Mapping cortical hubs in tinnitus

Scientific Reports

The present study used resting state MEG whole-head recordings to identify how chronic tonal tinnitus relates to altered functional connectivity of brain’s intrinsic cortical networks. Resting state MEG activity of 40 chronic tinnitus patients and 40 matched human controls was compared identifying significant alterations in intrinsic networks of the tinnitus population. Directed functional connectivity of the resting brain, at a whole cortex level, was estimated by means of a statistical comparison of the estimated phase Transfer Entropy (pTE) between the time-series of cortical activations, as reconstructed by LORETA. As pTE identifies the direction of the information flow, a detailed analysis of the connectivity differences between tinnitus patients and controls was possible. Results indicate that the group of tinnitus patients show increased connectivity from right dorsal prefrontal to right medial temporal areas. Our results go beyond previous findings by indicating that the rol...

BMC Neuroscience, 2009

Background: Subjective tinnitus is characterized by an auditory phantom perception in the absence of any physical sound source. Consequently, in a quiet environment, tinnitus patients differ from control participants because they constantly perceive a sound whereas controls do not. We hypothesized that this difference is expressed by differential activation of distributed cortical networks.

PLOS One, 2008

Background: Tinnitus is an auditory phantom perception that is most likely generated in the central nervous system. Most of the tinnitus research has concentrated on the auditory system. However, it was suggested recently that also non-auditory structures are involved in a global network that encodes subjective tinnitus. We tested this assumption using auditory steady state responses to entrain the tinnitus network and investigated long-range functional connectivity across various non-auditory brain regions.

Investigative Magnetic Resonance Imaging

One of the suggested potential mechanisms of tinnitus is an alteration in perception in the neural auditory pathway. The aim of this study was to investigate the difference in laterality in functional connectivity between tinnitus patients and healthy controls using resting state functional MRI (rs-fMRI). Materials and Methods: Thirty-eight chronic tinnitus subjects and 45 age-matched healthy controls were enrolled in this study. Connectivity was investigated using independent component analysis, and the laterality index map was calculated based on auditory (AN) and dorsal attention (DAN), default mode (DMN), sensorimotor, salience (SalN), and visual networks (VNs). The laterality index (LI) of tinnitus subjects was compared with that of normal controls using region-of-interest (ROI) and voxelbased methods and a two-sample unpaired t-test. Pearson correlation was conducted to assess the associations between the LI in each network and clinical variables. Results: The AN and VN showed significant differences in LI between the two groups in ROI analysis (P < 0.05), and the tinnitus group had clusters with significantly decreased laterality of AN, SalN, and VN in voxel-based comparisons. The AN was positively correlated with tinnitus distress (tinnitus handicap inventory), and the SalN was negatively correlated with symptom duration (P < 0.05). Conclusion: The results of this study suggest that various functional networks related to psychological distress can be modified by tinnitus, and that this interrelation can present differently on the right and left sides, according to the dominance of the network.

PLoS ONE, 2012

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. Citation: Maudoux A, Lefebvre P, Cabay J-E, Demertzi A, Vanhaudenhuyse A, et al. (2012) Auditory Resting-State Network Connectivity in Tinnitus: A Functional MRI Study. PLoS ONE 7(5): e36222.

BMC Neuroscience, 2012

Background: The objective was to examine functional connectivity linked to the auditory system in patients with bothersome tinnitus. Activity was low frequency (< 0.1 Hz), spontaneous blood oxygenation level-dependent (BOLD) responses at rest. The question was whether the experience of chronic bothersome tinnitus induced changes in synaptic efficacy between co-activated components. Functional connectivity for seed regions in auditory, visual, attention, and control networks was computed across all 2 mm 3 brain volumes in 17 patients with moderate-severe bothersome tinnitus (Tinnitus Handicap Index: average 53.5 ± 3.6 (range 38-76)) and 17 agematched controls. Results: In bothersome tinnitus, negative correlations reciprocally characterized functional connectivity between auditory and occipital/visual cortex. Negative correlations indicate that when BOLD response magnitudes increased in auditory or visual cortex they decreased in the linked visual or auditory cortex, suggesting reciprocally phase reversed activity between functionally connected locations in tinnitus. Both groups showed similar connectivity with positive correlations within the auditory network. Connectivity for primary visual cortex in tinnitus included extensive negative correlations in the ventral attention temporoparietal junction and in the inferior frontal gyrus and rostral insula -executive control network components. Rostral insula and inferior frontal gyrus connectivity in tinnitus also showed greater negative correlations in occipital cortex.

