Is fluid consumption necessary for the formation of context-illness associations? An evaluation using consumption and blocking tests

In two experiments, rats experienced two distinctive contexts, one of which was followed by an injection of lithium chloride and the other not. Half the subjects were allowed to consume water in the lithium-paired context, whereas for the remainder no fluid was made available. In the test phase of Experiment 1 all subjects received access to sucrose solution in the contexts. Those for whom water had been available on conditioning trials showed substantial suppression of sucrose consumption in the target context, relative to the nonpoisoned context. This effect was absent in the subjects that had not received access to water during training. Experiment 2, however, which employed a blocking procedure as the test for the associative strength of the context, found evidence for contextual conditioning in both groups of subjects. We argue that the blocking procedure provides a more accurate assessment of the associative strength acquired by contextual stimuli than does the traditional consumption test and is thus able to reveal the occurrence of context conditioning even in subjects given no access to fluid during training, (C) 1998 Academic Press.