Functional connectivity during modulation of tinnitus with orofacial maneuvers

Abstract

Objective: To determine changes in cortical neural networks as defined by resting-state functional connectivity magnetic resonance imaging during voluntary modulation of tinnitus with orofacial maneuvers.

Study design: Cross-sectional study.

Setting: Academic medical center.

Subjects and methods: Participants were scanned during the maneuver and also at baseline to serve as their own control. The authors chose, a priori, 58 seed regions to evaluate previously described cortical neural networks by computing temporal correlations between all seed region pairs. Seed regions whose correlations significantly differed between rest and maneuver (P < .05, uncorrected) entered into a second-stage analysis of computing the correlation coefficient between the seed region and time courses in each of the remaining brain voxels. A threshold-free cluster enhancement permutation analysis evaluated the distribution of these correlation coefficients after transformation to Fisher z scores and registration to a surface-based reconstruction using Freesurfer.

Results: The median age for the 16 subjects was 54 years (range, 27-72 years), and all had subjective, unilateral or bilateral, nonpulsatile tinnitus for 6 months or longer. In 9 subjects who could voluntarily increase the loudness of their tinnitus, there were no significant differences in functional connectivity in any cortical networks. A separate analysis evaluated results from 3 patients who decreased the loudness of their tinnitus. Four subjects were excluded because of excessive motion in the scanner.

Conclusion: The absence of significant differences in functional connectivity due to voluntary orofacial maneuvers that increased tinnitus loudness failed to confirm prior reports of altered cerebral blood flows during somatomotor behaviors.

Figure 1

Functional connectivity maps for a subject whose maneuver increased tinnitus loudness show no strong differences between maneuver and rest states. Colors represent the strength of association (z scores). Most z scores were close to zero. Lateral views (top row) and medial views (second row) are shown for the right and left hemispheres of the brain. The bottom row contains flat maps, which are able to show all cortical areas simultaneously.

Figure 2

Functional connectivity maps for 3 subjects (rows A, B, C) whose maneuvers decreased tinnitus loudness showed no strong differences between maneuver and rest states. Each subject is shown individually because of the small number of patients recruited that could decrease tinnitus loudness. Most z scores were close to zero, demonstrating no strong associations with the left auditory cortex seed. Flat maps, which are able to show all cortical areas simultaneously, are shown for the left and right hemispheres in each patient.