scholarly journals Distinct forms of synaptic plasticity during ascending vs. descending control of medial olivocochlear efferent neurons

2021 ◽  
Author(s):  
Gabriel E. Romero ◽  
Laurence O. Trussell
Keyword(s):  
Dynamic Range ◽  
Short Term ◽  
Wide Dynamic Range ◽  
Efferent System ◽  
Short Term Plasticity ◽  
Ventral Cochlear Nucleus ◽  
Brainstem Nucleus ◽  
Reflex Arc ◽  
Efferent Neurons ◽  
Medial Olivocochlear

AbstractActivity in each brain region is shaped by the convergence of ascending and descending axonal pathways, and the balance and characteristics of these determine neural output. The medial olivocochlear (MOC) efferent system is part of a reflex arc that critically controls auditory sensitivity. Multiple central pathways contact MOC neurons, raising the question of how a reflex arc could be engaged by diverse inputs. We examined functional properties of synapses onto brainstem MOC neurons from ascending (ventral cochlear nucleus, VCN), and descending (inferior colliculus, IC) sources in mice using an optogenetic approach. We found that these pathways exhibited opposing forms of short-term plasticity, with VCN input showing depression and IC input showing marked facilitation. By using a conductance clamp approach, we found that combinations of facilitating and depressing inputs enabled firing of MOC neurons over a surprisingly wide dynamic range, suggesting an essential role for descending signaling to a brainstem nucleus.

scholarly journals Distinct forms of synaptic plasticity during ascending vs descending control of medial olivocochlear efferent neurons

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Gabriel E Romero ◽  
Laurence O Trussell
Keyword(s):  
Dynamic Range ◽  
Short Term ◽  
Wide Dynamic Range ◽  
Efferent System ◽  
Short Term Plasticity ◽  
Ventral Cochlear Nucleus ◽  
Brainstem Nucleus ◽  
Reflex Arc ◽  
Efferent Neurons ◽  
Medial Olivocochlear

Activity in each brain region is shaped by the convergence of ascending and descending axonal pathways, and the balance and characteristics of these determine neural output. The medial olivocochlear (MOC) efferent system is part of a reflex arc that critically controls auditory sensitivity. Multiple central pathways contact MOC neurons, raising the question of how a reflex arc could be engaged by diverse inputs. We examined functional properties of synapses onto brainstem MOC neurons from ascending (ventral cochlear nucleus, VCN), and descending (inferior colliculus, IC) sources in mice using an optogenetic approach. We found that these pathways exhibited opposing forms of short-term plasticity, with VCN input showing depression and IC input showing marked facilitation. By using a conductance clamp approach, we found that combinations of facilitating and depressing inputs enabled firing of MOC neurons over a surprisingly wide dynamic range, suggesting an essential role for descending signaling to a brainstem nucleus.

scholarly journals The Cholinergic Lateral Line Efferent Synapse: Structural, Functional and Molecular Similarities With Those of the Cochlea

2021 ◽  
Vol 15 ◽  
Author(s):  
Paola V. Plazas ◽  
Ana Belén Elgoyhen
Keyword(s):  
Lateral Line ◽  
Sk Channels ◽  
Afferent Activity ◽  
Intact Specimen ◽  
Efferent System ◽  
Synaptic Physiology ◽  
Efferent Neurons ◽  
Medial Olivocochlear ◽  
Subsequent Activation ◽  
Mammalian Counterpart

