Hearing research
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Review
Auditory thalamic circuits and GABAA receptor function: Putative mechanisms in tinnitus pathology.
Tinnitus is defined as a phantom sound (ringing in the ears), and can significantly reduce the quality of life for those who suffer its effects. Ten to fifteen percent of the general adult population report symptoms of tinnitus with 1-2% reporting that tinnitus negatively impacts their quality of life. Noise exposure is the most common cause of tinnitus and the military environment presents many challenging high-noise situations. ⋯ Hyperpolarizing de-inactivation of T-type Ca2+ channels switches thalamocortical projection neurons into burst mode. Thalamocortical dysrhythmia originating in sensory thalamus has been postulated to underpin neuropathies including tinnitus and chronic pain. Here we review the relationship between noise-induced tinnitus and altered inhibition in the MGB.
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There is no standard diagnostic criterion for tinnitus, although some clinical assessment instruments do exist for identifying patient complaints. Within epidemiological studies the presence of tinnitus is determined primarily by self-report, typically in response to a single question. Using these methods prevalence figures vary widely. Given the variety of published estimates worldwide, we assessed and collated published prevalence estimates of tinnitus and tinnitus severity, creating a narrative synthesis of the data. The variability between prevalence estimates was investigated in order to determine any barriers to data synthesis and to identify reasons for heterogeneity. ⋯ Deriving global estimates of the prevalence of tinnitus involves combining results from studies which are consistent in their definition and measurement of tinnitus, survey methodology and in the reporting and analysis of the results. Ultimately comparison among studies is unachievable without such consistency. The strength of this systematic review is in providing a record of all the available, recent epidemiological data in each global region and in making recommendations for promoting standardisation.
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There is no standard diagnostic criterion for tinnitus, although some clinical assessment instruments do exist for identifying patient complaints. Within epidemiological studies the presence of tinnitus is determined primarily by self-report, typically in response to a single question. Using these methods prevalence figures vary widely. Given the variety of published estimates worldwide, we assessed and collated published prevalence estimates of tinnitus and tinnitus severity, creating a narrative synthesis of the data. The variability between prevalence estimates was investigated in order to determine any barriers to data synthesis and to identify reasons for heterogeneity. ⋯ Deriving global estimates of the prevalence of tinnitus involves combining results from studies which are consistent in their definition and measurement of tinnitus, survey methodology and in the reporting and analysis of the results. Ultimately comparison among studies is unachievable without such consistency. The strength of this systematic review is in providing a record of all the available, recent epidemiological data in each global region and in making recommendations for promoting standardisation.
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Tinnitus is a widespread auditory disorder affecting approximately 10-15% of the population, often with debilitating consequences. Although tinnitus commonly begins with damage to the auditory system due to loud-noise exposure, aging, or other etiologies, the exact neurophysiological basis of chronic tinnitus remains unknown. Many researchers point to a central auditory origin of tinnitus; however, a growing body of evidence also implicates other brain regions, including the limbic system. ⋯ Neuroimaging studies utilizing connectivity methods like resting-state fMRI and diffusion MRI continue to uncover tinnitus-related anomalies throughout auditory, limbic, and other brain systems. However, directly assessing interactions between these brain regions and networks has proved to be more challenging. Here, we review existing empirical support for models of tinnitus stressing a critical role for involvement of "non-auditory" structures in tinnitus pathophysiology, and discuss the possible impact of newly refined connectivity techniques from neuroimaging on tinnitus research.