Analyses of factors that determine the context dependency of conditioned aversion

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This study aimed to investigate the property of the context acquired in the context dependency of conditioned aversion in the rats. Context dependency of conditioned aversion is established during the context discrimination procedure, in which rats are given paired presentation of some fluid in one context while given the same fluid alone in another context. As a result, rats come to avoid consuming the fluid only in the former.Two possible explanations on the role of the context in the formation of the context dependency have been proposed. One assumes that the conditioned context directly associates with nausea, while the other argues that the context acquires the property of occasion setter, which determines the effectiveness of the fluid-nausea association.In order to evaluate the validity of these two explanations, factors that determine whether the context dependency acquired to a fluid transferred to a second fluid was examined in the several experiments. They showed that rats transferred the acquired context dependency to the second fluid irrespective of whether the fluid was novel or familiar. Rather, presentation of the same fluid both in the two contexts and the home cages of the subjects resulted in the context dependency of aversion which was specific to it. Furthermore, such a fluid-specific context dependency once established disappeared when the subjects were given some extended discrimination trainings.These findings can be explained by an assumption that both the context and the fluid directly associate with nausea, and that the apparent context dependency of aversion is a consequence of the summation effect of these two associations.