Sensory Processing and Anatomical Organization of the Central Complex in the Flesh Fly, Neobellieria Bullata

Abstract

Animals rely on information provided by their senses to perform the complicated series of motor actions that allow them to obtain food and shelter, locate mates, and avoid predators. Interpreting sensory information and using it to guide behavior is one of the principle roles of the nervous system. In the insect brain, a system of midline neuropils called the central complex is thought to be the site at which sensory information is integrated and converted into the signals that initiate or modify motor outputs. This dissertation addresses three important questions for understanding how the central complex processes sensory information and influences behavior. These questions are: 1. What kind of sensory information is represented in the central complex? 2. What is the relationship of central complex neuropils to other brain regions? 3. Are such regions simply relay stations, or do they support computations that contribute to phenomena cautiously ascribed to the central complex, such as visual learning and memory? Using the flesh fly, Neobellieria bullata, intracellular recordings and dye fills were conducted to explore the sensory parameters that are relayed to the central complex. The results of these experiments along with previously published observations suggest that the sensory information relayed to the central complex differs from species to species and is likely matched to the behavior of each. Reconstructions of neurons labeled during intracellular recordings, cobalt injections, Golgi impregnations, immunohistochemistry, and Bodian staining were used to further explore the relationship between the central complex and the superior protocerebrum. These studies suggest that the superior protocerebrum is a complicated computation center, more intricately related to the central complex than has been previously assumed. These results are used to propose a network model for how one circuit in the central complex may perform some of the functions the central complex has experimentally been shown to mediate. The differences between this model and the elaboration of the central complex in vivo suggest that circuits within the central complex also support a variety of other computations. Finally, future experiments are described, investigating the role of the central complex in orientation of migrating monarch butterflies.