Brain Activity Underlying Muscle Relaxation

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Front. Physiol., 03 December 2019 | https://doi.org/10.3389/fphys.2019.01457

Brain Activity Underlying Muscle Relaxation

Kouki Kato1,2*, Tobias Vogt3 and Kazuyuki Kanosue2

• 1Physical Education Center, Nanzan University, Nagoya, Japan
• 2Faculty of Sport Sciences, Waseda University, Tokorozawa, Japan
• 3Institute of Professional Sport Education and Sport Qualifications, German Sport University Cologne, Cologne, Germany

Neurological Disorders

Impairment of muscle relaxation (i.e., myotonia) is involved in a wide spectrum of movement disorders such as myotonic dystrophy, dystonia, stroke, and Parkinson’s disease.

Neural Mechanisms Underlying Muscle Relaxation

Motor Cortex
Muscle relaxation began to get attention after a study utilizing functional magnetic resonance imagery (fMRI) revealed that activity in the primary motor cortex (M1) and supplementary motor area (SMA) increased during voluntary muscle relaxation as well as during muscle contraction

Brain Regions Other Than Motor Cortex

In addition to M1 and SMA, regions such as the dorsolateral prefrontal cortex (DLPFC), anterior cingulate cortex (ACC), basal ganglia, and cerebellum might well be involved in muscle relaxation.
While relaxation involves the termination of a contraction that has already occurred, the No-go trial involves canceling a contraction that is about to be executed. One of corticobasal ganglia loops, the “hyper-direct pathway,” conveys cortical inputs to the substantia nigra pars reticulata through the subthalamic nucleus (STN). This pathway is thought to be related to motor programs of inhibition such as those involving the No-go trial and other types of relaxation. Event-related fMRI studies have demonstrated that the STN is strongly involved in the inhibitory process during No-go trials