Explaining How the Nose Knows

Smell is extremely important in the animal kingdom. It allows some species to find food, and distinguish between friend and foe, male or female.

However, it has been somewhat of a mystery how exactly some species pull off this impressive mastery of the nose. With so many smells in one place, how is it that species can focus on one smell in particular, ignoring all that 'backround smell?'

It certainly isn't as easy as with hearing. With hearing, two ears allow most animals to tell which sounds are closest and from what direction after determining when a specific sound wave hits each ear. Whith smell however, odors can be heavily affected by winds and mask one another.

"There is a continuous stream of information constantly arriving at our senses, coming from many different sources," researcher Venkatesh Murthy said in a statement. "The classic example would be a cocktail party - though it may be noisy, and there may be many people talking, we are able to focus our attention on one person, while ignoring the background noise."

According to Murthey, many animals can do the same thing with their sense of smell. However, this ability to focus is, in general, much more limited.

According to a study recently published in the journal Nature Neuroscience, Murthey led a team of researchers to determine just how exactly humans and mammals differentiate and focus on certain odors

After training mice to detect specific scents, the team presented these animals with a combination of smells - sometimes including the "target" scent and sometimes not. They found that mice were able to identify when a target scent was present with 85 percent accuracy or better.

However, imaging of brain activity while sensing certain odors showed the researchers that the mice did significantly worse if "background smells" happened to activate the same neurons as the target scent.

"Each odor gives rise to a particular spatial pattern of neural responses," Murthey explained. "The difficulty of picking out a particular smell among a jumble of other odors, depends on how much the background interferes with your target smell."

The authors of the study add that their work also shows how many connoisseurs of fine food and drink can break down the odors of a wine or dish to identify its various elements.

"One can also imagine that understanding how this is done may also allow us to build artificial olfactory systems that can detect specific chemicals in the air that are buried amidst a plethora of other odors."