Fig. 4. Recruited DN networks are required for forwards walking and grooming, but not for backwards walking.
a, In intact animals (left), activation of a comDN (green) recruits other DNs (orange) and leads to the execution of a complete behaviour. In headless animals (right), the axons of comDNs (green) can still be activated in the VNC. However, other DN axons (orange) cannot be recruited in the brain and remain silent. This comparison between intact and headless animals allows one to isolate the necessity of downstream DN networks to generate complete behaviours. b–e, Forwards walking velocities and behaviour probabilities for DNp09 (b), aDN2 (c), MDN (d) or control (e) flies. Mann–Whitney U-tests compare the difference between the means of the first 2.5 s of optogenetic stimulation across intact (black traces) versus headless (blue traces) animals. f, DNp09 stimulation in both intact and headless animals leads to abdominal contraction (change in Euclidian distance between the anal plate and the ventral side of the most posterior stripe). Mann–Whitney U-test compares the mean of the first 2.5 s of stimulation (blue bars) for headless DNp09 versus headless control animals (blue traces). g, aDN2 stimulation in both intact and headless animals leads to front leg approach (change in Euclidian distance between the front leg tibia–tarsus joint and the neck). Mann–Whitney U-test compares the first 2.5 s of stimulation (blue bars) between headless aDN2 and headless control animals (blue traces). All plots in b–g show data from n = 5 flies with 10 trials each (trial mean and 95% CI (shaded area)). Two-sided Mann–Whitney U-tests compare the trial mean across different flies. ***P < 0.001, **P < 0.01, *P < 0.05 and not significant (NS) P > 0.05. For exact P values, see Supplementary Table 5.