Figure 2.

Kinetics of CTA extinction immediately after retrieval. Groups were trained as described under Materials and Methods. Then, 3 d later, they were subjected to a retrieval trial in the absence of reinforcer (t = 0). This was followed by a second retrieval trial at the indicated times. Each group of rats was tested on a single time point only in addition to t = 0, that is, each time point in the graph represents a separate group. Extinction becomes apparent only at 2 h after time zero (closed circles). Control groups that were injected i.p. with saline instead of LiCl during CTA training did not show aversion (open circles). The amount of liquid consumed did not vary significantly between the groups and the different time points (closed gray squares, data of the experimental groups).