An animal’s behavioral state is reflected in the dynamics of population activity and its capacity to process sensory information. Previous studies in mammalian brains have demonstrated a relationship between behavioral states and information processing (Lee et al., 2016, 2019, 2020). However, these studies have been limited to exploring how population dynamics and sensory representation changes in specific cortical areas. Thanks to its transparency at early life stage and the advent of selective plane illumination microscopy, the zebrafish brain is an attractive model that allow for whole brain imaging at single-cellular resolution. Here, we developed 4 behavioral paradigms using high-speed videography and tracking with deep neural network, to assess how sensory representation is altered under a state of fear. N=602, 6dpf zebrafish (danio rerio) were exposed to either a dark visual flash or varying volumes of loud noise burst. These target stimuli were preceded by either a visual loom or an auditory crescendo, mimicking an approaching threat. Fish showed both startle and freezing behavior following a loom or crescendo and altered their startle response to the target stimuli. Interestingly, the probability of startle and freeze response was dependent on the intensity of the target stimulus following a threat stimulus. The observed changes in behavioral output suggest a possible change in sensory representation and decision-making. How these changes arise in specific brain areas and across the entire brain remains to unknown, but the parameters established here represents a fruitful starting point to integrate with selective plane illumination microscopy for further investigations.