Lucas Johnson: Visual Conditioning of Drosophila in Virtual Reality

Experiments in virtual reality that permit closed-loop movement are a powerful tool for studying the brain of many organisms, particularly for studying visual-dependent pro- cesses in the brain. Such experiments are versatile and lend themselves to a diverse array of potential applications and paradigms. They offer researchers considerable control of the stimuli presented to an organism and an opportunity to stretch the boundaries of what would otherwise be possible. Moreover, when used with head-fixed organisms, vir- tual reality experiments are compatible with other powerful tools for studying the brain such as targeted activation or inhibition of neurons and 2-photon imaging. The viability of experiments in virtual reality with head-fixed, walking Drosophila melanogaster has been established, but visual conditioning has only been demonstrated using punishing rewards, either in the form of true heat or shocks or in the form of optogenetic heat. Furthermore, no work has established a relationship between a stable sense of global heading-direction–tracked by a specific structure of neurons called the ellipsoid body in the Drosophila central complex–with visual place learning or landmark-based visual conditioning. This project addresses these limits of previous work with the following questions: can walking, head-fixed Drosophila navigating a 2-dimensional environment be successfully visually conditioned using a rewarding stimulus and does a stable sense of heading-direction improve the performance of this landmark-based visual condition- ing. Although neither of these questions are conclusively answered by this project, the results and analyses presented display distinct responses to the various paradigms and encourage further work in this direction.