Pavlovian-instrumental interactions in active avoidance: The bark of neutral trials

In active avoidance tasks, subjects have to learn to execute particular actions in order to avoid an aversive stimulus, such as a shock. Such paradigms pose a number of psychological and neural enigmas, and so have attracted substantial computational interest. However, the ratio of conjecture to confirmation remains high. Here, we perform a theoretical inquiry into a recent experiment by Gentry, Lee, and Roesch ('Phasic dopamine release in the rat nucleus accumbens predicts approach and avoidance performance', Nat. Commun., 7:13154) who measured phasic dopamine concentrations in the nucleus accumbens core of rats whilst they avoided shocks, acquired food, or acted to gain no programmed outcome. These last, neutral, trials turned out to be a perfect probe for the workings of avoidance, partly because of the substantial differences between subjects and sessions revealed in the experiment. We suggest a way to interpret this probe, gaining support for opponency-, safety-, and Pavlovian-influenced treatments of avoidance.