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Jack B. Kelly - One of the best experts on this subject based on the ideXlab platform.
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anatomical projections of the nuclei of the Lateral Lemniscus in the albino rat rattus norvegicus
The Journal of Comparative Neurology, 2009Co-Authors: Jack B. Kelly, Brian Van AdelAbstract:The ascending projections to the Lateral lemniscal nuclei and the inferior colliculus were investigated in the albino rat by using Fluoro-Gold, either alone or in combination with other retrograde tract tracers. Injections were made into the central nucleus of the inferior colliculus (ICC), the dorsal nucleus of the Lateral Lemniscus (DNLL), the intermediate nucleus of the Lateral Lemniscus (INLL), or the ventral nucleus of the Lateral Lemniscus (VNLL). The ICC receives both ipsiLateral and contraLateral projections from the DNLL and the Lateral superior olive, major ipsiLateral projections from the INLL, VNLL, medial superior olive, and superior paraolivary nucleus, and major contraLateral projections from both dorsal and ventral cochlear nucleus. The DNLL receives a similar pattern of projections from the auditory lower brainstem nuclei. The INLL, in contrast, receives its major projections from the ipsiLateral VNLL, Lateral superior olive, medial superior olive, superior paraolivary nucleus, and medial nucleus of the trapezoid body, but does not receive a heavy projection from the contraLateral Lateral superior olive. It receives a major contraLateral projection from the ventral cochlear nucleus, but a much lighter projection from the contraLateral dorsal cochlear nucleus. The VNLL receives projections from the ipsiLateral medial nucleus of the trapezoid body and the contraLateral ventral cochlear nucleus, but does not receive projections from the medial or Lateral superior olives, the superior paraolivary nucleus, or the dorsal cochlear nucleus. Thus, the three primary subdivisions of the rat's Lateral Lemniscus can be distinguished from each other on the basis of their distinctive projection patterns. J. Comp. Neurol. 512:573–593, 2009. © 2008 Wiley-Liss, Inc.
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anatomical projections of the nuclei of the Lateral Lemniscus in the albino rat rattus norvegicus
The Journal of Comparative Neurology, 2009Co-Authors: Jack B. Kelly, Brian Van Adel, Makoto ItoAbstract:The ascending projections to the Lateral lemniscal nuclei and the inferior colliculus were investigated in the albino rat by using Fluoro-Gold, either alone or in combination with other retrograde tract tracers. Injections were made into the central nucleus of the inferior colliculus (ICC), the dorsal nucleus of the Lateral Lemniscus (DNLL), the intermediate nucleus of the Lateral Lemniscus (INLL), or the ventral nucleus of the Lateral Lemniscus (VNLL). The ICC receives both ipsiLateral and contraLateral projections from the DNLL and the Lateral superior olive, major ipsiLateral projections from the INLL, VNLL, medial superior olive, and superior paraolivary nucleus, and major contraLateral projections from both dorsal and ventral cochlear nucleus. The DNLL receives a similar pattern of projections from the auditory lower brainstem nuclei. The INLL, in contrast, receives its major projections from the ipsiLateral VNLL, Lateral superior olive, medial superior olive, superior paraolivary nucleus, and medial nucleus of the trapezoid body, but does not receive a heavy projection from the contraLateral Lateral superior olive. It receives a major contraLateral projection from the ventral cochlear nucleus, but a much lighter projection from the contraLateral dorsal cochlear nucleus. The VNLL receives projections from the ipsiLateral medial nucleus of the trapezoid body and the contraLateral ventral cochlear nucleus, but does not receive projections from the medial or Lateral superior olives, the superior paraolivary nucleus, or the dorsal cochlear nucleus. Thus, the three primary subdivisions of the rat's Lateral Lemniscus can be distinguished from each other on the basis of their distinctive projection patterns.
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responses of neurons in the rat s ventral nucleus of the Lateral Lemniscus to amplitude modulated tones
Journal of Neurophysiology, 2006Co-Authors: Huiming Zhang, Jack B. KellyAbstract:Recordings were made from single neurons in the rat's ventral nucleus of the Lateral Lemniscus (VNLL) to determine responses to amplitude-modulated (AM) tones. The neurons were first characterized ...
