Lateral Superior Olive

2019 ◽  
pp. 328-394 ◽  
Author(s):  
Eckhard Friauf ◽  
Elisa G. Krächan ◽  
Nicolas I.C. Müller
Keyword(s):  
Neural Plasticity ◽  
Auditory Processing ◽  
Sound Intensity ◽  
Inhibitory Synapses ◽  
Superior Olivary Complex ◽  
Central Auditory Processing ◽  
Spatial Cues ◽  
Lateral Superior Olive ◽  
Superior Olive ◽  
Interaural Level Differences

Auditory neurons in the mammalian brainstem are involved in several basic computation processes essential for survival; for example, sound localization. Differences in sound intensity between the two ears, so-called interaural level differences (ILDs), provide important spatial cues for localizing sound in the horizontal plane, particularly for animals with high-frequency hearing. The earliest center of ILD detection is the lateral superior olive (LSO), a prominent component of the superior olivary complex (SOC) in the medulla oblongata. LSO neurons receive input from both ears of excitatory and inhibitory nature and perform a subtraction-like process. The LSO has become a model system for studies addressing inhibitory synapses, map formation, and neural plasticity. This review aims to provide an overview of several facets of the LSO, focusing on its functional and anatomical organization, including development and plasticity. Understanding this important ILD detector is fundamental in multiple ways—among others, to analyze central auditory processing disorders and central presbyacusis.

scholarly journals Temporal Alterations to Central Auditory Processing without Synaptopathy after Lifetime Exposure to Environmental Noise

2021 ◽  
Author(s):  
Florian Occelli ◽  
Florian Hasselmann ◽  
Jérôme Bourien ◽  
Jean-Luc Puel ◽  
Nathalie Desvignes ◽  
...  
Keyword(s):  
Hearing Loss ◽  
Auditory Cortex ◽  
Auditory Processing ◽  
Noise Exposure ◽  
Sound Intensity ◽  
Environmental Noise ◽  
Central Auditory Processing ◽  
Adult Rats ◽  
Cochlear Hair Cells ◽  
Lifetime Exposure

Abstract People are increasingly exposed to environmental noise through the cumulation of occupational and recreational activities, which is considered harmless to the auditory system, if the sound intensity remains <80 dB. However, recent evidence of noise-induced peripheral synaptic damage and central reorganizations in the auditory cortex, despite normal audiometry results, has cast doubt on the innocuousness of lifetime exposure to environmental noise. We addressed this issue by exposing adult rats to realistic and nontraumatic environmental noise, within the daily permissible noise exposure limit for humans (80 dB sound pressure level, 8 h/day) for between 3 and 18 months. We found that temporary hearing loss could be detected after 6 months of daily exposure, without leading to permanent hearing loss or to missing synaptic ribbons in cochlear hair cells. The degraded temporal representation of sounds in the auditory cortex after 18 months of exposure was very different from the effects observed after only 3 months of exposure, suggesting that modifications to the neural code continue throughout a lifetime of exposure to noise.

scholarly journals GABAB and Trk Receptor Signaling Mediates Long-Lasting Inhibitory Synaptic Depression

2001 ◽  
Vol 86 (1) ◽  
pp. 536-540 ◽  
Author(s):  
Vibhakar C. Kotak ◽  
Christopher DiMattina ◽  
Dan H. Sanes
Keyword(s):  
Synaptic Depression ◽  
Inhibitory Synapses ◽  
Receptor Signaling ◽  
Lateral Superior Olive ◽  
Superior Olive ◽  
Medial Nucleus ◽  
Dependent Form ◽  
Early Expression ◽  
Neurotrophin Signaling ◽  
Trapezoid Body

In many areas of the nervous system, excitatory and inhibitory synapses are reconfigured during early development. We have previously described the anatomical refinement of an inhibitory projection from the medial nucleus of the trapezoid body to the lateral superior olive in the developing gerbil auditory brain stem. Furthermore, these inhibitory synapses display an age-dependent form of long-lasting depression when activated at a low rate, suggesting that this process could support inhibitory synaptic refinement. Since the inhibitory synapses release both glycine and GABA during maturation, we tested whether GABAB receptor signaling could initiate the decrease in synaptic strength. When whole cell recordings were made from lateral superior olive neurons in a brain slice preparation, the long-lasting depression of medial nucleus of the trapezoid body–evoked inhibitory potentials was eliminated by the GABABreceptor antagonist, SCH-50911. In addition, inhibitory potentials could be depressed by repeated exposure to the GABAB receptor agonist, baclofen. Since GABAB receptor signaling may not account entirely for inhibitory synaptic depression, we examined the influence of neurotrophin signaling pathways located in the developing superior olive. Bath application of brain-derived neurotrophic factor or neurotrophin-3 depressed evoked inhibitory potentials, and use-dependent depression was blocked by the tyrosine kinase antagonist, K-252a. We suggest that early expression of GABAergic and neurotrophin signaling mediates inhibitory synaptic plasticity, and this mechanism may support the anatomical refinement of inhibitory connections.

