Descending Auditory Pathways and Plasticity

2018 ◽  
pp. 610-638
Author(s):  
Brett R. Schofield ◽  
Nichole L. Beebe
Keyword(s):  
Auditory System ◽  
Superior Olivary Complex ◽  
Descending Pathways ◽  
Auditory Pathways ◽  
System P ◽  
Multiple Levels ◽  
Ventral Nucleus ◽  
Descending Projections ◽  
Trapezoid Body ◽  
Major Target

Descending auditory pathways originate from multiple levels of the auditory system and use a variety of neurotransmitters, including glutamate, GABA, glycine, acetylcholine, and dopamine. Targets of descending projections include cells that project to higher or lower centers, setting up circuit loops and chains that provide top-down modulation of many ascending and descending circuits in the auditory system. Descending pathways from the auditory cortex can evoke plasticity in subcortical centers. Such plasticity relies, at least in part, on brainstem cholinergic systems that are closely tied to descending cortical projections. Finally, the ventral nucleus of the trapezoid body, a component of the superior olivary complex, is a major target of descending projections from the cortex and midbrain. Through its complement of different neurotransmitter phenotypes, and its wide array of projections, the ventral nucleus of the trapezoid body is positioned to serve as a hub in the descending auditory system.

scholarly journals The Untouchable Ventral Nucleus of the Trapezoid Body: Preservation of a Nucleus in an Animal Model of Autism Spectrum Disorder

2021 ◽  
Vol 15 ◽  
Author(s):  
Yusra Mansour ◽  
Randy J. Kulesza
Keyword(s):  
Autism Spectrum Disorder ◽  
Animal Model ◽  
Autism Spectrum ◽  
Repetitive Behaviors ◽  
Spectrum Disorder ◽  
Superior Olivary Complex ◽  
Medial Geniculate ◽  
Ventral Nucleus ◽  
Descending Projections ◽  
Trapezoid Body

Autism spectrum disorder (ASD) is a neurodevelopmental condition characterized by repetitive behaviors, poor social skills, and difficulties with communication and hearing. The hearing deficits in ASD range from deafness to extreme sensitivity to routine environmental sounds. Previous research from our lab has shown drastic hypoplasia in the superior olivary complex (SOC) in both human cases of ASD and in an animal model of autism. However, in our study of the human SOC, we failed to find any changes in the total number of neurons in the ventral nucleus of the trapezoid body (VNTB) or any changes in cell body size or shape. Similarly, in animals prenatally exposed to the antiepileptic valproic acid (VPA), we failed to find any changes in the total number, size or shape of VNTB neurons. Based on these findings, we hypothesized that the neurotransmitter profiles, ascending and descending axonal projections of the VNTB are also preserved in these neurodevelopmental conditions. We investigated this hypothesis using a combination of immunohistochemistry and retrograde tract tracing. We found no difference between control and VPA-exposed animals in the number of VNTB neurons immunoreactive for choline acetyltransferase (ChAT). Additionally, we investigated the ascending projections from the VNTB to both the central nucleus of the inferior colliculus (CNIC) and medial geniculate (MG) and descending projections to the cochlea. Our results indicate no significant differences in the ascending and descending projections from the VNTB between control and VPA-exposed animals despite drastic changes in these projections from surrounding nuclei. These findings provide evidence that certain neuronal populations and circuits may be protected against the effects of neurodevelopmental disorders.

scholarly journals Multiple Sources of Cholinergic Input to the Superior Olivary Complex

2021 ◽  
Vol 15 ◽  
Author(s):  
Nichole L. Beebe ◽  
Chao Zhang ◽  
R. Michael Burger ◽  
Brett R. Schofield
Keyword(s):  
Auditory System ◽  
Cholinergic Neurons ◽  
Auditory Brainstem ◽  
Cholinergic Innervation ◽  
Superior Olivary Complex ◽  
Multiple Sources ◽  
Cholinergic Modulation ◽  
Medial Nucleus ◽  
Trapezoid Body

