Monitoring odor landscape to study learned olfactory navigation in C. elegans

Animals flexibly adjust behavior in response to environmental contexts and learned experiences. In C. elegans, associative learning with an olfactory cue generates chemotactic behavior towards the cue if it was paired with food. However, it is unknown if olfactory learning modulates sensory-motor processing for a specific navigation strategy, such as the bias in a biased random walk, or alternatively modulates other strategies adaptively. The biophysics with which worms sense airborne cues is also not well understood. Here we investigate butanone-odor associative learning using an odor chamber to precisely measure the odor concentration experienced by worms during odor-guided navigation. We control airborne cues to form a stationary chemical landscape that we measure with an array of digital gas sensors. As worms navigate in the environment, we track their trajectories and posture. We also developed a statistical model to capture different strategies previously characterized in worms, including biased random walk and gradual change in angle towards high concentration. We will discuss progress towards quantitatively characterizing learned odor-guided navigation with our apparatus and our proposed model.