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responses of neurons in the rat s ventral nucleus of the Lateral Lemniscus to monaural and binaural tone bursts
Journal of Neurophysiology, 2006Co-Authors: Huiming Zhang, Jack B. KellyAbstract:Responses to monaural and binaural tone bursts were recorded from neurons in the rat's ventral nucleus of the Lateral Lemniscus (VNLL). Most of the neurons (55%) had V- or U-shaped frequency-tuning...
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excitation and inhibition in the dorsal nucleus of the Lateral Lemniscus influence binaural response properties of neurons in the rat s inferior colliculus
Journal of the Acoustical Society of America, 1999Co-Authors: Jack B. KellyAbstract:In vitro brain slice studies have shown that neurons in the rat’s dorsal nucleus of the Lateral Lemniscus (DNLL) are affected by both NMDA and non‐NMDA receptor‐mediated excitation and glycineric inhibition evoked by electrical stimulation of ascending afferent fibers in the Lateral Lemniscus and GABAergic inhibition evoked by stimulation of the commissure of Probst [Wu and Kelly, 1996]. The effects of excitatory and inhibitory events in the DNLL on binaural responses in the rat’s inferior colliculus are reported here for in vivo experiments. Receptor specific antagonists were injected locally into the DNLL before and after recording extracellular single‐neuron responses from the contraLateral inferior colliculus. Binaural responses were evoked by paired clicks delivered to the two ears. Both NMDA and non‐NMDA excitatory amino acid antatonists (NBQX and CPP) produced a release from binaural inhibition and glycinergic and GABAergic antagonists (strychnine and bicuculline) resulted in enhanced binaural inhi...
Ellen Covey - One of the best experts on this subject based on the ideXlab platform.
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functional role of gabaergic and glycinergic inhibition in the intermediate nucleus of the Lateral Lemniscus of the big brown bat
Journal of Neurophysiology, 2009Co-Authors: Andrew Kutscher, Ellen CoveyAbstract:The intermediate nucleus of the Lateral Lemniscus (INLL) is a major input to the inferior colliculus (IC), the auditory midbrain center where multiple pathways converge to create neurons selective for specific temporal features of sound. However, little is known about how INLL processes auditory information or how it contributes to integrative processes at the IC. INLL receives excitatory projections from the cochlear nucleus and inhibitory projections from the medial nucleus of the trapezoid body (MNTB), so it must perform some form of integration. To address the question of what role inhibitory synaptic inputs play in the INLL of the big brown bat (Eptesicus fuscus), we recorded sound-evoked responses of single neurons and iontophoretically applied bicuculline to block GABAA receptors or strychnine to block glycine receptors. Neither bicuculline nor strychnine had a consistent effect on response latency or frequency response areas. Bicuculline increased spike counts and response durations in most units, suggesting that GABAergic input suppressed the late part of the response and provided some gain control. Strychnine reduced the responses of some units with sustained discharge patterns to one or a few spikes at stimulus onset, but increased others. INLL is the only part of the auditory system where reduced responsiveness has been seen in vivo while blocking glycine. However, in vitro studies in the MNTB suggest that glycine can be facilitatory, possibly through presynaptic action. These results show that GABA consistently reduces spike counts and response durations, whereas glycine is suppressive in some INLL neurons but facilitatory in others.
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arctiid moths and bat echolocation broad band clicks interfere with neural responses to auditory stimuli in the nuclei of the Lateral Lemniscus of the big brown bat
Journal of Comparative Physiology A-neuroethology Sensory Neural and Behavioral Physiology, 1998Co-Authors: Jakob Tougaard, John H. Casseday, Ellen CoveyAbstract:Clicks emitted by arctiid moths interfere with the ranging ability of echolocating bats. To identify possible neural correlates of this interference, we recorded responses of single units in the nuclei of the Lateral Lemniscus to combinations of a broad-band click and a test signal (pure tones or frequency-modulated sweeps). In 77% of 87 units tested, clicks interfered with neural responses to the test stimuli. The interference fell into two categories: latency ambiguity and suppression. Units showing latency ambiguity responded to both the click and the test signal. However, when the click occurred within a window of approximately 3 ms before the onset of the test signal, the latency of the response to the test signal was affected. Units that were suppressed did not respond to clicks. Nevertheless, when a click was presented immediately before or simultaneously with a test signal, the response to the test signal was eliminated. Both types of units were found throughout the Lateral Lemniscus except for the columnar division of the ventral nucleus, where all units tested exhibited latency ambiguity. There is a close match between the single unit data and previous studies of range difference discrimination in the presence of clicks.
