Circuit architecture and dynamics of the insular cortex underlying motivational behaviors

Oregon Health & Science University, Portland OR

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Abstract

PROJECT SUMMARY The insular cortex (IC) is a multimodal hub that integrates interoceptive and exteroceptive information to control diverse aspects of animal behaviors related to cognition, emotion, and motivation. Among other functions, the IC receives information regarding an animal’s metabolic states and drives motivation and valence-specific behaviors. However, our understanding of the neuronal substrates and circuit principles underlying IC function is still in its infancy. An important step forward is to determine the activities of individual neurons within discrete IC circuits before, during, and after an animal behavior. To achieve this goal, a prerequisite is to delineate the events in individual IC neuronal types that give rise to the diverse functions in motivated behaviors. However, two major challenges exist. First, neuronal circuits are organized around subregions and neuronal types. It is increasingly clear that traditional classifications of IC subregions and cell types are insufficient to explain the functional diversity of the IC. Precise classification of subregions, neuronal types, and neuron-specific connectivity is needed. Second, an animal’s internal state is in part encoded by neuromodulators, such as dopamine, which dynamically modulate the functions of individual IC circuits. Despite recent progress in measuring extracellular dopamine and other neuromodulators, they trigger intracellular signaling events in a cell type-specific manner. Herein, we propose to overcome these barriers by integrating the latest complementary technological advances from the three PIs. First, we will use machine learning-based algorithms to comprehensively identify functional subdivisions, neuronal types, and cell-specific connectivity in the IC. Second, we will link the activities of individual IC cell types and subregions to animal vigor or valence using two-photon calcium imaging through a gradient-index (GRIN) lens. Third, we will simultaneously image the dynamics of cAMP/protein kinase A (PKA), a key intracellular signaling pathway mediating neuromodulation. Using these approaches, we aim to gain an unparalleled understanding of the activities and neuromodulations of discrete IC circuits that underlie vigor and valence processing, two essential and distinct aspects of motivated behaviors, at cellular resolution. We will test the hypothesis that different IC pyramidal neuronal types form distinct local and long-range circuits, which differentially yet cooperatively drive vigor and valence for motivated behaviors in a manner depending on neuromodulation.