Dynamic processing of sound in auditory cortex

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Project Summary: The perception of speech and language requires normal functioning of the auditory cortex (ACX). How ACX does this critically depends on the coordinated activity of populations of neurons: both across the cortex and throughout its multi-layered structure. The primary auditory cortex (A1) plays a key role for sound perception since it represents one of the first cortical processing stations. Recent results have shown that neural activity of A1 neurons depend not only on auditory stimuli themselves, but are influenced by the history of sounds, internal state, and behavioral context of the animal. For example, the selectivity of individual A1 neurons can rapidly and adaptively be reshaped when an animal is engaged in a behavioral task, or when listening conditions become more challenging. However, behaviorally relevant information is encoded in populations of neurons but to date it is not understood how behavioral influences shape the activity across A1 neural populations, and how the resulting population activity relates to task performance. Here we determine how sounds are dynamically encoded in diverse cell populations during behavior and the changing nature of their cellular interactions within and across A1 layers. By using in vivo 2-photon imaging in behaving mice we will determine the functional responses to complex stimuli in identified large populations of A1 neurons, how these neurons interact, reconstruct the functional networks present with A1, and shared external influences on these A1 networks. We then investigate how A1 networks change their responses and functional interactions during auditory behaviors of varying task difficulty. Thus, we determine how network changes depend on the identify and the difficulty of a task. Together, these experiments will reveal how A1 networks are dynamically reconfigured depending on the behavioral needs of the animal. Our prior work identified a region of the frontal cortex, the orbitofrontal cortex (OFC), as a source of inputs to A1 that can change A1 receptive fields. We thus investigate how OFC projections are engaged during auditory behaviors and if manipulating OFC projections to A1 will alter behavioral performance. Our work contributes to the mechanistic understanding of the ability of normal-hearing listeners to navigate complex or noisy acoustic environments and shift their attention between different sound sources. Thus, our work contributes to the understanding of diverse conditions such as tinnitus, aging, dyslexia, central auditory processing disorder (CAPD).