Motor cortex excitability is not differentially modulated following skill and strength training

Area of Science:

• Neuroscience
• Motor Control
• Motor Learning

Background:

• Motor training, including skill and strength exercises, can alter neural activity in the primary motor cortex (M1).
• These changes include increased corticospinal excitability (CSE) and reduced short-latency intra-cortical inhibition (SICI).
• The capacity for neural mechanisms to transfer effects between motor cortices (cross-transfer) and modulate the ipsilateral M1 (iM1) is of significant interest.

Purpose of the Study:

• To investigate whether skill training and different types of strength training influence neural adaptations in both the contralateral (cM1) and ipsilateral (iM1) primary motor cortex.
• To determine if these training modalities promote cross-transfer of neural effects to the iM1.

Main Methods:

• Participants underwent unilateral arm training: visuomotor tracking (skill), metronome-paced strength training (MPST), self-paced strength training (SPST), or a control condition.
• Transcranial magnetic stimulation (TMS) was used to measure CSE and SICI in both cM1 and iM1 before and immediately after the training session.

Main Results:

• Skill training and MPST led to increased CSE and decreased SICI in both cM1 and iM1 compared to baseline.
• SPST and the control condition did not show significant changes in CSE or SICI.
• Compared to SPST and control, skill and MPST showed enhanced CSE and reduced SICI in cM1, and reduced SICI in iM1 post-training.

Conclusions:

• Skill training and MPST effectively modulate neural excitability and inhibition in both M1s.
• The findings suggest that training involving synchronization to external cues (auditory or visual) promotes neural adaptations in the iM1.
• These adaptations in the iM1 are likely responsible for mediating the observed neural cross-transfer effects.