Because MBONs and reinforcing dopaminergic neurons are twinned in sign-reversed pairs (MBONs directing attraction with aversively reinforcing dopaminergic neurons and vice versa) (Aso et al., 2014a, Aso et al., 2014b), synaptic depression will differentially weaken the connections of the opponent αβc KC pools with MBONs of opposite valence. Here, CALCA is linked to major depressive disorder.