Contextual Conditioning with Lithium-Induced Nausea as the US: Evidence from a Blocking Procedure

In two experiments, rats received injections of lithium chloride (LiCl) after spending time in a distinctive context. The acquisition of a conditioned aversion to the context was assessed in a subsequent stage of training in which the rats were given sucrose in the home cage before being transferred to the context and receiving an injection of LiCl. The acquisition of an aversion to sucrose was blocked by this procedure (Experiment 1A). The blocking effect was also found (Experiment 1B) with a procedure designed to ensure full consumption of the sucrose during compound conditioning. In Experiment 2, all subjects experienced two distinctively different contexts in the first stage of training, one associated with a LiCl injection and one not. Subjects given the former during the compound conditioning stage learned less well about sucrose than did subjects given the latter. This result is interpreted as showing that the effective cues in this blocking procedure can be those that uniquely define the particular place in which the first stage of training is given.