a–c, Functional convergence of both olfactory systems mediated by the posterior MeA is pivotal for male urine reinforcement. a, Timeline of the preference assay. Mice were habituated in the chamber for ten days (1), then exposed to male-soiled bedding for 60 h in their home cage (2), followed by one additional day of habituation before male urine (with normal levels of darcin (1 μg μl−1)) was presented in one of the two ports (3). Urine was removed for the recall session one day later (4). Port preference was quantified from port entries. b, c, Cumulative poke counts during habituation (1), habituation after treatment (2), exposure to male urine (3) and recall (4) sessions for mice expressing eNpHR–eYFP (n = 10) with (b) and without (c) optical silencing of nNOS neurons. Poke counts were recorded on the days indicated by purple arrows in a. Mice were exposed to male urine in one port (red) and a blank filter (blue) in the second port (3). During habituation (1, 2) and recall (4) sessions both ports contained a blank filter. Mean (bold lines) and individual (fine lines) cumulative poke counts are shown. Poke counts were compared using the two-sided Wilcoxon signed-rank test (***P = 0.0002). The effect of silencing nNOS neurons is quantified with matched pair differences (male urine session comparisons, b (3) to c (3), P = 0.002) and recall of male urine with darcin (recall session comparisons, b (4) to c (4), P = 0.002) using the two-sided Wilcoxon signed-rank test, adjusted for multiple comparisons. d, e, Optical silencing of nNOS neurons does not affect recall of darcin memory. Cumulative poke counts during habituation (1), habituation after treatment (2), darcin (3) and recall (4) sessions in mice expressing eNpHR (n = 11) with optical silencing during all sessions (d (1–4)) and with optical silencing during recall sessions only (e (4)). Poke counts were recorded on the days indicated by purple arrows in a. Mice were exposed to darcin in one port (red) and a blank filter (blue) in the second port (3). During habituation (1, 2) and recall (4) sessions both ports contained a blank filter. Mean (bold lines) and individual (fine lines) cumulative poke counts are shown. Poke counts were compared using the two-sided Wilcoxon signed-rank test (**P = 0.001). The effect of silencing nNOS neurons during recall sessions was tested with matched pair differences (c, cue (e (3)) to recall (e (4)) comparisons, laser off (e (3)) and on (e (4)), P = 0.1, using the two-sided Wilcoxon signed-rank test, adjusted for multiple comparisons.