation, CV) revealed that the majority (82%) of units classified as pause/build and with steady-state discharge rates > 75 spikes/s (n = 142) were characterized by regular discharge patterns (CV = 0.41 +/- 0.15, mean +/- SD). 5. Units characterized by chopper or onset-type discharges were the next most frequently encountered units. The chopper units (n = 75) showed a regular discharge (CV = 0.39 +/- 0.17) similar to that found in recordings from the ventral division of the cochlear nucleus (VCN). One difference between many chopper units in the DCN compared with those recorded in the VCN was the relatively high value (> 5 ms) of the mean interspike interval (and thus the low steady-state discharge rate). The majority (44 of 59; 75%) of chopper units had monotonic rate-level functions. Onset units (n = 47) may represent several response types, linked by the predominance of discharges in response to stimulus onset, and the majority of onset units reported here bear little resemblance to onset units recorded in the VCN of the guinea pig. Approximately 10% of units did not fit easily into any of th

Classification of response patterns in cochlear nucleus of barn owl: correlation with functional response properties

1985 ◽  
Vol 53 (1) ◽  
pp. 201-216 ◽  
Author(s):  
W. E. Sullivan
Keyword(s):  
Stimulus Intensity ◽  
Cochlear Nucleus ◽  
Interspike Interval ◽  
Barn Owl ◽  
Dorsal Cochlear Nucleus ◽  
Response Patterns ◽  
Tyto Alba ◽  
Rate Intensity ◽  
Discharge Patterns ◽  
Intensity Functions

Response patterns of neurons in the cochlear nuclei of the barn owl (Tyto alba) were studied by obtaining poststimulus time histograms (PSTHs) and interspike interval histograms for the response to short tone bursts at the neuron's characteristic frequency. The observed response patterns can be classified according to the scheme developed for neurons of the mammalian cochlear nuclear complex (22). Neurons of the magnocellular cochlear nucleus (n. magnocellularis), which respond in a phase-locked manner to sinusoidal signals and do not show large increases in spike discharge rate with changes in stimulus intensity (26), have "primarylike" (PSTH) discharge patterns and broad interspike interval histograms. This indicates that magnocellular neurons have irregular firing patterns, with the timing of individual spikes being dependent on the phase of the stimulus waveform. Neurons of the angular cochlear nucleus (n. angularis), which show little or no phase-locking and large increases in spike rate with increasing intensity (26), had almost exclusively "transient chopper" discharge patterns. The interspike interval histograms of these angular units are sharp, indicating that their discharge is very regular. At the onset of the response where the chopper pattern is observed, both discharge regularity and rate-intensity sensitivity are at their maximum levels. Several "onset" units were isolated in the angular cochlear nucleus, but no "pauser" or "buildup" units were seen. Also, all of the units in the angular nucleus had monotonic rate-intensity functions. Thus no neural response patterns typical of mammalian dorsal cochlear nucleus units were observed. The relationship of response pattern type to neural function is discussed in relation to the acoustic cues used by the owl for two-dimensional sound localization. The primarylike, phase-locked discharge of magnocellular units is undoubtedly involved in the analysis of interaural differences in stimulus phase, which the owl uses for horizontal localization. There is strong evidence suggesting that the angular nucleus is involved in processing stimulus intensity information, which is important for determining sound elevation (due to asymmetries in vertical directionality of the owl's external ears). The predominant chopper patterns seen in the angular nucleus suggest that in the owl, this response type is correlated with stimulus intensity processing. Similarities in both anatomy and physiology suggest that the magnocellular nucleus is analogous to the spherical cell or bushy cell population of the anterior division of the mammalian anteroventral cochlear nucleus.(ABSTRACT TRUNCATED AT 400 WORDS)

Responses of single units in cerebellar vermis of the cat to monaural and binaural stimuli

1975 ◽  
Vol 38 (2) ◽  
pp. 418-429 ◽  
Author(s):  
L. M. Aitkin ◽  
J. Boyd
Keyword(s):  
Inferior Colliculus ◽  
Cochlear Nucleus ◽  
Single Units ◽  
Intensity Difference ◽  
Cerebellar Neurons ◽  
Monaural Stimulation ◽  
Sustained Responses ◽  
Maximal Discharge ◽  
Onset Responses ◽  
Stimulation Of

The responses of 146 cerebellar neurons to tone stimuli were studied in 29 cats anesthetized with chloralose-urethan and in 7 decerebrate preparations. Units were classified as onset or sustained firing. Onset spikes occurred on stimulation of either ear and showed binaural facilitation, while sustained discharges were frequently only excited by monaural stimulation. The latent periods of sustained discharges appeared to be shorter than those of onset responses, and sustained discharges were also more sharply tuned than the onset units. Evidence was presented suggesting that onset responses reflected input from the inferior colliculus and sustained responses, the cochlear nucleus. The sterotyped facilitatory behavior of onset units suggested that a maximal discharge might occur if sounds were of equal intensity at each ear; 26 neurons were examined with variable interaural time or intensity differences and 10 of these exhibited maximal firing when the interaural time and intensity difference was zero--i.e., if the sound was located directly in front of the head.

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