Response Properties and Location of Neurons Selective for Sinusoidal Frequency Modulations in the Inferior Colliculus of the Big Brown Bat

2007 ◽  
Vol 98 (3) ◽  
pp. 1364-1373 ◽  
Author(s):  
Qi Yue ◽  
John H. Casseday ◽  
Ellen Covey
Keyword(s):  
Spontaneous Activity ◽  
Inferior Colliculus ◽  
Specific Area ◽  
High Threshold ◽  
Response Properties ◽  
Big Brown Bat ◽  
Animal Vocalizations ◽  
Modulation Rate ◽  
Sinusoidal Frequency Modulations ◽  
Frequency Modulations

Most animal vocalizations, including echolocation signals used by bats, contain frequency-modulated (FM) components. Previous studies have described a class of neurons in the inferior colliculus (IC) of the big brown bat that respond exclusively to sinusoidally frequency modulated (SFM) signals and fail to respond to pure tones, noise, amplitude-modulated tones, or single FM sweeps. The aims of this study were to further characterize these neurons' response properties and to determine whether they are localized within a specific area of the IC. We recorded extracellularly from 214 neurons throughout the IC. Of these, 47 (22%) responded exclusively to SFM. SFM-selective cells were tuned to relatively low carrier frequencies (9–50 kHz), low modulation rates (20–210 Hz), and shallow modulation depths (3–10 kHz). Most had extremely low thresholds, with an average of 16.5 ± 7.6 dB SPL, and 89% had upper thresholds and closed response areas. For SFM-selective cells with spontaneous activity, the spontaneous activity was eliminated when sound amplitude exceeded their upper threshold and resumed after the stimulus was over. These findings suggest that SFM-selective cells receive low-threshold excitatory inputs and high-threshold inhibitory inputs. SFM-selective cells were clustered in the rostrodorsal part of the IC. Within this area, best modulation rate appeared to be correlated with best carrier frequency and depth within the IC.

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.

scholarly journals GABAergic and Glycinergic Inhibition Sharpens Tuning for Frequency Modulations in the Inferior Colliculus of the Big Brown Bat

1998 ◽  
Vol 80 (1) ◽  
pp. 71-82 ◽  
Author(s):  
U. Koch ◽  
B. Grothe
Keyword(s):  
Receptor Antagonist ◽  
Inferior Colliculus ◽  
Modulation Frequency ◽  
Drug Application ◽  
Direction Selectivity ◽  
Neuronal Inhibition ◽  
Big Brown Bat ◽  
Glycinergic Inhibition ◽  
Frequency Modulations ◽  
Lower Cutoff

Koch, U. and B. Grothe. GABAergic and glycinergic inhibition sharpens tuning for frequency modulations in the inferior colliculus of the big brown bat. J. Neurophysiol. 80: 71–82, 1998. Discrimination of amplitude and frequency modulated sounds is an important task of auditory processing. Experiments have shown that tuning of neurons to sinusoidally frequency- and amplitude-modulated (SFM and SAM, respectively) sounds becomes successively narrower going from lower to higher auditory brain stem nuclei. In the inferior colliculus (IC), many neurons are sharply tuned to the modulation frequency of SFM sounds. The purpose of this study was to determine whether GABAergic or glycinergic inhibition is involved in shaping the tuning for the modulation frequency of SFM sounds in IC neurons of the big brown bat ( Eptesicus fuscus). We recorded the response of 56 single units in the central nucleus of the IC to SFM stimuli before and during the application of the γ-aminobutyric acid-A (GABAA) receptor antagonist bicuculline or the glycine receptor antagonist strychnine. To evaluate tuning to the modulation frequency, the normalized spike count (normalized according to the maximal response for each condition tested) was plotted versus the modulation frequency and the upper and lower 50% cutoff points were determined. Bicuculline increased the upper cutoff in 46% of the neurons by ≥25%. The lower cutoff decreased in 48% of the neurons tested. In some neurons (∼30%), a sharpening of the tuning by bicuculline was observed. Strychnine induced an increase of the upper cutoff in almost half of the neurons. Compared with bicuculline these changes were smaller. The lower cutoff decreased in 50% of the neurons with strychnine. The synchronization coefficient (SC) was calculated and compared for three modulation frequencies (50, 100, and 200 Hz) between predrug and drug condition. For all neurons, synchronization decreased ( n = 36) or did not change ( n = 26) during drug application. This was mainly an effect of the prolonged discharge in response to each cycle. Under predrug conditions, many neurons exhibited selectivity to the direction of the FM, hence they only responded once to each cycle. In a minority of neurons, direction selectivity was abolished by drug application. The main finding was that neuronal inhibition sharpens tuning to the modulation frequency in the majority of neurons. In general, changes induced by bicuculline or strychnine were comparable.

