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Our work concerns the general problem of adaptive behavior in response to predatory threats, and of the neural mechanisms underlying a choice between strategies. Interacting predators and prey tightly regulate their motion, timing with precision when to hold, attack or escape. Motion cues are thus paramount in these interactions. Speed and (un)predictability have shaped the evolution of sensory and motor systems, the elucidation of which a great deal of research has been devoted. Much less attention has been paid to the role of motion as a social cue of threat or safety. We and others have found that prey animals use the movement of their neighbors to regulate their defensive responses. We have studied social regulation of freezing in rodents and found that rats use cessation of movement evoked sound, resulting from freezing, as a cue of danger. In addition, auto-conditioning, whereby rats learn the association between shock and their own freezing, during prior experience with shock, facilitates the use of freezing by others as an alarm cue. To further explore the social regulation of defensive responses we resorted to the use fruit flies as it easily allows testing of groups of varying sizes, the collection of large data sets and genetic access to individual neuronal types. We established that fruit flies in response to visual looming stimuli, simulating a large object on collision course, make rapid freeze/flee choices accompanied by lasting changes in the fly’s internal state, reflected in altered cardiac activity. Freezing in flies is also strongly modulated by the movement of surrounding neighbours. In contrast with rodents that use auditory cues, female flies use visual motion processed by visual projection neurons. Finally, I will discuss more preliminary findings suggesting that there are multiple states of freezing as measured by muscle activity in the fly legs. Having established the fly as a model to study freezing/fleeing decisions, we are in a great position to perform large scale integrative studies on the organization of defensive behaviours. Short Bio Marta Moita received her BSc degree in Biology at the University of Lisbon, in 1995. As part of Gulbenkian’s PhD programme in Biology and Medicine she developed her thesis work, on the encoding by place cells of threat conditioning under the supervision of Prof. Joseph Ledoux, at the New York University (1997-2002). In 2002, Marta Moita worked as a postdoctoral fellow in Dr. Tony Zador’s laboratory, at the Cold Spring Harbor Laboratory, to study the role of auditory cortex in sound discrimination. In 2004, she became a principal investigator, leading the Behavioral Neuroscience lab, at the Instituto Gulbenkian de Ciência. In 2008 her group joined the starting Champalimaud Neuroscience program. In 2018 and 2019 Marta Moita served as Deputy Director of Champalimaud Research. Her lab is primarily interested in understanding the mechanisms of behavior. To this end, the lab has focused on behaviors that are crucial for survival and present in a wide range of species, namely defensive behaviors triggered by external threats. Using a combination of state-of-the-art tools in Neuroscience (initially using rats and currently using fruit flies) and detailed quantitative descriptions of behavior, her lab aims to understand how contextual cues guide the selection between different defensive strategies and how the chosen defensive behavior and accompanying physiological responses are instantiated.