Rapid reacquisition occurs following 2 or 12 sessions of extinction. (A) Overview of the design of Experiment 1. 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. (B) Mean freezing during each extinction session (E1−12 or E1−2) in rats that received fear conditioning Days 1 and 2 (REC 12 Ext) or Days 11 and 12 (REC 2 EXT). (C) Mean freezing during Tests 1 and 2 for each group. Tick marks on the X-axis reflect 6-min time blocks. (*) REC 12 EXT vs. COND, P < 0.05; (#) REC 2 EXT vs. COND, P < 0.05, and combined REC groups vs. COND, P < 0.01. Error bars represent standard error of the mean.
