Auditory resting-state network connectivity in tinnitus: a functional MRI study

Abstract

The underlying functional neuroanatomy of tinnitus remains poorly understood. Few studies have focused on functional cerebral connectivity changes in tinnitus patients. The aim of this study was to test if functional MRI "resting-state" connectivity patterns in auditory network differ between tinnitus patients and normal controls. Thirteen chronic tinnitus subjects and fifteen age-matched healthy controls were studied on a 3 tesla MRI. Connectivity was investigated using independent component analysis and an automated component selection approach taking into account the spatial and temporal properties of each component. Connectivity in extra-auditory regions such as brainstem, basal ganglia/NAc, cerebellum, parahippocampal, right prefrontal, parietal, and sensorimotor areas was found to be increased in tinnitus subjects. The right primary auditory cortex, left prefrontal, left fusiform gyrus, and bilateral occipital regions showed a decreased connectivity in tinnitus. These results show that there is a modification of cortical and subcortical functional connectivity in tinnitus encompassing attentional, mnemonic, and emotional networks. Our data corroborate the hypothesized implication of non-auditory regions in tinnitus physiopathology and suggest that various regions of the brain seem involved in the persistent awareness of the phenomenon as well as in the development of the associated distress leading to disabling chronic tinnitus.

Figure 1. Analysis steps (Blue Box).

For the analysis, two independent groups were included. The data of the first group (group 1, healthy controls) were analyzed in order to define auditory regions of interest (ROIs) subsequently used to select the auditory independent component in the second group (group 2, healthy controls and tinnitus patients). Data from group 2 were used to compare the auditory resting-state fMRI activity of healthy subjects and tinnitus patients. Auditory component selection (Red Box). The independent component (IC) reflecting the auditory network was selected based on both spatial and temporal properties. Upper panel (from left to right): Fingerprint of the selected IC; Spatial map of the selected IC (black contours indicate average auditory map calculated on group 1); Connectivity graph representing significant connectivity edges between the selected ROIs of the auditory network. Lower panel: Anticorrelation-corrected score of each graph vs. the corresponding IC number. The component with the highest score will be selected as the auditory network (IC 21 in the present example).

Figure 2. Regions of the auditory resting state network identified in controls and chronic tinnitus patients.

Figure 3. Increased (in red) and decreased (in blue) functional connectivity in the auditory resting-state network in tinnitus.

Results are thresholded at cluster level corrected p<0.05. 1- Brainstem/Cerebellum, 2-Basal ganglia/NAc, 3-Parahippocampal gyri, 4-Superior temporal gyrus, 5-Orbitofrontal cortex, 6-Prefrontal cortex, 7-Prefrontal cortex, 8-Superior frontal gyrus, 9-Inferior frontal gyrus, 10-Fusiform gyrus, 11-Superior temporal gyrus, 12-Postcentral gyrus, 13-Precentral gyrus, 14-Cuneus/Precuneus.