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Frontiers in Neural Circuits 2015
Topics: Animals; Cerebellum; Cognition; Learning; Motor Activity; Neural Pathways; Neuronal Plasticity; Neurons; Olivary Nucleus
PubMed: 26793067
DOI: 10.3389/fncir.2015.00066 -
The Annals of Otology, Rhinology, and... Aug 2018Normative data on superior olivary nucleus neuron counts derived from human specimens are sparse, and little is known about their coherence with structure and function...
INTRODUCTION
Normative data on superior olivary nucleus neuron counts derived from human specimens are sparse, and little is known about their coherence with structure and function of the cochlea. The purpose of this study was to quantify the neuron populations of the divisions of the superior olivary nucleus in human subjects with normal hearing and presbycusis and investigate potential relationships between these findings and histopathology in the cochlea and hearing phenotype Methods: Histopathologic examination of temporal bone and brainstem specimens from 13 subjects having normal hearing or presbycusis was undertaken. The following was determined for each: number and density of superior olivary nucleus and cochlear nucleus neurons, inner and outer hair cell counts, spiral ganglion cell counts, and pure tone audiometry.
RESULTS
The results demonstrate a significant relationship between cells within structures of the cochlear nucleus and the number of neurons of the medial superior olivary nucleus. No relationship between superior olivary nucleus neuron counts/density and cochlear histopathology or hearing phenotype was encountered.
CONCLUSION
Normative data for superior olivary nucleus neuron populations are further established in the data presented in this study that includes subjects with normal hearing and also presbycusis.
Topics: Adolescent; Adult; Aged; Audiometry, Pure-Tone; Biopsy; Female; Hearing; Hearing Loss, Sensorineural; Humans; Male; Middle Aged; Presbycusis; Spiral Ganglion; Superior Olivary Complex; Young Adult
PubMed: 29862839
DOI: 10.1177/0003489418779405 -
Cerebellum (London, England) Oct 2015Enrico Mugnaini has devoted part of his long and fruitful neuroscientific career to investigating the structural similarities between the cerebellar cortex and one of... (Review)
Review
Enrico Mugnaini has devoted part of his long and fruitful neuroscientific career to investigating the structural similarities between the cerebellar cortex and one of the first relay stations of the mammalian auditory pathway: the dorsal cochlear nucleus. The hypothesis of the cerebellar-like nature of the superficial layers of the dorsal cochlear nucleus received definitive support with the discovery and extensive characterization in his laboratory of unipolar brush cells, a neuron type unique to certain regions of the cerebellar cortex and to the granule cell domains of the cochlear nuclei. Paradoxically, a different line of research carried out in his laboratory revealed that, unlike the mammalian cerebellar cortex, the dorsal cochlear nucleus receives direct projections from the cerebral cortex, a fact that constitutes one of the main differences between the cerebellum and the dorsal cochlear nucleus. In an article published in 1995, Mugnaini's group described in detail the novel direct projections from the rat auditory neocortex to various subcollicular auditory centers, including the nucleus sagulum, the paralemniscal regions, the superior olivary complex, and the cochlear nuclei (Feliciano et al., Auditory Neuroscience 1995; 1:287-308). This review gives Enrico Mugnaini credit for his seminal contribution to the knowledge of auditory corticosubcollicular projections and summarizes how this growing field has evolved in the last 20 years.
Topics: Animals; Auditory Pathways; Cerebral Cortex; Humans; Neurons; Olivary Nucleus
PubMed: 26142291
DOI: 10.1007/s12311-015-0694-4 -
Hearing Research Jun 2022The role of the mammalian auditory olivocochlear efferent system in hearing has long been the subject of debate. Its ability to protect against damaging noise exposure... (Review)
Review
The role of the mammalian auditory olivocochlear efferent system in hearing has long been the subject of debate. Its ability to protect against damaging noise exposure is clear, but whether or not this is the primary function of a system that evolved in the absence of industrial noise remains controversial. Here we review the behavioral consequences of olivocochlear activation and diminished olivocochlear function. Attempts to demonstrate a role for hearing in noise have yielded conflicting results in both animal and human studies. A role in selective attention to sounds in the presence of distractors, or attention to visual stimuli in the presence of competing auditory stimuli, has been established in animal models, but again behavioral studies in humans remain equivocal. Auditory processing deficits occur in models of congenital olivocochlear dysfunction, but these deficits likely reflect abnormal central auditory development rather than direct effects of olivocochlear feedback. Additional proposed roles in age-related hearing loss, tinnitus, hyperacusis, and binaural or spatial hearing, are intriguing, but require additional study. These behavioral studies almost exclusively focus on medial olivocochlear effects, and many relied on lesioning techniques that can have unspecific effects. The consequences of lateral olivocochlear and of corticofugal pathway activation for perception remain unknown. As new tools for targeted manipulation of olivocochlear neurons emerge, there is potential for a transformation of our understanding of the role of the olivocochlear system in behavior across species.
