Functional connectivity networks in nonbothersome tinnitus

Abstract

Objective: To assess functional connectivity in cortical networks in patients with nonbothersome tinnitus compared with a normal healthy nontinnitus control group by measuring low-frequency (<0.1 Hz) spontaneous blood oxygenation level-dependent (BOLD) signals at rest.

Design: Case-control.

Setting: Academic medical center.

Participants: Nonbothersome, idiopathic subjective tinnitus for at least 6 months (n = 18) and a normal healthy nontinnitus control group (n = 23).

Main outcome measure: Functional connectivity differences in 58 a priori selected seed regions of interest encompassing cortical loci in the default mode, attention, auditory, visual, somatosensory, and cognitive networks.

Results: The median age of the 18 subjects was 54 years (interquartile range [IQR], 52-57), 66% were male, 90% were white, median Tinnitus Handicap Inventory (THI) score was 8 (IQR, 4-14), and a median Beck Depression Index score was 1 (IQR, 0-5). The median age for the control group was 46 years (IQR, 39-54), and 52% were male. Of the 58 seeds analyzed, no regions had significantly different functional connectivity among the nonbothersome tinnitus group when compared with the control group.

Conclusion: Among nonbothersome tinnitus patients, the tinnitus percept does not appear to alter the functional connectivity of the auditory cortex or other key cortical regions. Trial Registration ClinicalTrials.gov Identifier: NCT01049828.

Figure 1

Significant t test probabilities for the differences in connectivity within different seed regions between tinnitus and nontinnitus control groups. Black rectangles represent same-seed comparisons. Abbreviations for significant regions: LaIPL, left anterior inferior parietal lobule; LaPFC, left anterior prefrontal cortex; LAud_Ctx, left auditory cortex; LdlPFC, left dorsolateral prefrontal cortex; LIFG, left inferior frontal gyrus; LpIPS, left posterior intraparietal sulcus; LS1, left postcentral gyrus; LS2, left parietal operculum; LTPJ, left temporoparietal junction; LV1, left calcarine sulcal cortex; LV8, left fusiform gyrus; PCC, posterior cingulate cortex; RAI, right anterior insula; RaIPL, right anterior inferior parietal lobule; RAud, right auditory cortex; RdlPFC, right dorsolateral prefrontal cortex; RpIPS, right posterior intraparietal sulcus; RPOCS, right parieto-occipital sulcus; RSTS, right superior temporal sulcus; RvIPS, right ventral intraparietal sulcus.

Figure 2

Functional connectivity map for the left auditory cortex (LAud_Ctx) for the control and tinnitus groups. Functional connectivity for controls (column 1), tinnitus (column 2), and the difference between controls and tinnitus (column 3) displayed on a PALS-B12 atlas surface. The right hemisphere view (row 1), left hemisphere view (row 2), and auditory cortex seed region (black circle) are shown. The distribution of significant positive and negative correlations between time courses in the seed vs other brain regions is shown in shades of blue to yellow. The Difference column represents the difference in activity between controls and tinnitus based on Fisher z transforms of correlations. No significant clusters were identified using the left auditory cortex seed region.