Comparing immediate transient tinnitus suppression using tACS and tDCS: a placebo-controlled study.

Tinnitus is an auditory phantom percept with a tone, hissing, or buzzing sound in the absence of any objective physical sound source. Two forms of low-intensity cranial electrical stimulation exist for clinical and research purposes: transcranial direct current stimulation (tDCS) and transcranial alternating current stimulation (tACS). In a recent study, it was demonstrated that a single session of tDCS over the dorsolateral prefrontal cortex (DLPFC) (anode over right DLPFC) yields a transient improvement in subjects with chronic tinnitus and that repeated sessions can possibly be used as a treatment. In the present study, the effect of a single-session individual alpha-modulated tACS and tDCS applied at the DLPFC bilaterally is compared with tinnitus loudness and tinnitus annoyance. A total of fifty tinnitus patients were selected and randomly assigned to the tACS or tDCS treatment. Our main result was that bifrontal tDCS modulates tinnitus annoyance and tinnitus loudness, whereas individual alpha-modulated tACS does not yield a similar result. This study provides additional insights into the role of DLPFC in tinnitus modulation as well as the intersection between tinnitus and affective/attentional processing.