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Anatomy
Published in Stanley A. Gelfand, Hearing, 2017
Upon entering the brainstem, auditory nerve fibers synapse with cells in the cochlear nuclei, constituting the first level of way stations in the central auditory nervous system. Interested readers should see Irvine (1986) for comprehensive coverage of the auditory brainstem, and Cant (1992), Ryugo (1992), and Young and Oertel (2003, 2010) for detailed discussions of the cochlear nuclei and their synaptic connections. The cochlear nuclei are composed of three main sections: the anterior ventral cochlear nucleus (AVCN), the posterior ventral cochlear nucleus (PVCN), and the dorsal cochlear nucleus (DCN). The incoming type I auditory neurons (originating from the IHCs) bifurcate into ascending branches to the AVCN and descending branches to the PVCN and DCN. (Type II auditory neurons also project to the cochlear nuclei, following paths parallel to the type I fibers, but they terminate in different cellular regions [Leak-Jones and Snyder, 1982; Ruggero et al., 1982; Ryugo, 1992].) Auditory neurons arising from the more basal (higher-frequency) areas of the cochlea terminate in the dorsomedial parts of the cochlear nuclei, and fibers from the more apical (lower frequency) parts of the cochlea go to the ventrolateral parts of these nuclei. Frequency–place relationships extend throughout the central auditory nervous system, and are covered in the discussion of tonotopic organization in Chapter 6.
Specific Synonyms
Published in Terence R. Anthoney, Neuroanatomy and the Neurologic Exam, 2017
Cochlear (nuclear) complex (C&S. p. 366) Dorsal cochlear nucleus and ventral cochlear nucleus (B&K, p. 317) See, also, D: Nucleus vs. subnucleus vs. nuclear complex.
Altered Calcium Homeostasis in Old Neurons
Published in David R. Riddle, Brain Aging, 2007
Immunocytochemical determinations of calbindin (CB) and parvalbumin (PV) expression in animal models showed that age decreases the number of CB-positive neurons in the rabbit hippocampus without affecting the PV-positive neurons, although for the latter CaBP there were some subtler differences in subcellular distribution, with a proposed decrease in PV expression in the neurites [73]. A similar picture came from studies of human cortex, which showed a consistent trend for age-related decreases in the calbindin- and calretinin (CR)-positive neurons that attained a level of statistical significance only in few regions, while no change was recorded for parvalbumin (PV)-positive neurons [74]. These studies expanded on the previous one from the same group that showed a dramatic 60% loss of CB from the basal forebrain cholinergic neurons (BFCN) [75]. It is entirely possible, however, that the changes in CaBP expression are region specific and influenced by levels of activity. Thus, when assessing the number of PV- and CB-expressing neurons in the dorsal cochlear nucleus of mice, an age-related increase has been reported [76] This was consistent with the observation that excessive stimulation of neurons in the cochlear nucleus by noise exposure resulted in increased expression of the CaBP [77]. Similarly in human specimens, it was found that the number of CB-positive neurons in the temporal cortex increased with age, in contrast to the situation for the AD-afflicted specimens [78].
Adam Politzer (1835-1920) and the cochlear nucleus
Published in Journal of the History of the Neurosciences, 2021
Albert Mudry, John Riddington Young
This is also called the dorsal cochlear nucleus. Politzer’s anatomical description of the cochlear nucleus between 1878 and 1908 showed step by exciting step the dawning of the realization of the importance and practical value of the neurosciences in the specialty of otology. His meticulous recording of the continuing progress in the neuroanatomy of the cochlear nucleus and bringing that newly developed knowledge to the attention of a greater medical audience was where Politzer excelled. Of course, he did not perform any anatomical dissection of the midbrain himself. Things had moved on since the times of the eighteenth-century surgeon-anatomists. Politzer was busy in Vienna running the world’s first dedicated otology clinic. His great strength was in teaching his colleagues and recording in his excellent Lehrbuch (Teaching Book) the current state of medical and scientific knowledge.
Investigation of the effect of cochlear implantation on tinnitus, and its associated factors
Published in Acta Oto-Laryngologica, 2020
Wen-Hui Hsieh, Wen-Ting Huang, Hung-Ching Lin
Tinnitus, defined as the sensation of sound without an external acoustic stimulation, is one of the most common symptoms in patients with hearing impairments [1]. According to the measurability and audibility of tinnitus, a patient’s condition can be either objective or subjective. The majority of the patients present subjective tinnitus and is known only when reported. In 1970, the edge theory [2] claimed that tinnitus is an inappropriate response due to the reorganization of the tonotopic thalamus because of the reduction in afferent auditory signals in the damaged cochlear area. Twenty-three years later, Jastreboff and Hazell [3] proposed the discordant theory indicating that it is an unexpected signal arising from the depolarization of the inner hair cells owing to the abnormal movement of the basilar membrane and partial collapse of the outer hair cells and tectorial membrane. In the central auditory system, afferent signals are reorganized and transmitted in tandem to the other regions of the brain owing to the abnormality in acoustic signals arriving in the dorsal cochlear nucleus, which maintains the balance of afferent signals, and increasing the possibility of tinnitus [4]. The synchronized spontaneous firing between uncovered neurons and normal neurons could be one of the attributors [5]. Tinnitus can be triggered along the auditory pathway [6]. It is believed to be encoded in neurons within the auditory cortex. The majority of profound sensorineural tinnitus were due to pathology at the cochlea or cochlear nerve level.
A different view on the link between tinnitus and cognition; is there a reciprocal link?
Published in International Journal of Neuroscience, 2018
Elham Tavanai, Ghassem Mohammadkhani
Functional magnetic resonance imaging (fMRI), Single-Photon Emission Computed Tomography (SPECT) and positron emission tomography (PET) are imaging techniques that can be used for studying neural activity in the human brain directly. Available functional imaging studies have demonstrated different activation patterns in central auditory system of tinnitus patients. However, these differences might be due to differences in patient samples and study methods. Generally, result from these studies suggest abnormal structural and functional changes in tinnitus patients at several levels of brain [37]. Accordingly, in tinnitus sufferer, changes in neuronal excitability have been reported in the dorsal cochlear nucleus (DCN) [31,33,34], ventral cochlear nucleus (VCN) [6,22], inferior colliculus (IC) [5], medial geniculate body (MGB) [38], core and belt regions of auditory cortex [3,38], as well as several non-auditory regions [1–7]. In other words, tinnitus not only change the auditory pathways but also involve some of non-auditory brain regions [1–7].