To assess extinction retention, we conducted an extinction memory recall test approximately 24 hours after the extinction learning session (Day 3). This consisted of 20 non-reinforced presentations of each of the CSs (CS+E, CS+U, and CS−). In each experimental session (fear acquisition, extinction learning, and extinction recall test) all CSs were presented for 4 sec each and the mean inter-trial interval (ITI) was 12 sec (range: 6–18 sec). The designation of colored squares (blue, yellow, or red) as CS+E, CS+U, or CS− was counterbalanced across the participants and the order of trials was pseudo-randomized, such that no more than 2 presentations of the same colored square (red, yellow, or blue) occurred in a row.
