Fig. 1

Formation and extinction characteristics of generalization. a Schematic of fear memory in the training box (T-box) and generalization in a non-training similar box (G-box), measured at ∆ h after fear conditioning. b Generalization developed gradually in G-box over 24 h (n = 8 per group, but n  = 9 at 18 h). c Generalization extinction paradigm. d Extinction curves in the separate groups by exposing into T-box for 50 min. e Generalization was disrupted in all groups, but fear memory was largely impaired at 24 h extinction after fear conditioning. f Retraining after extinction resulted in gradual reformation of generalization over 24 h (0.5 h, n = 6; 12 h, n = 7; 24 h, n = 8). Statistical comparisons are performed by using repeated two-way ANOVA (*contrast effects, G-box vs. T-box; ^#parameter estimates, between T-box groups); *P < 0.05, **P < 0.01, *** or ^### P < 0.001. Error bars, s.e.m