Aberrant spontaneous brain activity in chronic tinnitus patients revealed by resting-state functional MRI

Abstract

ObjectiveThe neural mechanisms that give rise to the phantom sound of tinnitus are poorly understood. This study aims to investigate whether aberrant spontaneous brain activity exists in chronic tinnitus patients using resting-state functional magnetic resonance imaging (fMRI) technique.Materials and methodsA total of 31 patients with chronic tinnitus patients and 32 healthy age-, sex-, and education-matched healthy controls were prospectively examined. Both groups had normal hearing thresholds. We calculated the amplitude of low-frequency fluctuations (ALFFs) of fMRI signals to measure spontaneous neuronal activity and detect the relationship between fMRI information and clinical data of tinnitus.ResultsCompared with healthy controls, we observed significant increased ALFF within several selected regions including the right middle temporal gyrus (MTG), right superior frontal gyrus (SFG), and right angular gyrus; decreased ALFF was detected in the left cuneus, right middle occipital gyrus and bilateral thalamus. Moreover, tinnitus distress correlated positively with increased ALFF in right MTG and right SFG; tinnitus duration correlated positively with higher ALFF values in right SFG.ConclusionsThe present study confirms that chronic tinnitus patients have aberrant ALFF in many brain regions, which is associated with specific clinical tinnitus characteristics. ALFF disturbance in specific brain regions might be used to identify the neuro-pathophysiological mechanisms in chronic tinnitus patients.

Impairments of thalamic resting-state functional connectivity in patients with chronic tinnitus

“…The frontal cortex was hypothesized to play an important role in tinnitus and neuroimaging studies identified abnormalities in the frontal cortex which could account for tinnitus [27]. We also found that aberrant ALFF activity in the SFG was correlated with tinnitus distress [4]. Others have found that structural and functional differences in ventromedial prefrontal cortex were correlated with tinnitus characteristics such as subjective loudness; results suggesting the frontal cortex may contribute to certain perceptual features of tinnitus [13].…”

“…Our group recently found disrupted spontaneous neural activity in the visual cortex of chronic tinnitus patients [4]; disrupted spontaneous activity in the visual cortex of patients may be one factor contributing to the decreased functional connectivity between visual cortex and thalamus. Several frontal lobe regions showed disrupted connectivity to left or right thalamus in tinnitus.…”

“…Resting oxygenation level-dependent (BOLD) responses has proved to be a useful noninvasive technique to assess the underlying pathogenesis of tinnitus-induced neural dysfunction [4][5][6]. Recently, our group found that chronic tinnitus patients with normal hearing exhibited altered amplitude of low-frequency fluctuations (ALFF) in several brain regions, such as the middle temporal gyrus (MTG) and angular gyrus, regions previously implicated in tinnitus [4].…”

“…Resting oxygenation level-dependent (BOLD) responses has proved to be a useful noninvasive technique to assess the underlying pathogenesis of tinnitus-induced neural dysfunction [4][5][6]. Recently, our group found that chronic tinnitus patients with normal hearing exhibited altered amplitude of low-frequency fluctuations (ALFF) in several brain regions, such as the middle temporal gyrus (MTG) and angular gyrus, regions previously implicated in tinnitus [4]. Other resting state studies have focused on the functional connectivity among disparate brain areas; these measurements provide insights related to the temporal synchrony or interregional cooperation between two or more spatially separate regions [5,6].…”

“…High-field proton magnetic resonance spectroscopy (MRS) showed a downregulation of the inhibitory neurotransmitter, gamma-aminobutyric acid (GABA), in the thalamus of rats with chronic tinnitus [12]. Tinnitus was associated with decreased ALFF activity bilaterally in the thalamus function [4]. Other sound-evoked fMRI showed that tinnitus was associated with reduced functional connectivity between thalamus and cortex [13][14][15].…”