The superior olivary complex (SOC) is a major computation center in the brainstem auditory system. Despite previous reports of high expression levels of cholinergic receptors in the SOC, few studies have addressed the functional role of acetylcholine in the region. The source of the cholinergic innervation is unknown for all but one of the nuclei of the SOC, limiting our understanding of cholinergic modulation. The medial nucleus of the trapezoid body, a key inhibitory link in monaural and binaural circuits, receives cholinergic input from other SOC nuclei and also from the pontomesencephalic tegmentum. Here, we investigate whether these same regions are sources of cholinergic input to other SOC nuclei. We also investigate whether individual cholinergic cells can send collateral projections bilaterally (i.e., into both SOCs), as has been shown at other levels of the subcortical auditory system. We injected retrograde tract tracers into the SOC in gerbils, then identified retrogradely-labeled cells that were also immunolabeled for choline acetyltransferase, a marker for cholinergic cells. We found that both the SOC and the pontomesencephalic tegmentum (PMT) send cholinergic projections into the SOC, and these projections appear to innervate all major SOC nuclei. We also observed a small cholinergic projection into the SOC from the lateral paragigantocellular nucleus of the reticular formation. These various sources likely serve different functions; e.g., the PMT has been associated with things such as arousal and sensory gating whereas the SOC may provide feedback more closely tuned to specific auditory stimuli. Further, individual cholinergic neurons in each of these regions can send branching projections into both SOCs. Such projections present an opportunity for cholinergic modulation to be coordinated across the auditory brainstem.

scholarly journals Autonomic and respiratory components of orienting behaviors are mediated by descending pathways originating from the superior colliculus

2021 ◽  
Author(s):  
Erin Lynch ◽  
Bowen Richard Dempsey ◽  
Eloise Monteiro ◽  
Anita J Turner ◽  
Christine Saleeba ◽  
...  
Keyword(s):  
Superior Colliculus ◽  
Brain Function ◽  
Physiological Responses ◽  
Neural Pathways ◽  
Descending Pathways ◽  
Medullary Reticular Formation ◽  
Premotor Pathways ◽  
Descending Projections ◽  
Major Target ◽  
Stimulation Of

The ability to discriminate competing, ecologically relevant stimuli, and initiate contextually appropriate behaviors, is a key brain function. Neurons in the deep superior colliculus (dSC) integrate multisensory inputs and activate descending projections to premotor pathways responsible for orienting and attention, which often involve adjustments to respiratory and cardiovascular parameters. However, the neural pathways that subserve physiological components of orienting are poorly understood. We report that orienting responses to optogenetic dSC stimulation are accompanied by short-latency autonomic, respiratory and electroencephalographic effects in conscious rats, closely mimicking those evoked by naturalistic alerting stimuli. Physiological responses occurred in the absence of detectable aversion or fear and persisted under urethane anesthesia, indicating independence from emotional stress. Moreover, autonomic responses were replicated by selective stimulation of dSC inputs to the medullary reticular formation, a major target of dSC motor efferents, This disynaptic pathway represent a likely substrate for autonomic components of orienting.

Efferent Innervation to the Cochlea

2018 ◽  
pp. 58-94
Author(s):  
Ana Belén Elgoyhen ◽  
Carolina Wedemeyer ◽  
Mariano N. Di Guilmi
Keyword(s):  
Auditory System ◽  
Cochlear Nucleus ◽  
Medial Geniculate Body ◽  
Superior Olivary Complex ◽  
Auditory Neurons ◽  
Olivocochlear System ◽  
System P ◽  
Medial Geniculate ◽  
Central Auditory Neurons ◽  
The Brain

The auditory system consists of ascending and descending neuronal pathways. The best studied is the ascending pathway, whereby sounds that are transduced in the cochlea into electrical signals are sent to the brain via the auditory nerve. Before reaching the auditory cortex, auditory ascending information has several central relays: the cochlear nucleus and superior olivary complex in the brainstem, the lateral lemniscal nuclei and inferior colliculus in the midbrain, and the medial geniculate body in the thalamus. The function(s) of the descending corticofugal pathway is less well understood. It plays important roles in shaping or even creating the response properties of central auditory neurons and in the plasticity of the auditory system, such as reorganizing cochleotopic and computational maps. Corticofugal projections are present at different relays of the auditory system. This review focuses on the physiology and plasticity of the medial efferent olivocochlear system.

