INTEGRATION OF VISUAL INFORMATION AND BEHAVIORAL HISTORY ACROSS MULTIPLE TIMESCALES DRIVES PHOTOTACTIC NAVIGATIONAL STRATEGIES IN LARVAL ZEBRAFISH

Experience shapes how we perceive and respond to negative stimuli. To study how the brain integrates immediate sensory inputs, historical context, and the outcomes of past actions to make decisions, we use zebrafish larvae. This vertebrate model enables single-cell resolution imaging thanks to its optical transparency. Zebrafish larvae navigate towards light, which is accomplished by directed turning decisions based on lighting cues. One well-established response is the strong turning response to sudden darkness (“dark-flash”), which can be either left or right. Using a variety of custom behavioral assays, we have shown that this turning-direction decision is not random and is based on context at different time-scales. Initially, larvae respond to a dark-flash by turning in the same direction as they last turned before the stimulus (“repeat”). However, after frequent exposure to the stimulus they change strategies by turning in the opposite direction to their previous turn (“switch”). Therefore, this simple vertebrate adopts opposing strategies in response to an aversive stimulus based on how often they experience it. We believe this can open a new window into understanding how the brain shifts behavioral strategies when facing salient stimuli, which is critical for producing well-adapted behavior in differing contexts. To this end we are performing simultaneous behavioral tracking based on tail-flicks in head-fixed larvae, closed-loop visual stimulation, and 2-photon calcium imaging. Our goal is to identify the neuronal basis for these directional decisions, and how these are modulated by recent experience.