How dynamic is the continuous tinnitus percept?

Objective: Subjective tinnitus is defined as an auditory perception in the absence of any physically identifiable source for it. About 5-10% of the population report a continuous perception of the tinnitus sound – but how continuous is this perception? Is the tinnitus constantly “on”, or are there also periods were the tinnitus is perceived less? Indeed, more than 60% of the chronic tinnitus subjects report a variability of the tinnitus perception between days. The heterogeneity of this variability is currently largely unexplored. Results: Chronic tinnitus is usually associated with a decrease of the alpha frequency oscillatory power in temporal areas. Here we show, that also the moment-to-moment variability of the alpha activity is largely reduced in chronic tinnitus. Most importantly, it can be shown that this neuronal variability is associated with the tinnitus duration. Subjects with a longer history of tinnitus show less alpha variability in auditory regions. Preliminary data on the variability of the tinnitus perception will be presented.