The influence of descending cholinergic connections on information processing in the initial stages of the central auditory pathway

• Applicant: Dr. Thomas Künzel
• Subject Area: Cognitive, Systems and Behavioural Neurobiology
• Term: from 2019 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 420733146

Excitability of principal neurons in the ventral cochlear nucleus is modulated by acetylcholine. The role of this neuromodulation in auditory information processing is not well understood. We thus want to iontophoretically apply cholinergic agonists and antagonists in the ventral cochlear nucleus of the anesthetized mongolian gerbil (Meriones unguiculatus) while simultaneously recording the sound driven responses of principal neurons. A subset of cholinergic axons entering the ventral cochlear nucleus arises from neurons in the pontomesencephalic tegmentum, which are known to be responsive to sound stimulation. The stimulus tuning and the functional role of the descending cholinergic connectivity with subcortical auditory areas during sound processing is unknown. We want to record from neurons in the pontomesencephalic tegmentum and explore the sound stimulus conditions that best drive these neurons. Furthermore we want to map their connectivity with subcortical sensory areas in the mongolian gerbil by injection of axonal tracer substances and subsequent histological analysis. Finally, we want to directly measure the effect of descending connections on sound processing in the ventral cochlear nucleus. For this we will electrically activate neurons in the pontomesencephalic while simultaneously recording sound-driven responses from principal neurons in the ventral cochlear nucleus. The experiments in this project proposal will help to understand and quantify the effects of descending neuromodulation on information processing in a subcortical sensory pathway.

• DFG Programme: Research Grants