Short-term Effects of Single rTMS Sessions on Auditory Evoked Activity in Chronic

27 28 Subjective tinnitus is the perception of a sound without any external source. Repetitive 29 transcranial magnetic stimulation has been examined as a treatment tool for chronic tinnitus 30 for several years trying to target hyperactivity / abnormal synchronization within the auditory 31 cortex putatively underlying the auditory phantom percept. However, its exact impact on 32 auditory cortical activity remains largely unknown. This study’s objective was to 33 systematically examine changes in auditory responses (N1, auditory steady state response) 34 measured by means of magnetoencephalography after single sessions of stimulation with 35 different transcranial magnetic stimulation paradigms. Subjects with chronic tinnitus (n=10) 36 underwent five sessions of repetitive transcranial magnetic stimulation in which they received 37 one of five different stimulation protocols (1Hz, individual alpha frequency, continuous theta 38 burst stimulation, intermittent theta burst stimulation, and sham) in randomized order using a 39 single-blind study design. Cortical steady state responses to 40 Hz amplitude-modulated tones 40 were measured before and after each magnetic stimulation protocol. The results demonstate a 41 reduction of the cortical response to the auditory steady state stimulus after magnetic 42 stimulation, whereas the N1 response was slightly enhanced or remained unchanged. 43 Furthermore, the reduction of the auditory steady state response was driven by effects of 44 intermittent theta burst stimulation, continuous theta burst stimulation, and 1Hz stimulation. 45 Correspondingly, behavioral measures demonstrated the greatest reduction of tinnitus 46 loudness after the respective rTMS protocols. The current study offers an interesting insight 47 into the effects of repetitive transcranial magnetic stimulation on auditory cortical activity. 48 The results of the study are discussed in context of the current limitations of transcranial 49 magnetic stimulation for the treatment of chronic tinnitus. 50 51