The mesencephalic locomotor region recruits V2a reticulospinal neurons to drive forward locomotion in larval zebrafish
Martin Carbó-Tano, Mathilde Lapoix, Xinyu Jia, Olivier Thouvenin, Marco Pascucci, François Auclair, Feng B. Quan, Shahad Albadri, Vernie Aguda, Younes Farouj, Elizabeth M. C. Hillman, Rubén Portugues, Filippo Del Bene, Tod R. Thiele, Réjean Dubuc, Claire Wyart
Abstract
(V2a) reticulospinal neurons (RSNs) is poorly understood. Here, to overcome this challenge, we uncovered the locus of MLR in transparent larval zebrafish and show that the MLR locus is distinct from the nucleus of the medial longitudinal fasciculus. MLR stimulations reliably elicit forward locomotion of controlled duration and frequency. MLR neurons recruit V2a RSNs via projections onto somata in pontine and retropontine areas, and onto dendrites in the medulla. High-speed volumetric imaging of neuronal activity reveals that strongly MLR-coupled RSNs are active for steering or forward swimming, whereas weakly MLR-coupled medullary RSNs encode the duration and frequency of the forward component. Our study demonstrates how MLR neurons recruit specific V2a RSNs to control the kinematics of forward locomotion and suggests conservation of the motor functions of V2a RSNs across vertebrates.