Just like animals, humans use chemical communication. Scent molecule Hedione triggers different brain activities in men and women.
The question if humans can communicate via pheromones in the same way as animals is under debate. Cell physiologists at the Ruhr-Universität Bochum have demonstrated that the odorous substance Hedione activates the putative pheromone receptor VN1R1, which occurs in the human olfactory epithelium. Together with colleagues from Dresden, the Bochum-based researchers showed that the scent of Hedione generates sex-specific activation patterns in the brain, which do not occur with traditional fragrances. “These results constitute compelling evidence that a pheromone effect different from normal olfactory perception indeed exists in humans,” says scent researcher Dr. Hanns Hatt. The team published the results in the journal NeuroImage.
Hedione activates pheromone receptor in olfactory epithelium
Using genetic-analysis approaches, the researchers from Bochum confirmed the pheromone receptor’s existence in human olfactory mucosa. Subsequently, they transferred the genetic code for the receptor into cell cultures and, using these cells, demonstrated that Hedione activates the receptor. Hedione – derived from the Greek word “hedone”, for fun, pleasure, lust – has a pleasant fresh jasmine-magnolia scent and is utilized in many perfumes. It is also called the scent of success.
Sex-specific brain activation may be related to the release of sex hormones
Together with the team headed by Dr Thomas Hummel from the University Hospital Dresden, the group from Bochum analysed what happens in the brain when a person smells Hedione. They compared the results with the effects triggered by phenylethyl alcohol, a traditional floral fragrance. Hedione activated brain areas in the limbic system significantly more strongly than phenylethyl alcohol. The limbic system is associated with emotions, memory and motivation. In addition, Hedione activated a specific hypothalamic region, in women more strongly than in men. This activation pattern is typical for controlling sexual behaviour via the endocrine system.
Next steps are in progress
“In the next stage, we want to find out which physiological and psychological parameters are affected when Hedione activates the pheromone receptor,” explains Hanns Hatt. “We have already launched the relevant studies. But we also have to search for scent molecules in bodily secretions, which resemble Hedione and activate the receptor. With its help, humans could actually communicate with each other.”
Pheromone receptors in humans and animals
Pheromones are substances that facilitate chemical communication between members of the same species. They trigger a homogeneous, repeatable reaction. In the animal kingdom, this kind of communication is very widespread. Mice have approximately 300 different genes for pheromone receptors; in humans, probably only five of them are still functional. Most mammals have a special organ located at the base of the nasal septum, i.e. the vomeronasal organ. According to contemporary research, this organ fulfills no function in humans anymore. However, researchers at RUB and other institutes have demonstrated in the recent years that pheromone receptors may also occur in the olfactory epithelium in humans and in mice.
The smelling of Hedione results in sex-differentiated human brain activity
A large family of vomeronasal receptors recognizes pheromone cues in many animals including most amphibia, reptiles, rodents, and other mammals. Humans possess five vomeronasal-type 1 receptor genes (VN1R1–VN1R5), which code for proteins that are functional in recombinant expression systems. We used two different recombinant expression systems and identified Hedione as a ligand for the putative human pheromone receptor VN1R1 expressed in the human olfactory mucosa. Following the ligand identification, we employed functional magnetic resonance imaging (fMRI) in healthy volunteers to characterize the in-vivo action of the VN1R1 ligand Hedione. In comparison to a common floral odor (phenylethyl alcohol), Hedione exhibited significantly enhanced activation in limbic areas (amygdala, hippocampus) and elicited a sex-differentiated response in a hypothalamic region that is associated with hormonal release.
Utilizing a novel combination of methods, our results indicate that the putative human pheromone receptor VN1R1 is involved in extra-olfactory neuronal activations induced by the odorous substance Hedione. The activation of VN1R1 might play a role in gender-specific modulation of hormonal secretion in humans.
“The smelling of Hedione results in sex-differentiated human brain activity” by I. Wallrabenstein, J. Gerber, S. Rasche, I. Croy, S. Kurtenbach, T. Hummel, and H. Hatt in NeuroImage. Published online March 19 2015 doi:10.1016/j.neuroimage.2015.03.029
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