Top: When male mice detect the ESP1 sex pheromone, they display enhanced aggressive behavior toward other male mice. A region referred to as MeApv in the part of the brain called the amygdala acts as a 'switch' that passes ESP1 information to different regions of the hypothalamus, another area of the brain, depending on the sex of the recipient mouse: the MPA subregion in males and VMHd subregion in females. Middle: ESP1 enhances sexual behaviors in female mice. The neural circuit, identified in the study, is responsible for this effect. Bottom: ESP1 and a predator cue (snake skin), which elicits defensive behaviors, use intermingled but mostly different neural circuits, extending from the peripheral receptive organ to the hypothalamus.