• A map for the sense of smell

    From ScienceDaily@1:317/3 to All on Mon Jan 31 21:30:44 2022
    A map for the sense of smell
    Evolution has structured flies with an energy-efficient olfactory system


    Date:
    January 31, 2022
    Source:
    University of California - San Diego
    Summary:
    Our sensory systems provide us with immediate information about
    the world around us. Researchers have created the first sensory map
    for smell. The map details how the fruit fly's olfactory receptor
    neurons, the components that sense smell, are organized within
    the insect's sensory hairs.



    FULL STORY ==========================================================================
    The distinctive smell of a flower... the unmistakable aroma of
    coffee... the dangers linked with inhaling smoke fumes. Sensory systems
    have evolved to provide us with immediate, finely tuned information
    about the world around us, whether they are colors processed through
    our visual system or certain pitches interpreted through our hearing.


    ==========================================================================
    This barrage of information is processed by our sensory
    systems. Scientists have uncovered maps that depict how sensory neurons
    are arranged based on their function to effectively process such
    information. This kind of functional map, however, had not yet been
    identified for the sense of smell. University of California San Diego researchers have now described such a smell sensory map in fruit flies. On
    the surface of fly antennae, where odorous chemicals are detected, the scientists have discovered how the fly olfactory system is organized,
    and why.

    This new map was published in the Proceedings of the National Academy
    of Sciences by a team lead by graduate student Shiuan-Tze Wu from the laboratory of Biological Sciences Associate Professor Chih-Ying Su. The
    study details how the fly's olfactory receptor neurons, the components
    that sense smell, are organized within the sensory hairs.

    "We are constantly being bombarded by hundreds of odorous chemicals in
    our environment," said Su, the corresponding author of the study. "We
    have described a peripheral mechanism that has allowed the fly to make
    sense of such overwhelmingly complex stimuli." The researchers provide evidence that the fruit fly's olfactory system, which Su described as
    simple yet elegant, is structured to give the insect the ability to
    make quick assessments of odors in an unusual way that circumvents
    synaptic communication, which is metabolically expensive. Rather,
    the insect's olfactory receptor neurons (ORNs) communicate through
    electrical interactions with nearby ORNs. This offers an energy-saving, "metabolically cheap" way to process "meaningful odor blends without
    involving costly synaptic computation," the researchers note in the paper.

    The study describes how compartments with two ORNs are arranged to detect
    cues with opposite meanings for the fly. Such cues either promote or
    inhibit certain behaviors -- to quickly and efficiently assess complex
    odors in their environment.

    "This arrangement provides a means to both evaluate and shape the countervailing sensory signals relayed to higher brain centers for
    further processing," according to the paper.

    In this study, the Su lab collaborated with UC San Diego Neurobiology
    Assistant Professor Johnatan Aljadeff, who built a mathematical model
    which explains how electrical interactions help in extracting relevant information.

    "In asking questions about the functional meaning of this organization,
    we found that nature has chosen a specific way of structuring this sensory assay," said Aljadeff. "If we can understand the principle of this type
    of processing, there could be future engineering applications." Aljadeff
    is funded by a Defense Advanced Research Projects Agency (DARPA) Young
    Faculty Award to investigate such questions.

    Wu, the first author of the study, is proud to be part of the team that
    made this fundamental discovery. He marvels at the elegance of the system
    by which fly ORNs compute countervailing cues and points to parallels
    in the way that visual systems contrast color shades to help us perceive
    the difference between red and green, for example.

    The full author list is: Shiuan-Tze Wu, Jen-Yung Chen, Vanessa Martin,
    Renny Ng, Ye Zhang, Dhruv Grover, Ralph Greenspan, Johnatan Aljadeff
    and Chih-Ying Su.

    ========================================================================== Story Source: Materials provided by
    University_of_California_-_San_Diego. Original written by Mario
    Aguilera. Note: Content may be edited for style and length.


    ========================================================================== Journal Reference:
    1. Shiuan-Tze Wu, Jen-Yung Chen, Vanessa Martin, Renny Ng, Ye Zhang,
    Dhruv
    Grover, Ralph J. Greenspan, Johnatan Aljadeff, Chih-Ying Su. Valence
    opponency in peripheral olfactory processing. Proceedings of the
    National Academy of Sciences, 2022; 119 (5): e2120134119 DOI:
    10.1073/ pnas.2120134119 ==========================================================================

    Link to news story: https://www.sciencedaily.com/releases/2022/01/220131110515.htm

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