Figure 2.

Sub-threshold training induces 2-h and 24-h memory in previously trained animals. Phase I: Trained animals (n = 10) exhibited robust LTM after sensitization training, whereas controls (n = 10) remained at baseline. Phase II: Two days after the decay of initial LTM, trained animals and matched controls were trained with two spaced tail shocks (TS). Tests at 2 and 24 h following training showed the induction of memory at 2 h (2 HR) and 24 h (24 HR) in previously trained animals, but not in matched controls. All T-SWR responses are normalized to baseline responding. In this and all subsequent figures, within-group significance is depicted by P-values within histograms, and between-group significance by the indicated comparisons; all probability values are two-tailed. Data are expressed as means ±SEM.