Vertebrate hair cell (HC) systems are innervated by efferent fibers that modulate their response to external stimuli. In mammals, the best studied efferent-HC synapse, the cholinergic medial olivocochlear (MOC) efferent system, makes direct synaptic contacts with HCs. The net effect of MOC activity is to hyperpolarize HCs through the activation of α9α10 nicotinic cholinergic receptors (nAChRs) and the subsequent activation of Ca2+-dependent SK2 potassium channels. A serious obstacle in research on many mammalian sensory systems in their native context is that their constituent neurons are difficult to access even in newborn animals, hampering circuit observation, mapping, or controlled manipulation. By contrast, fishes and amphibians have a superficial and accessible mechanosensory system, the lateral line (LL), which circumvents many of these problems. LL responsiveness is modulated by efferent neurons which aid to distinguish between external and self-generated stimuli. One component of the LL efferent system is cholinergic and its activation inhibits LL afferent activity, similar to what has been described for MOC efferents. The zebrafish (Danio rerio) has emerged as a powerful model system for studying human hearing and balance disorders, since LL HC are structurally and functionally analogous to cochlear HCs, but are optically and pharmacologically accessible within an intact specimen. Complementing mammalian studies, zebrafish have been used to gain significant insights into many facets of HC biology, including mechanotransduction and synaptic physiology as well as mechanisms of both hereditary and acquired HC dysfunction. With the rise of the zebrafish LL as a model in which to study auditory system function and disease, there has been an increased interest in studying its efferent system and evaluate the similarity between mammalian and piscine efferent synapses. Advances derived from studies in zebrafish include understanding the effect of the LL efferent system on HC and afferent activity, and revealing that an α9-containing nAChR, functionally coupled to SK channels, operates at the LL efferent synapse. In this review, we discuss the tools and findings of these recent investigations into zebrafish efferent-HC synapse, their commonalities with the mammalian counterpart and discuss several emerging areas for future studies.

scholarly journals Synaptic plasticity of inhibitory synapses onto medial olivocochlear efferent neurons

2022 ◽  
Author(s):  
Lester Torres Cadenas ◽  
Hui Cheng ◽  
Catherine J.C. Weisz
Keyword(s):  
Brain Slices ◽  
Synaptic Depression ◽  
Extracellular Calcium ◽  
Outer Hair Cells ◽  
Inhibitory Synapses ◽  
Short Term ◽  
Sound Stimulation ◽  
Efferent Neurons ◽  
Medial Olivocochlear

The descending auditory system modulates the ascending system at every level. The final descending, or efferent stage, is comprised of lateral olivocochlear (LOC) and medial olivocochlear (MOC) neurons. MOC somata in the ventral brainstem project axons to the cochlea to synapse onto outer hair cells (OHC), inhibiting OHC-mediated cochlear amplification. MOC suppression of OHC function is implicated in cochlear gain control with changing sound intensity, detection of salient stimuli, attention, and protection against acoustic trauma. Thus, sound excites MOC neurons to provide negative feedback of the cochlea. Sound also inhibits MOC neurons via medial nucleus of the trapezoid body (MNTB) neurons. However, MNTB-MOC synapses exhibit short-term depression, suggesting reduced MNTB-MOC inhibition during sustained stimuli. Further, due to high rates of both baseline and sound-evoked activity in MNTB neurons in vivo, MNTB-MOC synapses may be tonically depressed. To probe this, we characterized short-term plasticity of MNTB-MOC synapses in mouse brain slices. We mimicked in vivo-like temperature and extracellular calcium conditions, and in vivo-like activity patterns of fast synaptic activation rates, sustained activation, and prior tonic activity. Synaptic depression was sensitive to extracellular calcium concentration and temperature. During rapid MNTB axon stimulation, post-synaptic currents (PSCs) in MOC neurons summated but with concurrent depression, resulting in smaller, sustained currents, suggesting tonic inhibition of MOC neurons during rapid circuit activity. Low levels of baseline MNTB activity did not significantly reduce responses to subsequent rapid activity that mimics sound stimulation, indicating that, in vivo, MNTB inhibition of MOC neurons persists despite tonic synaptic depression.

scholarly journals Single-unit labeling of medial olivocochlear neurons: the cochlear frequency map for efferent axons

2014 ◽  
Vol 111 (11) ◽  
pp. 2177-2186 ◽  
Author(s):  
M. Christian Brown
Keyword(s):  
Hair Cells ◽  
Single Unit ◽  
Dynamic Range ◽  
Organ Of Corti ◽  
Nerve Fibers ◽  
Outer Hair Cells ◽  
Cochlear Amplifier ◽  
Noise Masking ◽  
Efferent Neurons ◽  
Medial Olivocochlear