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the columnar region of the ventral nucleus of the Lateral Lemniscus in the big brown bat eptesicus fuscus synaptic arrangements and structural correlates of feedforward inhibitory function
Cell and Tissue Research, 1997Co-Authors: Marianne Vater, Ellen Covey, John H. CassedayAbstract:Neurons of the columnar region of the ventral nucleus of the Lateral Lemniscus of Eptesicus fuscus respond with high-precision constant-latency responses to sound onsets and possess remarkably broad tuning. To study the synaptic basis for this specialized monaural auditory processing and to elucidate the excitatory or inhibitory nature of the input and output circuitry, we have used classical transmission electron microscopy, and postembedding immunocytochemistry for gamma aminobutyric acid (GABA) and glycine on serial semithin sections. The dominant putatively excitatory perisomatic input is provided by large calyx-like terminals that possess round synaptic vesicles and asymmetric synaptic contacts. Additionally, calyces contact the dendrites of neighboring neurons. Putatively inhibitory small boutons possess pleomorphic or flattened synaptic vesicles and symmetrical contacts and are sparsely distributed on somata and dendrites. Almost all neurons are glycine-immunoreactive. There is a moderate amount of glycine-immunoreactive puncta; GABA-immunoreactive puncta are rare. This suggests that (1) there is a fast robust excitatory synaptic input via calyx-like perisomatic endings, (2) calyx-like endings distribute frequency-specific excitatory input across isofrequency sheets by virtue of parallel synapses to somata and adjacent dendrites, and thus, dendritic integration may contribute to the broadening of frequency tuning, (3) the columnar region forms an inhibitory glycinergic feedforward relay in the ascending auditory pathway, a relay that is probably involved in creating filters for time-varying signals.
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origin of ascending projections to the nuclei of the Lateral Lemniscus in the big brown bat eptesicus fuscus
The Journal of Comparative Neurology, 1995Co-Authors: Russell F Huffman, Ellen CoveyAbstract:The nuclei of the Lateral Lemniscus in the echolocating bat, Eptesicus fuscus, are large and highly differentiated. In each nucleus, different characteristic response properties predominate. To determine whether the dissimilar response properties are due in part to differential ascending input, we examined the retrograde transport from small deposits of horseradish peroxidase (HRP) or HRP conjugated with wheat germ agglutinin (WGA-HRP) in the nuclei of the Lateral Lemniscus. The intermediate nucleus (INLL) and the two divisions of the ventral nucleus (VNLL) receive almost exclusively monaural input from the anteroventral and posteroventral cochlear nuclei and from the medial nucleus of the trapezoid body. Lesser inputs originate in the Lateral nucleus of the trapezoid body and the ventral periolivary area. Although the three monaural nuclei of the Lateral Lemniscus all receive input from the same set of nuclei, and from the same identified cell types in the cochlear nucleus, there is a difference in the relative proportions of input from these sources. The dorsal nucleus (DNLL) receives input mostly from binaural structures, the Lateral and medial superior olives and the contraLateral DNLL, with only a minor projection from the cochlear nucleus. The Lateral and medial superior olives project biLaterally; the biLateral projection from the medial superior olive is unusual in that it is found in only a few mammalian species. The results show a segregated pattern of binaural projections to DNLL and monaural projections to INLL and VNLL that is consistent with the binaural response properties found in DNLL and the exclusively monaural response properties found in INLL and VNLL. The differences in response properties between monaural nuclei, however, are not due to input from different nuclei or cell types but may be influenced by differing magnitudes of the constituent ascending projections.
