Effect of reactivation on stability of consolidated memory after a massed (A) or a spaced (B) protocol. A, Zero, one, three, or five cycles of CS+ re-exposure after massed conditioning (control group: n = 16 per group; CXM-treated group: n = 15–16 per group) B, Zero, one, three or five cycles of CS+ re-exposure 24 h after spaced conditioning (control group: 0 cycle, n = 36; 1 cycle, n = 12; 3 cycles, n = 12; 5 cycles, n = 20; CXM-treated group: 0 cycle, n = 36; 1 cycle, n = 12; 3 cycles, n = 12; 5 cycles, n = 19) (*p < 0.05; **p < 0.01). Error bars show SEM.