Modulation of spatial representations within the early auditory pathway by active sensing

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Localizing and identifying sensory objects while navigating the environment are fundamental brain functions. However, how individual objects are neuronally represented during unrestricted self-motion is mostly unexplored. Based on an earlier project funded by the DFG, we recently developed a new freely moving experimental paradigm to study auditory processing and sound perception (Sensory Island Task, SIT). Using SIT, we observed previously unreported spatial sound-source representations in primary auditory cortex (A1): the egocentric angle preference of A1 neurons changed significantly depending on the task-specific identity of the sound-source, revealing a novel cortical computation principle for naturalistic sensing during self-motion. These profoundly new findings raise fundamental questions about the underlying circuits and mechanisms. Specifically, the recurrent connectivity between the midbrain hub of the Inferior Colliculus (IC), the Medial Geniculate Body (MGB) in the thalamus and A1 has been suggested to be involved in the transformation and selective gating of sensory information to form perceptual representations. It follows that this network is a prime candidate for the organization of the new spatial representations that we have identified. Thus, to gain a mechanistic understanding of our findings of identity-specific spatial tuning in A1, we aim to study how the same behavioral paradigm affect spatial representations in IC and MGB. To this end, we plan to record chronically in these brain regions during active localization and unrestricted self-motion in SIT. Inspired by our findings in A1, we will determine to what extent spatial representations differ from traditionally observed pure egocentric tuning. Moreover, using targeted optogenetic manipulations, we will dissect the role of the prominent feedback of A1 to IC and MGB for the generation of spatial representations during SIT as well as for behavioral performance.