Changes in gray and white matter in subgroups within the tinnitus population.

In this study, we investigated gray and white matter changes in subgroups within the larger tinnitus population related to differences in severity or duration of tinnitus symptoms. Tinnitus is the illusory perception of sound in the absence of an external source, most often experienced as a chronic condition. The psychological reaction to the sound constitutes the severity, or degree of discomfort experienced, and the duration refers to the time since onset of chronic tinnitus. We used voxel- and surface-based morphometry to investigate gray matter changes and diffusion tensor imaging (using fractional anisotropy, or FA, metrics) to assess changes in orientation of white matter tracts, using both whole brain and region of interest analyses. Whole brain analyses revealed decreased cortical thickness in the left parahippocampal gyrus in those with more severe tinnitus compared to a group with a milder reaction, and reduced gray matter volume in left anterior cingulate in those with mild tinnitus compared to a normal hearing control group without tinnitus. In the analysis based on FA, no significant differences were revealed between the subgroups or with respect to control groups in either whole brain or region of interest analyses. Our results suggest that these subgroups within the tinnitus population likely exhibit different anatomical alterations related to the disorder, which may explain the variable findings in the literature, particularly in terms of gray matter.

Increased Frontal Response May Underlie Decreased Tinnitus Severity.

OBJECTIVES: The overall goal of the study was to identify functional and behavioral differences between individuals with higher tinnitus distress and individuals with lower tinnitus distress. Subsequent exploratory analyses were conducted to investigate the role physical activity may have on the observed results between high and low distress groups. The purpose of the experiment was to identify brain regions to be targeted in future intervention studies for tinnitus. DESIGN: A total of 32 individuals with varying levels of tinnitus severity were recruited from the Urbana-Champaign area. Volunteers were divided into higher tinnitus distress (HD) and lower tinnitus distress (LD) groups. Note that these groups also significantly differed based on physical activity level and were subsequently stratified into higher and lower physical activity level subgroups for exploratory analysis. While in a functional magnetic resonance imaging (fMRI) scanner, subjects listened to affective sounds classified as pleasant, neutral or unpleasant from the International Affective Digital Sounds database. RESULTS: The HD group recruited amygdala and parahippocampus to a greater extent than the LD group when listening to affective sounds. The LD group engaged frontal regions to a greater extent when listening to the affective stimuli compared to the HD group. Both higher physical activity level subgroups recruited more frontal regions, and both lower levels of physical activity subgroups recruited more limbic regions respectively. CONCLUSION: Individuals with lower tinnitus distress may utilize frontal regions to better control their emotional response to affective sounds. Our analysis also suggests physical activity may contribute to lower tinnitus severity and greater engagement of the frontal cortices. We suggest that future intervention studies focus on changes in the function of limbic and frontal regions when evaluating the efficacy of treatment. Additionally, we recommend further investigation concerning the impact of physical activity level on tinnitus distress.

Neural Plasticity of Mild Tinnitus: An fMRI Investigation Comparing Those Recently Diagnosed with Tinnitus to Those That Had Tinnitus for a Long Period of Time.

Objectives. The aim of the study was to compare differences in neural correlates of tinnitus in adults with recent onset and others who had the disorder for longer than a year. Design. A total of 25 individuals with tinnitus were divided into groups based on the amount of time for which they had experienced tinnitus: <1 year (RTIN) or >1 year (LTIN). Subjects underwent an fMRI scan while listening to affective sounds from the International Affective Digital Sounds database. Resting state functional connectivity data were also collected. Results. The RTIN group recruited the posterior cingulate and insula to a greater extent than the LTIN group when processing affective sounds. In addition, we found that the LTIN group engaged more frontal regions when listening to the stimuli compared to the RTIN group. Lastly, we found increased correlations between the default mode network and the precuneus in RTIN patients compared to LTIN at rest. Conclusion. Our results suggest that the posterior cingulate and insula may be associated with an early emotional reaction to tinnitus in both task and resting states. Over time, tinnitus patients may recruit more frontal regions to better control their emotional response and exhibit altered connectivity in the default mode network.

Alterations to the attention system in adults with tinnitus are modality specific.

Generation and persistence of tinnitus following hearing loss may be due to aberrant engagement of attention. Here, functional MRI was used to determine differences in auditory and visual attention processing in adults with tinnitus and hearing loss compared to two age-matched control groups, one with matched hearing loss and the other with normal hearing thresholds. Attentional processing was investigated using a short-term memory task with varying loads, employing unfamiliar Korean letters in the visual condition and non-speech sounds in the auditory condition. We found similar behavioral response across the three groups for both modalities and tasks. For the auditory modality, the response of the attention network was suppressed in the tinnitus group compared to the control groups for both task loads, with the effect being more pronounced at high load. In contrast, in the visual modality, the tinnitus group exhibited greater response of the attention network, regardless of memory load, compared to the control groups. The results increase our understanding of the neural mechanisms of tinnitus and suggest that interventions that manipulate attention, especially in the visual domain, should be further investigated.

Physical Activity, Tinnitus Severity, and Improved Quality of Life.

