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Investigating the Neural Circuit for Carbon Dioxide Avoidance Behavior in Caenorhabditis elegans


Carbon dioxide (CO2) is a byproduct of oxidative metabolism that can be sensed by different species including mammals, insects, and nematodes and can lead to both physiological and behavioral responses. In the free-living nematode Caenorhabditis elegans the behavioral response can be either avoidance or neutral to CO2, indicating that the behavior is flexible. In this thesis, I investigated the neural basis of behavioral flexibility. We found that the CO2 circuit can be modulated by diverse sensory neurons that respond to ambient oxygen (O2), temperature, and food odor. Additionally, we identified two interneurons downstream of the CO2-sensing BAG neurons, AIY and RIG, that have opposing roles in CO2-evoked responses. A decrease in AIY activity and an increase in RIG activity promote appropriate avoidance behavior to CO2 levels. Our results show that just like thermosensory and oxygen circuits, the CO2 circuit can exhibit a network of multisensory integration to enable animals to generate flexible behaviors to changing environments.

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