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response properties of single units in the dorsal nucleus of the Lateral Lemniscus and paralemniscal zone of an echolocating bat
Journal of Neurophysiology, 1993Co-Authors: Ellen CoveyAbstract:1. Connectional evidence suggests that the dorsal nucleus of the Lateral Lemniscus (DNLL) and the paralemniscal zone (PL) function as centers for binaural analysis interposed between the superior olivary complex and the midbrain. In addition, the DNLL is known to be a major source of inhibitory input to the midbrain. The aim of this study was to characterize the response properties of neurons in DNLL and PL of the echolocating bat Eptesicus fuscus, a species that utilizes high-frequency hearing and that might be expected to have a large proportion of neurons responsive to interaural differences in sound level. 2. Auditory stimuli were presented monaurally or binaurally to awake animals, and responses of single units were recorded extra-cellularly with the use of glass micropipettes. 3. Below the ventroLateral border of the inferior colliculus is a region that contains large gamma-aminobutyric acid-positive neurons. On the basis of its immunohistochemical reactivity, this entire region could be considered as DNLL. However, within the area, there was an uneven distribution of binaural responses. Caudally, binaural neurons made up 84% (41/49) of those tested, but rostrally only 29% (6/21). For this reason the rostral area is considered as a separate functional subdivision and referred to as the dorsal paralemniscal zone (DPL). PL is located ventral to DPL and medial to the intermediate and ventral nuclei of the Lateral Lemniscus; in PL 88% (14/16) of neurons were binaural. 4. Most neurons responded only to a contraLateral stimulus when sounds were presented monaurally. Out of 49 neurons in DNLL, 42 responded only to a contraLateral sound, 1 responded only to an ipsiLateral sound, and 6 responded to sound at either ear. In the DPL, all of the 21 neurons tested responded to a contraLateral sound and none to an ipsiLateral sound. Out of 16 neurons in the PL, 11 responded only to a contraLateral sound, 1 responded only to an ipsiLateral sound, and 4 responded to sound at either ear. 5. When sounds were presented at both ears simultaneously, several different patterns of binaural interaction occurred. The most common pattern was suppression of the response to sound at one ear by sound at the other ear. In DNLL, 57% (28/49) of neurons showed this type of binaural interaction. Another 10% (5/49) showed facilitation at some interaural level differences and suppression at others, and another 10% (5/49) showed facilitation at some interaural level differences but no suppression.(ABSTRACT TRUNCATED AT 400 WORDS)
George D Pollak - One of the best experts on this subject based on the ideXlab platform.
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Reversible inactivation of the dorsal nucleus of the Lateral Lemniscus reveals its role in the processing of multiple sound sources in the inferior colliculus of bats,” The
2013Co-Authors: Michael R. Burger, George D PollakAbstract:Neurons in the inferior colliculus (IC) that are excited by one ear and inhibited by the other [excitatory—inhibitory (EI) neurons] can code interaural intensity disparities (IIDs), the cues animals use to localize high frequencies. Although EI properties are first formed in a lower nucleus and imposed on some IC cells via an excitatory projection, many other EI neurons are formed de novo in the IC. By reversibly inactivating the dorsal nucleus of the Lateral Lemniscus (DNLL) in Mexican free-tailed bats with kynurenic acid, we show that the EI properties of many IC cells are formed de novo via an inhibitory projection from the DNLL on the opposite side. We also show that signals excitatory to the IC evoke an inhibition in the opposite DNLL that persists for tens of milliseconds after the signal has ended. During that period, strongly suppressed EI cells in the IC are deprived of inhibition from the DNLL and respond to binaural signals a
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inhibitory projections from the ventral nucleus of the Lateral Lemniscus and superior paraolivary nucleus create directional selectivity of frequency modulations in the inferior colliculus a comparison of bats with other mammals
Hearing Research, 2011Co-Authors: George D Pollak, Joshua X Gittelman, Ruili XieAbstract:This review considers four auditory brainstem nuclear groups and shows how studies of both bats and other mammals have provided insights into their response properties and the impact of their convergence in the inferior colliculus (IC). The four groups are octopus cells in the cochlear nucleus, their connections with the ventral nucleus of the Lateral Lemniscus (VNLL) and the superior paraolivary nucleus (SPON), and the connections of the VNLL and SPON with the IC. The theme is that the response properties of neurons in the SPON and VNLL map closely onto the synaptic response features of a unique subpopulation of cells in the IC of bats whose inputs are dominated by inhibition. We propose that the convergence of VNLL and SPON inputs generates the tuning of these IC cells, their unique temporal responses to tones, and their directional selectivities for frequency modulated (FM) sweeps. Other IC neurons form directional properties in other ways, showing that selective response properties are formed in multiple ways. In the final section we discuss why multiple formations of common response properties could amplify differences in population activity patterns evoked by signals that have similar spectrotemporal features.
