A GABAergic neuron (MBON-γ1pedc) postsynaptic to γm neurons mediates gene expression required for LTM formation. (A and B) Activation of the MBON-γ1pedc neuron by pulsed red light (40 Hz, 1 min) during the shock periods of the last three sessions of spaced training impaired 1-d memory (Kruskal–Wallis test, P = 0.0001; n = 8–10) (A), and Arc2 mRNA expression at 1 h after spaced training (Kruskal–Wallis test, P = 0.0025; n = 6) (B). CsChrimson was expressed in the MBON-γ1pedc neuron using MB112C (SI Appendix, Fig. S6C). (C) Nuclear pERK expression was decreased in the MBON-γ1pedc neuron after spaced training. The MBON-γ1pedc neuron was labeled with nlsGFP using MB112C (Scale bar, 2 μm). n = 7–14 for all data. Data are represented as a mean ± SEM. n.s., not significant, P > 0.05; *P < 0.05; **P < 0.01; ***P < 0.001.