• Ready, set...GO! Scientists discover a b

    From ScienceDaily@1:317/3 to All on Monday, March 14, 2022 22:30:38
    Ready, set...GO! Scientists discover a brain circuit that triggers the execution of planned movement

    Date:
    March 14, 2022
    Source:
    Max Planck Florida Institute for Neuroscience
    Summary:
    Planned movement is essential to our daily lives, and it often
    requires delayed execution. As children, we stood crouched and
    ready but waited for the shout of 'GO!' before sprinting from the
    starting line. As adults, we wait until the traffic light turns
    green before making a turn.

    New research explores how cues in our environment can trigger
    planned movement.



    FULL STORY ========================================================================== Planned movement is essential to our daily lives, and it often requires
    delayed execution. As children, we stood crouched and ready but waited
    for the shout of "GO!" before sprinting from the starting line. As adults,
    we wait until the traffic light turns green before making a turn. In both situations, the brain has planned our precise movements but suppresses
    their execution until a specific cue (e.g., the shout of "GO!" or the
    green light). Now, scientists have discovered the brain network that
    turns plans into action in response to this cue.


    ==========================================================================
    The discovery, published in the scientific journal Cell, results from
    a collaboration of scientists at the Max Planck Florida Institute for Neuroscience, HHMI's Janelia Research Campus, the Allen Institute for
    Brain Science, and others. Led by co-first authors Dr. Hidehiko Inagaki
    and Dr. Susu Chen and senior author Dr. Karel Svoboda, the scientists
    set out to understand how cues in our environment can trigger planned
    movement.

    "The brain is like an orchestra," said Dr. Inagaki. "In a symphony,
    instruments play diverse tunes with different tempos and timbres. The collective of these sounds shapes a musical phrase. Similarly, neurons
    in the brain are active with diverse patterns and timing. The ensemble
    of neuronal activities mediates specific aspects of our behavior." For example, the motor cortex is a brain area that controls movement. Activity patterns in the motor cortex are dramatically different between the
    planning and execution phases of movement. The transition between these patterns is critical to trigger movement. Yet, the brain areas controlling
    this transition were unknown. "There must be brain areas acting as the conductor," described Dr. Inagaki. "Such areas monitor environmental cues
    and orchestrate neuronal activities from one pattern to the other. The conductor ensures that plans are converted into action at the right time."
    To identify the neural circuit that serves as the conductor to initiate
    planned movement, the team simultaneously recorded the activity of
    hundreds of neurons while a mouse performed a cue-triggered movement
    task. In this task, mice were trained to lick to the right if whiskers
    were touched or to the left if whiskers were not touched. If the animals
    licked in the correct direction, they received a reward. However, there
    was a catch. The animals had to delay their movement until a tone, or
    "go cue," was played. Only correct movements after the go cue would be rewarded. Therefore, mice maintain a plan of the direction they will
    lick until the go cue and execute the planned lick after.

    The scientists then correlated complex neuronal activity patterns to
    relevant stages of the behavioral task. The researchers found brain
    activity occurring immediately after the go cue and during the switch
    between motor planning and execution. This brain activity arose from a
    circuit of neurons in the midbrain, thalamus, and cortex.

    To test whether this circuit acted as a conductor, the team used
    optogenetics.

    This approach enabled the scientists to activate or inactivate this
    circuit using light. Activating this circuit during the planning phase
    of the behavioral task switched the mouse's brain activity from motor
    planning to execution and caused the mouse to lick. On the other hand,
    turning off the circuit while playing the go cue suppressed the cued
    movement. The mice remained in a motor planning stage as if they had
    not received the go cue.

    This work by Dr. Inagaki and his colleagues identified a neural
    circuit critical for triggering movement in response to environmental
    cues. Dr. Inagaki explains how their findings demonstrate generalizable features of behavioral control. "We have found a circuit that can change
    the activity of the motor cortex from motor planning to execution at the appropriate time. This gives us insight into how the brain orchestrates neuronal activity to produce complex behavior. Future work will focus on understanding how this circuit and others reorganize neuronal activity
    across many brain regions." In addition to these fundamental advances in understanding how the brain functions, this work has important clinical implications. In motor disorders, such as Parkinson's disease, patients experience difficulty in self-initiated movement, including difficulty
    in walking. However, adding environmental cues to trigger movements,
    such as lines on the floor or auditory tones, can dramatically improve
    a patient's mobility. This phenomenon, known as paradoxical kinesia,
    suggests that different mechanisms in the brain are recruited for self-initiated movement and cue-triggered movement. Discovering the brain networks involved in cue-triggered movements, which are relatively spared
    in Parkinson's disease, may help to optimize treatment.


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


    ========================================================================== Journal Reference:
    1. Hidehiko K. Inagaki, Susu Chen, Margreet C. Ridder, Pankaj Sah,
    Nuo Li,
    Zidan Yang, Hana Hasanbegovic, Zhenyu Gao, Charles R. Gerfen,
    Karel Svoboda. A midbrain-thalamus-cortex circuit reorganizes
    cortical dynamics to initiate movement. Cell, 2022; DOI:
    10.1016/j.cell.2022.02.006 ==========================================================================

    Link to news story: https://www.sciencedaily.com/releases/2022/03/220314181502.htm

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