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Authors & Affiliations
Leandro Scholz, Manxiu Ma, Sarah J. Stednitz, Conrad C.Y. Lee, Gilles C. Vanwalleghem, Ethan K. Scott
Abstract
Animals must react to threatening stimuli in a way that increases their chance of survival. The visual loom is a known threatening stimulus that emulates an approaching predator and mainly elicits the C-startle escape response in larval zebrafish. However, the behavioral space of the response to the visual looms may also involve freezing and other types of swim bouts. In this work, we carried out free swimming behavioral experiments and immunofluorescence imaging protocols to explore the differences between types of visual looms and how they affect behavioral output through habituation and changes in internal states. We compared three types of visual looms: avoidable, inescapable, and escapable. In our habituation stimulus train, we observed differences in the proportion of escape responses and freezing behaviour between these paradigms and notable differences in the extent of habituation after 3 blocks of 10 visual loom presentations. By classifying the observed swim bout types and observing the swim bout sequences, we also found differences in bout transition probabilities between paradigms that may indicate that each paradigm causes different shifts in internal states: inescapable looms cause greater habituation, whereas escapable looms increase arousal and avoidable looms could contribute to anxiety like behaviour and helplessness. Our MAPK/pERK immunofluorescence analysis indicates that the habenula and thalamus could be involved in these shifts in behaviour. In future work, we aim to evaluate the same paradigms using whole-brain two-photon calcium imaging and virtual reality stimulus controls to further elucidate the neural circuits involved in habituation and shifts in internal states.