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Disorders of Hearing
Published in Anthony N. Nicholson, The Neurosciences and the Practice of Aviation Medicine, 2017
Linda M. Luxon, Ronald Hinchcliffe
The auditory signal generated in the inner hair cells travels through the auditory nerve to the ipsilateral cochlear nucleus, and from thence the majority of the afferent auditory fibres project to the contralateral superior olivary complex, the lateral lemniscus, the inferior colliculus, the medial geniculate body and to the auditory cortex (Figure 19.3a) (Chermak and Musiek, 1997). The auditory efferent pathway (Figure 19.3b) arises in the auditory cortex and descends parallel to the afferent tracts to the level of the cochlear nuclei (Suga et al., 2000). The anatomy of the higher efferent auditory system remains ill-defined, but within the brainstem the olivocochlear bundle projects from the superior olivary complex to the cochlea (reviewed by Warr, 1992), and has two main pathways: the medial olivocochlear system that projects mainly to the contralateral cochlea and connects to the outer hair cells, andthe lateral olivocochlear system that projects to the ipsilateral cochlea and ends on the type 1 afferent dendrites that connect to the inner hair cells.
Auditory System
Published in Joseph D. Bronzino, Donald R. Peterson, Biomedical Engineering Fundamentals, 2019
Ben M. Clopton and Herbert F. Voigt
e central auditory system consists of the cochlear nuclei; groups of brainstem nuclei including the superior olivary complex (SOC), nuclei of the lateral lemniscus (LL), and inferior colliculus (IC); and the auditory thalamocortical system consisting of the medial geniculate in the thalamus and multiple areas of the cerebral cortex. Figure 5.4 schematically indicates the nuclear levels and pathways. Eerent pathways are not shown. Page constraints prevent us from providing uniform detail for all levels of the auditory system.
A Summary of Recent Literature (2007–2017) on Neurobiological Effects of Radio Frequency Radiation
Published in Marko Markov, Mobile Communications and Public Health, 2018
There are studies on the effects of cell phone radiation and the auditory system. Most research (Bhagat et al., 2016; Gupta et al., 2015; Kwon 2009, 2010a,b; Parazzini et al., 2009; Stefanics et al., 2007, 2008) reported no effects, which seems to agree with the pre-2007 studies in this area. However, there are two reports by Kaprana et al. (2011) and Khullar et al. (2013) showing effects on auditory brainstem response, two papers by Panda et al. (2010, 2011) that concluded: “Long-term and intensive GSM and Code-Division Multiple Access (CDMA) mobile phone use may cause damage to cochlea as well as the auditory cortex.,” and a paper (Mandalà et al., 2014) reporting an effect on auditory-evoked cochlear nerve response. Maskey and Kim (2014) reported a decrease in neurotrophins that are important in the regulation of neuron survival in the superior olivary complex, a neural component of the auditory system, in mice after chronic exposure to RFR. Velayutham et al. (2014) reported hearing loss in cell phone users and Sudan et al. (2013) observed weak associations between cell phone use and hearing loss in children at age 7. These effects may not be caused by the radiation. However, there is a study (Seckin et al., 2014) showing structural damage in the cochlea of the rat after prenatal exposure to RFR. And Özgür et al. (2015) reported neuronal degeneration in the cochlear nucleus of the auditory system in the rat after chronic exposure to RFR. Kwon et al. (2010b) reported that short-term exposure to cell phone radiation did not significantly affect the transmission of sensory stimuli from the cochlea to the midbrain along the auditory nerve and brainstem auditory pathways, and (Kwon et al., 2010a) no significant effect on auditory sensory memory in children. More recently, Çeliker et al. (2017) also reported no significant change in auditory brainstem responses, but increases in neuronal degeneration and apoptosis in the cochlear nucleus in rats exposed to a 2100-MHz field for 30 days.
Hearing loss, lead (Pb) exposure, and noise: a sound approach to ototoxicity exploration
Published in Journal of Toxicology and Environmental Health, Part B, 2018
Krystin Carlson, Richard L. Neitzel
Studies displaying positive results for auditory dysfunction following high doses of Pb predominately used auditory brainstem response (ABR) and analysis of thresholds or waveforms. ABR can be performed in humans and rodents; five main waves are measured as neuronal signals pass from the cochlea to the auditory cortex in the brain. These main waves comprise an afferent pathway traveling sequentially through five major components of auditory processing: Eighth cranial nerve fibers beginning in the cochlea; eighth cranial nerve fiber upon entry to the Cochlear nucleus; action potentials exiting the cochlear nucleus and projecting to the superior Olivary complex; the signal in the Lateral lemniscus; and finally the Inferior colliculus within the midbrain of the brainstem (easily remembered as the underlined text shows ECOLI) (Jewett and Williston 1971; Picton et al. 1974). Following this succession of action potentials, the afferent signal is sent to the medial geniculate within the thalamus and further to the auditory cortex where processing occurs within the temporal lobe (Bartlett 2013). These last processing steps are essential for understanding and recognition of human speech.