Behavioral pattern transitions and habituation to pulsed mechanical vibration in crawling Drosophila larvae

How the brain receives, stores, and deploys information to create an adaptive response depends on external stimuli. Mechanical vibrations affect animal behavior, and are useful tool for understanding the correlation between neuron function and response. Using the Drosophila larva model system, a slow-moving animal with readily quantifiable behavior, we elicit a discrete set of observable avoidance responses: pause, turn, and reversal (strong) with vibration. We characterize in detail how each response type depends on vibration timing (pulse spacing and duration) and intensity (frequency and amplitude). Through precise larva tracking, we find that intensity above a threshold value increases the frequency of the reverse crawl behavior. Stimulus timing affects the probability of the each behavior: both prolonged and repeated vibration bursts over time reduce the proportion of animals reverse crawling (habituation). Additionally, memory deficient fly mutants show altered responses to repeated and sustained vibrations, suggesting the possible mechanism underlying habituated response. Drawing an analogy to a capacitor charging circuit, we model the possible relationship between biological mechanisms and habituated behavior in general.