Journal of the Korean Society of Radiology, 2016

Purpose: To identify potential differences in resting-state networks according to laterality of tinnitus using resting-state functional MRI (fMRI). Materials and Methods: A total of 83 age-matched subjects consisting of 19 patients with right-sided tinnitus (Rt-T), 22 patients with left-sided tinnitus (Lt-T), 22 patients with bilateral tinnitus (Bil-T), and 20 healthy controls underwent restingstate blood oxygenation-level dependent fMRI scans. Independent component analysis was used to obtain the functional connectivities in the auditory network (AN) and the default mode network (DMN), which were compared between each group using the voxel-wise one-way ANOVA. In addition, lateralization of the auditory cortex was assessed within each group using a region of interest (ROI). Results: Comparisons between tinnitus groups showed unusual clusters with different functional connectivities in the AN and the DMN. The Rt-T group had large clusters with higher functional connectivity in the right middle temporal gyrus and temporopolar area compared with the Lt-/Bil-T and control groups. ROI analysis showed that the Rt-/Lt-T groups had dominant functional connectivity in the right auditory cortex and the Bil-T and control groups had left-dominant auditory connectivity. Conclusion: These results suggest that chronic tinnitus is related to aberrant laterality of the auditory cortex. These findings help clarify the neural mechanism of tinnitus and specify the targets for localization of treatment.

Brain Structure and Function, 2013

Neuroimaging studies of tinnitus suggest the involvement of wide-spread neural networks for perceptual, attentional, memory, and emotional processes encompassing auditory, frontal, parietal, and limbic areas. Despite sparse findings for tinnitus duration and laterality, tinnitus distress has been shown to be related to changes in non-auditory cortical areas. The aim of this study was to correlate tinnitus characteristics with grey matter volume in two large samples of tinnitus patients. High-resolution brain images were obtained using a 1.5 T magnetic resonance imaging scanner and analysed by means of voxel-based morphometry. In sample one (n = 257), tinnitus distress correlated negatively with grey matter volume in bilateral auditory areas including the Heschl's gyrus and insula, that is, the higher the tinnitus distress the lower the grey matter volume. The effects of this correlation were small, but stable after correction for potential confounders such as age, gender, and audiometric parameters. This negative correlation was replicated in a second independent sample (n = 78). Our results support the notion that the role of the auditory cortex in tinnitus is not restricted to perceptual aspects. The distress observed was dependent on grey matter alterations in the auditory cortex, which could reflect reverberations between perceptual and distress networks.

PLoS ONE, 2014

Tinnitus is characterized by the perception of sound in the absence of an external auditory stimulus. The network connectivity of auditory and non-auditory brain structures associated with emotion, memory and attention are functionally altered in debilitating tinnitus. Current studies suggest that tinnitus results from neuroplastic changes in the frontal and limbic temporal regions. The objective of this study was to use Single-Photon Emission Computed Tomography (SPECT) to evaluate changes in the cerebral blood flow in tinnitus patients with normal hearing compared with healthy controls. Methods: Twenty tinnitus patients with normal hearing and 17 healthy controls, matched for sex, age and years of education, were subjected to Single Photon Emission Computed Tomography using the radiotracer ethylenedicysteine diethyl ester, labeled with Technetium 99 m (99 mTc-ECD SPECT). The severity of tinnitus was assessed using the ''Tinnitus Handicap Inventory'' (THI). The images were processed and analyzed using ''Statistical Parametric Mapping'' (SPM8). Results: A significant increase in cerebral perfusion in the left parahippocampal gyrus (pFWE ,0.05) was observed in patients with tinnitus compared with healthy controls. The average total THI score was 50.8+18.24, classified as moderate tinnitus. Conclusion: It was possible to identify significant changes in the limbic system of the brain perfusion in tinnitus patients with normal hearing, suggesting that central mechanisms, not specific to the auditory pathway, are involved in the pathophysiology of symptoms, even in the absence of clinically diagnosed peripheral changes. Citation: Laureano MR, Onishi ET, Bressan RA, Castiglioni MLV, Batista IR, et al. (2014) Memory Networks in Tinnitus: A Functional Brain Image Study. PLoS ONE 9(2): e87839.

PLOS Medicine, 2005

Here, we show that the spontaneous neuronal activity of a group of individuals with tinnitus (n = 17) is characterised by a marked reduction in alpha (8-12 Hz) power together with an enhancement in delta (1.5-4 Hz) as compared to a normal hearing control group (n = 16). This pattern was especially pronounced for temporal regions. Moreover, correlations with tinnitusrelated distress revealed strong associations with this abnormal spontaneous activity pattern, particularly in right temporal and left frontal areas. Overall, effects were stronger for the alpha than for the delta frequency band. A data stream of 5 min, recorded with a whole-head neuromagnetometer under a resting condition, was sufficient to extract the marked differences.