A Brain Module for Scalable Control of Complex, Multi-motor Threat Displays

Threat displays are a universal feature of agonistic interactions. Whether threats are part of a continuum of aggressive behaviors or separately controlled remains unclear. We analyze threats in Drosophila and show they are triggered by male cues and visual motion, and comprised of multiple motor elements that can be flexibly combined. We isolate a cluster of ∼3 neurons whose activity is necessary for threat displays but not for other aggressive behaviors, and whose artificial activation suffices to evoke naturalistic threats in solitary flies, suggesting that the neural control of threats is modular with respect to other aggressive behaviors. Artificially evoked threats suffice to repel opponents from a resource in the absence of contact aggression. Depending on its level of artificial activation, this neural threat module can evoke different motor elements in a threshold-dependent manner. Such scalable modules may represent fundamental “building blocks” of neural circuits that mediate complex multi-motor behaviors. •Fly threat displays are comprised of multiple motor elements•Modular AIP neurons control threat displays independently of other aggressive behaviors•AIP neuron activation can mimic bimodal sensory cues and evoke variable motor output•Threat displays promote, but are not required for, conspecific target repulsion Duistermars et al. characterize threat displays in flies and the sensory cues required for this behavior. They also identify a compact neural module that controls flexible threat behavior according to its level of activity.