How to Make Your Fish Work for You: Tips from Ethology and Ecology for Finding Appropriate Unconditioned Stimuli for...

A key requirement of associative learning studies is the ability to motivate the subject to acquire memory of the conditioned stimulus-unconditioned stimulus (CS-US) association. Although zebrafish have been found capable of acquiring CS-US associative memory, in many studies, the fish failed to learn. One reason for the failure, I argue in this perspective article, is that we do not yet know how to motivate zebrafish. I illustrate this problem using examples, and offer some solutions, based upon results obtained in my own laboratory for appetitive associative learning tasks for zebrafish. I highlight the value of considering the ethology and ecology of the zebrafish. I discuss why food may have been an ineffective US for zebrafish. I provide examples for how to improve the rewarding properties of food based upon the foraging behaviour of zebrafish in nature. I discuss the efforts to identify alternative USs, including the sight of conspecifics or the presence of other ecologically relevant stimuli. I theorize about conflicting motivators in zebrafish learning studies, including the effect of human handling versus that of experimenter-controlled USs. I conclude that systematic analyses of different USs are needed, along with detailed studies on how they may be optimized for the analysis of learning and memory in zebrafish.