Microsecond interaural time differences of acoustic transients are decoded by inhibitory-excitatory interactions in neurons of the lateral superior olive

2017 ◽  
Vol 141 (5) ◽  
pp. 3570-3571 ◽  
Author(s):  
Tom P. Franken ◽  
Philip H. Smith ◽  
Philip X. Joris
Keyword(s):  
Lateral Superior Olive ◽  
Interaural Time Differences ◽  
Superior Olive ◽  
Acoustic Transients

Envelope coding in the lateral superior olive. I. Sensitivity to interaural time differences

1995 ◽  
Vol 73 (3) ◽  
pp. 1043-1062 ◽  
Author(s):  
P. X. Joris ◽  
T. C. Yin
Keyword(s):  
High Frequency ◽  
Response Rate ◽  
Discharge Rate ◽  
Modulation Frequency ◽  
Good Correspondence ◽  
Afferent Pathways ◽  
Lateral Superior Olive ◽  
Interaural Time Differences ◽  
Superior Olive ◽  
Naturally Occurring

1. Interaural level differences (ILDs), created by the head and pinna, have long been known to be the dominant acoustic cue for azimuthal localization of high-frequency tones. However, psychophysical experiments have demonstrated that human subjects can also lateralize complex high-frequency sounds on the basis of interaural time differences (ITDs) of the signal envelope. The lateral superior olive (LSO) is one of two pairs of binaural nuclei where the primary extraction of binaural cues for sound source location occurs. "IE" cells in LSO are inhibited by stimuli to the contralateral and excited by stimuli to the ipsilateral ear, and their response rate is therefore dependent on ILD. Anatomic specializations in the afferent pathways to the LSO suggest that this circuit also has a function in the detection of timing cues. We hypothesized that, besides ILD sensitivity, the IE property also conveys a sensitivity to ITDs of amplitude-modulated (AM) tones and could provide the physiological substrate for the psychophysical effect mentioned above. 2. In extracellular recordings from binaural LSO cells in barbiturate-anesthetized cats, response rate was a periodic function of ITDs of AM stimuli, i.e., all cells displayed ITD sensitivity. Binaural responses were smaller than responses to stimulation of the ipsilateral ear alone and were minimal when the envelopes in both ears were in-phase or nearly so. There was good correspondence between responses to ITDs and to dynamic interaural phase differences (IPDs), created by a difference in the envelope frequency to the two ears. Qualitatively, the responses were consistent with the outcome of an IE operation on temporally structured inputs. 3. To compare the relative importance of ILD and ITD, responses to combinations of the two cues were obtained. Despite robust ITD sensitivity in all binaural LSO cells encountered, the changes in response rate that would occur in response to naturally occurring ITDs were small in comparison with the changes expected for naturally occurring ILDs. The main limitation on ITD sensitivity was a steep decline in average discharge rate as the modulation frequency exceeded several hundred Hertz. 4. ITD sensitivity was also present to broadband stimuli, again with minimal rates occurring near 0 ITD. The sensitivity depended in a predictable fashion on the passband of filtered noise and was absent to binaurally uncorrelated noise bands. In response to clicks, ILDs interacted with ITD in a complicated fashion involving amplitude and latency effects. 5. Three low-characteristic frequency (CF) LSO cells were encountered that were IE and showed ITD sensitivity to the fine structure of low-frequency stimuli.(ABSTRACT TRUNCATED AT 400 WORDS)

scholarly journals GABA is a modulator, rather than a classical transmitter, in the medial nucleus of the trapezoid body–lateral superior olive sound localization circuit

2019 ◽  
Vol 597 (8) ◽  
pp. 2269-2295 ◽  
Author(s):  
Alexander U. Fischer ◽  
Nicolas I. C. Müller ◽  
Thomas Deller ◽  
Domenico Del Turco ◽  
Jonas O. Fisch ◽  
...  
Keyword(s):  
Sound Localization ◽  
Lateral Superior Olive ◽  
Superior Olive ◽  
Medial Nucleus ◽  
Trapezoid Body

Glutamatergic Calcium Responses in the Developing Lateral Superior Olive: Receptor Types and Their Specific Activation by Synaptic Activity Patterns

2003 ◽  
Vol 90 (4) ◽  
pp. 2581-2591 ◽  
Author(s):  
F. Aura Ene ◽  
Paul H. M. Kullmann ◽  
Deda C. Gillespie ◽  
Karl Kandler
Keyword(s):  
Calcium Channels ◽  
Intracellular Calcium ◽  
Glutamate Receptors ◽  
Cochlear Nucleus ◽  
Metabotropic Glutamate Receptors ◽  
Lateral Superior Olive ◽  
Voltage Gated ◽  
Superior Olive ◽  
Metabotropic Glutamate ◽  
Voltage Gated Calcium Channels

The lateral superior olive (LSO) is a binaural auditory brain stem nucleus that plays a central role in sound localization. Survival and maturation of developing LSO neurons critically depend on intracellular calcium signaling. Here we investigated the mechanisms by which glutamatergic afferents from the cochlear nucleus increase intracellular calcium concentration in LSO neurons. Using fura-2 calcium imaging in slices prepared from neonatal mice, we found that cochlear nucleus afferents can activate all major classes of ionotropic and metabotropic glutamate receptors, each of which contributes to an increase in intracellular calcium. The specific activation of different glutamate receptor classes was dependent on response amplitudes and afferent stimulus patterns. Low-amplitude responses elicited by single stimuli were entirely mediated by calcium-impermeable AMPA/kainate receptors that activated voltage-gated calcium channels. Larger-amplitude responses elicited by either single stimuli or stimulus trains resulted in additional calcium influx through N-methyl-d-aspartate receptors. Finally, high-frequency stimulation also recruited group I and group II metabotropic glutamate receptors, both of which mobilized intracellular calcium. This calcium release in turn activated a strong influx of extracellular calcium through a membrane calcium channel that is distinct from voltage-gated calcium channels. Together, these results indicate that before hearing onset, distinct patterns of afferent activity generate qualitatively distinct types of calcium responses, which likely serve in guiding different aspects of LSO development.

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.

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