A memory of recent oxygen experience switches pheromone valence inC. elegans

ABSTRACT Animals adjust their behavioral priorities according to momentary needs and prior experience. We show that C. elegans changes how it processes sensory information according to the oxygen environment it experienced recently. C.elegans acclimated to 7% O 2 are aroused by CO 2 and repelled by pheromones that attract animals acclimated to 21% O 2 . This behavioral plasticity arises from prolonged activity differences in a circuit that continuously signals O 2 levels. A sustained change in the activity of O 2 sensing neurons reprograms the properties of their post-synaptic partners, the RMG hub interneurons. RMG is gap-junctionally coupled to the ASK and ADL pheromone sensors that respectively drive pheromone attraction and repulsion. Prior O 2 experience has opposite effects on the pheromone responsiveness of these neurons. These circuit changes provide a physiological correlate of altered pheromone valence. Our results suggest C. elegans stores a memory of recent O 2 experience in the RMG circuit and illustrate how a circuit is flexibly sculpted to guide behavioral decisions in a context-dependent manner.