Craig Ferris of the University of Massachusetts Medical School and his colleagues used functional magnetic resonance imaging (fMRI) to analyze the brains of male marmoset monkeys. The creatures were exposed to scents from a variety of females, some close to ovulation (and therefore sexually attractive) and some that had had their ovaries removed and were therefore less desirable. "We were surprised to observe high levels of neural activity in areas of the brain important for decision making, as well as in purely sexual arousal areas, in response to olfactory clues," remarks study co-author Charles T. Snowdon of the University of Wisconsin-Madison. "Lighting up far more brightly than we expected were areas associated with decision making and memory, emotional processing and reward, and cognitive control."
The authors note that the monkey MRIs showed surprising similarity to studies carried out on humans. Notes Snowdon, "The benefit of the nonhuman primate model is that we can control and know the developmental and social histories of our study subjects, to carry out studies not possible in humans."