Humans Can Discriminate More than 1 Trillion Odors!

As you know from my other blog entries, I’m fascinated with scents!

This new study by the Journal of Science (Humans Can Discriminate More than 1 Trillion Olfactory Stimuli) is intriguing.

Bushdid, C., Magnasco, M. O., Vosshall, L. B. & Keller, A. (Authors’)

The study disproved the common belief that the human nose could detect only 10,000 scents, that belief had put our sense of smell as being less efficient than sight and hearing.

Schematic of the early olfactory system including the olfactory epithelium and bulb. Each ORN expresses one OR which responds to different odorants. Odorant molecules bind to ORs on cilia. ORs activate ORNs which transduce the input signal into action potentials. Glomeruli generally receive input from ORs of one specific type and connect to the principal neurons of the OB, mitral and tufted cells (MT cells). – Benjamin Auffarth, Bernhard Kaplan, Anders Lansner
http://www.frontiersin.org/systems_neuroscience/10.3389/fnsys.2011.00084/full

In the study scent mixtures with 10, 20, or 30 components that were chosen from a selection of of 128 odor molecules.  Twenty-six volunteers sampled three vials of scents at a time to see if they could detect which was the irregularity; by preforming 264 comparisons, two that were the same and one that was different; when the two scents contained components that overlapped by more than about 51%.  Most volunteers had a hard time discriminating between them. The authors then calculated the number of possible mixtures that overlap by less than 51% to arrive at their estimate of how many smells a human nose (the human nose has roughly 400 types of scent receptors some people might have more) can detect: at least 1 trillion.  It is still a mystery the exact chain of events that cause neural responses that attract a persons awareness to an odor.

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