scholarly journals Tinnitus impairs segregation of competing speech in normal-hearing listeners

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Yang Wenyi Liu ◽  
Bing Wang ◽  
Bing Chen ◽  
John J. Galvin ◽  
Qian-Jie Fu
Keyword(s):  
Sex Differences ◽  
Speech Recognition ◽  
Auditory Processing ◽  
Normal Hearing ◽  
Central Auditory Processing ◽  
Informational Masking ◽  
Spatial Cues ◽  
Processing Resources ◽  
Lexical Interference ◽  
Competing Speech

AbstractMany tinnitus patients report difficulties understanding speech in noise or competing talkers, despite having “normal” hearing in terms of audiometric thresholds. The interference caused by tinnitus is more likely central in origin. Release from informational masking (more central in origin) produced by competing speech may further illuminate central interference due to tinnitus. In the present study, masked speech understanding was measured in normal hearing listeners with or without tinnitus. Speech recognition thresholds were measured for target speech in the presence of multi-talker babble or competing speech. For competing speech, speech recognition thresholds were measured for different cue conditions (i.e., with and without target-masker sex differences and/or with and without spatial cues). The present data suggest that tinnitus negatively affected masked speech recognition even in individuals with no measurable hearing loss. Tinnitus severity appeared to especially limit listeners’ ability to segregate competing speech using talker sex differences. The data suggest that increased informational masking via lexical interference may tax tinnitus patients’ central auditory processing resources.

scholarly journals Evidence of a Functionally Segregated Pathway from Lateral Superior Olive to Inferior Colliculus

2019 ◽  
Author(s):  
Nathaniel T. Greene ◽  
Kevin A. Davis
Keyword(s):  
Inferior Colliculus ◽  
Excitatory Amino Acid ◽  
Excitatory Input ◽  
Central Nucleus ◽  
Type I ◽  
Lateral Superior Olive ◽  
Reversible Inactivation ◽  
Superior Olive ◽  
Receptive Field Organization ◽  
Interaural Level Differences

ABSTRACTNeurons in the central nucleus of the inferior colliculus (ICC) of decerebrate cats show three major response patterns when tones of different frequencies and levels are presented to the contralateral ear. The frequency response maps of type I units uniquely exhibit a narrowly tuned I-shaped area of excitation around best frequency (the most sensitive frequency) and flanking regions of inhibition at lower and higher frequencies. Type I units receive ipsilateral inhibition, and show binaural excitatory/inhibitory interactions. Lateral superior olive (LSO) principal cells display a similar receptive field organization and sensitivity to interaural level differences (ILDs) and project directly to the ICC, therefore are supposed to be the dominant source of excitatory input for type I units. To test this hypothesis, the responses of ICC units were compared before and after reversible inactivation of the LSO by injection of the non-specific excitatory amino-acid antagonist kynurenic acid. When excitatory activity within the LSO was blocked, many ICC type I units (~50%) were silenced or showed substantially decreased activitycomparable. By contrast, the responses of the other two ICC unit types were largely unaffected. With regard to the origins of unaffected ICC type I units, evidence indicates that the LSO was inactivated in an incomplete, anisotropic manner, and the monaural and binaural responses of such units are similar to those of affected type I units. Taken together, these results support the interpretation that most type I units are the midbrain components of a functionally segregated ILD processing pathway initiated by the LSO.

Membrane Properties of Principal Neurons of the Lateral Superior Olive

2001 ◽  
Vol 86 (2) ◽  
pp. 922-934 ◽  
Author(s):  
T. J. Adam ◽  
P. G. Finlayson ◽  
D.W.F. Schwarz
Keyword(s):  
Sound Intensity ◽  
Membrane Properties ◽  
Intensity Difference ◽  
Lateral Superior Olive ◽  
Voltage Range ◽  
Superior Olive ◽  
Temporal Properties ◽  
Cable Properties ◽  
Voltage Dependent ◽  
Cochlear Hearing Loss

