Determinants of Neural Plastic Changes Induced by Motor Practice

Area of Science:

• Neuroscience
• Motor Control
• Neuroplasticity

Background:

• Short-term motor practice induces plasticity in the primary motor cortex (M1).
• Understanding factors influencing corticospinal tract (CST) excitability post-motor practice is crucial.

Purpose of the Study:

• Investigate how muscle activity level and goal-setting influence CST excitability after motor practice.
• Determine if forceful activity combined with a constant level goal uniquely affects M1 plasticity.

Main Methods:

• Fifteen healthy subjects performed four thumb adduction tasks: comfortable (C), forceful (F), comfortable with a goal (CG), and forceful with a goal (FG).
• Transcranial magnetic stimulation (TMS) assessed M1 excitability before and after tasks and paired associative stimulation (PAS25).
• Electromyography measured muscle activity levels during tasks.

Main Results:

• Only the forceful with a goal task (FG) significantly increased motor-evoked potential (MEP) amplitude.
• FG also decreased resting motor threshold (RMT), indicating M1 neuronal depolarization.
• MEP increase after FG correlated with that after PAS25, suggesting shared plasticity mechanisms.

Conclusions:

• Task-dependent plasticity is driven by the synergistic effect of forceful muscle activity and maintaining a constant activity level goal.
• Forceful motor practice with a specific goal enhances M1 plasticity and corticospinal excitability.