Topics: Acoustic Stimulation; Animals; Auditory Perception; Cochlea; Efferent Pathways; Hearing; Hyperacusis; Mammals; Noise; Olivary Nucleus
PubMed: 33674070
DOI: 10.1016/j.heares.2021.108207 -
Frontiers in Neural Circuits 2015
Topics: Animals; Auditory Pathways; Auditory Perception; Neural Inhibition; Olivary Nucleus
PubMed: 26388739
DOI: 10.3389/fncir.2015.00045 -
World Neurosurgery Apr 2018Hypertrophic olivary degeneration (HOD) occurs because of posterior fossa or brainstem lesions that disrupt the dentato-rubro-olivary tract, well known as the... (Review)
Review
BACKGROUND
Hypertrophic olivary degeneration (HOD) occurs because of posterior fossa or brainstem lesions that disrupt the dentato-rubro-olivary tract, well known as the Guillain-Mollaret triangle. Clinical and radiologic hallmarks of this condition are palatal myoclonus and T2 hyperintensity of the inferior olivary complex on magnetic resonance imaging (MRI), respectively. Because symptomatic HOD can complicate the recovery of patients with posterior fossa or brainstem lesions, the purpose of this study is to evaluate clinical and imaging findings of patients with HOD.
METHODS
Sixteen patients (8 female and 8 male) with a mean age of 40.7 years, (range, 5-83 years) years were included in this study based on clinical symptoms and MRI findings.
RESULTS
We reviewed the clinical and imaging findings in 16 cases of HOD at our institution. Seven patients (43.7%) had posterior fossa tumors, 6 patients (37.5%) had cavernoma, 2 patients (12.5%) sustained traumatic brain injury, and only 1 patient (6.2%) had cerebellar infarction. Posterior fossa surgery was performed in 13 (81.2%) of these patients. HOD was detected a mean of 7.2 months (range, 0.5-18 months) after surgery or primary neurologic insult. Unilateral HOD was observed in 10 patients (62.5%), while bilateral HOD was observed in only 6 patients (37.5%). Seven patients (43.7%) were asymptomatic for HOD, whereas 5 patients (31.2%) had symptoms attributable to HOD. Two patients died because of primary tumors, although mean follow-up after detection of HOD on MRI was 52.2 months (range, 1-120 months) in the remaining 14 patients. In these cases, no change in clinical symptoms or imaging findings was detected during follow-up.
CONCLUSIONS
In this series, posterior fossa tumors and cavernomas were the most common causes of HOD. Although most of the patients with HOD remained asymptomatic, HOD complicated the course of recovery in almost one quarter of the patients included in this study. Neurosurgeons should be aware of HOD, which has characteristic clinical and imaging findings. In addition, HOD can complicate the recovery of patients with disruption to the dentato-rubro-olivary tract.
Topics: Adolescent; Adult; Aged; Aged, 80 and over; Brain Infarction; Brain Injuries, Traumatic; Child; Child, Preschool; Female; Hemangioma, Cavernous, Central Nervous System; Humans; Hypertrophy; Infratentorial Neoplasms; Male; Middle Aged; Nerve Degeneration; Olivary Nucleus; Young Adult
PubMed: 29382617
DOI: 10.1016/j.wneu.2018.01.150 -
Hearing Research Nov 2015Perineuronal nets (PNs) are a unique and complex meshwork of specific extracellular matrix molecules that ensheath a subset of neurons in many regions of the central... (Review)
Review
Perineuronal nets (PNs) are a unique and complex meshwork of specific extracellular matrix molecules that ensheath a subset of neurons in many regions of the central nervous system (CNS). PNs appear late in development and are supposed to restrict synaptic plasticity and to stabilize functional neuronal connections. PNs were further hypothesized to create a charged milieu around the neurons and thus, might directly modulate synaptic activity. Although PNs were first described more than 120 years ago, their exact functions still remain elusive. The purpose of the present review is to propose the nuclei of the auditory system, which are highly enriched in PN-wearing neurons, as particularly suitable structures to study the functional significance of PNs. We provide a detailed description of the distribution of PNs from the cochlear nucleus to the auditory cortex considering distinct markers for detection of PNs. We further point to the suitability of specific auditory neurons to serve as promising model systems to study in detail the contribution of PNs to synaptic physiology and also more generally to the functionality of the brain.
