Predictability and hierarchy inDrosophilabehavior

Abstract

<p id="d6428739e192">How an animal chooses to order its activities—moving, grooming, resting, and so on—is essential to its ability to survive, adapt, and reproduce. Here we investigate the temporal pattern of behaviors performed by fruit flies, finding that their movements are organized in a hierarchical manner that exhibits long time scales. This organization is likely advantageous for adaptability and ease of neural representation and provides hints as to the form of the fly’s internal representations of behavioral programs. </p><p class="first" id="d6428739e195">Even the simplest of animals exhibit behavioral sequences with complex temporal dynamics. Prominent among the proposed organizing principles for these dynamics has been the idea of a hierarchy, wherein the movements an animal makes can be understood as a set of nested subclusters. Although this type of organization holds potential advantages in terms of motion control and neural circuitry, measurements demonstrating this for an animal’s entire behavioral repertoire have been limited in scope and temporal complexity. Here, we use a recently developed unsupervised technique to discover and track the occurrence of all stereotyped behaviors performed by fruit flies moving in a shallow arena. Calculating the optimally predictive representation of the fly’s future behaviors, we show that fly behavior exhibits multiple time scales and is organized into a hierarchical structure that is indicative of its underlying behavioral programs and its changing internal states. </p>