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spectral determination of responses to species specific calls in the dorsal nucleus of the Lateral Lemniscus
Journal of Neurophysiology, 2002Co-Authors: Eric E Bauer, Achim Klug, George D PollakAbstract:This study evaluated how neurons in the dorsal nucleus of the Lateral Lemniscus (DNLL) in Mexican free-tailed bats respond to both tone bursts and species-specific calls. Up to 20 calls were presented to each neuron, of which 18 were social communication and 2 were echolocation calls. We also measured excitatory response regions (ERRs): the range of tone burst frequencies that evoked discharges at a fixed intensity. Neurons were unselective for one or another call in that each neuron responded to any call so long as the call had energy that encroached on its ERR. Additionally, responses were evoked by the same set of calls, and with similar spike counts, when they were presented normally or reversed. By convolving activity in the ERRs with the spectrogram of each call, we showed that responses to tones accurately predicted discharge patterns evoked by species-specific calls. DNLL cells are remarkably homogeneous in that neurons having similar BFs responded to each of the species-specific calls with similar response profiles. The homogeneity was further illustrated by the ability to accurately predict the response profiles of a particular DNLL cell to species-specific calls from the ERR of another similarly tuned DNLL cell. Thus DNLL neurons tuned to the same or similar frequencies responded to species-specific calls with latencies and temporal discharge patterns that were so similar as to be virtually interchangeable. What this suggests is that DNLL responses evoked by complex sounds can be largely explained by a simple summation of the excitation in each neuron's ERR. Finally, superimposing the spectrograms of each call on the responses evoked by that call revealed that the DNLL population response re-creates both the spectral and the temporal features of each signal.
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features of ipsiLaterally evoked inhibition in the dorsal nucleus of the Lateral Lemniscus
Hearing Research, 1998Co-Authors: Lichuan Yang, George D PollakAbstract:The dorsal nucleus of the Lateral Lemniscus (DNLL) is a binaural nucleus whose neurons are excited by stimulation of the contraLateral ear and inhibited by stimulation of the ipsiLateral ear. Here we report on several features of the ipsiLaterally evoked inhibition in 95 DNLL neurons of the mustache bat. These features include its dependence on intensity, its tuning and the types of stimuli that are capable of evoking it. Inhibition was studied by evoking discharges with the iontophoretic application of glutamate, and then evaluating the strength and duration of the inhibition of the glutamate evoked background activity produced by stimulation of the ipsiLateral ear. Excitatory responses were evoked by stimulation of the contraLateral ear with best frequency (BF) tone bursts. Glutamate evoked discharges could be inhibited in all DNLL neurons and the inhibition often persisted for periods ranging from 10 to 50 ms beyond the duration of the tone burst that evoked it. The duration of the persistent inhibition increased with stimulus intensity. Stimulus duration had little influence on the duration of the persistent inhibition. Signals as short as 2 ms suppressed discharges for as long as 30 ms after the signal had ended. The frequency tuning of the total period of inhibition and the period of persistent inhibition were both closely matched to the tuning evoked by stimulation of the contraLateral ear. Moreover, the effectiveness of complex signals for evoking persistent inhibition, such as brief FM sweeps and sinusoidally amplitude and frequency modulated signals, was comparable to that of tone bursts at the neuron's excitatory BF, so long as the complex signal contained frequencies at or around the neuron's excitatory BF. We also challenged DNLL cells with binaural paradigms. In one experiment, we presented a relatively long (40 ms) BF tone burst of fixed intensity to the contraLateral ear, which evoked a sustained discharge, and a shorter, 10 ms signal of variable intensity to the ipsiLateral ear. As the intensity of the 10 ms ipsiLateral signal increased, it generated progressively longer periods of persistent inhibition and thus the discharges were suppressed for periods far longer than the 10 ms duration of the ipsiLateral signal. With interaural time disparities, ipsiLateral signals that led contraLateral signals evoked a persistent inhibition that suppressed the responses to the trailing contraLateral signals for periods of a least 15 ms. This suggests that an initial binaural sound that favors the ipsiLateral ear should suppress the responses to trailing sounds that normally would be excitatory if they were presented alone. We hypothesize a circuit that generates the persistent inhibition and discuss how the results with binaural signals support that hypothesis.
