Processing of neural signals in the Drosophila olfactory system

The fruit fly Drosophila melanogaster has recently emerged as an important model organism for the study of neural circuits. This preparation has several advantages: flies have a smaller number of neurons than many other experimental organisms, and researchers have developed a wide array of genetic tools and the ability to record from neurons in vivo . The early olfactory system of Drosophila has turned out to be one of the most tractable circuits to investigate, and much has been learned about its architecture, physiological mechanisms, and responses to sensory stimuli. However, much is still unknown about how the elements in the circuit operate and what overall role the circuit serves. Here I describe my research into how neural signals are processed by the early olfactory circuit. Using imaging and electrophysiological data, I built a passive compartmental model of a second-order olfactory neuron to analyze how electrical signals spread throughout the cell. I found that the neurons are electrotonically extensive and that the presynaptic neurons likely distribute their synaptic contacts across the postsynaptic dendritic tree to form strong synapses. In addition, I investigated the mechanisms underlying the relatively depolarized resting membrane potential in these cells. I also contributed to a collaborative project in which we analyzed the transformation of the odor representation between first- and second-order neurons. We found that processing in the antennal lobe influences second-order neuron odor responses, and that a linear decoder can more easily discriminate between odors using the responses of the second-order neurons. Finally, I discuss a project in which I attempted to alter synaptic function in the circuit to assess its effects on odor processing. Together, these results contribute to a more complete understanding of the processing of sensory information by the brain.