Neurophysiological correlates of residual inhibition in tinnitus: Hints for trait-like EEG power spectra

Objective To investigate oscillatory brain activity changes following acoustic stimulation in tinnitus and whether these changes are associated with behavioral measures of tinnitus loudness. Moreover, differences in ongoing brain activity between individuals with and without residual inhibition (RI) are examined (responders vs. non-responders). Methods Three different types of noise stimuli were administered for acoustic stimulation in 45 tinnitus patients. Subjects resting state brain activity was recorded before and after stimulation via EEG alongside with subjective measurements of tinnitus loudness. Results Delta, theta and gamma band power increased, whereas alpha and beta power decreased from pre to post stimulation. Acoustic stimulation responders exhibited reduced gamma and a trend for enhanced alpha activity with the latter localized in the right inferior temporal gyrus. Post stimulation, individuals experiencing RI showed higher theta, alpha and beta power with a peak power difference in the alpha band localized in the right superior temporal gyrus. Neither correlations with behavioral tinnitus measures nor stimulus-specific changes in EEG activity were present. Conclusions Our observations might be indicative of trait-specific forms of oscillatory signatures in different subsets of the tinnitus population related to acoustic tinnitus suppression. Significance Results and insights are not only useful to understand basic neural mechanisms behind RI but are also valuable for general neural models of tinnitus