E-field guided repetitive transcranial magnetic stimulation modulates oscillatory brain activity dynamics in tinnitus
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Introduction
The auditory phantom sound perception tinnitus is accompanied by maladaptive neurophysiological changes. In tinnitus treatment, repetitive transcranial magnetic stimulation (rTMS) is applied to counteract these pathological alterations. Previous work showed that single-session rTMS can reduce tinnitus loudness and modulate tinnitus-associated oscillatory brain activity. This study aimed to contribute to this research branch by addressing previous methodological shortcomings, including the absence of neuronavigation and adequate sham control. The objective was to assess tinnitus loudness and ongoing brain activity changes following various rTMS protocols, and to characterize modulations related to patient-specific most effective protocols, potentially uncovering electrophysiological markers of tinnitus suppression.
Methods
Three active protocols (1,10,20 Hz; 200 pulses) and one sham protocol (0.1 Hz; 20 pulses) were delivered to the left and right temporo-parietal junction of 22 chronic subjective tinnitus patients using e-field-guided neuronavigation. Resting state EEG was recorded before and after each stimulation, along with tinnitus loudness ratings. Patient-specific protocols eliciting maximal suppression were identified via significant pre-to-post loudness reductions exceeding sham.
Results
Right 10 Hz rTMS induced strongest loudness suppressions. Significant and sham-superior EEG modulations were observed after right 10 Hz, right 20 Hz and left 20 Hz. Power increases in the Delta, Theta, Alpha and Gamma frequency bands were mainly observed in frontal and temporal areas but did not correlate with reported tinnitus suppression. In 16 patients it was feasible to identify a protocol inducing significant loudness reduction exceeding sham. Here suppression was associated with increased Alpha activity in the frontal cortex.
Conclusions
Our findings demonstrate that brief rTMS protocols can transiently suppress tinnitus and modulate tinnitus-related oscillatory brain activity dynamics. Frontal Alpha power increases might reflect local enhanced inhibitory processes and reduced tinnitus percept processing, emphasizing frontal Alpha as a candidate marker for effective tinnitus suppression.
