March 10, 2011

Super Sense Of Smell Must Be Learned

New research says that people who make a high-class living smelling perfumes and wines are not born with an exceptional sense of smell but acquire it with many years of sniffing.

French researchers conducted experiments using both novice and veteran perfume makers. They found that the ability to detect and identify thousands of different odors depends mainly on how much training each individual had.

"To be a 'nose' you have to practice, just as a pianist plays his scales," said Jean-Pierre Royet, a neuroscientist at the Universite Claude Bernard in Lyon, France, and the originator of a study published this week in the journal Human Brain Mapping.

The study also showed, over time, that activity in the brain shifts from the area that governs conscious effort to a region in which actions are performed automatically, like breathing and swallowing. This makes it possible to move on from technical competence to pure artistry, argue the researchers.

Previous research had shown that vigorous training changes brain activity in musicians and athletes, but there has not been any studies on whether the same holds true for olfaction, the ability to detect odors.

Royet and his colleagues took 28 volunteers, half of them novice perfumers, and the other half veteran scent makers with as much as 35 years experience. Researchers scanned the brains of both groups during two different tests. In the first, the subjects were asked to identify dozens of odors selected from a standard palate of 300 chemicals. In the second, they had to imagine the smells after looking at their chemical names.

Both groups scored well in both tests. However, the team found that the pros were more accurate and faster, especially when it came to retrieving smells by memory. What surprised the team is that different parts of the brain lit up.

In the novice group, activity was more concentrated in the frontal cortex, responsible for conscious perception. In the veterans, neurons fired more vigorously in the parahippocampal gyrus, an area involved in memory recall and mental imagery.

"Our findings demonstrate the extraordinary ability of the brain to adapt to environmental demands and reorganize with experience," Royet told AFP in a phone interview.

The findings also show that "mental imaging of odors develops from daily practice and is not an innate skill," he added.

But not all experts agree that odor detection is purely a matter of learning.

Patrick Mac Leod, former head of the Laboratory for Sensorial Neurobiology, near Versailles, says that olfactory thresholds vary dramatically. "No two people will ever smell the same thing in the same way," he noted. "When we perceive an odor the exact nature of the sensation that is produced depends as much on the observer as the object."

In separate experiments, Mac Leod has shown that a small percentage of a given molecule may be imperceptible for one person and easily detected by another. And depending on the chemical, the roles could be reversed. These thresholds could easily vary from person to person by a factor of a thousand.

Mac Leod also noted that the human genome contains nearly 350 olfactory genes -- many more than visions and hearing have -- resulting in highly individualized odor detection. "You are never going to transform someone who is insensitive to a certain molecule into someone who smells it well," he told the French news agency.

But even these variations in perception and genes do not change the finding that practice leads to perfection when it comes to sniffing out certain odors over others, he acknowledged. "It's a little like a policeman who combs through dozens of clues to find the truth. With training, the nose becomes a keen investigator of anything related to odors," said Mac Leod.


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