• Study finds neurons that encode the outc

    From ScienceDaily@1:317/3 to All on Fri Mar 25 22:30:40 2022
    Study finds neurons that encode the outcomes of actions

    Date:
    March 25, 2022
    Source:
    Massachusetts Institute of Technology
    Summary:
    A group of neurons in the brain's striatum encodes information about
    the potential outcomes of different decisions. These cells become
    particularly active when a behavior leads a different outcome than
    what was expected, which the researchers believe helps the brain
    adapt to changing circumstances.



    FULL STORY ==========================================================================
    When we make complex decisions, we have to take many factors into
    account. Some choices have a high payoff but carry potential risks;
    others are lower risk but may have a lower reward associated with them.


    ==========================================================================
    A new study from MIT sheds light on the part of the brain that helps us
    make these types of decisions. The research team found a group of neurons
    in the brain's striatum that encodes information about the potential
    outcomes of different decisions. These cells become particularly active
    when a behavior leads a different outcome than what was expected, which
    the researchers believe helps the brain adapt to changing circumstances.

    "A lot of this brain activity deals with surprising outcomes, because
    if an outcome is expected, there's really nothing to be learned. What
    we see is that there's a strong encoding of both unexpected rewards and unexpected negative outcomes," says Bernard Bloem, a former MIT postdoc
    and one of the lead authors of the new study.

    Impairments in this kind of decision-making are a hallmark of many neuropsychiatric disorders, especially anxiety and depression. The
    new findings suggest that slight disturbances in the activity of these
    striatal neurons could swing the brain into making impulsive decisions
    or becoming paralyzed with indecision, the researchers say.

    Rafiq Huda, a former MIT postdoc, is also a lead author of the paper,
    which appears in Nature Communications. Ann Graybiel, an MIT Institute Professor and member of MIT's McGovern Institute for Brain Research,
    is the senior author of the study.

    Learning from experience The striatum, located deep within the brain,
    is known to play a key role in making decisions that require evaluating outcomes of a particular action. In this study, the researchers wanted to
    learn more about the neural basis of how the brain makes cost-benefit decisions, in which a behavior can have a mixture of positive and
    negative outcomes.



    ==========================================================================
    To study this kind of decision-making, the researchers trained mice
    to spin a wheel to the left or the right. With each turn, they would
    receive a combination of reward (sugary water) and negative outcome
    (a small puff of air). As the mice performed the task, they learned to
    maximize the delivery of rewards and to minimize the delivery of air
    puffs. However, over hundreds of trials, the researchers frequently
    changed the probabilities of getting the reward or the puff of air,
    so the mice would need to adjust their behavior.

    As the mice learned to make these adjustments, the researchers recorded
    the activity of neurons in the striatum. They had expected to find
    neuronal activity that reflects which actions are good and need to be
    repeated, or bad and that need to be avoided. While some neurons did
    this, the researchers also found, to their surprise, that many neurons
    encoded details about the relationship between the actions and both
    types of outcomes.

    The researchers found that these neurons responded more strongly when
    a behavior resulted in an unexpected outcome, that is, when turning
    the wheel in one direction produced the opposite outcome as it had in
    previous trials. These "error signals" for reward and penalty seem to
    help the brain figure out that it's time to change tactics.

    Most of the neurons that encode these error signals are found in the
    striosomes -- clusters of neurons located in the striatum. Previous
    work has shown that striosomes send information to many other parts of
    the brain, including dopamine-producing regions and regions involved in planning movement.

    "The striosomes seem to mostly keep track of what the actual outcomes
    are," Bloem says. "The decision whether to do an action or not, which essentially requires integrating multiple outcomes, probably happens
    somewhere downstream in the brain." Making judgments


    ==========================================================================
    The findings could be relevant not only to mice learning a task, but
    also to many decisions that people have to make every day as they weigh
    the risks and benefits of each choice. Eating a big bowl of ice cream
    after dinner leads to immediate gratification, but it might contribute
    to weight gain or poor health.

    Deciding to have carrots instead will make you feel healthier, but you'll
    miss out on the enjoyment of the sweet treat.

    "From a value perspective, these can be considered equally good,"
    Bloem says.

    "What we find is that the striatum also knows why these are good, and it
    knows what are the benefits and the cost of each. In a way, the activity
    there reflects much more about the potential outcome than just how
    likely you are to choose it." This type of complex decision-making is
    often impaired in people with a variety of neuropsychiatric disorders, including anxiety, depression, schizophrenia, obsessive-compulsive
    disorder, and posttraumatic stress disorder. Drug abuse can also lead
    to impaired judgment and impulsivity.

    "You can imagine that if things are set up this way, it wouldn't be
    all that difficult to get mixed up about what is good and what is bad,
    because there are some neurons that fire when an outcome is good and
    they also fire when the outcome is bad," Graybiel says. "Our ability to
    make our movements or our thoughts in what we call a normal way depends
    on those distinctions, and if they get blurred, it's real trouble."
    The new findings suggest that behavioral therapy targeting the stage at
    which information about potential outcomes is encoded in the brain may
    help people who suffer from those disorders, the researchers say.

    The research was funded by the National Institutes of Health/National
    Institute of Mental Health, the Saks Kavanaugh Foundation, the William
    N. and Bernice E.

    Bumpus Foundation, the Simons Foundation, the Nancy Lurie Marks Family Foundation, the National Eye Institute, the National Institute of
    Neurological Disease and Stroke, the National Science Foundation, the
    Simons Foundation Autism Research Initiative, and JSPS KAKENHI.


    ========================================================================== Story Source: Materials provided by
    Massachusetts_Institute_of_Technology. Original written by Anne
    Trafton. Note: Content may be edited for style and length.


    ========================================================================== Journal Reference:
    1. Bernard Bloem, Rafiq Huda, Ken-ichi Amemori, Alex S. Abate, Gayathri
    Krishna, Anna L. Wilson, Cody W. Carter, Mriganka Sur, Ann
    M. Graybiel.

    Multiplexed action-outcome representation by striatal
    striosome-matrix compartments detected with a mouse cost-benefit
    foraging task. Nature Communications, 2022; 13 (1) DOI:
    10.1038/s41467-022-28983-5 ==========================================================================

    Link to news story: https://www.sciencedaily.com/releases/2022/03/220325122706.htm

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