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4 Publications

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    Reiser LabFlyLightFly Functional ConnectomeFly Facility
    12/15/22 | Eye structure shapes neuron function in Drosophila motion vision
    Arthur Zhao , Eyal Gruntman , Aljoscha Nern , Nirmala A. Iyer , Edward M. Rogers , Sanna Koskela , Igor Siwanowicz , Marisa Dreher , Miriam A. Flynn , Connor W. Laughland , Henrique D.F. Ludwig , Alex G. Thomson , Cullen P. Moran , Bruck Gezahegn , Davi D. Bock , Michael B. Reiser
    bioRxiv. 2022 Dec 15:. doi: 10.1101/2022.12.14.520178

    Many animals rely on vision to navigate through their environment. The pattern of changes in the visual scene induced by self-motion is the optic flow1, which is first estimated in local patches by directionally selective (DS) neurons24. But how should the arrays of DS neurons, each responsive to motion in a preferred direction at a specific retinal position, be organized to support robust decoding of optic flow by downstream circuits? Understanding this global organization is challenging because it requires mapping fine, local features of neurons across the animal’s field of view3. In Drosophila, the asymmetric dendrites of the T4 and T5 DS neurons establish their preferred direction, making it possible to predict DS responses from anatomy4,5. Here we report that the preferred directions of fly DS neurons vary at different retinal positions and show that this spatial variation is established by the anatomy of the compound eye. To estimate the preferred directions across the visual field, we reconstructed hundreds of T4 neurons in a full brain EM volume6 and discovered unexpectedly stereotypical dendritic arborizations that are independent of location. We then used whole-head μCT scans to map the viewing directions of all compound eye facets and found a non-uniform sampling of visual space that explains the spatial variation in preferred directions. Our findings show that the organization of preferred directions in the fly is largely determined by the compound eye, exposing an intimate and unexpected connection between the peripheral structure of the eye, functional properties of neurons deep in the brain, and the control of body movements.

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    12/15/22 | Neural coding of distinct motor patterns during Drosophila courtship song
    Hiroshi M. Shiozaki , Kaiyu Wang , Joshua L. Lillvis , Min Xu , Barry J. Dickson , David L. Stern
    bioRxiv. 2022 Dec 15:. doi: 10.1101/2022.12.14.520499

    Animals flexibly switch between different actions by changing neural activity patterns for motor control. Courting Drosophila melanogaster males produce two different acoustic signals, pulse and sine song, each of which can be promoted by artificial activation of distinct neurons. However, how the activity of these neurons implements flexible song production is unknown. Here, we developed an assay to record neuronal calcium signals in the ventral nerve cord, which contains the song motor circuit, in singing flies. We found that sine-promoting neurons, but not pulse-promoting neurons, show strong activation during sine song. In contrast, both pulse- and sine-promoting neurons are active during pulse song. Furthermore, population calcium imaging in the song circuit suggests that sine song involves activation of a subset of neurons that are also active during pulse song. Thus, differential activation of overlapping, rather than distinct, neural populations underlies flexible motor actions during acoustic communication in D. melanogaster.

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    10/26/22 | Rapid reconstruction of neural circuits using tissue expansion and lattice light sheet microscopy
    Joshua L. Lillvis , Hideo Otsuna , Xiaoyu Ding , Igor Pisarev , Takashi Kawase , Jennifer Colonell , Konrad Rokicki , Cristian Goina , Ruixuan Gao , Amy Hu , Kaiyu Wang , John Bogovic , Daniel E. Milkie , Edward S. Boyden , Stephan Saalfeld , Paul W. Tillberg , Barry J. Dickson
    eLife. 2022 Oct 26:. doi: 10.7554/eLife.81248

    Electron microscopy (EM) allows for the reconstruction of dense neuronal connectomes but suffers from low throughput, limiting its application to small numbers of reference specimens. We developed a protocol and analysis pipeline using tissue expansion and lattice light-sheet microscopy (ExLLSM) to rapidly reconstruct selected circuits across many samples with single synapse resolution and molecular contrast. We validate this approach in Drosophila, demonstrating that it yields synaptic counts similar to those obtained by EM, can be used to compare counts across sex and experience, and to correlate structural connectivity with functional connectivity. This approach fills a critical methodological gap in studying variability in the structure and function of neural circuits across individuals within and between species.

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    03/14/22 | A population of descending neurons that regulates the flight motor of Drosophila.
    Namiki S, Ros IG, Morrow C, Rowell WJ, Card GM, Korff W, Dickinson MH
    Current Biology. 2022 Mar 14;32(5):1189-1196. doi: 10.1016/j.cub.2022.01.008

    Similar to many insect species, Drosophila melanogaster is capable of maintaining a stable flight trajectory for periods lasting up to several hours. Because aerodynamic torque is roughly proportional to the fifth power of wing length, even small asymmetries in wing size require the maintenance of subtle bilateral differences in flapping motion to maintain a stable path. Flies can even fly straight after losing half of a wing, a feat they accomplish via very large, sustained kinematic changes to both the damaged and intact wings. Thus, the neural network responsible for stable flight must be capable of sustaining fine-scaled control over wing motion across a large dynamic range. In this study, we describe an unusual type of descending neuron (DNg02) that projects directly from visual output regions of the brain to the dorsal flight neuropil of the ventral nerve cord. Unlike many descending neurons, which exist as single bilateral pairs with unique morphology, there is a population of at least 15 DNg02 cell pairs with nearly identical shape. By optogenetically activating different numbers of DNg02 cells, we demonstrate that these neurons regulate wingbeat amplitude over a wide dynamic range via a population code. Using two-photon functional imaging, we show that DNg02 cells are responsive to visual motion during flight in a manner that would make them well suited to continuously regulate bilateral changes in wing kinematics. Collectively, we have identified a critical set of descending neurons that provides the sensitivity and dynamic range required for flight control.

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