Figure 2. A-MNs execute directional, rhythmic locomotion without premotor INs.

(A) Schematics of the motor circuit components and connectivity of animals of respective genotypes, upon co-ablation of premotor INs and B-MNs (i), premotor INs and A-MNs (ii), or premotor INs and D-MNs (iii). (B) Representative curvature kymograms along the entire length of moving animals, without (Control) and with (Ablated) LED illumination-induced neuronal ablation. Black arrows pointing upwards and downwards on kymograms denote posteriorly or anteriorly propagating body bending, respectively. The horizontal arrow denotes the absence of bending propagation. Animals without premotor INs and B-MNs (i, lower panel) exhibit backward locomotion, as posterior to anterior propagating deep body bends, regardless of the propagation direction of head bending. Those without premotor INs and A-MNs (ii, lower panel) often exhibit slow forward locomotion, consisted of slowly propagating, anterior to posterior, shallow body bends. Animals without premotor INs and D-MNs (iii, lower panel) lead to kinker postures as in premotor INs-ablated animals. (C) Distribution of instantaneous velocity of animals of respective genotypes, represented by the mid-point displacement. The forward velocity (ii) is drastically reduced, whereas reversal velocity (i) is less affected than upon abaltion of premotor INs. n = 10 in each group, p<0.001 against the respective non-ablated Control group by the Kolmogorov-Smirnov test.