Medial olivocochlear (MOC) neurons are efferent neurons that project axons from the brain to the cochlea. Their action on outer hair cells reduces the gain of the “cochlear amplifier,” which shifts the dynamic range of hearing and reduces the effects of noise masking. The MOC effects in one ear can be elicited by sound in that ipsilateral ear or by sound in the contralateral ear. To study how MOC neurons project onto the cochlea to mediate these effects, single-unit labeling in guinea pigs was used to study the mapping of MOC neurons for neurons responsive to ipsilateral sound vs. those responsive to contralateral sound. MOC neurons were sharply tuned to sound frequency with a well-defined characteristic frequency (CF). However, their labeled termination spans in the organ of Corti ranged from narrow to broad, innervating between 14 and 69 outer hair cells per axon in a “patchy” pattern. For units responsive to ipsilateral sound, the midpoint of innervation was mapped according to CF in a relationship generally similar to, but with more variability than, that of auditory-nerve fibers. Thus, based on CF mappings, most of the MOC terminations miss outer hair cells involved in the cochlear amplifier for their CF, which are located more basally. Compared with ipsilaterally responsive neurons, contralaterally responsive neurons had an apical offset in termination and a larger span of innervation (an average of 10.41% cochlear distance), suggesting that when contralateral sound activates the MOC reflex, the actions are different than those for ipsilateral sound.

scholarly journals Short-Term Plasticity Combines with Excitation–Inhibition Balance to Expand Cerebellar Purkinje Cell Dynamic Range

2018 ◽  
Vol 38 (22) ◽  
pp. 5153-5167 ◽  
Author(s):  
Anais Grangeray-Vilmint ◽  
Antoine M. Valera ◽  
Arvind Kumar ◽  
Philippe Isope
Keyword(s):  
Purkinje Cell ◽  
Dynamic Range ◽  
Cerebellar Purkinje Cell ◽  
Short Term ◽  
Short Term Plasticity

The Cochlear Nuclei

2018 ◽  
pp. 94-122 ◽  
Author(s):  
Donata Oertel ◽  
Xiao-Jie Cao ◽  
Alberto Recio-Spinoso
Keyword(s):  
Sensory Information ◽  
Short Term ◽  
Temporal Precision ◽  
Short Term Plasticity ◽  
Ventral Cochlear Nucleus ◽  
Cochlear Nuclei ◽  
Electrophysiological Studies ◽  
The Face ◽  
The Brain

Plasticity in neuronal circuits is essential for optimizing connections as animals develop and for adapting to injuries and aging, but it can also distort the processing, as well as compromise the conveyance of ongoing sensory information. This chapter summarizes evidence from electrophysiological studies in slices and in vivo that shows how remarkably robust signaling is in principal cells of the ventral cochlear nucleus. Even in the face of short-term plasticity, these neurons signal rapidly and with temporal precision. They can relay ongoing acoustic information from the cochlea to the brain largely independently of sounds to which they were exposed previously.

Slow-Scan CCD Observation of Backscattering Patterns in SEM

1992 ◽  
Vol 50 (2) ◽  
pp. 1308-1309
Author(s):  
F. Ouyang ◽  
D. A. Ray ◽  
O. L. Krivanek
Keyword(s):  
Electron Beam ◽  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Dynamic Range ◽  
High Sensitivity ◽  
Lens System ◽  
Wide Dynamic Range ◽  
Peltier Cooler ◽  
Diffraction Patterns ◽  
Scanning Electron

Electron backscattering Kikuchi diffraction patterns (BKDP) reveal useful information about the structure and orientation of crystals under study. With the well focused electron beam in a scanning electron microscope (SEM), one can use BKDP as a microanalysis tool. BKDPs have been recorded in SEMs using a phosphor screen coupled to an intensified TV camera through a lens system, and by photographic negatives. With the development of fiber-optically coupled slow scan CCD (SSC) cameras for electron beam imaging, one can take advantage of their high sensitivity and wide dynamic range for observing BKDP in SEM.We have used the Gatan 690 SSC camera to observe backscattering patterns in a JEOL JSM-840A SEM. The CCD sensor has an active area of 13.25 mm × 8.83 mm and 576 × 384 pixels. The camera head, which consists of a single crystal YAG scintillator fiber optically coupled to the CCD chip, is located inside the SEM specimen chamber. The whole camera head is cooled to about -30°C by a Peltier cooler, which permits long integration times (up to 100 seconds).

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