Tinnitus and Stochastic Resonance

• Applicant: Privatdozent Dr. Patrick Krauss
• Subject Area: Cognitive, Systems and Behavioural Neurobiology
• Term: from 2020 to 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 436456810

Subjective tinnitus is the perception of a sound in the absence of any acoustic stimulus. In western civilizations, up to 15% of the general population suffer from subjective tinnitus. In severe cases this phantom percept may lead to comorbidities like insomnia or psychological disorders. Despite the high prevalence and distress of affected patients, an effective cure for tinnitus still does not exist, since the exact mechanisms leading to the development of tinnitus are still unknown.Numerous studies have indicated that tinnitus is correlated with increased spontaneous firing rates of neurons along the auditory pathway, and that tinnitus is often accompanied by a hearing loss.There are several models of tinnitus development that try to explain the mutual relations between hearing loss, neuronal hyperactivity and subjective tinnitus. All classical models can be divided into two main classes, namely lateral inhibition models and central gain models. However, these classical models provide no sufficient mechanistic understanding of how hearing loss, neuronal hyperactivity and subjective tinnitus are related to each other. Recently, we developed an alternative model of the development of tinnitus based on stochastic resonance (SR).SR, refers to the phenomenon that weak signals that are sub-threshold for a given sensor still can be detected and transmitted by that sensor if noise (i.e. a random signal of arbitrary type like spontaneously spiking neurons [=neuronal noise] or randomly changing sound pressure levels [=acoustic noise]) of sufficient amplitude is added to the sensor input. In self-adaptive signal detection systems based on SR, the optimum noise level is continuously adjusted via a feed-back loop, so that the system's response in terms of information throughput remains optimal, even if the properties of the input signal change. Using a computational model, we demonstrated that adaptive SR might be the primary cause of tinnitus development after hearing loss.The main objective of this proposal is to experimentally validate and to extend our new mechanistic SR-based model of tinnitus development and thereby to gain further insight into the complex phenomenon of tinnitus.Our current model already implicated a new treatment approach (exposure to moderate levels of acoustic white noise) that seems to do well in an animal model. However, a deeper and more detailed understanding of the neural processes underlying tinnitus development may lead to even better treatment options for tinnitus: i.e. other types of acoustic noise - adjusted to the animal’s individual hearing loss - that are more effective than white noise. Both, deeper theoretical understanding and individual treatment approaches may help to improve the translation from animal models to human patients.Whereas our recent model focuses on bottom-up processes, in a follow-up proposal, we will further extend our model to top-down processes.

• DFG Programme: Research Grants