Stress can induce depression, and the hippocampus regulates cognitive aspects of this response. In a recent study, hippocampal neurons that were active during a pleasant experience were genetically labelled in mice. Subsequent exposure of these mice to chronic immobilization stress resulted in depression-like behaviours that were transiently attenuated by acute optogenetic reactivation of the labelled neurons. Simultaneous inhibition of neurons projecting from the basolateral amygdala to the nucleus accumbens blocked the antidepressive effect, suggesting a circuit by which activation of a positive engram might alter current affective state.