Biological complexity: how we smell odors (Introduction)

by David Turell @, Tuesday, August 13, 2019, 21:10 (114 days ago) @ David Turell

A new review:

https://www.scientificamerican.com/article/how-we-are-wired-for-smell/?utm_source=newsl...

"Olfactory neurons in your nose have evolved some 400 odor receptors, and each neuron contains only one. Receptors are tuned to detect a few basic odors apiece: some detect geranium petals or pine needles, while others detect the by-products of putrefaction. To organize all this information, your olfactory neurons wire into an “olfactory map” on your brain’s olfactory bulb. Olfactory neurons are one of the few types of neurons that are born throughout your life, and each of the roughly 10,000 such neurons born each day in your nose subsequently wires into the olfactory map in your brain.

"Incredibly, all the neurons containing a given odor receptor wire to the same spot on the map, such that each half of your olfactory bulb has 400 distinct regions. The combination of regions turned on by a given odor is what makes it seem unique. This fact may be why odors are so evocative: that glass of wine reminds you of a freshly opened can of tennis balls because whatever was in the can is also in the wine.

***

"Working in mice—which have more than 1,000 odor receptors—the study’s authors showed that each receptor, in the absence of an odor, produces a specific type of electrical noise. This might mean firing in short bursts between long pauses; it could also mean firing on specific intervals. These noise events then exquisitely control the set of genes directing an olfactory neuron’s growth as it wires to the olfactory map. Because two neurons with the same odor receptor will experience very similar noise, they will end up wiring to the same place. And because all 400 of your receptors are different—if only slightly—the noise they produce is different, too, causing them to wire to distinct locations. The end result is a 400-location map that functions like the perfumer’s organ equivalent of the “The Library of Babel.”

"These discoveries open up a number of avenues for further work. For example, we do not understand how noisy electrical activity could so precisely control the activity of genes involved in neuronal wiring.

Comment: Amazing setup. One neuron, one odor. It is obvious that these are special focused neurons Which had to designed to work from the beginning of noses starting to operate 'smelling' odor identification, which is learned from each new experience.


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