Neural mechanisms of behavioral coordination in Hydra

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PROJECT SUMMARY How do animals coordinate their many parts to generate coherent, adaptive behavior? Are there neural mechanisms that coordinate whole animal neural activity thereby coordinating whole animal behavior? Numerous low-resolution studies in mammals have revealed a highly conserved hierarchy of spontaneous brain- wide oscillations spanning a wide range of frequencies in which slower, more global oscillations appear to coordinate and constrain faster, more local oscillations via various cross-frequency coupling mechanisms. However, whether and how slow global oscillations might coordinate whole brain activity and, thus, whole animal behavior, remains obscure due to the difficulty of measuring, manipulating, and modeling whole mammalian brains with high spatiotemporal resolution. Fortunately, spontaneous brain-wide oscillations have also been found in zebrafish, bees, fruit flies, and even the cnidarian, Hydra vulgaris, indicating significant evolutionary conservation of these oscillations, particularly the ultraslow (0.01-0.1 Hz) rhythms. Hydra possesses the simplest known nervous system and allows simultaneous calcium imaging of its entire nervous system during behavior, enabling observation of all rhythms in parallel with single cell resolution. In addition, Hydra exhibits robust behaviors that have been categorized and quantified using machine learning, allowing precise correlation of global neural activity with fine-grained behavior. Thus, here I propose to use this highly tractable system to test the hypothesis that the spontaneous ultraslow network of Hydra—rhythmic potential 1 (RP1, 0.1-0.01 Hz)— serves as an organizer and coordinator of global neural activity to generate unified, coherent behavior. I predict that disruption of RP1 activity will result in disorganized global neural activity and uncoordinated behavior, as preliminary data indicate. The studies proposed here will directly test the causal link between spontaneous ultraslow oscillations and global neural activity and behavior. To elucidate the role of RP1 in Hydra, I will first employ single neuron resolution whole nervous system calcium imaging and behavioral analysis to determine if RP1 activity is predictive of both global neural activity and behavior and whether it regulates the other major networks in the animal via cross-frequency coupling. Next, I will determine if development of distinct RP1 networks is correlated with development of distinct and uncoordinated global neural activity and behavior in budding Hydra. I will then disrupt the RP1 network physically, optically, and pharmacologically to determine if its disruption results in uncoordinated global neural activity and behavior. Together, this proposal will shed light on a major unanswered question within neuroscience: the role of spontaneous neural activity, particularly ultraslow oscillations, and whether they might serve to coordinate global neural activity and behavior. This project will also provide me with the training I need to launch a successful independent research career.