Figure 3. Strong aversive experience drives co-reactivation of the Neutral ensemble with the Neutral ∩ Aversive ensemble.

A) Representation of the quantification of independent participation during bursts versus non-bursting periods. Burst events were defined by the whole recorded population, as in Figure 2E (outlined by yellow rectangles). However, now the z-scored mean population activity of the Aversive, Neutral, and Neutral ∩ Aversive ensembles was computed to ask how frequently each ensemble participated in whole population bursts independently of one another. Independent participation meant one ensemble participated while the other two did not.

B) During burst periods, the Neutral ∩ Aversive ensemble participated independently in more bursts than the Aversive ensemble (t₁₄ = 7.95, p = 0.000002) and more than the Neutral ensemble (t₁₄ = 5.59, p = 0.0001) but there was no difference in participation across Low vs High Shock mice (F_1,13 = 1.43, p = 0.25) and no interaction (F_2,26 = 2.49, p = 0.10) (Low Shock, N = 7 mice; High Shock, N = 8 mice).

C) During non-burst periods, there was no difference in participation across ensembles (F_2,26 = 0.38, p = 0.69) or between Low and High Shock mice (F_1,13 = 0.73, p = 0.41), and no interaction (F_2,26 = 0.36, p = 0.70) (Low Shock, N = 7 mice; High Shock, N = 8 mice).

D) Representation of the quantification of co-participation during bursts vs non-bursting periods. As in Figure 3B, the whole population was used to define bursts and the z-scored mean population activities were used to define participation of each ensemble. Co-participation was defined as a whole population burst (outlined by yellow rectangles) during which multiple ensembles participated simultaneously. There were four possible combinations (from left to right: N∩A x N, N∩A x A, N x A, N∩A x N x A) (N∩A = Neutral ∩ Aversive; N = Neutral; A = Aversive).

E) During burst periods, there was a significant interaction between Ensemble Combination and Low vs High Shock (p = 0.01), suggesting that the patterns of co-bursting varied in Low vs High Shock mice. Post-hoc tests revealed that in Low Shock mice, co-participation between all 3 ensembles was less likely to occur than the other combinations (t₁₈ = 4.73, p = 0.0003), while in High Shock mice, co-participation between all 3 ensembles occurred no differently than the other combinations (t₂₁ = 0.358, p = 0.72). Additionally, in the High Shock group, the N∩A ensemble preferentially co-participated with the Neutral ensemble compared to with the Aversive ensemble (t₂₁ = 2.373, p = 0.05), whereas in the Low Shock group, the N∩A ensemble participated no differently with the Neutral and Aversive ensembles (t₁₈ = 1.196, p = 0.25) (Low Shock, N = 7 mice; High Shock, N = 8 mice).

F) During non-burst periods, co-participation between all 3 ensembles was less likely than the other combinations (t₃₉ = 10.92, p = 1.98e-13); however, there was no effect of Low vs High Shock (F_1,13 = 0.038, p = 0.847) and no interaction (F_3,39 = 0.198, p = 0.897) (Low Shock, N = 7 mice; High Shock, N = 8 mice).