Differential Acquisition of Aversion by Two Distinctive Contexts Paired with Lithium-Induced Illness

In three experiments using rats as subjects, we investigated the role of the hedonic properties of the CS in context aversion conditioning. In Experiment 1, rats were allowed to drink water in two different contexts, L-S (Light room and Small cage) and D-B (Dark room and Big cage). Rats' consumption of water was higher in the D-B than in the L-S context. This result was taken as evidence for the L-S context eliciting a state of uneasiness that interferes with drinking plain water. In Experiments 2 and 3, rats were injected with lithium after placement in the L-S or the D-B context. In a blocking test (Symonds & Hall, 1997), the L-S context showed conditioning since it blocked the acquisition of aversion by a novel taste, quinine (Experiment 2) or salt (Experiment 3). By contrast, the D-B context failed to show conditioning, that is, no blocking was observed with salt or quinine. These results suggest that the hedonic properties of the context used as the CS may affect its acquisition of associative strength when paired with an internal aversive stimulus.