Abstract
We investigated auditory, dorsal attention, and default mode networks in adults with tinnitus and hearing loss in a resting state functional connectivity study. Data were obtained using continuous functional magnetic resonance imaging (fMRI) while the participants were at “rest” and were not performing any task. Participants belonged to one of three groups: middle-aged adults with tinnitus and mild-to-moderate high frequency hearing loss (TIN), age-matched controls with normal hearing and no tinnitus (NH), and a second control group with mild-to-moderate high frequency hearing loss without tinnitus (HL). After standard preprocessing, (a) a group independent component analysis (ICA) using 30 components and (b) a seeding-based connectivity analysis were conducted. In the group ICA, the default mode network was the only network to display visual differences between subject groups. In the seeding analysis, we found increased connectivity between the left parahippocampus and the auditory resting state network in the TIN group when compared to NH controls. Similarly, there was also an increased correlation between the right parahippocampus and the dorsal attention network when compared to HL controls. Other group differences in this attention network included decreased correlations between the seed regions and the right supramarginal gyrus in TIN patients when compared to HL controls. In the default mode network, there was a strong decrease in correlation between the seed regions and the precuneus when compared to both control groups. The findings of this study identify specific alterations in the connectivity of the default mode, dorsal attention, and auditory resting state networks due to tinnitus. The results suggest that therapies for tinnitus that mitigate the increased connectivity of limbic regions with auditory and attention resting state networks and the decreased coherence of the default mode network could be effective at reducing tinnitus-related distress.
Highlights
Spontaneous fluctuations in the blood oxygenation leveldependent (BOLD) response have been shown to reliably organize into spatially independent networks [1,2,3,4,5]
Our study examined three resting state networks likely to be influenced by tinnitus: the auditory resting state network, as tinnitus is an auditory phenomenon; the default mode network, which exhibits the most coherent activity at rest; and the dorsal attention network, as tinnitus patients often attend to their phantom percept
The auditory resting state network (RSN), DMN, and dorsal attention network (DAN) were all located within 30 components for each group using spatial sort, with each network visually matching the patterns in fluctuations similar to those found by other studies [2,4]
Summary
Spontaneous fluctuations in the blood oxygenation leveldependent (BOLD) response have been shown to reliably organize into spatially independent networks [1,2,3,4,5]. The DMN is found to be active during rest, when no task is being performed. The regions of this network include the medial prefrontal cortex, posterior cingulate cortex, precuneus, bilateral superior frontal gyri, and bilateral inferior parietal lobules [4]. Many other resting state networks have since been identified [4,6]. The non-invasive, relatively simple data collection associated with the resting state has made it an appealing way to study differences in connectivity between healthy controls and various populations with neurological disorders, including Alzheimer’s disease [7,8,9,10,11,12], schizophrenia [13,14,15,16,17,18], depression [19], and post-traumatic stress disorder [20]
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