Cortical contribution to motor process before and after movement onset

Area of Science:

• Neuroscience
• Motor Control
• Human Physiology

Background:

• Understanding the neural basis of motor control is essential for diagnosing and treating movement disorders.
• The precise cortical networks involved in different phases of voluntary movement, such as reaction time and movement execution, are not fully elucidated.

Purpose of the Study:

• To identify specific cortical areas contributing to reaction time (RT), movement time, onset-peak time, peak velocity, and amplitude during index finger abduction.
• To investigate the relationship between movement parameters and the influence of transcranial magnetic stimulation (TMS) on these processes.

Main Methods:

• Eighteen healthy right-handed participants performed index finger abduction in response to a cue.
• Transcranial magnetic stimulation (TMS) was applied over various cortical areas, including the dorsal premotor cortex, dorsolateral prefrontal cortex, and posterior parietal cortex.
• Reaction time and movement kinematics were recorded and analyzed, comparing TMS trials to sham TMS trials.

Main Results:

• A positive correlation was found between peak velocity and amplitude, suggesting movements scale with size to maintain consistent timing.
• No significant correlation between RT and movement time indicated separate underlying motor processes.
• TMS over the dorsal premotor cortex, dorsolateral prefrontal cortex, or posterior parietal cortex significantly reduced RT.
• TMS over the posterior parietal cortex significantly shortened the onset-peak time, highlighting its role in the acceleration phase.

Conclusions:

• Cortical areas anterior and posterior to the primary motor cortex are involved in motor processes preceding movement onset.
• The posterior parietal cortex plays a particularly important role in the acceleration phase of the movement, influencing onset-peak time.