2018 Theses Doctoral

Visual memory in Drosophila melanogaster

Florence, Timothy Joseph

Despite their small brains, insects are capable of incredible navigational feats. Even Drosophila melanogaster (the common fruit fly) uses visual cues to remember locations in the environment. Investigating sophisticated navigation behaviors, like visual place learning, in a genetic model organism enables targeted studies of the neural circuits that give rise to these behaviors. Recent work has shown that the ellipsoid body, a midline structure deep within the fly brain, is critical for certain navigation behaviors. However, nearly all aspects of visual place learning remain mysterious. What visual features are used to encode place? What is the site of learning? How do the learned actions integrate with the core navigation circuits? To begin to address these questions I have established an experimental platform where I can measure neural activity using a genetically encoded calcium indicator in head-fixed behaving Drosophila. I further developed a virtual reality paradigm where flies are conditioned to prefer certain orientations within a virtual environment. In dendrites of ellipsoid body neurons, I observe a range of specific visual responses that are modified by this training. Remarkably, I find that distinct calcium responses are observed during presentation of preferred visual features. These studies reveal learning-associated neural activity changes in the inputs to a navigation center of the insect brain.