Divergent Computation in an Olfactory Circuit
Date of Award
Spring 2024
Document Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Neuroscience
First Advisor
Jeanne, James
Abstract
Divergent processing of sensory information enables diversification of the possible repertoire of behavioral responses and is therefore critically important for survival. Although anatomical connectivity of sensory circuits, especially at the periphery, has been extensively characterized, we still lack an understanding of how divergent circuit motifs deeper in the brain functionally support parallelization of behaviorally relevant computations. The sheer scale of numerical complexity and the inability to assume stereotyped connectivity render this line of inquiry inherently challenging across many model systems. In efforts to mitigate these problems, we have leveraged the numerically compact and stereotyped olfactory circuit of Drosophila melanogaster to better bridge the gap between anatomical connectivity and functional synaptic connectivity. Here, we have investigated how two distinct types of third-order lateral horn neurons (LHNs) divergently transform their shared input from the same second-order projection neurons (PNs). We show that a difference in target-cell-specific short-term synaptic plasticity at each PN-LHN synapses implements unique response dynamics and temporally distinct representations of odor stimuli by each LHN type; while one LHN type adapts minimally and maintains a sustained, faithful representation of odor stimuli, the other LHN type adapts rapidly and is tuned to detect abrupt increases in odor intensity. We further show that this difference in short-term synaptic plasticity, mechanistically, emerges from presynaptic diversification and specialization, namely differential calcium dynamics at each presynaptic site. Crucially, by silencing one LHN type at a time in tethered walking flies, we demonstrate that divergent computations by the two LHN types contribute to temporally distinct elements of odor-evoked approach behavior, where the observed deficits align congruently with our understanding of their physiology. Finally, we find that the same PN-LHN divergence motif also differentially integrates the internal state of starvation with odor representations by the LHNs; while one LHN type exhibits starvation-dependent plasticity of odor-evoked activity, the other LHN type remains entirely insulated from such modulatory effects. Taken together, the findings from the present dissertation demonstrate how functional parallelization is implemented in neural circuitry, and thus contribute to building a more synaptic-centric view of neural computation.
Recommended Citation
Kim, Hyong Seok, "Divergent Computation in an Olfactory Circuit" (2024). Yale Graduate School of Arts and Sciences Dissertations. 1316.
https://elischolar.library.yale.edu/gsas_dissertations/1316