Auditory localization: role of auditory pathways in brain stem of the cat

1975 ◽  
Vol 38 (4) ◽  
pp. 842-858 ◽  
Author(s):  
J. H. Casseday ◽  
W. D. Neff
Keyword(s):  
Brain Stem ◽  
Inferior Colliculus ◽  
Auditory System ◽  
Superior Olivary Complex ◽  
Medial Superior Olive ◽  
Lateral Lemniscus ◽  
Localization Accuracy ◽  
Before And After ◽  
Localization Ability ◽  
Trapezoid Body

Cats were trained to localize sound in space. The animals' localization accuracy was determined before and after one of the following operations: 1) transection of the trapezoid body, 2) unilateral and 3) bilateral transection of the lateral lemniscus, 4) unilateral and 5) bilateral transection of the brachium of the inferior colliculus. The results after bilateral transections of the lateral lemniscus and the one deep bilateral transection of the brachium of the inferior colliculus indicate that some portion of the ascending auditory system must be intact above the medulla for an animal to be able to localize sound. A small loss in accuracy of localization was found after unilateral transection of the lateral lemniscus or brachium of the inferior colliculus. This loss, when compared with the much larger loss that monaural animals show, is an indication that binaural analysis, important for sound localization, occurs at the level of the medulla. Some transections of the trapezoid body resulted in a deficit in localization ability that appeared to be complete and permanent. The position of the lesions in the trapezoid body indicated that important encoding of the binaural cues to localization most likely occurs at the superior olivary complex, probably at the medial superior olive. But the trapezoid body or other commissures of the brain stem auditory system are probably also involved in transmission of information necessary for localization to higher centers.

Early Appearance of Inhibitory Input to the MNTB Supports Binaural Processing During Development

2005 ◽  
Vol 94 (6) ◽  
pp. 3826-3835 ◽  
Author(s):  
Joshua S. Green ◽  
Dan H. Sanes
Keyword(s):  
Auditory Processing ◽  
Inhibitory Neurons ◽  
Superior Olivary Complex ◽  
Inhibitory Input ◽  
Inhibitory Influence ◽  
Binaural Processing ◽  
Medial Nucleus ◽  
Level Difference ◽  
Postsynaptic Action ◽  
Trapezoid Body

Despite the peripheral and central immaturities that limit auditory processing in juvenile animals, they are able to lateralize sounds using binaural cues. This study explores a central mechanism that may compensate for these limitations during development. Interaural time and level difference processing by neurons in the superior olivary complex depends on synaptic inhibition from the medial nucleus of the trapezoid body (MNTB), a group of inhibitory neurons that is activated by contralateral sound stimuli. In this study, we examined the maturation of coding properties of MNTB neurons and found that they receive an inhibitory influence from the ipsilateral ear that is modified during the course of postnatal development. Single neuron recordings were obtained from the MNTB in juvenile (postnatal day 15–19) and adult gerbils. Approximately 50% of all recorded MNTB neurons were inhibited by ipsilateral sound stimuli, but juvenile neurons displayed a much greater suppression of firing as compared with those in adults. A comparison of the prepotential and postsynaptic action potential indicated that inhibition occurred at the presynaptic level, likely within the cochlear nucleus. A simple linear model of level difference detection by lateral superior olivary neurons that receive input from MNTB suggested that inhibition of the MNTB may expand the response of LSO neurons to physiologically realistic level differences, particularly in juvenile animals, at a time when these cues are reduced.

