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How is the brain capable of recognizing different odours?

Professor Giovanni Galizia is a scientist investigating the processing of odour cues. Working together with researchers from all over Germany, Galizia has initiated a DFG research priority on olfactory processing in humans and animals.

Professor Galizia, do you have a good sense of smell?

I would say, my sense of smell is kind of average. However, since I have been working with odours, my sense of smell has improved.

Do people process odour cues differently from animals?

Prof. Dr. Giovanni Galizia (Photo: University of Constance/Press Office)
No. Surprisingly, the principle of recognising and processing odours is basically the same in humans and the honeybee for example. However, there are also some important differences. These differences are also found within a single species. Did you know that many animals have several noses? Mice for example, have four different olfactory organs. Animals also differ from each other in the number and types of olfactory receptors they have. Mice have about 1,000 olfactory receptors, dogs 1,200, fruit flies 50 and humans 350. However, which receptor reacts to which odour has only been worked out in a few cases. Although we know the basic principles of odour processing, there is a lot of information which still needs to be elucidated. Our ability to learn to smell odours and the variety of odours we can smell is still shrouded in mystery.

Can you give me a few examples for this?

We can smell substances such as burnt plastic. These substances are new, i.e. our ancestors were not acquainted with them during our evolution. We also know that the odour of rooms is associated with performance. For example, a pupil who associates a particular room smell with a negative stress situation is more likely to achieve worse results in this particular situation. In general, our olfactory system has a greater capacity than is actually required by humans. However, intensive research is still required to find out which receptor reacts to which odour, and how the networks in the brain process this information.

Is this why you have initiated a DFG research priority on olfactory processing in humans and animals?

Yes. Olfactory research is still in its infancy. In order to understand how olfactory processing works, interdisciplinary cooperation is absolutely necessary: no group in Germany is able to solve this problem on its own; but there are many excellent groups of researchers in Germany that deal with such questions and that can jointly advance their work in this research priority.

Can you describe the nature of this research priority?

In Germany, there are about 30 groups with about 100 scientists working on the sense of smell. The new research priority, which is a project of the German Research Foundation, will grant funding for 16 to 17 projects involving about 32 research groups. Each project is a tandem project, which means that scientists from different disciplines will work together. What is smell? How do humans and animals process smell? How important are smells? How are the neurones connected with each other? What does the ability to smell mean for us and the behaviour of animals? These are questions that will be dealt with in projects starting in the middle of 2009 and initially run for three years. The research priority can be prolonged by another three years.

Will you also tell the broader public about your discoveries?

Yes, of course. Public relations work is an integral part of this research priority. We want to write chapters for schoolbooks, develop education units for different ages and use them from kindergarten upwards. We will, for example, develop an “odour memory game” which the children will use to learn to smell different kitchen odours. We want to teach children that there are smells and make them aware of their olfactory skills. The first step in our ability to perceive smells is our consciousness of smells. The teaching units will be published in German and English on our homepage from where they can be downloaded.

“I cannot smell him/her” – will you also be able to explain this phenomenon?

In humans, odours often have a very emotional component. The human olfactory brain has connections into the amygdale which governs our emotions to a large degree, i.e. which governs whether we like somebody or not. It is quite well known that such connections exist in the brain. In our conscious perception, our sense of smell is less dominant although taste has a very strong olfactory component. We perceive the taste of food by way of the odour clouds that float from the palate into the nose. That odours have limited importance for humans is reflected in the fact that our daily language has very few words to describe smells. It is different when we are tasting wine – many rare words are sometimes used to describe the taste and odour of wines.

The perfume industry is growing…

Perfume mixers are artists. They have many years of experience, artistic skills and an excellent nose. And they know that there are odours that everybody likes. The odour of perfumes must be 'pleasant'. The current knowledge about how odour cues are processed in the brain is still unsatisfactory for the perfume industry which could work on a completely different level if the processing of olfactory cues were better understood. That is why the perfume industry is very interested in the results of the new research priority.

Is there new hope for humans that are plagued by mosquitoes?

Diethyltoluamide (DEET) is a substance used in mosquito repellents and affects the olfactory perception of insects. We assume that our research priority will also provide us with further insights into this field.
Giovanni Galizia has been professor of zoology/neurology at the University of Constance since 2005. His major research focus concentrates on olfactory processing and the odour memory in the brain of insects, especially bees and fruit flies. He is interested in how bees recognise their favourite flowers or how fruit flies find fruit. Galizia’s research focuses on the responses of olfactory cells, the connection of neurones in the brain of insects and the changes to this connection when memory is stored. These investigations will help us to understand how mosquitoes recognise humans on the basis of their body odour, even if they stand in the middle of a cow herd. Giovanni Galizia studied biology in Berlin and did his doctorate in zoology in England. Prior to his current position in Constance, Giovanni Galizia was associate professor of entomology at the University of California, and before that the head of a research group at the Free University of Berlin.
Source: University of Constance - 6 November 2008 (mst 16 November 2008)
Website address: https://www.gesundheitsindustrie-bw.de/en/article/news/how-is-the-brain-capable-of-recognizing-different-odours