• Study reveals set of brain regions that

    From ScienceDaily@1:317/3 to All on Thursday, April 21, 2022 22:30:46
    Study reveals set of brain regions that control complex sequences of
    movement
    Findings in mice have potential to advance treatment of some brain
    injuries and illnesses

    Date:
    April 21, 2022
    Source:
    Johns Hopkins Medicine
    Summary:
    In a novel set of experiments with mice trained to do a sequence
    of movements and 'change course' at the spur of the moment,
    scientists report they have identified areas of the animals'
    brains that interact to control the ability to perform complex,
    sequential movements, as well as to help the mice rebound when
    their movements are interrupted without warning.



    FULL STORY ==========================================================================
    In a novel set of experiments with mice trained to do a sequence of
    movements and "change course" at the spur of the moment, Johns Hopkins scientists report they have identified areas of the animals' brains that interact to control the ability to perform complex, sequential movements,
    as well as to help the mice rebound when their movements are interrupted without warning.


    ==========================================================================
    The research, they say, could one day help scientists find ways to
    target those regions in people and restore motor function caused by
    injury or illness.

    Results of the Johns Hopkins-led experiments were published March 9
    in Nature.

    Based on brain activity measurements of the specially trained rodents,
    the investigators found that three main areas of the cortex have distinct
    roles in how the mice navigate through a sequence of movements: the
    premotor, primary motor and primary somatosensory areas. All are on
    the top layers of the mammals' brains and arranged in a fundamentally
    similar fashion in people.

    The team concluded that the primary motor and primary somatosensory
    areas are involved in controlling the immediate movements of the mice in
    real time, while the premotor area appears to control an entire planned sequence of movements, as well as how the mice react and adjust when
    the sequence is unexpectedly disrupted.

    As the animals perform sequential movements, the researchers say,
    it's likely that the premotor area sends electrical signals via special
    nerve cells to the two other sensorimotor cortex areas, and more studies
    are planned to chart the paths of those signals between and among the
    cortical layers.



    ========================================================================== "Whether it's an Olympian practicing a downhill ski run or a person
    doing an everyday chore such as driving, many tasks involve learned
    sequences of movements made over and over," says Daniel O'Connor, Ph.D., associate professor of neuroscience at the Johns Hopkins University
    School of Medicine. O'Connor led the research team. Such sequential
    movements may seem commonplace and simple, he says, but they involve
    complex organization and control in the brain, and the brain must not
    only direct each movement correctly but also organize them into an entire series of linked movements.

    When unexpected things happen to interrupt an ongoing sequence, O'Connor
    says, the brain must adapt and direct the body to re-configure the
    sequence in real time. Failure of this process can result in disaster --
    a fall or car accident, for example.

    Neuroscientists have long studied how mammals compensate when an
    individual movement -- such as reaching for a coffee cup -- is disrupted,
    but the new study was designed to address the challenges of tracking what happens when complex sequences of several movements must be reorganized
    in real time to compensate for unexpected events.

    In the case of the Olympic skier, for example, the skier expects to
    perform a planned series of movements to approach and pass through gates
    along a downhill run, but there will likely be moments when an obstacle disrupts the skier's trajectory and forces a change of course.

    "How the mammalian brain can take a sensory cue and, almost instantly,
    use it to completely switch from one ongoing sequence of movements to
    another remains largely a mystery." O'Connor worked with Duo Xu, Ph.D.,
    a former graduate student in O'Connor's laboratory, to design a set of experiments in mice to track the brain regions that process the "change
    course" cue.



    ==========================================================================
    For the study, the researchers first created a "course" for mice that
    were trained to stick out their tongues and touch a "port" -- a metal
    tube. When the investigators moved the port, the mice learned to touch
    the port again. Over the span of the course, when the port was moved
    to its final location, the mice that touched it with their tongues got
    a reward. All of this training was meant to simulate a repeated and
    expected sequence of learned movements, much as the skier's downhill run.

    To study how an unexpected cue can prompt the brain to change course,
    the researchers had the mice perform what scientists call a "backtracking trial." Instead of moving the port to the next in-sequence location,
    the researchers moved the port to an earlier location, so that when the
    mice extended their tongues, they failed to find the port, prompting
    them to reverse course, find the port, and progress through the course
    to get the treat.

    "Each sequence of port licks involves a series of complex movements
    that the mouse's brain needs to organize into a movement plan and then
    perform correctly, but also to rapidly reorganize when they find that
    the expected port isn't there," says O'Connor.

    During the experiments, the researchers used brain electrodes to track
    and record electrical signals among neurons in the sensorimotor cortex,
    which controls overall movement. An increase in electrical activity
    corresponds to increased brain activity. Because many areas of the
    cortex could be activated when the mice moved through the course in the experiment, the researchers used mice bred with genetically engineered
    brain cells that, in certain parts of the cortex, can be selectively
    "silenced" or deactivated. Thus, the scientists could narrow down the
    location of brain areas directly involved in the movements.

    "The results provide a new picture of how a hierarchy among neural
    networks in the sensorimotor cortex are managing sequential movements,"
    says O'Connor. "The more we learn about these interacting neural networks,
    the better positioned we are to understand sensorimotor dysfunction
    in humans and how to correct it." In addition to Xu and O'Connor,
    the following Johns Hopkins scientists contributed to the research:
    Mingyuan Dong, Yuxi Chen, Angel Delgado, Natasha Hughes and Linghua Zhang.

    The research was supported by the National Institutes of Health
    (R01NS089652, 1R01NS104834-01, P30NS050274).


    ========================================================================== Story Source: Materials provided by Johns_Hopkins_Medicine. Note:
    Content may be edited for style and length.


    ========================================================================== Journal Reference:
    1. Duo Xu, Mingyuan Dong, Yuxi Chen, Angel M. Delgado, Natasha
    C. Hughes,
    Linghua Zhang, Daniel H. O'Connor. Cortical processing of flexible
    and context-dependent sensorimotor sequences. Nature, 2022; 603
    (7901): 464 DOI: 10.1038/s41586-022-04478-7 ==========================================================================

    Link to news story: https://www.sciencedaily.com/releases/2022/04/220421130946.htm

    --- up 7 weeks, 3 days, 10 hours, 51 minutes
    * Origin: -=> Castle Rock BBS <=- Now Husky HPT Powered! (1:317/3)