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afferent connections to the dorsal nucleus of the Lateral Lemniscus of the mustache bat evidence for two functional subdivisions
The Journal of Comparative Neurology, 1996Co-Authors: Lichuan Yang, Qin Liu, George D PollakAbstract:The dorsal nucleus of the Lateral Lemniscus (DNLL) of the mustache bat, Pteronotus parnellii, was found to consist of two divisions. The neurons in each division were distinguished by their temporal discharge patterns evoked both by tone bursts and sinusoidal amplitude-modulated (SAM) signals. Neurons in the anterior one-third of the DNLL responded to tone bursts with an onset discharge pattern and only phase-locked to SAM signals with low modulation frequencies (< 300 Hz). Neurons in the posterior two-thirds of the DNLL responded to tone bursts with a sustained discharge pattern and phase-locked to SAM signals with much higher modulation frequencies (400-800 Hz). In addition, there was a different frequency representation in the two divisions. The frequency representation in the posterior division was from about 15 to 120 kHz, whereas in the anterior division it was only up to 62 kHz. The physiological differences were further supported by data from experiments that revealed the sources of afferent projections to the two DNLL divisions. Retrograde labeling showed that the afferent projections to the two divisions were from different neuronal populations. Input differences were of two types. Some nuclei projected to one or the other DNLL division, but not to both. For instance, the ventral nucleus of the Lateral Lemniscus projected predominately to the anterior DNLL and provided little or no inputs to the posterior DNLL, whereas the medial superior olive innervated the posterior but not the anterior DNLL. Other lower nuclei projected to both DNLL divisions. These include the contraLateral cochlear nucleus, the ipsi- and contraLateral Lateral superior olives, the intermediate nucleus of the Lateral Lemniscus, and the contraLateral DNLL. However, the projections to each division of the DNLL originate from different neuronal subpopulations in each lower nucleus. The functional implications of these findings are discussed in the context of the possible impacts that the two DNLL divisions exert on their postsynaptic targets in the inferior colliculus.
Douglas C Fitzpatrick - One of the best experts on this subject based on the ideXlab platform.
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processing of interaural temporal disparities in the medial division of the ventral nucleus of the Lateral Lemniscus
Journal of Neurophysiology, 2002Co-Authors: Ranjan Batra, Douglas C FitzpatrickAbstract:The medial division of the ventral nucleus of the Lateral Lemniscus (VNLLm) contains a specialized population of neurons that is sensitive to interaural temporal disparities (ITDs), a potent cue for sound localization along the azimuth. Unlike many ITD-sensitive neurons elsewhere in the auditory system, neurons in the VNLLm respond only at the onset of tones. An onset response may be significant for behavior because, under echoic conditions, tones require sharp onsets for accurate localization. In contrast, noise can generally be localized even with gradual onsets, presumably because transients occur at random intervals in noise. We recorded responses of neurons in the VNLLm to tones and noise in unanesthetized rabbits. We found that although tones elicited a transient response, noise elicited a sustained response as if it was a sequence of transients. The responses to tones indicate that these neurons represent a secondary stage in the processing of ITDs. The onset response to tones was only weakly synchronized to the phase of the tone, indicating that neurons in the VNLLm inherit their sensitivity to ITDs from their inputs. The latencies were short (∼8 ms), implying that the ITD sensitivity is derived from ascending inputs. Most neurons in the VNLLm discharged maximally at the same ITD at all frequencies, a characteristic shared with neurons of the medial superior olive. However, the latency of neurons in the VNLLm to interaurally delayed stimuli is linked strongly to the timing of the contraLateral stimulus. This suggests that these neurons receive a suprathreshold, contraLateral input that is modulated by a subthreshold input conveying information about ITDs. Other stations in the auditory pathway contain a subset of neurons that respond transiently to tones and are sensitive to ITDs. These neurons may represent a novel pathway that assists in localizing sounds in the presence of reflections.
