Stopping Muscle Contractions and Relaxations during Action Inhibition Involves Global and Targeted Control Dependent...

Area of Science:

• Neuroscience
• Motor Control
• Human Physiology

Background:

• The precise neural mechanisms controlling action inhibition, specifically the stopping of muscle contractions and relaxations, are not fully understood.
• It remains debated whether central stop commands are targeted to specific muscles or exert global influence.

Purpose of the Study:

• To investigate whether stop commands during action inhibition act globally on both task-active and task-passive muscles.
• To determine if global stop commands are muscle-state specific, differentiating between stopping contractions and relaxations.

Main Methods:

• Three stop-signal task experiments were conducted with 54 human participants.
• Electromyography (EMG) was used to detect stop-related muscle activity at the single-trial level.
• Participants maintained baseline force and responded to Go signals, with stop signals instructing them to cease task-active responses.

Main Results:

• Stop commands were found to influence both task-active and task-passive muscles, indicating global control.
• Global control was muscle-state specific: activity decreased when stopping contractions and increased when stopping relaxations.
• Stopping contractions showed more sustained suppression in task-active muscles than task-passive muscles, suggesting additional targeted control, which was absent when stopping relaxations.

Conclusions:

• Action inhibition is mediated by global stop commands that are sensitive to muscle state.
• These commands rapidly adjust muscle activity across the body, with additional targeted control for contracting, task-active muscles.
• This dual control mechanism may explain the inhibition of complex real-world actions.