Neural Mechanisms of Cross-modal Integration in the Fruit Fly

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It is scientifically daunting, yet society poses a grand challenge to neuroscientists to discover how complex brain function emerges from the activity patterns of individual neurons and the small interconnected circuits that they form. One important open question is how does the brain integrate different sensory inputs to create a cohesive perception of the world? Neuroscientists have a good understanding that senses are integrated at the cognitive level, for example that the perception of flavor is an integration of taste and smell. But the field has a poor understanding of the underlying mechanism - how circuits of brain cells wire multiple senses together. This project takes an interdisciplinary approach using genetics, live brain imaging, virtual reality behavior and engineering analysis to determine the elemental neural circuit mechanisms by which sensory modalities are integrated for perception. The researchers seek to identify the cellular identity, cell-cell connections, function, and neuro-chemical interactions that link sensory modalities together. For this work, the researchers use a powerful neuro-genetic model system: the fruit fly Drosophila, which exhibits a rich multi-sensory repertoire of behavior in the laboratory, and for which there exists a wealth of molecular-genetic tools to study and manipulate identified neurons and neural circuits. A large body of evidence has demonstrated that in flies olfactory signals boost the strength of visual stabilization reflexes analogous to our own gaze-stabilizing eye movements. The researchers will test the hypothesis that olfactory signaling alters the response strength of neurons within the visual processing pathway, and that olfactory sensory pathways are linked to visual pathways by neurosecretory cells releasing biogenic amines. The researchers make use of virtual reality flight simulators, and live imaging using state-of-the-art multi-photon excitation fluorescence microscopy to genetically target calcium reporters within select interneurons and neuromodulatory circuits innervating the visual regions of the brain. They expect to discover that neurosecretory cells are excited by odor, and release biogenic amines into visual processing centers, which in turn alter the membrane properties and synaptic integration of visual motion circuitry. They expect that genetically silencing these interactions eliminates behavioral responses to visual motion that are well known to be enhanced by simultaneous presentation of odor cues. The project is conceptually linked with an outreach effort to K-12 students by outfitting a Mobile Fly Lab to provide demonstration workshops at local elementary schools.