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Updated: Jul 19, 2026
09:48
Intracortical Inhibition Within the Primary Motor Cortex Can Be Modulated by Changing the Focus of Attention
Published on: September 11, 2017
Decreased input to the motor cortex increases motor cortical excitability
Gabrielle Todd1, Jane E Butler, S C Gandevia
1Discipline of Physiology, School of Molecular and Biomedical Science, The University of Adelaide, Adelaide 5005, Australia.
Summary
Short hand inactivity increases motor cortex excitability, as measured by motor evoked potentials (MEP). This change is linked to reduced voluntary drive, not peripheral input, impacting studies on relaxed subjects.
Area of Science:
- Neuroscience
- Motor Control
- Human Physiology
Background:
- Motor cortical excitability is crucial for motor control.
- Understanding factors influencing motor cortex excitability is essential for interpreting experimental results.
Purpose of the Study:
- To determine if a brief period of hand inactivity alters motor cortex excitability.
- To investigate the specific mechanisms behind any observed changes in excitability.
Main Methods:
- Ten subjects underwent transcranial magnetic stimulation (TMS) and peripheral ulnar nerve stimulation.
- Stimulation was applied before and after 20 minutes of hand inactivity.
- Surface electromyography (EMG) recorded evoked compound muscle action potentials in intrinsic hand muscles.
Main Results:
- Motor evoked potential (MEP) size significantly increased by 30-40% in both hand muscles post-inactivity (P=0.012).
- No significant changes were observed in F-wave size, indicating stable motoneurone excitability.
- Paired-pulse TMS revealed no alterations in intracortical inhibition or facilitation.
Conclusions:
- Increased MEP size suggests enhanced motor cortical excitability following inactivity.
- This excitability change is primarily attributed to reduced voluntary drive, not peripheral afferent input.
- Inactivity-induced alterations in cortical excitability must be considered when studying motor cortex function in relaxed individuals.
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