Coincidence and continuity: uncovering the neural basis of auditory object perception

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SUMMARY Auditory objects are the foundational building blocks of our auditory-perceptual world. Auditory objects are formed, in part, by the brain’s ability to extract and organize spectral and temporal regularities from the acoustic environment. This ability allows a person to hear their friend’s voice amongst the noise of a crowded restaurant. In many cases, temporal regularities are formed across multiple frequency channels. This example and several others suggest that the brain can track this temporally correlated neuronal activity across multiple frequency channels and uses this activity as a means to form auditory objects and organize the auditory environment. Despite its clear importance to auditory perception, there is little to no direct evidence in support of the hypothesis that temporal regularities are encoded as temporally correlated activity and that this activity can guide behavior. To fill this information gap, we combine rigorous psychophysics with high-density neuronal recordings and computational theory to identify the interaction of temporal regularities with dynamic network structures and perception. Thus, the overall goal of this proposal is to identify the mesoscopic circuits of the auditory cortical hierarchy that learn temporal regularities –i.e., coincidence and continuity– of the environment and how neuronal representations of these regularities contribute to two key components of auditory perception: figure-ground segregation and to perceptual invariance, respectively. In Aim 1, we posit that figure-ground segregation is facilitated by the dynamic imprinting into cortical circuits of instantaneous correlations (i.e. temporal coincidence) across frequency bands of the acoustic target. Thus, we test whether tone bursts with synchronous onsets increase the intrinsic noise correlations of cortical neurons, which, in turn, facilitates a listener’s ability to hear a figure stimulus amongst a noisy ground stimulus. In Aim 2, we hypothesize that stimulus invariances are learned from smooth (i.e., temporally continuous) changes in the spectrotemporal structure of auditory stimuli. Based on this theory, we hypothesize that the brain interprets temporally continuous variations in an auditory stimulus as natural transformations of underlying auditory objects and drives hierarchical learning of invariant perceptual representations. Individually and collectively, the Aims provide valuable, quantitative insights into auditory perception and its underlying neuronal mechanisms. The PIs are uniquely qualified to conduct this research with complementary expertise in psychophysics, population neuronal recordings, and computational/theoretical neuroscience.