a, b, Representative raster plots illustrating photostimulation-evoked behaviours in Esr1cre/+ females expressing either ChR2 (a) or EGFP (b) in VMHvl towards an intact male (upper), a castrated male (middle), or an intact female (lower). Note that CI (yellow) is augmented during photostimulation in the animal expressing ChR2, but not in the animal expressing EGFP. c, d, Quantification of CI by Esr1cre/+ females expressing EGFP (blue bars; n = 4 per intruder) or ChR2 (red bars; n = 3 per intruder) during 30 s before photostimulation (open symbols) vs during 30 s photostimulation period (solid symbols). *P < 0.05, **P < 0.01, ***P < 0.001; two-way ANOVA with Tukey’s multiple comparisons test. e, Raster plot illustrating that photostimulation of Esr1cre/+ female expressing ChR2 evokes mounting (green), but failed to elicit male-like aggression. f, g, Quantification of mounting parameters by Esr1cre/+ females expressing EGFP (open bars; n = 4 per intruder) or ChR2 (black bars; n = 3 per intruder) towards the indicated intruders. Two-way ANOVA with Tukey’s multiple comparisons test, *P = 0.02 (f) and *P = 0.03 (g) without correction for multiple comparisons, but not significant when corrected (P = 0.07 (f) and P = 0.06 (g)). Data are mean ± s.e.m. n = number of animals.