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Auditory-Somatosensory Stimulation Alleviates Tinnitus in Human Subjects
Susan E. Shore1; Kendra Marks2; David T. Martel1; Gregory J. Basura3; Larry E. Roberts4; Kara Leyzac2
1Department of Otolaryngology, Kresge Hearing Re search Institute, University of Michigan, Ann Arbor, MI
48109, USA; 2University of Michigan; 3Dept of Otolaryngology; Center for Human Growth and Development;
University of Michigan; 4McMaster University
Background
A majority of tinnitus subjects are able to modulate their tinnitus by moving or applying pressure to their head or neck, so called, 'somatic' tinnitus [1]. This ability is mediated, at least in part, by the dorsal cochlear nucleus (DCN), which integrates auditory and somatosensory information [2]. DCN circuitry is altered in tinnitus to produce hypersynchrony and heightened spontaneous firing rates in output neurons [3]. Pairing auditory- with somatosensory stimuli can induce long-term increases or decreases in firing rates and synchrony in these neurons, depending on the precise timing of the bimodal intervals [3]. By presenting bimodal intervals that depressed firing rates and synchrony, we were able to decrease physiological and behavioral evidence of tinnitus in animals [4]. Here, we extend these findings to a human population.
Methods
Twenty human subjects with constant, bothersome somatic tinnitus were recruited to participate in a double-blinded, sham-controlled, cross-over study. Subjects were randomly assigned to sham (auditory only) or active (bimodal auditory-somatosensory) stimulation treatment. Somatosensory stimulation was achieved by pads placed on the face or neck. Using a take- home device, treatments consisted of 30 minutes a day of auditory only (sham) or bimodal (auditory-electric) stimulation for four weeks. Each sham or active period was followed by a four-week washout period. Throughout the sixteen-week study, subjects completed the Tinnitus functional Index (TFI) and loudness match- ing tasks to monitor their tinnitus on a weekly basis.
Results
Bimodal but not unimodal stimulation resulted in significant reductions in loudness matching (mean decrease of -7.334 dB) and total TFI score (mean decrease of 6.11 points), with11 of the subjects showing greater than a 13 point reduction in their TFI scores.
Conclusion
Bimodal auditory-somatosensory stimulation alters tinnitus circuitry to alleviate tinnitus in human subjects and could be a safe and effective treatment for a large number of tinnitus patients.
1. Levine, R., Somatic modulation of Tinnitus appears to be a fundamental attribute of tinnitus. Proceedings of the 6th International Tinnitus Seminar, Cambridge UK., 1999. 1: p. 93-197.
2. Koehler, S.D. and S.E. Shore, Stimulus timing-de- pendent plasticity in dorsal cochlear nucleus is altered in tinnitus. Journal of Neuroscience, 2013. 33(50): p. 19647-56.
3. Wu, C., D.T. Martel, and S.E. Shore, Increased Synchrony and Bursting of Dorsal Cochlear Nucleus Fusiform Cells Correlate with Tinnitus. J Neurosci, 2016. 36(6): p. 2068-73.
4. Martel, D., C. Wu, and S. Shore, Bimodal stimulation desynchronizes the tinnitus circuit in guinea pigs. ARO Abstracts, 2017.
https://clinicaltrials.gov/ct2/show/NCT02974543?term=tinnitus&rank=21