scholarly journals Contextualizing Neuroticism in the Hierarchical Taxonomy of Psychopathology

2019 ◽  
Author(s):  
Cassandra M Brandes ◽  
Jennifer L Tackett
Keyword(s):  
Mental Illness ◽  
Personality Trait ◽  
System P ◽  
Strongly Connected ◽  
Multiple Levels ◽  
And Behaviors ◽  
Psychopathology Symptoms ◽  
The Relationship

Neuroticism is the personality trait most consistently and strongly connected to psychopathology. The majority of research on the relationship between traits and mental illness has focused on neuroticism’s connection with broad psychopathology spectra or discrete disorders. However, both personality and psychopathology are hierarchically-organized domains that may be examined at multiple levels of fidelity and bandwidth from very specific thoughts, feelings, and behaviors (i.e., nuance traits or symptoms) to very broad patterns indexing many interrelated tendencies (i.e., general factors). The Hierarchical Taxonomy of Psychopathology (HiTOP) is a recently proposed nosologic framework for psychopathology symptoms and domains that accounts for this tiered organization. Here, we illustrate how neuroticism-psychopathology relationships—both what is known and unknown—may be elucidated through the HiTOP system.

scholarly journals Efferent feedback enforces bilateral coupling of spontaneous activity in the developing auditory system

2020 ◽  
Author(s):  
Yixiang Wang ◽  
Maya Sanghvi ◽  
Alexandra Gribizis ◽  
Yueyi Zhang ◽  
Lei Song ◽  
...  
Keyword(s):  
Spontaneous Activity ◽  
Auditory System ◽  
Activity Patterns ◽  
Descending Pathways ◽  
Efferent System ◽  
Cholinergic Pathway ◽  
The Central Nervous System ◽  
Necessary And Sufficient ◽  
Circuit Formation

SummaryIn the developing auditory system, spontaneous activity generated in the cochleae propagates into the central nervous system to promote circuit formation before hearing onset. Effects of the evolving peripheral firing pattern on spontaneous activity in the central auditory system are not well understood. Here, we describe the wide-spread bilateral coupling of spontaneous activity that coincides with the period of transient efferent modulation of inner hair cells from the medial olivochlear (MOC) system. Knocking out the α9/α10 nicotinic acetylcholine receptor, a requisite part of the efferent cholinergic pathway, abolishes these bilateral correlations. Pharmacological and chemogenetic experiments confirm that the MOC system is necessary and sufficient to produce the bilateral coupling. Moreover, auditory sensitivity at hearing onset is reduced in the absence of pre-hearing efferent modulation. Together, our results demonstrate how ascending and descending pathways collectively shape spontaneous activity patterns in the auditory system and reveal the essential role of the MOC efferent system in linking otherwise independent streams of bilateral spontaneous activity during the prehearing period.

scholarly journals Harmonic Cancellation

2021 ◽  
Author(s):  
Alain de Cheveigné
Keyword(s):  
Auditory System ◽  
Time Domain ◽  
Experimental Results ◽  
Target Sound ◽  
Neural Representations ◽  
Behavioral Studies ◽  
System P ◽  
Harmonic Cancellation ◽  
The Time Domain

This paper reviews the hypothesis of {\em harmonic cancellation}\ according to which an interfering sound is suppressed or canceled on the basis of its harmonicity (or periodicity in the time domain). It defines the concept, discusses theoretical arguments in its favor, and reviews experimental results that support it, or not. If correct, the hypothesis likely draws on time domain processing of temporally-accurate neural representations within the brainstem, as required also by the classic Equalization-Cancellation (EC) model of binaural unmasking. It predicts that a target sound corrupted by interference will be easier to hear if the interference is harmonic than inharmonic, all else being equal. This prediction is borne out in a number of behavioral studies, but not all. The paper reviews those results, with the aim to understand the inconsistencies and come up with a reliable conclusion for, or against, the hypothesis of harmonic cancellation within the auditory system.

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