Fig. 1

(A) Schematic of a sensorimotor circuit comprising a sensory (blue) and motor pathway (yellow). Efference copy or corollary discharge signals (crimson) can arise from almost any level of the motor pathway and target any level in the sensory pathway. In the zebrafish, centrifugal fibers from the brain target the neuromasts directly. Adapted from Crapse and Sommer². (B) Left: lateral view of a 7 dpf larva expressing GFP in lateral line sensory neurons (black). Anterior Lateral Line ganglion (ALLg) neurons innervate head neuromasts, and Posterior Lateral Line ganglion (PLLg) neurons innervate dorsal and tail neuromasts. Neuromasts with hair cells stained with DiASP (blue). Backfills of the posterior lateral line nerve (PLLn) via dye injections (magenta cross). Right: hair cells (HC) expressing GFP in a posterior neuromast of a 7 dpf larva. (C) Maximum intensity projection of the brain of a 6 dpf larva that received bilateral injections of fluorescent dextrans in the PLLn. Labeling reveals 3 cell clusters: the PLLg, the DELL, and the OEN with its caudal, rostral and supra-rostral subdivisions. In this fish only the caudal OEN was labeled. (D) Diagram showing the major components of the PLL circuit in the brain (light gray) and periphery. Neuromasts, sensory organs (gray), are activated by mechanosensory stimuli. Signals are transmitted to primary sensory/afferents neurons in the PLLg (light-blue). Descending inputs originate from the DELL (orange) and from the OEN (red). Afferent and efferent neurites join in the PLLn, and extend collateral branches to individual neuromasts. The circuit is midline (ml) symmetric but only one side is illustrated for clarity. See also Figure S1.