Predictable transcranial magnetic stimulation suppresses corticospinal excitability: a TMS experiment

Area of Science:

• Neuroscience
• Motor Control
• Human Physiology

Background:

• Motor skill learning is vital for human function.
• Transcranial magnetic stimulation (TMS) assesses corticospinal excitability (CSE) to study motor learning.
• Variability in TMS predictability may confound CSE interpretations.

Purpose of the Study:

• To investigate the effect of TMS predictability on CSE.
• To compare motor-evoked potential (MEP) responses under predictable versus unpredictable TMS conditions.

Main Methods:

• Twenty right-handed participants received TMS-EMG recordings.
• Participants observed either a predictable (moving bar) or unpredictable (static bar) visual cue.
• MEP amplitudes were recorded from the first dorsal interosseous (FDI) muscle and normalized.

Main Results:

• Unpredictable TMS resulted in significantly larger MEP amplitudes compared to predictable TMS.
• This indicates that TMS predictability substantially modulates CSE.

Conclusions:

• TMS predictability is a critical factor influencing CSE.
• Inconsistent stimulation predictability can confound findings in motor learning and action observation studies.
• Standardizing TMS predictability is crucial for accurate interpretation of CSE changes.