One of the more interesting Nobel Prizes in 2004 was the one for medicine.  Two Americans, Richard Axel and Linda Buck won their prize for discovering how we can recognize and remember some ten thousand odours, from rotten fish, to the perfume of our first sweetheart.

Their work mapped the most enigmatic of our senses, the sense of smell revealing how odour sensing proteins in the nose send their information to the brain.

Axel and Buck discovered a large family of genes devoted to producing different odour sensing protein receptors in the nose.  They estimated that we have some 350 – 400 types of odour receptors, each of which can detect a limited number of odours.

When we sniff a perfume, a mix of different types of molecules flows over the receptors in the nose.  The molecules activate these receptors that are primed to respond to a particular molecule.  The brain notes which receptors are activated and interprets this pattern as a smell.

The researchers found that only one kind of receptor appears on each of the five million or so odour sensing nerve cells in the nose.  They also showed how these nerve cells are wired to the brain.

These discoveries may explain why scents often remind us of childhood and cooking.

So next time you encounter an odour, remember a lot is happening in detecting and transmitting its distinctive smell to your brain.