Sense Of Smell Is Physiological, Not Psychological, Study Shows
Different strokes for different folks? Not necessarily, at least not when it comes to smells: A new research from the Weizmann Institute in Israel shows that odors can be rated on a scale of pleasantness.
The findings that were published in Nature Neuroscience Journal reveal a correlation between the response of certain nerves to particular scents and the pleasantness of those scents. Based on this correlation, the researchers could tell by measuring the nerve responses whether a subject found a smell pleasant or unpleasant.
Up until now the organizational principle for our sense of smell has remained a mystery. Unlike our sense of sight that was long understood as being arranged for efficiently mapping out visual coordinates and our hearing sense that was figured to be set up according to tonal scale, our sense of smell was never actually cracked by scientist. They have never been sure if there is such a scale for it.
Hints of such an organizational principle of the sense of smell have been seen in different research labs around the world, however without conclusive evidence. Up until now. The team of researchers headed by Prof. Noam Sobel of the Weizmann Institute's Neurobiology Department set out to search for that principle.
Sobel and his team thought that smell receptors in the nose — of which there are some 400 subtypes — could be arranged on the nasal membrane according to a scale. This hypothesis goes against the conventional view, which claims that the various smell receptors are mixed — distributed evenly, but randomly, around the membrane.
In their experiment, the researchers inserted electrodes into the nasal passages of volunteers and measured the nerves' responses to different smells in various sites. Each measurement actually captured the response of thousands of smell receptors, as these are densely packed on the membrane.
The scientists found that the strength of the nerve signal varies from place to place on the membrane. It appeared that the receptors are not evenly distributed, but rather, that they are grouped into distinct sites, each engaging most strongly with a particular type of scent.
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