Senses - Flavors, aromas, and chemical signals released...

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Unformatted text preview: Flavors, aromas, and chemical signals released From animals can make the mouth water, evoke vivid memories, and perhaps even signal stress or Fertility. how does the brain sort it all out? common By RichaRd SaltuS illustration by hannah stouFFer SenSeS 16 HHMI BULLETIN | February 2007 “ouR SenSoRy expeRienceS RepReSent a Beautifully oRcheStRated ReSponSe to a wide Range of Stimuli.” tWENTY-FvE YEArs AGO, the physician and writer Lewis Thomas predicted that the progress of biological research would be measured by how long it took to gain a complete understanding of odor. “It may not seem a profound enough problem to domi- nate all the life sciences,” he observed, “but it contains, piece by piece, all the mysteries.” How an organism recognizes a “vast universe” of odors is indeed “a fascinating problem in molecular recognition and perceptual discrimination,” agrees Richard Axel, an HHMI investigator at New York’s Columbia University. Put simply, how do we know what we’re smelling? Scientists are exploring this ques- tion in everything from worms to fruit flies to mice to humans, bringing a variety of new molecular tools and computational methods to bear. Only in the last decade and a half, scien- tists, including Axel and HHMI investigator Linda Buck at Seattle’s Fred Hutchinson Cancer Research Center, have begun breaking the code the olfactory system uses to define different incoming odor mole- cules—the first step in recognizing them. They have revealed how the coded information for a smell is represented or “mapped” in certain parts of the brain. Now the scientists are in hot pursuit of the next steps. “How does the brain transform that map into meaningful neural informa- tion so that odors will elicit appropriate cognitive responses and behaviors?” Axel says. “This is the central problem facing my laboratory.” The nasal cavity and the tongue are laced with cells that detect chemical compounds—millions of neurons in the nose and specialized taste bud cells on the tongue. These cells are wired to relay stations and processing centers in the brain, which are thought to create sensory “images” of the perceived odors or flavors. In parallel with the main olfactory system used for odor sensing, evolution has also spawned a separate “accessory olfac- tory system” in some animals for detecting “pheromones”—chemical signals used by individuals of the same species to mark territory, warn of danger, identify close relations, and induce mating. The lack of accessory olfactory structures in humans has suggested a corresponding lack of human pheromones. But interesting new discoveries are rewriting the textbook, demonstrating that in some mammals, at least, pheromones can be detected by the odor-sensing olfactory system as well....
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This note was uploaded on 02/16/2011 for the course FST 10 taught by Professor Jack during the Spring '08 term at UC Davis.

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Senses - Flavors, aromas, and chemical signals released...

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