OBJECTIVES: The objective of this study was to examine the effects of tinnitus severity on quality of life (QOL) and the benefits physical activity may have on tinnitus severity and QOL. The authors hypothesized that (1) QOL would be negatively correlated with tinnitus severity, (2) physical activity would be negatively correlated with tinnitus severity, (3) tinnitus severity and physical activity would have significant independent effects on QOL, and (4) physical activity would have significant and independent effects on tinnitus severity. DESIGN: An online survey was used to collect data from adults with tinnitus; 1030 individuals initiated the survey. Approximately 40% of responses were not included in data analysis due to incomplete data. The following measures were included in the survey: the Tinnitus Functional Index, the Godin Leisure-Time Exercise Question, the Medical Outcomes Study 36-item short form (Physical Component Score [PCS]; Mental Component Score [MCS]), and the Satisfaction with Life Scale (SWLS). Descriptive statistics, Pearson correlations, and multiple linear regression analyses were conducted. RESULTS: Higher levels of physical activity were significantly associated with improved health-related and global QOL and lower levels of tinnitus severity. Both tinnitus severity (12.3% SWLS, 3.8% PCS, and 21.2% MCS) and physical activity (1.1% SWLS, 5.8% PCS, and 1.1% MCS) accounted for significant unique variations in the QOL measures. Physical activity accounted (0.8% Tinnitus Functional Index) for significant unique variation in tinnitus severity. CONCLUSIONS: Physical activity had a small but statistically significant correlation with QOL and tinnitus distress. Our results suggest that physical activity may be a management strategy for those with tinnitus, but further testing is necessary to assess the relationship between physical activity and tinnitus severity.

Alterations of the emotional processing system may underlie preserved rapid reaction time in tinnitus.

Although alterations of the limbic system have been linked to tinnitus persistence, the neural networks underlying such alteration are unclear. The present study investigated the effect of tinnitus on emotional processing in middle-aged adults using functional magnetic resonance imaging and stimuli from the International Affective Digital Sounds database. There were three groups of participants: bilateral hearing loss with tinnitus (TIN), age- and gender-matched controls with bilateral hearing loss without tinnitus (HL) and matched normal hearing controls without tinnitus (NH). In the scanner, subjects rated sounds as pleasant, unpleasant, or neutral. The TIN and NH groups, but not the HL group, responded faster to affective sounds compared to neutral sounds. The TIN group had elevated response in bilateral parahippocampus and right insula compared to the NH group, and left parahippocampus compared to HL controls for pleasant relative to neutral sounds. A region-of-interest analysis detected increased activation for NH controls in the right amygdala when responding to affective stimuli, but failed to find a similar heightened response in the TIN and HL groups. All three groups showed increased response in auditory cortices for the affective relative to neutral sounds comparisons. Our results suggest that the emotional processing network is altered in tinnitus to rely on the parahippocampus and insula, rather than the amygdala, and this alteration may maintain a select advantage for the rapid processing of affective stimuli despite the hearing loss. The complex interaction of tinnitus and the limbic system should be accounted for in development of new tinnitus management strategies.

The effect of mild-to-moderate hearing loss on auditory and emotion processing networks.

We investigated the impact of hearing loss (HL) on emotional processing using task- and rest-based functional magnetic resonance imaging. Two age-matched groups of middle-aged participants were recruited: one with bilateral high-frequency HL and a control group with normal hearing (NH). During the task-based portion of the experiment, participants were instructed to rate affective stimuli from the International Affective Digital Sounds (IADS) database as pleasant, unpleasant, or neutral. In the resting state experiment, participants were told to fixate on a "+" sign on a screen for 5 min. The results of both the task-based and resting state studies suggest that NH and HL patients differ in their emotional response. Specifically, in the task-based study, we found slower response to affective but not neutral sounds by the HL group compared to the NH group. This was reflected in the brain activation patterns, with the NH group employing the expected limbic and auditory regions including the left amygdala, left parahippocampus, right middle temporal gyrus and left superior temporal gyrus to a greater extent in processing affective stimuli when compared to the HL group. In the resting state study, we observed no significant differences in connectivity of the auditory network between the groups. In the dorsal attention network (DAN), HL patients exhibited decreased connectivity between seed regions and left insula and left postcentral gyrus compared to controls. The default mode network (DMN) was also altered, showing increased connectivity between seeds and left middle frontal gyrus in the HL group. Further targeted analysis revealed increased intrinsic connectivity between the right middle temporal gyrus and the right precentral gyrus. The results from both studies suggest neuronal reorganization as a consequence of HL, most notably in networks responding to emotional sounds.

Default mode, dorsal attention and auditory resting state networks exhibit differential functional connectivity in tinnitus and hearing loss.

We investigated auditory, dorsal attention, and default mode networks in adults with tinnitus and hearing loss in a resting state functional connectivity study. Data were obtained using continuous functional magnetic resonance imaging (fMRI) while the participants were at "rest" and were not performing any task. Participants belonged to one of three groups: middle-aged adults with tinnitus and mild-to-moderate high frequency hearing loss (TIN), age-matched controls with normal hearing and no tinnitus (NH), and a second control group with mild-to-moderate high frequency hearing loss without tinnitus (HL). After standard preprocessing, (a) a group independent component analysis (ICA) using 30 components and (b) a seeding-based connectivity analysis were conducted. In the group ICA, the default mode network was the only network to display visual differences between subject groups. In the seeding analysis, we found increased connectivity between the left parahippocampus and the auditory resting state network in the TIN group when compared to NH controls. Similarly, there was also an increased correlation between the right parahippocampus and the dorsal attention network when compared to HL controls. Other group differences in this attention network included decreased correlations between the seed regions and the right supramarginal gyrus in TIN patients when compared to HL controls. In the default mode network, there was a strong decrease in correlation between the seed regions and the precuneus when compared to both control groups. The findings of this study identify specific alterations in the connectivity of the default mode, dorsal attention, and auditory resting state networks due to tinnitus. The results suggest that therapies for tinnitus that mitigate the increased connectivity of limbic regions with auditory and attention resting state networks and the decreased coherence of the default mode network could be effective at reducing tinnitus-related distress.