Rapid reacquisition of contextual fear occurs after 3 or 6 sessions of extinction and is specific to the context of reconditioning. (A) Overview of the design of Experiment 2. The times listed represent the total time of exposure to the context for a given session. A “+” sign indicates a single 0.75 mA shock and a “−” sign indicates the exposure to the context without shock. The treatment context is represented by A or B. (B) Mean freezing during each extinction session (E1−6 or E1−3) in rats that received fear conditioning Days 1 and 2 (REC 6 EXT) or Days 4 and 5 (REC 3 EXT and REC 3 SWITCH). (C) Mean freezing during the three tests for each group. Tick marks on the X-axis reflect 6-min time blocks. (*) REC groups vs. SWITCH, P < 0.005, REC 6 EXT vs. COND, P < 0.05; (#) SWITCH vs. all other groups, P < 0.005; (^) REC groups vs. COND, P’s < 0.05. Error bars represent the standard error of the mean.
