From Single Cells to Far-Field Potentials in the Auditory Brainstem

• Applicants: Dr. Paula Kuokkanen; Professorin Dr. Christine Köppl
• Subject Area: Experimental and Theoretical Network Neuroscience
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 502188599

Extracellular field potentials recorded at the skull's surface (electroencephalograms) are an important tool in both research and clinical contexts because they enable non-invasive and objective assessments of brain activity. However, their origins are not sufficiently understood which often restricts their diagnostic value. Realistic modeling of the multiple origins of extracellular fields and their complex interactions has become possible only fairly recently and needs experimental validation from a broader variety of neural structures. This project focuses on the Auditory Brainstem Potential, a non-invasively recorded far-field potential used widely in both basic research and, e.g., in newborn screening for hearing loss. The project is based on tight integration of computational modeling and experimental neurophysiology, including state-of-the-art experimental manipulation with optogenetic techniques. Our experimental model is the brainstem of birds, primarily the barn owl. We make creative use of the relative simplicity and detailed knowledge of its brainstem circuit dedicated to the coding of interaural time differences. The owl, and for salient morphological variation the chicken, are used as tools to distill general rules about the generation of extracellular field potentials by different neural sources. Our previous work on this system suggests that axonal tracts connecting nuclei can be significant dipole sources, and assumptions about the dominance of synaptic origins of extracellular field potentials thus need to be revised. The ultimate aim is to understand the Auditory Brainstem Response in birds and then to generalize these rules to extracellular field potentials for cases of different but also well known neuronal morphologies, connections, and response synchrony to relevant stimuli.

• DFG Programme: Research Grants