Male subjects who could not perceive the pheromone 5a-Androst-16-en-3-one, produced similar orbitofrontal changes on PET compared with perceptible phenylethyl alcohol (rose)

Background: The aim of this study was to evaluate in how far cerebral blood flow changes in male subjects when exposed to a pheromone that they cannot consciously smell. Methods: We used a boar taint steroid (5a-Androst-16-en-3-one), which is similar to human axillary sweat but could not be detected by the human volunteers who participated in this study. Results: The pheromone produced activation of the orbitofrontal and frontal cortex in comparison to a baseline condition. The same regions were activated when the subjects smelled a rose-like odour. Conclusion: This study shows that a pheromone, which is not consciously detected, can evoke a response in the brain that is similar to a detectable odour.