a, Averaged firing rate during freezing and no freezing periods for ANs and ONs (n = 7 mice, two-way ANOVA, factor 1: AN versus ON, P < 0.05; factor 2: freezing versus no freezing, P > 0.05; F1 × F2: P > 0.05; Student–Newman–Keuls post-hoc test within freezing, **P < 0.01, *P < 0.05). b, Average neuronal assembly rate during no freezing periods and during freezing episodes within or outside CS+ presentations (n = 7 mice, Friedman repeated-measures one-way ANOVA on ranks test, no freezing versus freezing (inside or outside CS+), P < 0.05; Student–Newman–Keuls post-hoc test, *P < 0.05). c, Z-score-normalized peri-stimulus time histograms of individual dmPFC ANs (n = 117) and ONs (n = 172) during freezing episodes. d–f, Left: mean z-score of CS+-evoked significant excitatory (d), unchanged (e) or significant inhibited (f) neuronal responses for dmPFC AN and ON. Grey and pink shaded areas correspond to mean ± s.e.m. Right: corresponding percentage of AN and ON (n = 7 mice, χ2 test, P > 0.05 in all cases; CS+-evoked excitation: AN: 38.5%, ON: 32.6%; CS+-evoked no changes: AN: 45.3%, ON: 55.8%; CS+-evoked inhibition: AN: 16.2%, ON: 11.6%). g, The probability of observing assembly activation is not affected by CS+ (repeated-measures one-way ANOVA on ranks, P > 0.05). Error bars, mean ± s.e.m.