Humans and other mammals have a remarkable ability to recognize patterns of visual, auditory, or olfactory cues; deficits in this ability, such as prosopagnosia (face-blindness), can result in significant dysfunction. To better understand the neural processes of pattern recognition, we study the recognition of complex, behaviorally relevant scents in mice. These pheromonal scents are detected and recognized by the accessory olfactory system and convey information about individual characteristics--such as the sex, strain, and estrous status--of other mice. This system is of interest because of the particular compactness and accessibility of the neural circuitry. We will use multielectrode extracellular recording to learn how neurons in the primary sensory organ (the vomeronasal organ) respond to different natural odors. We will also use multielectrode recording and analytical chemistry to learn more about the identity of the individual compounds in these scents, and how these differences are detected by the sensory neurons. These studies will shed light on the properties of natural olfactory stimuli and their neural receptors that underlie olfactory pattern recognition.