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monaural and binaural processing in the ventral nucleus of the Lateral Lemniscus a major source of inhibition to the inferior colliculus
Hearing Research, 2002Co-Authors: Ranjan Batra, Douglas C FitzpatrickAbstract:The ventral nucleus of the Lateral Lemniscus (VNLL) is a major source of input to the inferior colliculus. This paper reviews recent studies of neural responses in the VNLL of the unanesthetized rabbit. The VNLL has generally been viewed as a monaural nucleus, with its neurons responding primarily to stimulation of the contraLateral ear. In the rabbit, the VNLL is divided into a medial division (VNLLm) comprising neurons intercalated in the medial limb of the Lemniscus, a compact Lateral division (VNLLl), and a dorsal division. The VNLLm contains an abundance of neurons sensitive to interaural temporal disparities (ITDs), one of the major binaural cues for sound localization. These neurons respond only at the onset of tones, and therefore appear to encode the ITDs of transients. Even in the VNLLl, many neurons are sensitive to binaural stimulation. The VNLLl contains a variety of neurons with different discharge patterns, the two most common of which are sustained and onset. The discharge patterns, frequency-tuning and dynamic ranges of VNLLl neurons indicate that this division is able to supply the inferior colliculus with a variety of inputs, each serving a different function in the analysis of sound.
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discharge patterns of neurons in the ventral nucleus of the Lateral Lemniscus of the unanesthetized rabbit
Journal of Neurophysiology, 1999Co-Authors: Ranjan Batra, Douglas C FitzpatrickAbstract:The ventral nucleus of the Lateral Lemniscus (VNLL) is a major auditory nucleus that sends a large projection to the inferior colliculus. Despite its prominence, the responses of neurons in the VNL...
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neurons sensitive to interaural temporal disparities in the medial part of the ventral nucleus of the Lateral Lemniscus
Journal of Neurophysiology, 1997Co-Authors: Ranjan Batra, Douglas C FitzpatrickAbstract:Batra, Ranjan and Douglas C. Fitzpatrick. Neurons sensitive to interaural temporal disparities in the medial part of the ventral nucleus of the Lateral Lemniscus. J. Neurophysiol. 78: 511–515, 1997...
Ranjan Batra - One of the best experts on this subject based on the ideXlab platform.
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responses of neurons in the ventral nucleus of the Lateral Lemniscus to sinusoidally amplitude modulated tones
Journal of Neurophysiology, 2006Co-Authors: Ranjan BatraAbstract:Fluctuations in the amplitude of a sound play an important role in our perception of pitch and acoustic space, but their neural analysis has not been fully elucidated. The ventral nucleus of the Lateral Lemniscus (VNLL) has been implicated in the processing of such temporal features of a sound. This study examines responses of neurons in the VNLL of unanesthetized rabbits to sinusoidally amplitude modulated tones, a type of stimulus that has often been used to investigate encoding of temporal information. Modulation transfer functions of responses were calculated in two ways: based on discharge rates (rMTFs) and on synchronization to the envelope (tMTFs). Among the variety of rMTFs, two types were readily identifiable: flat and band-pass. The responses of neurons exhibiting these types of rMTF differed in several ways. Neurons with flat rMTFs typically had moderate rates of spontaneous activity, sustained responses to short tone bursts, and low-pass or band-pass tMTFs. Neurons with band-pass rMTFs typically had low spontaneous activity, onset responses to short tone bursts, and flat tMTFs. The vast majority synchronized strongly to the modulation envelope. The best modulation frequencies of neurons with band-pass rMTFs extended from 14 to 283 Hz. The presence of neurons with band-pass rMTFs in the VNLL suggests that this nucleus plays a role in converting the temporal code for modulation frequency used in lower structures into a rate-based code for use higher in the auditory pathway. The substantial number of neurons with more complex modulation transfer functions indicates that the VNLL has other functions.
