Decoded: How you sniff that jasmine smell

Do you know why some people can easily detect faint whiffs of coffee or wine buried amid a plethora of odours? An Indian American researcher says they have a better inbuilt system to sniff out a particular smell in complex olfactory environments.

In experiments with mice, a Harvard University team led by Venkatesh Murthy showed that while the animals can be trained to detect specific odourants embedded in random mixtures, their performance drops steadily with increasing background components.

"We are bombarded with many smells all jumbled up. Can we pick out one smell 'object' - the smell of jasmine, for example, amid a riot of other smells? Our experience tells us indeed we can," said Murthy, a professor of molecular and cellular biology at Harvard.

But how do we pick out the ones that we need to pay attention to, and what are the limitations?

After training mice to detect specific scents, researchers presented the animals with a combination of smells - sometimes including the "target" scent, sometimes not.

The findings showed that mice were able to identify when a target scent was present with 85 percent accuracy or better.

"Although the mice do well overall, they perform progressively poorer when the number of background odours increases," Murthy said.

Each odour gives rise to a particular spatial pattern of neural responses.

When the spatial pattern of the background odours overlapped with the target odour, the mice did much more poorly at detecting the target.

Therefore, the difficulty of picking out a particular smell among a jumble of other odours depends on how much the background interferes with your target smell, researchers said.

Murthy said: "This study is interesting because it first shows that smells are not always perceived as one whole object - they can be broken down into their pieces."

This may also allow us to build artificial olfactory systems that can detect specific chemicals in the air, researchers concluded in the study described in the journal Nature Neuroscience.