Chronic Estrogen Sensitizes a Subset of Mechanosensitive Afferents Innervating the Uterine Cervix

2005 ◽  
Vol 93 (4) ◽  
pp. 2167-2173 ◽  
Author(s):  
Baogang Liu ◽  
James C. Eisenach ◽  
Chuanyao Tong
Keyword(s):  
Spontaneous Activity ◽  
Uterine Cervix ◽  
Firing Frequency ◽  
High Threshold ◽  
Group 13 ◽  
Ovx Rats ◽  
Afferent Fibers ◽  
Low Threshold ◽  
Group 5 ◽  
Afferent Response

Estrogen increases reflex nocifensive responses to distension of the uterus and the urinary bladder, but estrogen's effects on afferent response to distension of the uterine cervix, the site of obstetric and some gynecologic pain, has not been studied. Here, single fiber recording of hypogastric nerve responses to uterine cervical distension were obtained from ovariectomized (OVX) rats and OVX rats treated with estrogen (ES). Spontaneous activity was greater in the ES group (13 of 24 units; 54%) than in the OVX group (6 of 27 units; 22%). ES differentially altered the response of low- and high-threshold units to distension. For high-threshold units, firing frequency was increased two- to fourfold with 60–100 gm distension in ES compared with OVX groups ( P < 0.05). In contrast, the response of low-threshold units to distension was not altered by ES. About one-half of units tested in each group responded to a temperature increase from 35 to 49°C. A greater proportion of thermosensitive units were also mechanosensitive in the ES group (7 of 8 afferents, 88%) than in the OVX group (5 of 11 afferents, 45%). Acute application of ES in OVX rats failed to evoke or increase distension-induced responses. These data show the polymodal nature of afferent fibers innervating the uterine cervix. Increased spontaneous activity with ES may play a part in remodeling of the cervical tissue, whereas selective sensitization of high-threshold units by ES might underlie increased pain responses to cervical distension. Failure of acute ES treatment to mimic this suggests a genomic effect.

Brief exposure of juvenile rats to noise impairs the development of the response properties of inferior colliculus neurons

2009 ◽  
Vol 29 (9) ◽  
pp. 1921-1930 ◽  
Author(s):  
Jolana Grécová ◽  
Zbyněk Bureš ◽  
Jiří Popelář ◽  
Daniel Šuta ◽  
Josef Syka
Keyword(s):  
Inferior Colliculus ◽  
Juvenile Rats ◽  
Response Properties

Responses of neurons in the auditory pathway of the barn owl to partially correlated binaural signals

1995 ◽  
Vol 74 (4) ◽  
pp. 1689-1700 ◽  
Author(s):  
Y. Albeck ◽  
M. Konishi
Keyword(s):  
Inferior Colliculus ◽  
Cross Correlation ◽  
Frequency Tuning ◽  
Neuronal Response ◽  
Interaural Time Difference ◽  
Central Nucleus ◽  
High Threshold ◽  
Correlation Model ◽  
Response Curves ◽  
The Cross

