Role of frequency band integration in sharpening frequency tunings of the inferior colliculus neurons in the big brown bat, Eptesicus fuscus

2004 ◽  
Vol 49 (10) ◽  
pp. 1026 ◽  
Author(s):  
Feijian WU
Keyword(s):  
Inferior Colliculus ◽  
Frequency Band ◽  
Eptesicus Fuscus ◽  
Big Brown Bat

Neural Selectivity and Tuning for Sinusoidal Frequency Modulations in the Inferior Colliculus of the Big Brown Bat, Eptesicus fuscus

1997 ◽  
Vol 77 (3) ◽  
pp. 1595-1605 ◽  
Author(s):  
John H. Casseday ◽  
Ellen Covey ◽  
Benedikt Grothe
Keyword(s):  
Inferior Colliculus ◽  
High Frequency ◽  
Limited Range ◽  
Eptesicus Fuscus ◽  
Fm Signals ◽  
Big Brown Bat ◽  
Pure Tones ◽  
Sinusoidal Frequency Modulations ◽  
Frequency Modulations ◽  
Neural Selectivity

Casseday, John H., Ellen Covey, and Benedikt Grothe. Neural selectivity and tuning for sinusoidal frequency modulations in the inferior colliculus of the big brown bat, Eptesicus fuscus. J. Neurophysiol. 77: 1595–1605, 1997. Most communication sounds and most echolocation sounds, including those used by the big brown bat ( Eptesicus fuscus), contain frequency-modulated (FM) components, including cyclical FM. Because previous studies have shown that some neurons in the inferior colliculus (IC) of this bat respond to linear FM sweeps but not to pure tones or noise, we asked whether these or other neurons are specialized for conveying information about cyclical FM signals. In unanesthetized bats, we tested the response of 116 neurons in the IC to pure tones, noise with various bandwidths, single linear FM sweeps, sinusoidally amplitude-modulated signals, and sinusoidally frequency-modulated (SFM) signals. With the use of these stimuli, 20 neurons (17%) responded only to SFM, and 10 (9%) responded best to SFM but also responded to one other test stimulus. We refer to the total 26% of neurons that responded best to SFM as SFM-selective neurons. Fifty-nine neurons (51%) responded about equally well to SFM and other stimuli, and 27 (23%) did not respond to SFM but did respond to other stimuli. Most SFM-selective neurons responded to a limited range of modulation rates and a limited range of modulation depths. The range of modulationrates over which individual neurons responded was 5–170 Hz( n = 20). Thus SFM-selective neurons respond to low modulation rates. The depths of modulations to which the neurons responded ranged from ±0.4 to ±19 kHz ( n = 15). Half of the SFM-selective neurons did not respond to the first cycle of SFM. This finding suggests that the mechanism for selective response to SFM involves neural delays and coincidence detectors in which the response to one part of the SFM cycle coincides in time either with the response to a later part of the SFM cycle or with the response to the first part of the next cycle. The SFM-selective neurons in the IC responded to a lower and more limited range of SFM rates than do neurons in the nuclei of the lateral lemniscus of this bat. Because the FM components of biological sounds usually have low rates of modulation, we suggest that the tuning of these neurons is related to biologically important sound parameters. The tuning could be used to detect FM in echolocation signals, modulations in high-frequency sounds that are generated by wing beats of some beetles, or social communication sounds of Eptesicus.

Stimulus-specific adaptation in specialized neurons in the inferior colliculus of the big brown bat, Eptesicus fuscus

2012 ◽  
Vol 291 (1-2) ◽  
pp. 34-40 ◽  
Author(s):  
Jessica M. Thomas ◽  
Christina Morse ◽  
Lindsey Kishline ◽  
Alex O’Brien-Lambert ◽  
Ariel Simonton ◽  
...  
Keyword(s):  
Inferior Colliculus ◽  
Eptesicus Fuscus ◽  
Specific Adaptation ◽  
Big Brown Bat

Neural Tuning to Sound Duration in the Inferior Colliculus of the Big Brown Bat, Eptesicus fuscus

1997 ◽  
Vol 77 (5) ◽  
pp. 2360-2372 ◽  
Author(s):  
Daphna Ehrlich ◽  
John H. Casseday ◽  
Ellen Covey
Keyword(s):  
Inferior Colliculus ◽  
Stimulus Duration ◽  
Frequency Tuning ◽  
Temporal Structure ◽  
Eptesicus Fuscus ◽  
Broadband Noise ◽  
Inhibitory Input ◽  
Echolocation Calls ◽  
Big Brown Bat ◽  
Sound Duration

Ehrlich, Daphna, John H. Casseday, and Ellen Covey. Neural tuning to sound duration in the inferior colliculus of the big brown bat, Eptesicus fuscus. J. Neurophysiol. 77: 2360–2372, 1997. Neural tuning to different sound durations may be a useful filter for identification of certain sounds, especially those that are biologically important. The auditory midbrains of mammals and amphibians contain neurons that appear to be tuned to sound duration. In amphibians, neurons are tuned to durations of sound that are biologically important. The purpose of this study was to characterize responses of neurons in the inferior colliculus (IC) of the big brown bat, Eptesicus fuscus, to sounds of different durations. Our aims were to determine what percent of neurons are duration tuned and how best durations are correlated to durations of echolocation calls, and to examine response properties that may be relevant to the mechanism for duration tuning, such as latency and temporal firing pattern; we also examined frequency tuning and rate-level functions. We recorded from 136 single units in the central nucleus of the IC of unanesthetized bats. The stimuli were pure tones, frequency-modulated sweeps, and broadband noise. The criterion for duration tuning was an increase in spike count of ≥50% at some durations compared with others. Of the total units sampled, 36% were tuned to stimulus duration. All of these units were located in the caudal half of the IC. Best duration for most units ranged from <1 to 10 ms, but a few had best durations up to ≥20 ms. This range is similar to the range of durations of echolocation calls used by Eptesicus. All duration-tuned neurons responded transiently. The minimum latency was always longer than the best duration. Duration-tuned units have best durations and best frequencies that match the temporal structure and frequency range of the echolocation calls. Thus the results raise the hypothesis that neurons in the IC of Eptesicus, and probably the auditory midbrain of other vertebrates, are tuned to biologically important sound durations. We suggest a model for duration tuning consisting of three components: 1) inhibitory input that is correlated with the onset of the stimulus and is sustained for the stimulus duration; 2) transient excitation that is correlated with the offset of the stimulus; and 3) transient excitation that is correlated with the onset of the stimulus but is delayed in time relative to the onset of inhibition. For the neuron to fire, the two excitatory events must coincide in time; noncoincident excitatory events are not sufficient.

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