V3-IN laser ablation reduces the proportion of MNs that are active during fictive swimming. MNs in Tg(vglut2a:DsRed)nns9 larvae were loaded with Calcium Green-1 AM dye and assigned ROIs during recording. Synchronous MN fluorescence and fictive swimming recordings were compared between Control, V3-IN Ablated, and Sham ablated preparations. A, B, Pseudocolored Calcium Green-1 AM fluorescence panels correspond to numbered time points in aligned ΔF/F (each gray line represents a MN) and PN traces in a Control preparation (A) and a V3-IN Ablated preparation (B). Color indicates fluorescence intensity. C, D, Cumulative probability distributions (C) and percent of MNs active (D) during fictive swimming. Asterisks indicate significant differences at p < than 0.01. Error bars represent SD.