We found that the DIMD shows a nearly identical activity profile to the DCMD ( Figures 7C and 7D). There was no significant difference in the amplitude of the peak firing rate between the two neurons ( Figure S5A) except at l/|v| = 10 ms. The DCMD peak firing rate, however, occurred slightly earlier than the DIMD for small l/|v| values ( Figure S5B).

The simplest explanation for these results is that the DCMD and the DIMD—given its close resemblance to the DCMD—can interchangeably and equally well mediate jump escape behaviors. According to this hypothesis, because EPSPs elicited in the FETi by these neurons summate, the reduction in jump probability and the increase in variability following nerve cord sectioning would be at least partially click here explained by the absence of one of them, resulting in delayed cocontraction and a smaller number of subsequent extensor spikes. We conclude that the DCMD is not necessary for jump escape behaviors, provided that the

second nerve cord remains intact, check details since the DIMD can presumably take over its role. Next, we selectively ablated the DCMD in one nerve cord by filling it intracellularly with 6-carboxy-fluorescein, a phototoxic dye, and shining laser light onto it (Experimental Procedures). In addition, we sectioned the other nerve cord. This allowed us to determine whether the DCMD is necessary among descending contralateral neurons for the generation of looming-evoked escape behaviors. Since other axons, including the DIMD Ergoloid receiving input from the ipsilateral eye, should remain intact in the spared nerve cord, we used stimulation of the ipsilateral

eye as a control ( Figure 8, inset). We could successfully carry out the ablation procedure in 9 locusts (out of 40 locusts in which the procedure was attempted), as evidenced by the selective disappearance of the DCMD spikes from extracellular recordings in response to looming stimuli (Figures S6A and S6B and Laser Ablation Optical Setup). We could subsequently elicit jumps in four of these locusts. An additional five animals prepared for but did not carry out a jump in response to looming stimuli to either eye. Since these experiments were carried out without a telemetry backpack, we analyzed the jump preparation sequence in these nine locusts based on simultaneously acquired video recordings. The timing of the IJM (see Figure 1 and Figure 3), which is a proxy for the activation onset of flexor motor neurons in intact animals (Fotowat and Gabbiani, 2007), did not differ when stimulating the eye ipsi- or contralateral to the remaining nerve cord. However, it showed higher variability in response to stimulation of the contralateral eye and a lower correlation with l/|v| (Figure 8; ρcontra = 0.48, p = 0.009; ρipsi = 0.69, p < 10−9).