Distress-dependent temporal variability of regions encoding domain-specific and domain-general behavioral manifestations of phantom percepts.

ABSTRACT

Tinnitus is the perception of a phantom sound characterized behaviorally by a loudness and a distress component. Although a wealth of information is available about the relationship between these behavioral correlates and changes in static functional connectivity, its relationship with dynamic changes in network connectivity is yet unexplored. The aim of this study was thus to investigate changes in the flexibility and stability of temporal variability in tinnitus and its relation to loudness and distress using continuous resting-state EEG. We observe an increase in temporal variability at the whole-brain level in tinnitus, which is spatiotemporally distributed at the nodal level. Behaviorally, we observe changes in the relationship between temporal variability and loudness and distress depending on the amount of distress experienced. In patients with low distress, there is no relationship between temporal variability and loudness or distress, demonstrating a resilience in dynamic connectivity of the brain. However, patients with high distress exhibit a direct relationship with increasing loudness in the primary auditory cortex and parahippocampus, and an inverse relationship with increasing distress in the parahippocampus. In tinnitus, the specific sensory (loudness) component related to increased temporal variability possibly reflects a Bayesian search for updating deafferentation-based missing information. On the other hand, the decreased temporal variability related to the nonspecific distress component possibly reflects a more hard-wired or less adaptive contextual processing. Therefore, our findings may reveal a way to understand the changes in network dynamics not just in tinnitus, but also in other brain disorders.