Tinnitus- and Task-Related Differences in Resting-State Networks

Abstract

We investigated tinnitus-related differences in functional networks in adults with tinnitus by means of a functional connectivity study. Previously it was found that various networks show differences in connectivity in patients with tinnitus compared to controls. How this relates to patients' ongoing tinnitus and whether the ecological sensory environment modulates connectivity remains unknown. Twenty healthy controls and twenty patients suffering from chronic tinnitus were enrolled in this study. Except for the presence of tinnitus in the patient group, all subjects were selected to have normal or near-normal hearing. fMRI data were obtained in two different functional states. In one set of runs, subjects freely viewed emotionally salient movie fragments ("fixed-state") while in the other they were not performing any task ("resting-state"). After data pre-processing, Principal Component Analysis was performed to obtain 25 components for all datasets. These were fed into an Independent Component Analysis (ICA), concatenating the data across both groups and both datasets, to obtain group-level networks of neural origin, each consisting of spatial maps with their respective time-courses. Subject-specific maps and their time-course were obtained by back-projection (Dual Regression). For each of the components a mixed-effects linear model was composed with factors group (tinnitus vs. controls), task (fixed-state vs. resting state) and their interaction. The neural components comprised the visual, sensorimotor, auditory, and limbic systems, the default mode, dorsal attention, executive-control, and frontoparietal networks, and the cerebellum. Most notably, the default mode network (DMN) was less extensive and shows significantly less connectivity in tinnitus patients than in controls. This group difference existed in both paradigms. At the same time, the DMN was stronger during resting-state than during fixed-state in the controls but not the patients. We attribute this pattern to the unremitting engaging effect of the tinnitus percept.

Heidelberg Neuro-Music Therapy Enhances Task-Negative Activity in Tinnitus Patients

“…However, the relationship between distress and precuneus involvement is still unclear. Following the observations of Lanting et al (2016) and Schmidt et al (2013), we argued that the state of mental rest may be corrupted by the tinnitus, since it induces a salient stimulus that in turn reduces DMN activation at rest. We measured task-positive and task-negative activity using fMRI in a visual word recognition task in tinnitus patients and healthy controls both treated with HNMT, as well as in untreated tinnitus patients.…”

“…Lanting et al (2016) observed suppressed addressability of DMN by TNAs in tinnitus patients in comparison to healthy controls. Ueyama et al (2013) measured reduced global connectivity in the DMN-specific RSN regions, including the PCC, with increasing loudness of tinnitus.…”

“…Ueyama et al (2013) measured reduced global connectivity in the DMN-specific RSN regions, including the PCC, with increasing loudness of tinnitus. This means that suffering from tinnitus can cause a degradation of the PCC/precuneus functions in task-negative phases (Lanting et al, 2016). Independent component analysis using resting-state fMRI also partly indicated a reduced engagement of this DMN region in tinnitus patients due to a more task-based state due to perception of the internal noise (Schmidt et al, 2013).…”

“…The intrinsic DMN activation has been shown to be reduced in patients with psychiatric disorders (Broyd et al, 2009; Sripada et al, 2012) but also in patients experiencing tinnitus-related distress (De Ridder et al, 2014; Husain and Schmidt, 2014; Lanting et al, 2016; Leaver et al, 2016). However, opposite findings with respect to recent-onset tinnitus have been observed, though focused on the precuneus, too (Carpenter-Thompson et al, 2015).…”

“…Findings on TNAs and neural connectivity results from resting-state fMRI indicated that the PCC/precuneus region is also corrupted by tinnitus (Schmidt et al, 2013; Han et al, 2015; Vanneste and De Ridder, 2015; Lanting et al, 2016) due to its role in the brain's sleep control (Shannon et al, 2013) which in turn is impaired by tinnitus (Alster et al, 1993). However, the relationship between distress and precuneus involvement is still unclear.…”