Fig. 1
Reinstating encoding context makes cLTM retrievable. a Basic experimental schemes. Left: aversive olfactory classical conditioning. The training tube contains a copper grid surface to deliver the electric shock. Middle: classical memory testing in the T-maze. Right: modified testing with context reinstatement. The testing arms contain a copper grid to reinstate training context. b Memory retention curves tested with different methods. Context reinstatement enables context-dependent long-term memory (cLTM) to be retrieved using conditioned odours. The cLTM is measurable 3 h after training and lasts for at least 14 days without decay (n = 10–12). c cLTM retrieval requires multiple contextual conditions all matched. Any inconsistent contextual condition (i.e. light colour, temperature or absence of copper grid) abolishes cLTM retrieval (n = 8). Crosses denote different conditions from training and circles denote same conditions. d Protein synthesis inhibitor (cycloheximide) and cold-shock treatment cannot destroy cLTM (n = 8–12). e Copper grid improves 3-min memory performance after cold shock (n = 14). f Both immediate memory (3 min) and 24-h memory are significantly improved when the copper grid is present after weak training with a 20-V electric shock, which avoids the ceiling effect that occurs immediately after norma training (n = 8–12). g cLTM was not impaired in nSyb-Gal4;UAS-dCREB2b (n = 8). h cLTM was not impaired in ru1 and rut2080 mutants (n = 4–6). In all figures data show mean performance indices ± SEM; individual data points are displayed as dots. Asterisks denote a significant difference (*P < 0.05 by ANOVA or t test)
