Objectives: The ability of a treatment method to interfere with tinnitus-related neural activity patterns, such as cortical gamma rhythms, has been suggested to indicate its potential in relieving tinnitus. Therapeutic modulation of gamma-band oscillations with vagus nerve stimulation has been recently reported in epileptic patients. The aim of this study was to investigate the effects of transcutaneous vagus nerve stimulation (tVNS) on neural oscillatory patterns.
Design: We calculated the power spectral density and synchrony of magnetoencephalography recordings during auditory stimulation in seven tinnitus patients and eight normal-hearing control subjects. Comparisons between subject groups were performed to reveal electrophysiological markers of tinnitus. tVNS-specific effects within each group were studied by comparing recording blocks with and without tVNS. We also investigated the correlation of each measure with individual ratings of tinnitus distress, as measured by the tinnitus handicap inventory questionnaire.
Results: Tinnitus patients differed from controls in the baseline condition (no tVNS applied), measured by both cortical oscillatory power and synchronization, particularly at beta and gamma frequencies. Importantly, we found tVNS-induced changes in synchrony, correlating strongly with tinnitus handicap inventory scores, at whole-head beta-band (r = −0.857, p = 0.007), whole-head gamma-band (r = −0.952, p = 0.0003), and frontal gamma-band (r = −0.952, p = 0.0003).
Conclusions: We conclude that tVNS was successful in modulating tinnitus-related beta- and gamma-band activity and thus could have potential as a treatment method for tinnitus.
The authors studied brain activity patterns of tinnitus patients and controls with MEG and found differences in baseline oscillatory power spectral density and synchrony between the two groups. Transcutaneous Vagus Nerve Stimulation (tVNS) further induced changes in beta- and gamma-band synchrony, which correlated with individual rankings of tinnitus distress, as measured by Tinnitus Handicap Inventory scores. tVNS successfully modulated tinnitus-related activity and could thus have potential as a treatment method for tinnitus.
1Department of Otorhinolaryngology–Head and Neck Surgery, Helsinki University Central Hospital and University of Helsinki, Helsinki, Finland; 2Department of Biomedical Engineering and Computational Science, Aalto University School of Science, Espoo, Finland; 3School of Medicine, University of Tampere, Tampere, Finland; 4BioMag Laboratory, HUS Medical Imaging Center, Helsinki University Central Hospital, Helsinki, Finland; and 5Helsinki Ear Institute, Helsinki, Finland.
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The work of P.H. was supported by grants from the Paulo Foundation and the Research Foundation of Helsinki University of Technology.
The authors declare no other conflicts of interest.
Received March 10, 2014; accepted September 29, 2014.
Address for correspondence: Petteri Hyvärinen, P.O. Box 220, FI-00029 HUS, Helsinki, Finland. E-mail: firstname.lastname@example.org