A map of pheromone receptor activation in the mammalian brain

In mammals, the detection of pheromones is mediated by the vomeronasal syst em. We have employed gene targeting to visualize the pattern of projections of axons from vomeronasal sensory neurons in the accessory olfactory bulb. Neurons expressing a specific receptor project to multiple glomeruli that reside within spatially restricted domains. The formation of this sensory m ap in the accessory olfactory bulb and the survival of vomeronasal organ se nsory neurons require the expression of pheromone receptors. In addition, w e observe individual glomeruli in the accessory olfactory bulb that receive input from more than one type of sensory neuron. These observations indica te that the organization of the vomeronasal sensory afferents is dramatical ly different from that of the main olfactory system, and these differences have important implications for the logic of olfactory coding in the vomero nasal organ.