Olfactory input to the mushroom body in a complete electron microscopy volume of the adult Drosophila brain
Embargo until
2023-05-01
Date
2019-01-11
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Publisher
Johns Hopkins University
Abstract
Structures of neural circuits constrain hypotheses about how computation is performed in the nervous system. Large-scale electron microscopy (EM) imaging, followed by reconstruction of neural circuits, enables analysis of neuronal geometry and circuit structure at synaptic level. High-throughput transmission EM (TEM) systems were used to image the entire brain of a female Drosophila melanogaster at synaptic resolution. To validate the dataset, reconstruction and analysis in the volume were focused on the fly olfactory system, since the inputs provided by ~120 olfactory projection neurons (PNs) are well-characterized physiologically and morphologically at the level of light microscopy. The PNs provide inputs to ~2,000 Kenyon cells (KCs) in the calyx of the mushroom body, and olfactory information is transformed via the PN-to-KC network for subsequent olfactory association and behaviors. The fan-out connectivity from ~120 PNs to ~2000 KCs forms a crucial stage of a network architecture analogous to other brain structures including the mammalian cerebellum and hippocampus. Analysis of PN arbors in the calyx revealed unexpected clustering of homotypic PNs, suggesting biased sampling of olfactory inputs by KCs. Preliminary analysis of PN inputs to ~300 randomly sampled KCs suggests that a specific subset of PNs preferentially converges to common KCs, revealing previously unrecognized order in network structure that may reflect the underlying olfactory stimulus space.
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Keywords
electron microscopy, connectomics, neural circuits, Drosophila melanogaster, mushroom body, olfaction, neurogeometry