In the lateral superior olive (LSO) the firing rate of principal neurons is a linear function of inter-aural sound intensity difference (IID). The linearity and regularity of the “chopper response” of these neurons have been interpreted as a result of an integration of excitatory ipsilateral and inhibitory contralateral inputs by passive soma-dendritic cable properties. To account for temporal properties of this output, we searched for active time- and voltage-dependent nonlinearities in whole cell recordings from a slice preparation of the rat LSO. We found nonlinear current-voltage relations that varied with the membrane holding potential. Repetitive regular firing, supported by voltage oscillations, was evoked by current pulses injected from holding potentials near rest, but the response was reduced to an onset spike of fixed short latency when the pulse was injected from de- or hyperpolarized holding potentials. The onset spike was triggered by a depolarizing transient potential that was supported by T-type Ca2+-, subthreshold Na+-, and hyperpolarization-activated ( I H) conductances sensitive, respectively, to blockade with Ni2+, tetrodotoxin (TTX), and Cs+. In the hyperpolarized voltage range, the I H, was largely masked by an inwardly rectifying K+ conductance ( I KIR) sensitive to blockade with 200 μM Ba2+. In the depolarized range, a variety of K+ conductances, including A-currents sensitive to blockade with 4-aminopyridine (4-AP) and additional tetraethylammonium (TEA)-sensitive currents, terminated the transient potential and firing of action potentials, supporting a strong spike-rate adaptation. The “chopper response,” a hallmark of LSO principal neuron firing, may depend on the voltage- and time-dependent nonlinearities. These active membrane properties endow the LSO principal neurons with an adaptability that may maintain a stable code for sound direction under changing conditions, for example after partial cochlear hearing loss.

Binaural interaction in the lateral superior olive: time difference sensitivity studied in mouse brain slice

1992 ◽  
Vol 68 (4) ◽  
pp. 1151-1159 ◽  
Author(s):  
S. H. Wu ◽  
J. B. Kelly
Keyword(s):  
Brain Slice ◽  
Response Probability ◽  
Interpulse Interval ◽  
Superior Olivary Complex ◽  
Lead Times ◽  
Complete Suppression ◽  
Lateral Superior Olive ◽  
Superior Olive ◽  
Trapezoid Body ◽  
Stimulation Of

1. The sensitivity of lateral superior olive (LSO) neurons to interaural time differences was examined in an in vitro brain slice preparation. Brain slices, 400-500 microns, were taken through the superior olivary complex of C57 BL/6J mice and were maintained in an oxygenated saline solution for single-unit recording. Both extracellular and intracellular recordings were made with glass pipettes filled with 4 M potassium acetate. Responses were elicited by applying current pulses to the trapezoid body through bipolar stimulating electrodes located ipsilateral or contralateral to the olivary complex. Binaural interactions were studied by manipulating the timing and intensity of paired ipsilateral and contralateral pulses. 2. In extracellular recordings, stimulation of the ipsilateral trapezoid body usually elicited a single action potential, whereas stimulation of the contralateral trapezoid body failed to produce a spike response. Bilateral stimulation resulted in the complete suppression of the evoked spike, indicating the presence of a contralateral inhibitory effect. The degree of inhibition depended on the interpulse interval between ipsilateral and contralateral stimulation. With sufficiently large ipsilateral lead times, the probability of eliciting an extracellular spike was 1.0. As the interpulse interval was gradually shifted to reduce the ipsilateral lead time, the response probability precipitously dropped to 0.0. Most neurons could be completely suppressed by simultaneous stimulation. The dynamic range, defined as the range of interpulse intervals over which response probability changed from 0.9 to 0.1, was between 125 and 225 microseconds for most cells tested. 3. With increasing contralateral lead times, the extracellularly recorded spike was eventually released from inhibition.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Glycinergic axonal inhibition subserves acute spatial sensitivity to sudden increases in sound intensity

2020 ◽  
Author(s):  
Tom P. Franken ◽  
Brian J. Bondy ◽  
David B. Haimes ◽  
Nace L. Golding ◽  
Philip H. Smith ◽  
...  
Keyword(s):  
Light And Electron Microscopy ◽  
Sound Intensity ◽  
Inhibitory Synapses ◽  
Structural Basis ◽  
Time Of Arrival ◽  
Medial Superior Olive ◽  
Superior Olive ◽  
Binaural Processing

AbstractLocomotion generates adventitious sounds which enable detection and localization of predators and prey. Such sounds contain brisk changes or transients in amplitude. We investigated the hypothesis that ill-understood temporal specializations in binaural circuits subserve lateralization of such sound transients, based on different time of arrival at the ears (interaural time differences, ITDs). We find that Lateral Superior Olive (LSO) neurons show exquisite ITD-sensitivity, reflecting extreme precision and reliability of excitatory and inhibitory postsynaptic potentials, in contrast to Medial Superior Olive neurons, traditionally viewed as the ultimate ITD-detectors. In vivo, inhibition blocks LSO excitation over an extremely short window, which, in vitro, required synaptically-evoked inhibition. Light and electron microscopy revealed inhibitory synapses on the axon initial segment as the structural basis of this observation. These results reveal a neural vetoing mechanism with extreme temporal and spatial precision and establish the LSO as the primary nucleus for binaural processing of sound transients.

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