CALB1 and Anxiety: To verify whether the optogenetic manipulation of vCA1Calb1+ neurons can shift avoidance-approach balance and, thus, modulate anxiety-related behaviours, ChR2–eYFP fluorescent fusion protein was targeted to vCA1Calb1+ neurons using a Cre-dependent strategy in Calb1-IRES2-Cre-D knock-in mice (Supplementary Fig. 12).