a, Average normalized mean fluorescence within session. There was no difference between the mean fluorescence across the 3 sessions (one-way repeated measures ANOVA, F2,7 = 0.423, not significant). b, Average normalized mean fluorescence within session. There was no difference between the mean fluorescence across a 10-min session (one-way repeated measures ANOVA, F9,22 = 1.108, not significant). Results show mean ± s.d. c, Higher ensemble overlap with 5 h interval than 7 days. Normalized ensemble overlap is calculated as the ensemble overlap between contexts separated by 5 h divided by the ensemble overlap between contexts separated by 7 days. A normalized overlap value of 1 signifies that there is no difference between the overlap at 5 h and 7 days. The minimum number of calcium events required from each cell for the cell to be considered ‘active’ (inclusion criteria) was systematically increased and the ratio of the ensemble overlap for the different context was calculated. For all inclusion criteria, there is higher ensemble overlap with a 5 h, rather than 7 day, interval (one-sample t-test against 1, (1) t7 = 3.00, P = 0.02, (2) t7 = 2.57, P = 0.04, (3) t7 = 2.42, P = 0.04, (4) t7 = 2.50, P = 0.04, (5) t7 = 2.32, P = 0.05). Results show mean ± s.e.m.