Figure 2. Somatotopic organization of MNs in adult zebrafish. A, Schematic showing the sites of injections into the different parts of the axial muscles (red, slow; green, intermediate; gray, fast). B, Slow MNs labeled by injection of slow muscle. C, Depth analysis shows that slow MNs are located in the lateral aspect of the motor column. D, Slow and intermediate MNs labeled by injection of a fluorescent dye in slow and intermediate muscles. E, The labeled MNs are located in the ventral aspect of the motor column and extend along the lateromedial axis. F, Graph showing the distance of the MNs retrogradely labeled by injecting a fluorescent dye in slow, intermediate/slow, and fast muscle. G, Position of the different MNs in the motor column labeled by injections into only slow muscles, into slow and intermediate muscles, and into fast muscles. The dorsoventral position of the different MNs is set relative to the Mauthner axon and dorsal edge of the spinal cord.