1. Extracellular single-unit recording in anesthetized barn owls was used to study neuronal response to dichotic stimuli of variable binaural correlation (BC). Recordings were made in the output fibers of nucleus laminaris (NL), the anterior division of the ventral lateral lemniscal nucleus (VLVa), the core of the central nucleus of the inferior colliculus (ICcC), the lateral shell of the central nucleus of the inferior colliculus (ICcLS), and the external nucleus of the inferior colliculus (ICx). 2. The response of all neurons sensitive to interaural time difference (ITD) varied with BC. The relationship between BC and impulse number fits a linear, a parabolic, or a ramp model. A linear or parabolic model fits most neurons in low-level nuclei. Higher order neurons in ICx did not respond to noise bursts with strong negative binaural correlation, creating a ramp-like response to BC. 3. A neuron's ability to detect ITD varied as a function of BC. Conversely, a neuron's response to BC changed with ITD. Neurons in NL, VLVa, and ICcC show almost periodic ITD response curves. In these neurons peaks and troughs of ITD response curves diminished as BC decreased, creating a flat ITD response when BC = 0. When BC was set to -1, the most favorable ITD became the least favorable one and vice versa. The ITD response curve of ICx neurons usually has a single dominant peak. The response of those neurons to a negatively correlated noise pair (BC = -1) showed two ITD peaks, flanking the position of the primary peak. 4. The parabolic BC response of NL neurons fits the prediction of the cross-correlation model, assuming half-wave rectification of the sound by the cochlea. Linear response is not predicted by the model. However, the parabolic and the linear neurons probably do not belong to two distinct groups as the difference between them is not statistically significant. Thus, the cross-correlation model provides a good description of the binaural response not only in NL but also in VLVa and ICcC. 5. Almost all ramp neurons occurred in either ICx or ICcLS where neurons are more broadly tuned to frequency than those in the lower nuclei. The synthesis of this response type requires, however, not only the convergence of different frequency channels but also inhibition between different ITD channels. We modeled the ramp response as a three-step process. First, different spectral channels converge to create broad frequency tuning. The response to variation in BC will be linear (or parabolic) because it is a sum of linear (parabolic) responses. Second, the activity in some adjacent ITD channels is subtracted by lateral inhibition. Finally, the result is rectified using a high threshold to avoid negative activity.

Maturation of Cutaneous Sensory Neurons From Normal and NGF-Overexpressing Mice

2000 ◽  
Vol 83 (3) ◽  
pp. 1722-1732 ◽  
Author(s):  
Amy M. Ritter ◽  
C. Jeffery Woodbury ◽  
Kathryn Albers ◽  
Brian M. Davis ◽  
H. Richard Koerber
Keyword(s):  
Conduction Velocity ◽  
Sensory Neurons ◽  
Physiological Response ◽  
Membrane Properties ◽  
High Threshold ◽  
Neuron Development ◽  
Wild Type ◽  
Skin Preparation ◽  
Response Properties

In the rodent, cutaneous sensory neurons mature over the first two postnatal weeks, both in terms of their electrical properties and their responses to mechanical stimulation of the skin. To examine the coincidence of these events, intracellular recordings were made from neurons in the dorsal root ganglion (DRG) in an in vitro spinal cord, DRG, and skin preparation from mice between the ages of postnatal day 0 and 5 ( P0–P5). We also examined mice in which nerve growth factor (NGF) is overexpressed in the skin. NGF has been shown to be involved in a number of aspects of sensory neuron development and function. Therefore we ask here whether excess target-derived NGF will alter the normal course of development, either of somal membrane properties, physiological response properties, or neuropeptide content. In wild-type mice, somal action potentials (APs) were heterogeneous, with some having simple, uninflected falling phases and some displaying an inflection or break on the falling limb. The proportion of neurons lacking an inflection increased with increasing age, as did mean conduction velocity. A variety of rapidly and slowly adapting responses could be obtained by gently probing the skin; however, due to relatively low thresholds and firing frequencies, as well as lack of mature peripheral receptors such as hairs, it was not possible to place afferents into the same categories as in the adult. No correlation was seen between the presence or absence of an inflection on the somal AP (a marker for high-threshold mechanoreceptors in adult animals) and either peripheral threshold or calcitonin-gene related peptide (CGRP) content. Small differences in the duration and amplitude of the somal AP were seen in the NGF-overexpressing mice that disappeared by P3–P5. Excess target-derived NGF did not alter physiological response properties or the types of neurons containing CGRP. The changes that did occur, including a loss of the normal relationship between AP duration and conduction velocity, and a decrease in mean conduction velocity in the inflected population, might best be explained by an increase in the relative proportions of myelinated nociceptors. Of greatest interest was the finding that in both NGF overexpressers and wild-type mice, the correlation between mechanical threshold and presence or absence of an inflection on the somal spike is not apparent by P5.

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