The brain that smells sweat

Johan Lundström, in 2004 a PhD-student at the Department of Psychology, Uppsala university, then spent the fall term at Montreal Neurological Institute, McGill University, Canada, with support from the STINT Foundation.

Johan does research within the field of pheromonal communication. He is presently a postdoc at McGill University.

The perspiring odor from the old man sitting beside you on the bus, the fresh smell of newly cut grass, the foul odor of the garbage truck passing, or the appetizing odors from the bakery you walk by. Odors surround us in countless forms, both positive and negative, but few, if any, stop to think about them. Humans have long been considered “microsmatic animals”, where the olfactory sense plays only a minor part in our everyday lives. Interestingly, an increasing number of studies paints the picture that this view of our olfactory inabilities is inaccurate and widely underestimates the role that olfactory information plays in our everyday decisions.

Olfactory cues have been demonstrated in a large number of species to be important information for both mate selection and kin recognition. That this was also the case in humans was, for a long time, simply dismissed with the explanation that we are too evolved and not animals. Although the implications can be discussed, we now know that humans use olfactory information of some sort in mate selection, kin recognition, and everyday social interactions. Behavioral studies to date have demonstrated that our body odor carries with it information that allows us to identify individuals, direct us toward a partner with genetic dissimilarity, and that our individual odor has a genetic basis rather than reflecting only dietary and hygiene factors. A long-withstanding question has, until now, been whether body odors are processed in the brain by the normal olfactory system or by a specialized subsystem dedicated to these so-called social odors.

This basic question had, for a long time, been hovering over my thesis work as a graduate student at Uppsala University. The intricate difficulties in studying the cortical processing of these specialized odors had, however, long prevented us from pursuing this problem. Luckily, a Kulturvetarstipendium from STINT came to my rescue. The generous grant enabled me to visit the Montreal Neurological Institute (MNI) at McGill University, Canada, for six months where I addressed this question in a recent study. MNI is presently one of the leading brain research institutes in the world and also the place where, among others, Drs. Wilder Penfield and Brenda Milner formed the new scientific field of neuropsychology in the fifties. The collaborative effort between two labs at the institute and my home lab in Sweden, paired with the uniquely resourceful environment of the institute, enabled us to conduct an experiment that clearly answered the above question about the function of the olfactory system. Besides being an interesting environment in itself, MNI is, as the name implies, situated in the interesting city of Montreal. That Montreal is in the French-speaking part of Canada adds extra flavor to an already interesting mixture between a North American and central European city. The multiflavor of the city together with the hospitality of its inhabitants left little to wish for when it came to the social parts of my visit. I left Montreal after six months with many new friends and with more new knowledge than I thought was possible to obtain in such a short time. This was my second longer pre-doctoral visit to a North American university and I can testify they both have played, and will play, a very important part of my future carrier in academia.

Besides giving me interesting publications, they have helped me to build a network of collaborators, increased my knowledge about different topics, and have been a continuous source of interesting experiences. For those graduate students that hesitate about whether a pre-doctoral visit to an interesting lab would be a good idea or not, I can only say this – do it! Come prepared with an open mind and you will surely not regret your visit.

But, what did our study finally reveal about how our brain processes body odors? Using positron emission tomography (PET), we were able to conclude that the human brain processes body odors differently than common non-body odors. Not only is the common olfactory system recruited, but also a specialized subsystem that processes social odors. So, the next time you sit next to a person that smells like sweat on the bus, you now know that the odor is properly analyzed by two separate systems in the brain.

Johan Lundström
Uppsala University/McGill University

Senast uppdaterad: 06-07-07 08:49