All-optical investigation reveals a hierarchical organization of vsx2+ reticulospinal neurons coordinating steering and forward locomotion

All-optical investigation reveals a hierarchical organization of vsx2+ reticulospinal neurons coordinating steering and forward locomotion | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article All-optical investigation reveals a hierarchical organization of vsx2+ reticulospinal neurons coordinating steering and forward locomotion Claire Wyart, Xinyu Jia, Akshey Kumar, Ninon Peysson, Martin Carbo-Tano, and 4 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7216842/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted You are reading this latest preprint version Abstract Locomotion requires the precise coordination of descending motor commands, but how distinct motor programs are organized and initiated at the brainstem level remains unclear. Reticulospinal neurons (RSNs) are known to transmit motor commands to the spinal cord. Yet, the nature of RSNs that initiate forward locomotion and coordinate with steering movement remains elusive. Here, we use a high-precision all-optical approach to map the spatial and functional organization of vsx2⁺ RSNs in larval zebrafish. From population imaging, we identify among them two clusters of putative ‘Start’ neurons that are consistently recruited ~300 ms before movement onset. Using patterned optogenetics and behavioral recordings, we demonstrate that RSNs triggering forward swimming are spatially segregated from those triggering steering. Caudal medullary vsx2⁺ RSNs in rhombomere (‘r’) 8 form a hub triggering forward locomotion and receive inputs from more rostral ‘Start’ and ‘Steering’ RSNs in retropontine (r6) and rostral medulla (r7). This hierarchical and modular circuit architecture across RSNs can allow rapid transitions between motor programs while maintaining stability — a hallmark of locomotion. Biological sciences/Neuroscience/Neural circuits Biological sciences/Neuroscience/Motor control Reticulospinal neurons (RSNs) vsx2 locomotion motor control Start neurons movement initiation recurrent connectivity brainstem zebrafish all-optical neurophysiology Full Text Additional Declarations There is NO Competing Interest. Supplementary Files SupplementaryVideo02Middle20210216F7.avi Photoconversion of vsx2+ RSN axons at middle spinal cord labels vsx2+ RSNs projecting beyond segment 10. SupplementaryVideo01Rostral20210105F2.avi Photoconversion of vsx2+ RSN axons at rostral spinal cord labels vsx2+ RSNs. SupplementaryVideo05timefromstimonsetSteering.mp4 Tail bend in response to unilateral stimulation of steering-related vsx2⁺ neurons. SupplementaryVideo08startcrossingaxonsfish24flmt5720220209F8.avi Single cell reconstruction of a putative rostral vsx2⁺ ‘start’ neurons SupplementaryVideo10medullartbifurcating20210816F1hbsc3ALL.avi Single cell morphology of an example medullary neuron with bifurcating axons SupplementaryVideo03Caudal20210216F9.avi Photoconversion of vsx2+ axons at caudal spinal cord labels long projecting vsx2+ RSNs. SupplementaryVideo07timefromstimonsetForward.mp4 Tail bend in response to unilateral stimulation of forward-triggering vsx2⁺ neurons. SupplementaryVideo11medullarydescending20211214nacre05hbsc3.avi Single cell reconstruction of a medullary neuron with descending axons SupplementaryVideo06timefromstimonsetTurn.mp4 Tail bend in response to unilateral stimulation of turning-related vsx2⁺ neurons. SupplementaryVideo09startbroadcasting20211214nacre04hbsc2.avi Single cell morphology of a rostral vsx2⁺ neurons SupplementaryVideo14spinalinterneuron20220223F9all1.avi Single cell morphology of a spinal V2a interneurons with bifurcating axons SupplementaryVideo12medullarydescending20220223F6all.avi Single cell morphology of a medullary neuron with descending axons SupplementaryVideo13medullacrossingr8rSC202202231.avi Single cell reconstruction of a medullary neuron with contralateral axons at the obex and rostral spinal cord SupplementaryVideo04successfultargetactivtaion.mov All-optical interrogation of vsx2+ neuronal network responses to single-cell activation Cite Share Download PDF Status: Under Review Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-7216842","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":497129084,"identity":"2cc13d97-0bbb-4644-9772-551a23010ceb","order_by":0,"name":"Claire 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Reticulospinal neurons (RSNs) are known to transmit motor commands to the spinal cord. Yet, the nature of RSNs that initiate forward locomotion and coordinate with steering movement remains elusive. Here, we use a high-precision all-optical approach to map the spatial and functional organization of vsx2⁺ RSNs in larval zebrafish. From population imaging, we identify among them two clusters of putative ‘Start’ neurons that are consistently recruited ~300 ms before movement onset. Using patterned optogenetics and behavioral recordings, we demonstrate that RSNs triggering forward swimming are spatially segregated from those triggering steering. Caudal medullary vsx2⁺ RSNs in rhombomere (‘r’) 8 form a hub triggering forward locomotion and receive inputs from more rostral ‘Start’ and ‘Steering’ RSNs in retropontine (r6) and rostral medulla (r7). 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