scholarly journals The Adverse Effects of Heavy Metals with and without Noise Exposure on the Human Peripheral and Central Auditory System: A Literature Review

2016 ◽  
Vol 13 (12) ◽  
pp. 1223 ◽  
Author(s):  
Marie-Josée Castellanos ◽  
Adrian Fuente
Keyword(s):  
Heavy Metals ◽  
Literature Review ◽  
Adverse Effects ◽  
Auditory System ◽  
Noise Exposure ◽  
Central Auditory System ◽  
System A

scholarly journals Evoked Potentials Reveal Noise Exposure–Related Central Auditory Changes Despite Normal Audiograms

2020 ◽  
Vol 29 (2) ◽  
pp. 152-164 ◽  
Author(s):  
Naomi F. Bramhall ◽  
Christopher E. Niemczak ◽  
Sean D. Kampel ◽  
Curtis J. Billings ◽  
Garnett P. McMillan
Keyword(s):  
Auditory System ◽  
Noise Exposure ◽  
Otoacoustic Emission ◽  
Auditory Brainstem ◽  
Auditory Nerve Fiber ◽  
Central Auditory System ◽  
Distortion Product Otoacoustic Emission ◽  
Distortion Product ◽  
Brainstem Response ◽  
Latency Response

Purpose Complaints of auditory perceptual deficits, such as tinnitus and difficulty understanding speech in background noise, among individuals with clinically normal audiograms present a perplexing problem for audiologists. One potential explanation for these “hidden” auditory deficits is loss of the synaptic connections between the inner hair cells and their afferent auditory nerve fiber targets, a condition that has been termed cochlear synaptopathy . In animal models, cochlear synaptopathy can occur due to aging or exposure to noise or ototoxic drugs and is associated with reduced auditory brainstem response (ABR) wave I amplitudes. Decreased ABR wave I amplitudes have been demonstrated among young military Veterans and non-Veterans with a history of firearm use, suggesting that humans may also experience noise-induced synaptopathy. However, the downstream consequences of synaptopathy are unclear. Method To investigate how noise-induced reductions in wave I amplitude impact the central auditory system, the ABR, the middle latency response (MLR), and the late latency response (LLR) were measured in 65 young Veterans and non-Veterans with normal audiograms. Results In response to a click stimulus, the MLR was weaker for Veterans compared to non-Veterans, but the LLR was not reduced. In addition, low ABR wave I amplitudes were associated with a reduced MLR, but with an increased LLR. Notably, Veterans reporting tinnitus showed the largest mean LLRs. Conclusions These findings indicate that decreased peripheral auditory input leads to compensatory gain in the central auditory system, even among individuals with normal audiograms, and may impact auditory perception. This pattern of reduced MLR, but not LLR, was observed among Veterans even after statistical adjustment for sex and distortion product otoacoustic emission differences, suggesting that synaptic loss plays a role in the observed central gain. Supplemental Material https://doi.org/10.23641/asha.11977854

scholarly journals Detecting Noise-Induced Cochlear Synaptopathy by Auditory Brainstem Response in Tinnitus Patients With Normal Hearing Thresholds: A Meta-Analysis

2021 ◽  
Vol 15 ◽  
Author(s):  
Feifan Chen ◽  
Fei Zhao ◽  
Nadeem Mahafza ◽  
Wei Lu
Keyword(s):  
Auditory System ◽  
Auditory Brainstem Response ◽  
Noise Exposure ◽  
Meta Analysis ◽  
Auditory Brainstem ◽  
Normal Hearing ◽  
Central Auditory System ◽  
Gain Enhancement ◽  
Hearing Thresholds ◽  
Brainstem Response

