Auditory network connectivity in tinnitus patients: a resting-state fMRI study

Abstract

Objective: Resting-state functional magnetic resonance imaging (fMRI) uncovers correlated activity between spatially distinct functionally related brain regions and offers clues about the integrity of functional brain circuits in people with chronic subjective tinnitus. We chose to investigate auditory network connectivity, adopting and extending previously used analyses methods to provide an independent evaluation of replicability.

Design: Independent components analysis (ICA) was used to identify coherent patterns arising from spontaneous brain signals within the resting-state data. The auditory network component was extracted and evaluated. Bivariate and partial correlation analyses were performed on pre-defined regions of bilateral auditory cortex to assess functional connectivity.

Study sample: Our design carefully matched participant groups for possible confounds, such as hearing status. Twelve patients (seven male, five female; mean age 66 years) all with chronic constant tinnitus and eleven controls (eight male, three female; mean age 68 years) took part.

Results: No significant differences were found in auditory network connectivity between groups after correcting for multiple statistical comparisons in the analysis. This contradicts previous findings reporting reduced auditory network connectivity; albeit at a less stringent statistical threshold.

Conclusions: Auditory network connectivity does not appear to be reliably altered by the experience of chronic subjective tinnitus.

Figure 1.

Mean average hearing thresholds for tinnitus and no tinnitus groups. Post hoc t-tests of average hearing thresholds found no significant differences between or within participant groups (P > 0.05). Error bars represent one standard error of the mean.

Figure 2. (A) Auditory network component and time-course. (B) Whole group one-sample t-test of auditory component, masked with auditory template (P < 0.05, uncorrected). Primary auditory cortex regions (circled in green). Nonprimary auditory cortex regions (circled in blue). (C) Whole group one-sample t-test of auditory network component (P < 0.001, uncorrected). (D) Tinnitus > No tinnitus two-sample t-test (P < 0.01, uncorrected, 48 voxel extent threshold) showing increased connectivity in the right supramarginal gyrus and increased connectivity in the left posterior middle temporal gyrus.

Figure 3. (A) Average bivariate correlation coefficients (beta values) for each paired ROI. The ‘auditory network’ refers to a combined mean average derived from the BOLD time-series of primary auditory and auditory association cortical seed regions. (B) Average partial correlation coefficients for each paired ROI. Error bars represent one standard error of the mean. PAC = primary auditory cortex, NAC = nonprimary auditory cortex, L = left, R = right, Ti = tinnitus group, No Ti = no tinnitus control group.