Japanese researchers explain how herbs and spices can cover the odour of rotten food, finding that these foodstuffs seem to activate an area in the brain's olfactory bulb that is similar to that signalled by the smell of rotten foods.
Kensaku Mori and colleagues at the graduate school of medicine, University of Tokyo, Japan claim that this is how man has succeeded in covering up the odour of spoiled foods for centuries.
Smell is intimately related to how human beings taste food but has long remained the most enigmatic of our senses. The average human nose can detect nearly 10,000 distinct scents, a feat that requires about 1,000 olfactory genes, or roughly 3 per cent of the human genome.
Using intrinsic signal imaging of the brain in rats, Mori and his research team mapped alkylamine-responsive glomeruli (important waystations in the pathway from the nose to the olfactory cortex) to the fishy odour areas in the odour maps of the rat olfactory bulb.
The scientists noted that individual cells responded to the alkylamines in addition to acids and aldehydes. When the rats were then exposed to fennel and clove oils, known to mask these unpleasant odours, glomeruli in surrounding clusters in the olfactory bulb were activated.
"This suggested that the odour masking was mediated, in part, by lateral inhibitory connections in the odour maps of the olfactory bulb," write the authors in the 6 October 2004 issue of Journal of Neuroscience, 24(40):8690-8694.
Earlier this month researchers were rewarded for the studies into the complex olfactory system with pioneering scientists Richard Axel and Linda Buck reaping a joint Nobel Prize in Physiology or Medicine for 2004 from the Swedish jury.
In 1991 the two scientists jointly published a fundamental paper in which they described the large family of 1,000 olfactory genes.
"The basic principles for recognising and remembering about 10,000 different odours were not understood. This year's Nobel Laureates in Physiology or Medicine have solved this problem and in a series of pioneering studies clarified how our olfactory system works," said the Nobel Assembly at Karolinska Institutet.