How specific scents are identified decoded

Ever wondered how some people can detect faint whiffs of coffee or wine within the complex mixture of flavours? Scientists led by an Indian-origin researcher may have found an answer!
Mice can identify specific odours amid complex olfactory environments, according to a new Harvard study.
A team of researchers led by Venkatesh Murthy, Professor of Molecular and Cellular Biology at Harvard University, showed that while mice 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, amidst a riot of other smells? Our experience tells us indeed we can, but how do we pick out the ones that we need to pay attention to, and what are the limitations?" Murthy said.

After training mice to detect specific scents, researchers presented the animals with a combination of smells - sometimes including the "target" scent, sometimes not.
Their findings showed that mice were able to identify when a target scent was present with 85 per cent accuracy or better.

"Although the mice do well overall, they perform progressively poorer when the number of background odours increases," Murthy explained.
The researchers sought to describe scents according to how they activated neurons in the brain.
Using fluorescent proteins, they created images that show how each of 14 different odours stimulated neurons in the olfactory bulb.

What they found was that the ability of mice to identify a particular smell was markedly diminished if background smells activated the same neurons as the target odour.
"Each odour gives rise to a particular spatial pattern of neural responses," Murthy said.
"When the spatial pattern of the background odours overlapped with the target odour, the mice did much more poorly at detecting the target. 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.
"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," he added.

"This is perhaps not a surprise - there are in fact coffee or wine specialists that can detect faint whiffs of particular elements within the complex mixture of flavours in each coffee or wine. But by doing these studies in mice, we can now get a better understanding of how the brain does this," he said.
The study was published in the journal Nature Neuroscience.