Encoding Human Sexual Chemosensory Cues in the Orbitofrontal and Fusiform Cortices

Abstract

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, indicating that this particular chemosensory compound is encoded holistically in the brain. Our findings provide neural evidence that socioemotional meanings, including the sexual ones, are conveyed in the human sweat.

Summary of the Study by SinglePheromones.com:

There have been no experiments so far in which scientists have attempted to study the sweat of sexually aroused humans. This is a groundbreaking study in which researchers examined sweat occurring in natural conditions. The study was conducted using functional magnetic resonance imaging (fMRI). Four substances were compared: (1) sweat of sexually aroused individuals, (2) PSP, (3) neutral sweat, and (4) ethyl alcohol. Nineteen healthy, heterosexual women who were not using hormonal contraception and were in the peri-ovulatory phase participated in the study. They inhaled each substance twice in five series, for 12 seconds each time. The participants were unaware of which substance they were inhaling.

Sweat was collected from 20 heterosexual, non-smoking men who did not use deodorants or other scented products during the study. The sweat was collected on swabs placed under their armpits while they watched: (1) 20-minute erotic films showing sexual intercourse between a man and a woman, and (2) documentary films. The men’s skin conductance was checked to confirm sexual arousal. Ultimately, samples from three men who were most aroused were used.

Results:
When women smelled the sexual sweat, specific parts of the brain were activated, which did not occur with the other substances. Most importantly, there were no significant differences in brain activation between the other three substances. All three activated a similar area. It should be noted that most women did not associate the substance with sweat, confirming that the compounds were perceived subconsciously. Researchers conclude that neutral sweat is perceived holistically by the human brain, while sexual sweat carries emotional value and affects specific, selected areas of the brain in its right hemisphere (responsible for smell, social behavior, and emotions). The human brain recognizes socio-emotional information present in human sexual sweat.