Two US scientists won the 2004 Nobel prize for medicine on Monday for showing how sense of smell enables people to recall, for instance, the scent of spring lilac in winter or the stench of rotten food eaten long ago.
Scientists Richard Axel and Linda Buck, who published their ground-breaking research in 1991, discovered a large gene pool containing the blueprint for sensors in the nose that identify smells wafting through the air and send signals to the brain.
"Until Axel and Buck's studies the sense of smell was a mystery," said Professor Sten Grillner of the Nobel Assembly.
Columbia University professor Axel, 58, and 57-year-old Buck, of the Fred Hutchinson Cancer Research Centre in Seattle, discovered a large family of 1,000 different genes, three percent of the total in the human body, that give rise to an equivalent number of sensors in the nose that identify smells.
"I'm ecstatic, it's quite an honour," Axel told Swedish radio after winning half of the 10 million crown ($1.38 million) award from the Nobel Assembly of Sweden's Karolinska Institute.
The Nobel citation said their work had illustrated the role of the nose in distinguishing good and bad.
"A single clam that is not fresh and will cause malaise can leave a memory that stays with us for years and prevent us from ingesting any dish, however delicious, with clams in it."
"(On the other hand)...we can consciously experience the smell of a lilac flower in the spring and recall this olfactory memory at other times."
The sensors, known as "olfactory receptor types", sit on cells in the back the nose and identify smells.
Each receptor cell has only one type of sensor, but the sensors react to more than one odour, explaining why humans can detect and remember around 10,000 different smells.
Dogs, renowned for their acute sense of smell, have a scent area in the nose 40 times larger than a human's.
The receptor cells in turn send signals back to the parts of the brain responsible for smell.
The Nobel award said fish had around 100 odour sensors, while mice, which the two researchers studied, have about 1,000. Humans have a slightly smaller number than mice.
The Nobel prizes, first awarded in 1901, were created in the will of Swedish industrialist Alfred Nobel, inventor of dynamite who died in 1896. They are presented in glittering ceremonies in Stockholm and Oslo on December 10, the anniversary of his death. The Nobel season continues with chemistry, physics, literature and peace prizes this week and economics next week.
Fellow researchers hailed Axel and Buck's work.
"It has also prompted a lot of research into related areas such as taste," Professor Tim Jacob of Cardiff University in Wales, who also works on the sense of smell, told Reuters.