Olfactory fingerprints for major histocompatibility complex-determined body odors

Recognition of individual body odors is analogous to human face recognition in that it provides information about identity. Individual body odors dete rmined by differences at the major histocompatibility complex (MHC or H-2) have been shown to influence mate choice, pregnancy block, and maternal beh avior in mice. Unfortunately, the mechanism and extent of the main olfactor y bulb (MOB) and accessory olfactory bulb (AOB) involvement in the discrimi nation of animals according to H-2-type has remained ambiguous. Here we stu dy the neuronal activation patterns evoked in the MOB in different individu als on exposure to these complex, biologically meaningful sensory stimuli. We demonstrate that body odors from H-2 disparate mice evoke overlapping bu t distinct maps of neuronal activation in the MOB. The spatial patterns of odor-evoked activity are sufficient to be used like fingerprints to predict H-2 identity using a novel computer algorithm. These results provide funct ional evidence for discrimination of H-2-determined body odors in the MOB, but do not preclude a role for the AOB. These data further our understandin g of the neural strategies used to decode socially relevant odors.