The mechanisms of tinnitus: Perspectives from human functional neuroimaging

Abstract

In this review, we highlight the contribution of advances in human neuroimaging to the current understanding of central mechanisms underpinning tinnitus and explain how interpretations of neuroimaging data have been guided by animal models. The primary motivation for studying the neural subtrates of tinnitus in humans has been to demonstrate objectively its representation in the central auditory system and to develop a better understanding of its diverse pathophysiology and of the functional interplay between sensory, cognitive and affective systems. The ultimate goal of neuroimaging is to identify subtypes of tinnitus in order to better inform treatment strategies. The three neural mechanisms considered in this review may provide a basis for TI classification. While human neuroimaging evidence strongly implicates the central auditory system and emotional centres in TI, evidence for the precise contribution from the three mechanisms is unclear because the data are somewhat inconsistent. We consider a number of methodological issues limiting the field of human neuroimaging and recommend approaches to overcome potential inconsistency in results arising from poorly matched participants, lack of appropriate controls and low statistical power. AbstractIn this review, we highlight the contribution of advances in human neuroimaging to the current understanding of central mechanisms underpinning tinnitus and explain how interpretations of neuroimaging data have been guided by animal models. The primary motivation for studying the neural subtrates of tinnitus in humans has been to demonstrate objectively its representation in the central auditory system and to develop a better understanding of its diverse pathophysiology and of the functional interplay between sensory, cognitive and affective systems. The ultimate goal of neuroimaging is to identify subtypes of tinnitus in order to better inform treatment strategies. The three neural mechanisms considered in this review may provide a basis for TI classification. While human neuroimaging evidence strongly implicates the central auditory system and emotional centres in TI, evidence for the precise contribution from the three mechanisms is unclear because the data are somewhat inconsistent. We consider a number of methodological issues limiting the field of human neuroimaging and recommend approaches to overcome potential inconsistency in results arising from poorly matched participants, lack of appropriate controls and low statistical power.

Tinnitus

“…21 The current assumption is that the neural changes measured in the animal models of hearing loss are the neural correlates of the human clinical symptoms; however, this assumption has not yet been confi rmed. 22 An increased spontaneous fi ring rate of neurons in the central auditory system is one possibility for the neural substrate of tinnitus. Cochlear hearing loss reduces cochlear nerve activity, and this reduced activity within the aff ected peripheral auditory region downregulates inhibitory cortical processes.…”

Differential tinnitus-related neuroplastic alterations of cortical thickness and surface area

“…With the advent of neuroimaging techniques a considerable number of functional brain scan studies have been performed (for reviews, see [24,25]). The number of studies that scrutinized the neuroanatomical changes in the brain structure of TI is smaller, but for the time being, the results are notably inconsistent and 50 heterogeneous [26,27,28,29,30,31,32] (for a review, see [33]).…”

Rapid Increase in Neural Conduction Time in the Adult Human Auditory Brainstem Following Sudden Unilateral Deafness

“…These neural changes are thought to underlie sensory disorders such as neurogenic pain, phantom limbs and analogous hearing disorders such as tinnitus and hyperacusis (e.g. Rauschecker 1999;Salvi et al 2000;Woolf and Salter 2000;Adjamian et al 2009;Gu et al 2010;Irvine 2010;Zeng 2013). An improved understanding of injury-induced plasticity might therefore lead to the development of interventions for the resulting perceptual disorders.…”