Bild: Paul Szyszka
Bild: Paul Szyszka

Smelling the forest – not the trees

New study by the University of Konstanz: Animals are much better at smelling a complex “soup” of odorants rather than a single pure ingredient

As part of an international team, the University of Konstanz investigates how olfactory receptors and brain structures cope with mixtures and single odorants. At first, the researchers from the University of Konstanz in Germany, the University of Sussex in Great Britain, the Universidad de Buenos Aires in Argentina and the Arizona State University in the US expected that mixtures would mean complications. But it turned out there was no extra complications and in fact, it’s usually easier to smell mixtures than single odorants and the sensing is also slightly faster. “This wasn’t what we expected but this is what came out from our mathematical investigation”, says Dr Paul Szyszka, neurobiologist at the University of Konstanz. These findings have been published in the current edition of the scientific journal PloS Computational Biology.

The research team built a mathematical model of odor transduction, whose predictions are supported by physiological recordings of the olfactory system of fruit flies and honey bees. The actual result is that complex mixed odorants are detected more quickly and more reliably by olfactory receptors and can be identified over a wider concentration range than pure odorants.

This suggests that maybe our olfactory systems are not made to do this type of analytic smelling of pure compounds. Everything we take in from our environment is mixed smells, so it makes evolutionary sense that our olfactory systems would be better at those type of smells. Similarly, animals secrete odorant mixtures as communication signals (pheromones), so it is vital that they can quickly and accurately identify these chemical signals and thus can decode the message they are being sent.

The new findings shed new light on the nature of the sense of smell and could help develop more sophisticated artificial systems that could eventually emulate the ability of sniffer dogs to detect drugs and explosives as well as improve food safety with devices that could detect the quality and ripeness of produce.

Professor Thomas Nowotny, Director of Research and Knowledge Exchange at the University of Sussex, believes these findings could have serious ramifications for scientists around the world studying the growing field of scent which largely has focussed on researching with single compounds. Not only will the results expand our understanding of humans’ ability to smell, Thomas Nowotny thinks that the findings can also be expanded to other information transfer processes in the body such as cells’ detection of chemicals.

Next, the research team will look at the processing of scent information at receptors within the nose before reaching the brain which helps to distinguish between different smells.

Key facts:

  • Original publication: Ho Ka Chan, Fabian Hersperger, Emiliano Marachlian, Brian H Smith, Fernando Locatelli, Paul Szyszka, Thomas Nowotny: Odorant mixtures elicit less variable and faster responses than pure odorants.https://journals.plos.org/ploscompbiol/article?id=10.1371/journal.pcbi.1006536
  • Joint study by the University of Konstanz and the University of Sussex reveals that animals are much better at smelling a complex “soup” of odorants rather than a single pure ingredient
  • Members of the joint research project are: University of Konstanz (Germany), University of Sussex (GB), Universidad de Buenos Aires (Argentina) and Arizona State University (USA)
  • The research project in Konstanz was funded by the Human Frontiers Science Program with around 340,000 dollars between 2015 and 2019.

Press information: No. 123/2018