Stress-Related Functional Connectivity Changes Between Auditory Cortex and Cingulate in Tinnitus

The question arises whether functional connectivity (FC) changes between the distress and tinnitus loudness network during resting state depends on the amount of distress tinnitus patients' experience. Fifty-five patients with constant chronic tinnitus were included in this study. Electroencephalography (EEG) recordings were performed and seed-based (at the auditory cortex) source localized FC (lagged phase synchronization) was computed for the different EEG frequency bands. Results initially demonstrate that the correlation between loudness and distress is nonlinear. Loudness correlates with beta3 and gamma band activity in the auditory cortices, and distress with alpha1 and beta3 changes in the subgenual, dorsal anterior, and posterior cingulate cortex. In comparison to nontinnitus controls, seed-based FC differed between the left auditory cortices for the alpha1 and beta3 bands in a network encompassing the posterior cingulate cortex extending into the parahippocampal area, the anterior cingulate, and insula. Furthermore, distress changes the FC between the auditory cortex, encoding loudness, and different parts of the cingulate, encoding distress: the subgenual anterior, the dorsal anterior, and the posterior cingulate. These changes are specific for the alpha1 and beta3 frequency bands. These results fit with a recently proposed model that states that tinnitus is generated by multiple dynamically active separable but overlapping networks, each characterizing a specific aspect of the unified tinnitus percept, but adds to this concept that the interaction between these networks is a complex interplay of correlations and anti-correlations between areas involved in distress and loudness depending on the distress state of the tinnitus patient.