Analyses of factors that determine the context dependency of conditioned aversion

本研究旨在探讨大鼠条件厌恶情境依赖中获得情境的性质。在情境辨别过程中，大鼠在一个情境中被给予某种液体的配对呈现，而在另一个情境中被单独给予相同的液体，从而建立了条件厌恶的情境依赖性。结果，只有前者的老鼠才会避免摄入这种液体。关于语境在语境依赖形成中的作用，人们提出了两种可能的解释。一种假设条件情境与恶心直接相关，而另一种认为情境获得了场合设定者的属性，这决定了液体-恶心关联的有效性。为了评估这两种解释的有效性，在几个实验中检查了决定流体是否对转移到第二流体的环境依赖性的因素。他们发现，无论第二种液体是新鲜的还是熟悉的，大鼠都会将获得的环境依赖性转移到第二种液体中。相反，在两种情境和被试的家庭笼子中呈现相同的液体会导致厌恶的情境依赖，这是特定于它的。此外，这种流体特异性情境依赖一旦建立，当受试者接受一些扩展的辨别训练后就消失了。这些发现可以通过一个假设来解释，即环境和液体都与恶心直接相关，而厌恶的明显环境依赖性是这两种关联的总和效应的结果。

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.