Unravelling the tinnitus distress network using single trial auditory steady-state responses

Tinnitus refers to the persistent sensation of sound in the absence of a corresponding physical source. We suggest that both the perceptual and the affective aspects of this phantom sensation arise from a distributed cerebral network whereby the functional coupling between neural nodes involved would be realised through phase-synchrony of neural oscillations. In this study, we sought to excite this network by driving it with a 37 Hz amplitude-modulated sound using a carrier frequency similar to the individual tinnitus ringing. Phase coherence measures between different cortical regions revealed significant differences in the excitable network between 12 tinnitus and 10 control subjects. The alterations in tinnitus were closely related to the subjective tinnitus distress ratings and resembled the patterns that have been reported for focused auditory attention.