Date of Award
Doctor of Philosophy (PhD)
Many organisms that can locomote change their navigational strategies depending upon behavioral context. During foraging or exploration, for instance, many animals navigate by interspersing straight runs with turns whose direction and frequency may originate, at least at times, from largely stochastic processes. Conversely, during goal-directed navigation, animals may use stored heading and distance signals to travel efficiently to a desired location. This thesis explores the circuitry underlying these disparate navigational strategies in Drosophila. I first show that normal synaptic transmission in a genetically specified population of neurons is necessary for one to observe an appreciable rate of spontaneous flight turns in Drosophila, but synaptic transmission in these same neurons is dispensable for the execution of two types of visually evoked turns. I then describe experiments on a population of neurons whose coordinated activity is thought to represent the fly’s heading angle during walking. Specifically, I show that angular resolution of the heading estimate carried by this population of neurons is at most 5.625º, and may be even finer. Furthermore, it is known that the neurons that carry this heading signal can update their heading estimate either in reference to a visual landmark or, when such a landmark is absent, in reference to the animal's rotational body movements. I end the thesis by demonstrating that, when a fly stands still, the visual and non-visual estimates of the fly's heading angle are not always aligned and can in fact deviate by many tens of degrees. The functional purpose of this discrepancy remains unclear, but this difference might provide insight into how a heading system can store an angular memory in complete darkness, without significant drift, for many minutes.
Ferris, Bennett, "Spontaneity and Precision in the Drosophila Central Nervous System" (2019). Student Theses and Dissertations. 504.