Fig. 2.

Socially salient but not directly stressful experiences reactivate preexisting fear ensembles. (A) Schematic representation of the doxycycline (DOX)-mediated viral tagging construct (Left) and experimental design (Right). (B) Representative confocal images of DG and BLA histology visualizing cFos-tTa + Tre-EYFP–positive cells (active during FC; green) and cFos-positive cells (active during the different types of stress exposure; red). (C and E) Percentage of cFos-positive cells over DAPI-positive cells across brain regions in males and females. Males: DG: one-way ANOVAF_{(3, 24)} = 3.028, P = 0.0490, Holm–Sidak’s multiple comparisons: *P = 0.0339 for juvenile intruder vs. one-way mirror; BLA: one-way ANOVAF_{(3, 22)} = 2.710, P = 0.0697. Females: DG: one-way ANOVAF_{(2, 18)} = 0.4501, P = 0.6445; BLA: ANOVAF_(2,13) = 0.4962, P = 0.6199. (D and F) Degree of overlap between the two labeled populations normalized over chance (% cFos/DAPI × % EYFP/DAPI). One-sample t tests. Males: DG: juvenile intruder: t = 2.436, degrees of freedom (df) = 9, *P = 0.0376; one-way mirror: t = 2.656, df = 8, *P = 0.0290. BLA: juvenile intruder: t = 7.411, df = 9, ****P < 0.0001; restraint: t = 7.462, df = 4, **P = 0.0017. Females: BLA: one-way mirror: t = 3.387, df = 6, *P = 0.0147. See details for nonsignificant results in SI Appendix, Supplementary Text. Data are shown as mean ± SEM. Dotted lines represent chance. See also SI Appendix, Fig. S4.