Zwicker Tone and Tinnitus

• Applicant: Dr. Achim Schilling
• Subject Area: Cognitive, Systems and Behavioural Neurobiology
• Term: since 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 451810794

In Western societies, the prevalence of subjective tinnitus, i.e., the perception of sound in the absence of any physical sound source, is up to 15% of the general population. This phantom percept may lead to a severe psychological burden and in extreme cases may even result in suicide. Recent studies on tinnitus development indicate that tinnitus is always associated with hearing loss, though this hearing loss may be too weak to be identified by the measurement of pure tone audiograms (“hidden hearing loss”). Furthermore, it has been shown that the presence of a tinnitus percept always coincides with neural hyperactivity along the complete auditory pathway. Recently, our workgroup developed a novel mechanistic explanation of that neuronal hyperactivity. In particular, we propose stochastic resonance – a principle well established in neuroscience leading to enhanced detachability of a subthreshold signal by addition of internal or external noise – to be the physiological basis of the neural hyperactivity inthe auditory system, with the purpose to partly restore hearing thresholds in the time-range of seconds at the cost of tinnitus development. The proposed effects have been verified in a large database of human patient data by our group. Additionally, to an explanation for tinnitus percepts our novel model provides also an explanation for the so called Zwicker tone percept. The Zwicker tone is a phantom percept induced by the presentation of a loud broadband noise with a spectral gap (notched noise) at a certain frequency band. The spectrally notched noise can be seen as a model for a temporary, frequency dependent hearing loss as in the range of the notch frequency the auditory system receives less input compared to the surrounding frequency regions. According to our model, this reduced input will lead to an increase of the internal noise within that frequency range and thus to a temporary tinnitus-like percept, the Zwicker tone. The aim of the proposed project is to analyse the cortical neurophysiological representation of the Zwicker tone as a model for transient tinnitus using in vivo cortical recordings. In parallel, we will develop and cross validate a novel behavioral paradigm based on the standard GPIAS paradigm introduced by Turner and coworkers in 2006 to objectively measure Zwicker tone in rodents. The paradigm will provide novel insights on the frequency specificity of the GPIAS paradigm as well as a further information on the validity of the ”filling-in hypothesis”. These experiments are crucial as the GPIAS paradigm is a widely used behavioral method for tinnitus screening in rodents without satisfying validation data. The main objectives of the electrophysiology measurements as well as the behavioral testing are to test our model-based predictions on Zwicker tone, to validate the GPIAS paradigm for auditory phantom percept screening and finally to understand the influence of cross-modal stimulation on auditory phantom perception.

• DFG Programme: Research Grants