@article {68955, title = {A competitive disinhibitory network for robust optic flow processing in Drosophila}, journal = {bioRxiv}, year = {2023}, month = {2023 Aug 19}, abstract = {

Many animals rely on optic flow for navigation, using differences in eye image velocity to detect deviations from their intended direction of travel. However, asymmetries in image velocity between the eyes are often overshadowed by strong, symmetric translational optic flow during navigation. Yet, the brain efficiently extracts these asymmetries for course control. While optic flow sensitive-neurons have been found in many animal species, far less is known about the postsynaptic circuits that support such robust optic flow processing. In the fly\ Drosophila melanogaster, a group of neurons called the horizontal system (HS) are involved in course control during high-speed translation. To understand how HS cells facilitate robust optic flow processing, we identified central networks that connect to HS cells using full brain electron microscopy datasets. These networks comprise three layers: convergent inputs from different, optic flow-sensitive cells, a middle layer with reciprocal, and lateral inhibitory interactions among different interneuron classes, and divergent output projecting to both the ventral nerve cord (equivalent to the vertebrate spinal cord), and to deeper regions of the fly brain. By combining two-photon optical imaging to monitor free calcium dynamics, manipulating GABA receptors and modeling, we found that lateral disinhibition between brain hemispheres enhance the selectivity to rotational visual flow at the output layer of the network. Moreover, asymmetric manipulations of interneurons and their descending outputs induce drifts during high-speed walking, confirming their contribution to steering control. Together, these findings highlight the importance of competitive disinhibition as a critical circuit mechanism for robust processing of optic flow, which likely influences course control and heading perception, both critical functions supporting navigation.

}, doi = {10.1101/2023.08.06.552150}, url = {https://doi.org/10.1101/2023.08.06.552150}, author = {Mert Erginkaya and Tom{\'a}s Cruz and Margarida Brotas and Kathrin Steck and Aljoscha Nern and Filipa Torr{\~a}o and N{\'e}lia Varela and Davi Bock and Michael Reiser and M Eugenia Chiappe} } @article {65001, title = {Automated reconstruction of a serial-section EM drosophila brain with flood-filling networks and local realignment.}, journal = {bioRxiv}, year = {2019}, month = {2019 Apr 11}, abstract = {

Reconstruction of neural circuitry at single-synapse resolution is an attractive target for improving understanding of the nervous system in health and disease. Serial section transmission electron microscopy (ssTEM) is among the most prolific imaging methods employed in pursuit of such reconstructions. We demonstrate how Flood-Filling Networks (FFNs) can be used to computationally segment a forty-teravoxel whole-brain\ Drosophila\ ssTEM volume. To compensate for data irregularities and imperfect global alignment, FFNs were combined with procedures that locally re-align serial sections and dynamically adjust image content. The proposed approach produced a largely merger-free segmentation of the entire ssTEM\ Drosophila\ brain, which we make freely available. As compared to manual tracing using an efficient skeletonization strategy, the segmentation enabled circuit reconstruction and analysis workflows that were an order of magnitude faster.

}, doi = {10.1101/605634}, author = {Peter H. Li and Larry F. Lindsey and Micha{\l} Januszewski and Zhihao Zheng and Alexander Shakeel Bates and Istv{\'a}n Taisz and Mike Tyka and Matthew Nichols and Feng Li and Eric Perlman and Jeremy Maitin-Shepard and Tim Blakely and Laramie Leavitt and Gregory S.X.E. Jefferis and Davi Bock and Viren Jain} } @article {64997, title = {Neural circuit basis of aversive odour processing in drosophila from sensory input to descending output.}, journal = {bioRxiv}, year = {2018}, month = {2018 Aug 26}, abstract = {

Evolution has tuned the nervous system of most animals to produce stereotyped behavioural responses to ethologically relevant stimuli. For example, female\ Drosophila\ avoid laying eggs in the presence of geosmin, an odorant produced by toxic moulds. Using this system, we now identify third order olfactory neurons that are essential for an innate aversive behaviour. Connectomics data place these neurons in the context of a complete synaptic circuit from sensory input to descending output. We find multiple levels of valence-specific convergence, including a novel form of axo-axonic input onto second order neurons conveying another danger signal, the pheromone of parasitoid wasps. However we also observe a massive divergence as geosmin-responsive second order olfactory neurons connect with a diverse array of \~{}75 cell types. Our data suggest a transition from a labelled line organisation in the periphery to one in which olfactory information is mapped onto many different higher order populations with distinct behavioural significance.

}, doi = {10.1101/394403}, author = {Paavo Huoviala and Michael-John Dolan and Fiona M. Love and Shahar Frechter and Ruair{\'\i} J.V. Roberts and Zane Mitrevica and Philipp Schlegel and Alexander Shakeel Bates and Yoshinori Aso and Tiago Rodrigues and Hannah Cornwall and Marcus Stensmyr and Davi Bock and Gerald M. Rubin and Marta Costa and Gregory S.X.E. Jefferis} }