Figure 5. Multiple A-MNs are phase coupled to generate backward locomotion in the absence of premotor INs and B-MNs.

(A) Schematics of the morphology and trajectory of the VA10, DA7, VA11 MN somata and processes. (B) Upper panel: example traces of calcium activities of three A-MNs, in animals where all premotor INs and B-MNs have been ablated. The VA10 and VA11 innervate adjacent ventral body wall muscles; the DA7 innervates dorsal muscles in opposition to those by the VA10 and VA11. Periodic Ca²⁺ oscillations were observed in all neurons, represented by changes in the GCaMP6/RFP ratio (Y-axis) over time (X-axis). Lower panel: the animal’s instantaneous velocity (Y-axis) simultaneously recorded during calcium imaging, was represented by the displacement of the VA11 soma. Values above and below 0 indicate forward (displacement toward the head) and backward (displacement toward the tail) locomotion, respectively. This animal exhibited continuous reversals. Note that the speed of Ca²⁺ change during oscillation correlates with reversal velocity. (C) Phasic relationships among DA7, VA10, and VA11. DA7's activity change is anti-phasic to that of VA10 and V11, whereas the activity changes of VA10 and VA11 exhibit a small phase shift, with VA11 preceding VA10. The red line denotes the mean of all recordings. n = 7 animals.