Decision-making requires animals to integrate information from the environment with their experiences and their internal state in order to select appropriate behaviors. Although animals continuously make decisions critical for their survival, the genetic and molecular pathways underlying the assembly and function of decision-making circuits in vertebrates are not well understood. We recently developed an assay of larval zebrafish that measures in response to an acoustic stimulus the behavioral choice between a rapid escape behavior and a reorientation-like behavior (Jain et al., in preparation). We will present data demonstrating that this assay fulfills key criteria of decision-making, including dynamic biasing in response to stimulus quality, stimulus history, and internal state.
Using this assay, we conducted a forward genetic screen to identify genes required for this simple decision behavior. This screen yielded nine mutant lines in which decision-making is disrupted. While overall responsiveness is largely unaffected in these mutants, their response bias is shifted such that stimuli that preferentially result in an escape response in wild type instead preferentially elicit a reorientation-like behavior. We will present ongoing efforts to identify the causative mutations, as well as progress in applying whole-brain imaging (Randlett et al. Nature Methods 2015) to identify neurons selectively active during reorientation-like behaviors. Together, these approaches will yield new understanding of how the circuits involved in simple vertebrate decision-making develop and function.