The issue being addressed
We humans trust our nose over our eyes and ears in two of the most critical decisions we make: what we eat, and with whom we mate. Our reliance on our nose for key survival-related decisions such as eating and mating is subserved by an astonishingly keen olfactory system. We have in our nose ~6 million olfactory receptors, that as far as we know, are not different in their design and function from those of a rat or a dog. These receptors feed into olfactory bulbs that are, in proportion to the rest of our brain, much smaller than those of rodents, but in absolute terms, bigger than even the entire brain of some rodents. These bulbs then convey information to a human cortical olfactory and limbic system that is fully intact. Indeed, using this system, humans can detect odorants at parts-per-trillion dilution, they can discriminate between a huge number of molecules that differ by the smallest of molecular perturbations, and they can learn to achieve olfactory feats as unlikely as scent-tracking. One of the major uses of olfaction by macrosmatic mammals is in chemical communication. Mammals emit bodily-sourced odorants through urine and other secretions, and these odorants signal meaningful information to conspecifics. Some mammalian chemosignals induce effects that are nothing less than dramatic. For example, the Bruce effect describes the phenomena whereby a pregnant rodent will miscarry if exposed to the odorant of a non-fathering male within a critical early stage of pregnancy. It is hard to imagine a decision with greater evolutionary cost than a voluntary miscarriage, and this "decision" is made based on a chemosignal.
With the above in mind, the major objective of this proposal is to test the hypothesis that like all mammals, humans constantly exchange chemosignals that influence brain activity, hormonal state, and behavior.
Importance for society
Understanding the mechanisms of human chemosignaling will provide a better understanding of the link between brain and behavior, and may uncover specific chemosignaling molecules with important pharmacological implications.
Overall objectives
In Aim 1 we will ask what else do human social chemosignals signal? We will test the novel hypotheses that human social chemosignals communicate social status (dominance/submissiveness).
In Aim 2 we will ask how do humans exchange social chemosignals? We will test the novel hypotheses that handshaking is a chemosignaling mechanism, and that humans constantly chemo-investigate each other.
In Aim 3 we will ask what are the brain mechanisms that subserve human social chemosignaling? We will test the hypothesis that human social chemosignaling is independent of the main olfactory system.
In Aim 4 we will ask what happens when human social chemosignaling goes wrong? We will test the novel hypothesis that altered chemosignaling is a component of autism spectrum disorder.
Taken together, the answers to these questions promise to provide a novel framework for understanding human behavior in both health and disease.