Noise-induced cochlear synaptopathy (CS) is defined as a permanent loss of synapses in the auditory nerve pathway following noise exposure. Several studies using auditory brainstem response (ABR) have indicated the presence of CS and increased central gain in tinnitus patients with normal hearing thresholds (TNHT), but the results were inconsistent. This meta-analysis aimed to review the evidence of CS and its pathological changes in the central auditory system in TNHT. Published studies using ABR to study TNHT were reviewed. PubMed, EMBASE, and Scopus databases were selected to search for relevant literature. Studies (489) were retrieved, and 11 were included for meta-analysis. The results supported significantly reduced wave I amplitude in TNHT, whereas the alternations in wave V amplitude were inconsistent among the studies. Consistently increased V/I ratio indicated noise-induced central gain enhancement. The results indicated the evidence of noise-induced cochlear synaptopathy in tinnitus patients with normal hearing. However, inconsistent changes in wave V amplitude may be explained by that the failure of central gain that triggers the pathological neural changes in the central auditory system and/or that increased central gain may be necessary to generate tinnitus but not to maintain tinnitus.

scholarly journals Effect of tinnitus on the performance of central auditory system: a review

2021 ◽  
Author(s):  
Behieh Kohansal ◽  
Mehdi Asghari ◽  
Sirvan Najafi ◽  
Fahimeh Hamedi
Keyword(s):  
Speech Perception ◽  
Auditory System ◽  
Auditory Processing ◽  
Central Auditory Processing ◽  
Central Auditory System ◽  
Speech In Noise ◽  
Keywords Tinnitus ◽  
System A ◽  
Standardized Protocol ◽  
The Impact

Background and Aim: Tinnitus is one of the most difficult challenges in audiology and oto­logy. Previous studies have been shown that tinn­itus may interfere with the function of central auditory system (CAS). Involvement of CAS abilities including speech perception and audi­tory processing has led to serious problems in people with tinnitus. Due to the lack of enough information about the impact of tinnitus on CAS and its function, and given that there is no standardized protocol for assessment and mana­gement of tinnitus, this study aimed to review the studies on the effect of tinnitus on the CAS function. Recent Findings: Sixteen eligible articles were reviewed. Temporal and spectral resolution, fre­quency differentiation and speech perception deficits were reported in patients with tinnitus, especially in background noise. This was repor­ted even in tinnitus patients with normal hearing. Conclusion: Assessment of central auditory pro­cessing and speech perception in noise seems to be useful for proper management of tinnitus in clinical practice. Keywords: Tinnitus; auditory system; central auditory processing; speech in noise performance  

Plastic Changes in the Central Auditory System After Hearing Loss, Restoration of Function, and During Learning

2002 ◽  
Vol 82 (3) ◽  
pp. 601-636 ◽  
Author(s):  
Josef Syka
Keyword(s):  
Auditory Cortex ◽  
Auditory System ◽  
Hair Cells ◽  
Noise Exposure ◽  
Modern World ◽  
World Population ◽  
Common Denominator ◽  
Central Auditory System ◽  
Prosthetic Devices ◽  
Plastic Changes

Traditionally the auditory system was considered a hard-wired sensory system; this view has been challenged in recent years in light of the plasticity of other sensory systems, particularly the visual and somatosensory systems. Practical experience in clinical audiology together with the use of prosthetic devices, such as cochlear implants, contributed significantly to the present view on the plasticity of the central auditory system, which was originally based on data obtained in animal experiments. The loss of auditory receptors, the hair cells, results in profound changes in the structure and function of the central auditory system, typically demonstrated by a reorganization of the projection maps in the auditory cortex. These plastic changes occur not only as a consequence of mechanical lesions of the cochlea or biochemical lesions of the hair cells by ototoxic drugs, but also as a consequence of the loss of hair cells in connection with aging or noise exposure. In light of the aging world population and the increasing amount of noise in the modern world, understanding the plasticity of the central auditory system has its practical consequences and urgency. In most of these situations, a common denominator of central plastic changes is a deterioration of inhibition in the subcortical auditory nuclei and the auditory cortex. In addition to the processes that are elicited by decreased or lost receptor function, the function of nerve cells in the adult central auditory system may dynamically change in the process of learning. A better understanding of the plastic changes in the central auditory system after sensory deafferentation, sensory stimulation, and learning may contribute significantly to improvement in the rehabilitation of damaged or lost auditory function and consequently to improved speech processing and production.

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