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Updated: Jul 14, 2026
Intracortical Inhibition Within the Primary Motor Cortex Can Be Modulated by Changing the Focus of Attention
Published on: September 11, 2017
Intracortical inhibition in the human trigeminal motor system
Shapour Jaberzadeh1, Sophie L Pearce, Timothy S Miles
1Discipline of Physiology & Research Centre for Human Movement Control, School of Molecular and Biomedical Science, The University of Adelaide, Adelaide, SA 5005, Australia.
Short-interval intracortical inhibition (SICI) was found in the human trigeminal motor system, affecting both digastric muscles similarly. This finding suggests analogous inhibitory modulation within the motor cortex for these muscles.
Area of Science:
- Neuroscience
- Motor Control
- Human Physiology
Background:
- Short-interval intracortical inhibition (SICI) is a key inhibitory mechanism in the motor cortex.
- Investigating SICI in the trigeminal motor system provides insights into facial muscle control.
Purpose of the Study:
- To determine if SICI is present in the human trigeminal motor system.
- To characterize the features of SICI in the digastric muscles.
Main Methods:
- Surface and intramuscular electromyogram (EMG) recordings from digastric muscles.
- Paired-pulse transcranial magnetic stimulation (TMS) to assess motor evoked potentials (MEPs).
- Varied TMS intensity and interstimulus intervals (ISIs) at rest and during muscle activation.
Main Results:
- Paired-pulse TMS at specific intensities and ISIs (1-4 ms) reduced digastric MEP amplitude bilaterally.
- Inhibition was similar in both left and right digastric muscles.
- Voluntary activation reduced SICI effectiveness, with no side differences.
Conclusions:
- SICI is demonstrable in the human trigeminal motor system's face area.
- Cortical representations of left and right digastric muscles receive analogous SICI modulation.
- This technique can help study movement disorders affecting masticatory muscles.
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