From Zou and Chen, showing that two areas of women's brains respond to chemical signals in the sweat of sexually aroused men. Their edited abstract, and a figure:
Chemosensory communication of affect and motivation is ubiquitous among animals. In humans, emotional expressions are naturally associated with faces and voices. Whether chemical signals play a role as well has hardly been addressed. Here, we use functional magnetic resonance imaging to show that the right orbitofrontal cortex, right fusiform cortex, and right hypothalamus respond to airborne natural human sexual sweat (distinguishing it from neutral sweat, and a nonsocial control), indicating that this particular chemosensory compound is encoded holistically in the brain. Interestingly, with the exception of hypothalamus, neither the OFC nor the fusiform region is implicated in sexual motivation and behavior. Hence, our results implied that the chemosensory information from natural human sexual sweat was encoded more holistically in the brain rather than specifically for its sexual quality. Our findings provide neural evidence that socioemotional meanings, including the sexual ones, are conveyed in the human sweat.
Figure - Brain responses to social chemosensory compounds. a, Coronal view showing an activated area in the right orbitofrontal cortex. d. Sagittal view showing an activated region in the right fusiform gyrus.
(I might as well also repeat this link from a post several days ago, on the debate raging over MRI studies of social cognition that has been started off by a paper titled "Voodoo correlations in social neuroscience".)