Neural Basis of Sun-Compass Navigation

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Navigation is a fundamental behavior for nearly all animals and has long fascinated human observers both in terms of its physiological and behavioral virtuosity. Long-distance migrations of arctic terns flying pole-to-pole or monarch butterflies crossing North America capture the imagination, but even the common fruit fly can travel 20 kilometers across over open desert, a feat that requires navigational cues. Many insects, including honey bees and monarch butterflies, are known to use the position of the sun to navigate; however, by studying fruit flies the large number of genetic tools available to understand the neurobiology underlying this behavior can be brought to bear. This research will employ state-of-the-art neuroscience techniques to identify neurons that allow fruit flies to orient using the sun and test laboratory findings under natural conditions. The research will provide many opportunities for the training and mentorship of a diverse pool of students. Working with local high school students, lab members will study the dispersal abilities of fruit flies at a field site in the Mojave Desert, focusing on determining how far and fast they fly and in which directions. Laboratory aspects of the research will train undergraduates in a wide-range of cutting-edge techniques. This integrative approach will further the understanding of how brains can process visual information in an ancient and ecologically important behavior. A better understanding of the computational strategies underlying navigation may be important for the design of autonomous robots.This research will examine the neural basis of sun navigation in fruit flies (Drosophila melanogaster) by employing behavioral, genetic, physiological, and ecological approaches. Although previously not considered a model for navigation research, laboratory experiments suggest that fruit flies can use the sun as a long distance orientation cue. In a closed-loop flight simulator, flies will actively hold a small, bright spot at a fixed angular location. Each fly adopts a different heading when they initially take off, and individuals will remember this orientation preference if flight is interrupted for short intervals. Using this flight simulator, the role of prior experience on subsequent heading preference will be tested by attempting to train flies to prefer particular headings. To explore the roles of specific neurons, genetic approaches will be used to silence cell classes while measuring the effect on sun navigation in a flight simulator. Two-photon imaging and electrophysiology will also be employed to study the circuits responsible for sun-compass navigation and investigate the functional role of individual cells. To relate these mechanistic investigations to natural behavior, a series of field experiments will be conducted, which will be coordinated with outreach efforts, to investigate the role of sun-compass navigation in dispersal. Collectively, these complementary approaches will yield a mechanistic understanding of animal navigation that ranges from cell physiology to ecology. Results will shed light on fundamental questions of systems neuroscience, such as how sensorimotor experience shapes future behavior, while also forwarding the understanding of fly natural history.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.