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processing of interaural temporal disparities in the medial division of the ventral nucleus of the Lateral Lemniscus
Journal of Neurophysiology, 2002Co-Authors: Ranjan Batra, Douglas C FitzpatrickAbstract:The medial division of the ventral nucleus of the Lateral Lemniscus (VNLLm) contains a specialized population of neurons that is sensitive to interaural temporal disparities (ITDs), a potent cue for sound localization along the azimuth. Unlike many ITD-sensitive neurons elsewhere in the auditory system, neurons in the VNLLm respond only at the onset of tones. An onset response may be significant for behavior because, under echoic conditions, tones require sharp onsets for accurate localization. In contrast, noise can generally be localized even with gradual onsets, presumably because transients occur at random intervals in noise. We recorded responses of neurons in the VNLLm to tones and noise in unanesthetized rabbits. We found that although tones elicited a transient response, noise elicited a sustained response as if it was a sequence of transients. The responses to tones indicate that these neurons represent a secondary stage in the processing of ITDs. The onset response to tones was only weakly synchronized to the phase of the tone, indicating that neurons in the VNLLm inherit their sensitivity to ITDs from their inputs. The latencies were short (∼8 ms), implying that the ITD sensitivity is derived from ascending inputs. Most neurons in the VNLLm discharged maximally at the same ITD at all frequencies, a characteristic shared with neurons of the medial superior olive. However, the latency of neurons in the VNLLm to interaurally delayed stimuli is linked strongly to the timing of the contraLateral stimulus. This suggests that these neurons receive a suprathreshold, contraLateral input that is modulated by a subthreshold input conveying information about ITDs. Other stations in the auditory pathway contain a subset of neurons that respond transiently to tones and are sensitive to ITDs. These neurons may represent a novel pathway that assists in localizing sounds in the presence of reflections.
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monaural and binaural processing in the ventral nucleus of the Lateral Lemniscus a major source of inhibition to the inferior colliculus
Hearing Research, 2002Co-Authors: Ranjan Batra, Douglas C FitzpatrickAbstract:The ventral nucleus of the Lateral Lemniscus (VNLL) is a major source of input to the inferior colliculus. This paper reviews recent studies of neural responses in the VNLL of the unanesthetized rabbit. The VNLL has generally been viewed as a monaural nucleus, with its neurons responding primarily to stimulation of the contraLateral ear. In the rabbit, the VNLL is divided into a medial division (VNLLm) comprising neurons intercalated in the medial limb of the Lemniscus, a compact Lateral division (VNLLl), and a dorsal division. The VNLLm contains an abundance of neurons sensitive to interaural temporal disparities (ITDs), one of the major binaural cues for sound localization. These neurons respond only at the onset of tones, and therefore appear to encode the ITDs of transients. Even in the VNLLl, many neurons are sensitive to binaural stimulation. The VNLLl contains a variety of neurons with different discharge patterns, the two most common of which are sustained and onset. The discharge patterns, frequency-tuning and dynamic ranges of VNLLl neurons indicate that this division is able to supply the inferior colliculus with a variety of inputs, each serving a different function in the analysis of sound.
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discharge patterns of neurons in the ventral nucleus of the Lateral Lemniscus of the unanesthetized rabbit
Journal of Neurophysiology, 1999Co-Authors: Ranjan Batra, Douglas C FitzpatrickAbstract:The ventral nucleus of the Lateral Lemniscus (VNLL) is a major auditory nucleus that sends a large projection to the inferior colliculus. Despite its prominence, the responses of neurons in the VNL...
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neurons sensitive to interaural temporal disparities in the medial part of the ventral nucleus of the Lateral Lemniscus
Journal of Neurophysiology, 1997Co-Authors: Ranjan Batra, Douglas C FitzpatrickAbstract:Batra, Ranjan and Douglas C. Fitzpatrick. Neurons sensitive to interaural temporal disparities in the medial part of the ventral nucleus of the Lateral Lemniscus. J. Neurophysiol. 78: 511–515, 1997...
