Study Protocol: Dynamics of the noise-induced neurodegeneration in the central nervous system - a correlative MRI and histology study

Exposure to sound at high intensities can lead to a temporary or permanent shift in the auditory threshold, peripheral changes, but also central nervous changes. A permanent threshold shift is related to dramatic anatomical and physiological changes within the central auditory pathway. In several studies, cell body and tissue shrinkage, axon degeneration and synaptic plasticity were observed as a result of noise exposure (Aarnisalo et al., 2000; Benson et al., 1997; Jean‐Baptiste & Morest, 1975; J. Kim et al., 1997; J. J. Kim et al., 2004). Decreases in cell density, increases in axon degeneration, reduction of inhibitory influences, elevation of excitatory transmission and an elevation of neuronal spontaneous activity as well as an overexcitation of neuronal structures, have been reported to be present in higher auditory structures at different time points as a consequence of noise exposure (Fröhlich et al., 2017; Gröschel et al., 2010). In this study, we want to investigate neuroplasticity and neuropathologies in key structures of the central auditory pathway upon noise exposure over a defined time period in two tonotopically organized core regions of the auditory pathway: The central inferior colliculus (ICc) and the ventral medial geniculate body (vMGB). Magnetic resonance imaging (MRI) will be used to identify noninvasive biomarkers as a correlate for noise-induced pathophysiology and validated by immunohistochemical methods. By merging of the histological and MRI data, an experimental prediction model of functional outcome after noise exposure will be established.