Topics: Aggrecans; Animals; Auditory Cortex; Auditory Pathways; Cochlear Nucleus; Extracellular Matrix; Geniculate Bodies; Humans; Hyaluronic Acid; Inferior Colliculi; Models, Neurological; Neuronal Plasticity; Neurons; Shaw Potassium Channels; Superior Olivary Complex; Synaptic Transmission
PubMed: 25580005
DOI: 10.1016/j.heares.2014.12.012 -
Current Opinion in Physiology Dec 2020During development and adulthood, the normal activity of the auditory nerve plays a critical role in the maintenance of both fundamental structural, molecular, and...
During development and adulthood, the normal activity of the auditory nerve plays a critical role in the maintenance of both fundamental structural, molecular, and functional parameters of auditory nerve synapses, and the postsynaptic excitatory or inhibitory neurons within the cochlear nucleus (CN). In addition, normal activity within the synaptic circuits of the CN is key to developing and maintaining appropriate synapse connectivity as well as the initiation of binaural sound processing in the superior olivary complex (SOC). Development plays a critical role in the proper neuronal connectivity and establishes a topographic map along the entire auditory pathway. Furthermore, evidence shows that neurons and synaptic circuits in the auditory brainstem are not hard-wired, but instead are plastic in response to hearing deficits. Whether this plasticity in response to hearing loss is compensatory or pathological is still unknown.
PubMed: 33103017
DOI: 10.1016/j.cophys.2020.07.002 -
Neuroscience Insights 2021Hypertrophic olivary degeneration is a rare condition caused by a lesion in the Guillain-Mollaret triangle which leads to trans-synaptic degeneration resulting in the... (Review)
Review
Hypertrophic olivary degeneration is a rare condition caused by a lesion in the Guillain-Mollaret triangle which leads to trans-synaptic degeneration resulting in the degenerative hypertrophy of the inferior olivary nucleus. This condition presents clinically with palatal tremor but can also produce ocular myoclonus or cerebellar signs. While any lesion that occurs within the Guillian-Mollaret triangle and results in the deafferentation of the inferior olive can lead to hypertrophic olivary degeneration, the most common etiologies include ischemic and hemorrhagic stroke, vascular malformation, neoplasm, and iatrogenic injury related to surgery. We report a series of 7 patients who presented with this condition bilaterally on MRI imaging, including 1 case which represents the first report of toxoplasmosis leading to the development of bilateral hypertrophic olivary degeneration and only the third reported case, unilateral or bilateral, related to an infectious etiology.
PubMed: 34485912
DOI: 10.1177/26331055211007445 -
Hearing Research Nov 2022The cochlear efferent system comprises multiple populations of brainstem neurons whose axons project to the cochlea, and whose responses to acoustic stimuli lead to... (Review)
Review
The cochlear efferent system comprises multiple populations of brainstem neurons whose axons project to the cochlea, and whose responses to acoustic stimuli lead to regulation of auditory sensitivity. The major groups of efferent neurons are found in the superior olivary complex and are likely activated by neurons of the cochlear nucleus, thus forming a simple reflex pathway back to the cochlea. The peripheral actions of only one of these efferent cell types has been well described. Moreover, the efferent neurons are not well understood at the cellular- and circuit-levels. For example, ample demonstration of descending projections to efferent neurons raises the question of whether these additional inputs constitute a mechanism for modulation of relay function or instead play a more prominent role in driving the efferent response. Related to this is the question of synaptic plasticity at these synapses, which has the potential to differentially scale the degree of efferent activation across time, depending on the input pathway. This review will explore central nervous system aspects of the efferent system, the physiological properties of the neurons, their synaptic inputs, their modulation, and the effects of efferent axon collaterals within the brainstem.
Topics: Acoustic Stimulation; Auditory Pathways; Brain Stem; Cochlea; Cochlear Nucleus; Efferent Pathways; Neurons, Efferent; Olivary Nucleus
PubMed: 35606211
DOI: 10.1016/j.heares.2022.108516